PPP(8) BSD System Manager's Manual PPP(8)NAMEppp - Point to Point Protocol (a.k.a. user-ppp)
SYNOPSISppp [-mode] [-nat] [-quiet] [-unitN] [system ...]
DESCRIPTION
This is a user process PPP software package. Normally, PPP is implemented
as a part of the kernel (e.g., as managed by pppd(8)) and it's thus some-
what hard to debug and/or modify its behaviour. However, in this imple-
mentation PPP is done as a user process with the help of the tunnel dev-
ice driver, tun(4).
The -nat flag does the equivalent of a "nat enable yes", enabling ppp's
network address translation features. This allows ppp to act as a NAT or
masquerading engine for all machines on an internal LAN. Refer to the
NETWORK ADDRESS TRANSLATION (PACKET ALIASING) section of this manual page
for details on how to configure NAT in ppp.
The -quiet flag tells ppp to be silent at startup rather than displaying
the mode and interface to standard output.
The -unit flag tells ppp to only attempt to open /dev/tunN. Normally, ppp
will start with a value of 0 for N, and keep trying to open a tunnel dev-
ice by incrementing the value of N by one each time until it succeeds. If
it fails three times in a row because the device file is missing, it
gives up.
The following modes are understood by ppp:
-auto
ppp opens the tun interface, configures it, then goes into the
background. The link isn't brought up until outgoing data is
detected on the tun interface at which point ppp attempts to
bring up the link. Packets received (including the first one)
while ppp is trying to bring the link up will remain queued for a
default of 2 minutes. See the set choked command below.
In -auto mode, at least one system must be given on the command
line (see below) and a set ifaddr must be done in the system pro-
file that specifies a peer IP address to use when configuring the
interface. Something like "10.0.0.1/0" is usually appropriate.
See the "pmdemand" system in /etc/ppp/ppp.conf.sample for an ex-
ample.
-background
Here, ppp attempts to establish a connection with the peer im-
mediately. If it succeeds, ppp goes into the background and the
parent process returns an exit code of 0. If it fails, ppp exits
with a non-zero result.
-foreground
In foreground mode, ppp attempts to establish a connection with
the peer immediately, but never becomes a daemon. The link is
created in background mode. This is useful if you wish to control
ppp's invocation from another process.
-direct
This is used for communicating over an already established con-
nection, usually when receiving incoming connections accepted by
getty(8). ppp ignores the set device line and uses descriptor 0
as the link. ppp will also ignore any configured chat scripts un-
less the "force-scripts" option has been enabled.
If callback is configured, ppp will use the set device informa-
tion when dialing back.
-dedicated
This option is designed for machines connected with a dedicated
wire. ppp will always keep the device open and will ignore any
configured chat scripts unless the "force-scripts" option has
been enabled.
-ddial
This mode is equivalent to -auto mode except that ppp will bring
the link back up any time it's dropped for any reason.
-interactive
This is a no-op, and gives the same behaviour as if none of the
above modes have been specified. ppp loads any sections specified
on the command line, then provides an interactive prompt.
One or more configuration entries or systems (as specified in
/etc/ppp/ppp.conf) may also be specified on the command line. ppp will
read the "default" system from /etc/ppp/ppp.conf at startup, followed by
each of the systems specified on the command line.
Major Features
Provides an interactive user interface. Using its command mode, the user
can easily enter commands to establish the connection with the remote
end, check the status of the connection and close the connection. All
functions can also be optionally password protected for security.
Supports both manual and automatic dialing. Interactive mode has a term
command which enables you to talk to the device directly. When you are
connected to the remote peer and it starts to talk PPP, ppp detects it
and switches to packet mode automatically. Once you have determined the
proper sequence for connecting with the remote host, you can write a chat
script to define the necessary dialing and login procedure for later con-
venience.
Supports on-demand dialup capability. By using -auto mode, ppp will act
as a daemon and wait for a packet to be sent over the PPP link. When this
happens, the daemon automatically dials and establishes the connection.
In almost the same manner -ddial mode (direct-dial mode) also automati-
cally dials and establishes the connection. However, it differs in that
it will dial the remote site any time it detects the link is down, even
if there are no packets to be sent. This mode is useful for full-time
connections where we worry less about line charges and more about being
connected full time. A third -dedicated mode is also available. This mode
is targeted at a dedicated link between two machines. ppp will never
voluntarily quit from dedicated mode - you must send it the "quit all"
command via its diagnostic socket. A SIGHUP will force an LCP renegotia-
tion, and a SIGTERM will force it to exit.
Supports client callback. ppp can use either the standard LCP callback
protocol or the Microsoft CallBack Control Protocol
(ftp://ftp.microsoft.com/developr/rfc/cbcp.txt).
Supports NAT or packet aliasing. Packet aliasing (a.k.a. IP masquerad-
ing) allows computers on a private, unregistered network to access the
Internet. The PPP host acts as a masquerading gateway. IP addresses as
well as TCP and UDP port numbers are NAT'd for outgoing packets and de-
NAT'd for returning packets.
Supports background PPP connections. In background mode, if ppp success-
fully establishes the connection, it will become a daemon. Otherwise, it
will exit with an error. This allows the setup of scripts that wish to
execute certain commands only if the connection is successfully esta-
blished.
Supports server-side PPP connections. In direct mode, ppp acts as server
which accepts incoming PPP connections on stdin/stdout.
Supports PAP and CHAP (RFC 1994, 2433, and 2759) authentication. With
PAP or CHAP, it is possible to skip the Unix style login(1) procedure,
and use the PPP protocol for authentication instead. If the peer requests
Microsoft CHAP authentication and ppp is compiled with DES support, an
appropriate MD4/DES response will be made.
Supports RADIUS (RFC 2138 & 2548) authentication. An extension to PAP
and CHAP, Remote Access Dial In User Service allows authentication infor-
mation to be stored in a central or distributed database along with vari-
ous per-user framed connection characteristics.
Supports Proxy Arp. ppp can be configured to make one or more proxy arp
entries on behalf of the peer. This allows routing from the peer to the
LAN without configuring each machine on that LAN.
Supports packet filtering. User can define four kinds of filters: the in
filter for incoming packets, the out filter for outgoing packets, the
dial filter to define a dialing trigger packet, and the alive filter for
keeping a connection alive with the trigger packet.
Tunnel driver supports bpf. The user can use tcpdump(8) to check the
packet flow over the PPP link.
Supports PPP over TCP and PPP over UDP. If a device name is specified as
host:port[/tcp|udp], ppp will open a TCP or UDP connection for transport-
ing data rather than using a conventional serial device. UDP connections
force ppp into synchronous mode.
Supports PPP over Ethernet (RFC 2516). PPP over Ethernet is supported
with the external program pppoe(8).
Supports IETF draft Predictor-1 (RFC 1978) and DEFLATE (RFC 1979)
compression. ppp supports not only VJ-compression but also Predictor-1
and DEFLATE compression. Normally, a modem has built-in compression
(e.g., v42.bis) and the system may receive higher data rates from it as a
result of such compression. While this is generally a good thing in most
other situations, this higher speed data imposes a penalty on the system
by increasing the number of serial interrupts the system has to process
in talking to the modem and also increases latency. Unlike VJ-
compression, Predictor-1 and DEFLATE compression pre-compresses all net-
work traffic flowing through the link, thus reducing overheads to a
minimum.
Supports Microsoft's IPCP extensions (RFC 1877). Name Server Addresses
and NetBIOS Name Server Addresses can be negotiated with clients using
the Microsoft PPP stack (i.e., Win95, WinNT)
Supports Multi-link PPP (RFC 1990). It is possible to configure ppp to
open more than one physical connection to the peer, combining the
bandwidth of all links for better throughput.
Supports MPPE (draft-ietf-pppext-mppe). MPPE is Microsoft Point to Point
Encryption scheme. It is possible to configure ppp to participate in
Microsoft's Windows VPN. For now, ppp can only get encryption keys from
CHAP 81 authentication. ppp must be compiled with DES for MPPE to
operate.
Supports IPV6CP (RFC 2023). An IPv6 connection can be made in addition
to or instead of the normal IPv4 connection.
PERMISSIONSppp is installed as user "root" and group "network", with permissions
04550. By default, ppp will not run if the invoking user ID is not zero.
This may be overridden by using the allow users command in
/etc/ppp/ppp.conf. When running as a normal user, ppp switches to user ID
0 in order to alter the system routing table, set up system lock files
and read the ppp configuration files. All external commands (executed via
the shell or !bg commands) are executed as the user ID that invoked ppp.
Refer to the 'ID0' logging facility if you're interested in what exactly
is done as user ID zero.
GETTING STARTED
When you first run ppp you may need to deal with some initial configura-
tion details:
+ Your kernel must include a tunnel device (the GENERIC kernel includes
one by default). If it doesn't, you'll need to rebuild your kernel
with the following line in your kernel configuration file:
pseudo-device tun
Tun interfaces can be created at runtime using the ifconfig tunN
create command or by opening the character special device /dev/tunN.
See ifconfig(8) and tun(4) for more information.
+ Check your /dev directory for the tunnel device entries /dev/tunN,
where 'N' represents the number of the tun device, starting at zero.
If they don't exist, you can create them by running "sh ./MAKEDEV
tunN". This will create tun devices 0 through N.
+ Make sure that your system has a group named "network" in the
/etc/group file and that the group contains the names of all users
expected to use ppp. Refer to the group(5) manual page for details.
Each of these users must also be given access using the allow users
command in /etc/ppp/ppp.conf.
+ Create a log file. ppp uses syslog(3) to log information. A common
log file name is /var/log/ppp.log. To make output go to this file,
put the following lines in the /etc/syslog.conf file:
!ppp
*.*<TAB>/var/log/ppp.log
It is possible to have more than one PPP log file by creating a link
to the ppp executable:
# cd /usr/sbin
# ln ppp ppp0
and using
!ppp0
*.*<TAB>/var/log/ppp0.log
in /etc/syslog.conf. Don't forget to send a HUP signal to syslogd(8)
after altering /etc/syslog.conf.
+ Although not strictly relevant to ppp's operation, you should config-
ure your resolver so that it works correctly. This can be done by
configuring a local DNS (using named(8)) or by adding the correct
"nameserver" lines to the file /etc/resolv.conf. Refer to the
resolv.conf(5) manual page for details.
Alternatively, if the peer supports it, ppp can be configured to ask
the peer for the nameserver address(es) and to update
/etc/resolv.conf automatically. Refer to the enable dns and resolv
commands below for details.
MANUAL DIALING
In the following examples, we assume that your machine name is
"awfulhak". When you invoke ppp (see PERMISSIONS above) with no argu-
ments, you are presented with a prompt:
ppp ON awfulhak>
The 'ON' part of your prompt should always be in upper case. If it is in
lower case, it means that you must supply a password using the "passwd"
command. This only ever happens if you connect to a running version of
ppp and have not authenticated yourself using the correct password.
You can start by specifying the device name and speed:
ppp ON awfulhak> set device /dev/cua00
ppp ON awfulhak> set speed 38400
Normally, hardware flow control (CTS/RTS) is used. However, under certain
circumstances (as may happen when you are connected directly to certain
PPP-capable terminal servers), this may result in ppp hanging as soon as
it tries to write data to your communications link as it is waiting for
the CTS (clear to send) signal - which will never come. Thus, if you have
a direct line and can't seem to make a connection, try turning CTS/RTS
off with "set ctsrts off". If you need to do this, check the "set accmap"
description below too - you'll probably need to "set accmap 000a0000".
Usually, parity is set to "none", and this is ppp's default. Parity is a
rather archaic error checking mechanism that is no longer used because
modern modems do their own error checking, and most link-layer protocols
(that's what ppp is) use much more reliable checking mechanisms. Parity
has a relatively huge overhead (a 12.5% increase in traffic) and as a
result, it is always disabled (set to "none") when PPP is opened. Howev-
er, some ISPs (Internet Service Providers) may use specific parity set-
tings at connection time (before PPP is opened). Notably, Compuserve in-
sist on even parity when logging in:
ppp ON awfulhak> set parity even
You can now see what your current device settings look like:
ppp ON awfulhak> show physical
Name: deflink
State: closed
Device: N/A
Link Type: interactive
Connect Count: 0
Queued Packets: 0
Phone Number: N/A
Defaults:
Device List: /dev/cua00
Characteristics: 38400bps, cs8, even parity, CTS/RTS on
Connect time: 0 secs
0 octets in, 0 octets out
Overall 0 bytes/sec
ppp ON awfulhak>
The term command can now be used to talk directly to the device:
ppp ON awfulhak> term
at
OK
atdt123456
CONNECT
login: myispusername
Password: myisppassword
Protocol: ppp
When the peer starts to talk in PPP, ppp detects this automatically and
returns to command mode.
ppp ON awfulhak> # No link has been established
Ppp ON awfulhak> # We've connected & finished LCP
PPp ON awfulhak> # We've authenticated
PPP ON awfulhak> # We've agreed IP numbers
If it does not, it's probable that the peer is waiting for your end to
start negotiating. To force ppp to start sending PPP configuration pack-
ets to the peer, use the ~p command to drop out of terminal mode and
enter packet mode.
If you never even receive a login prompt, it is quite likely that the
peer wants to use PAP or CHAP authentication instead of using Unix-style
login/password authentication. To set things up properly, drop back to
the prompt and set your authentication name and key, then reconnect:
~.
ppp ON awfulhak> set authname myispusername
ppp ON awfulhak> set authkey myisppassword
ppp ON awfulhak> term
at
OK
atdt123456
CONNECT
You may need to tell ppp to initiate negotiations with the peer here too:
~p
ppp ON awfulhak> # No link has been established
Ppp ON awfulhak> # We've connected & finished LCP
PPp ON awfulhak> # We've authenticated
PPP ON awfulhak> # We've agreed IP numbers
You are now connected! Note that 'PPP' in the prompt has changed to capi-
tal letters to indicate that you have a peer connection. If only some of
the three Ps go upper case, wait until either everything is upper case or
lower case. If they revert to lower case, it means that ppp couldn't suc-
cessfully negotiate with the peer. A good first step for troubleshooting
at this point would be:
ppp ON awfulhak> set log local phase lcp ipcp
...and try again. Refer to the set log command description below for
further details. If things fail at this point, it is quite important that
you turn logging on and try again. It is also important that you note any
prompt changes and report them to anyone trying to help you.
When the link is established, the show command can be used to see how
things are going:
PPP ON awfulhak> show physical
* Modem related information is shown here *
PPP ON awfulhak> show ccp
* CCP (compression) related information is shown here *
PPP ON awfulhak> show lcp
* LCP (line control) related information is shown here *
PPP ON awfulhak> show ipcp
* IPCP (IP) related information is shown here *
PPP ON awfulhak> show ipv6cp
* IPV6CP (IPv6) related information is shown here *
PPP ON awfulhak> show link
* Link (high level) related information is shown here *
PPP ON awfulhak> show bundle
* Logical (high level) connection related information is shown here *
At this point, your machine has a host route to the peer. This means that
you can only make a connection with the host on the other side of the
link. If you want to add a default route entry (telling your machine to
send all packets without another routing entry to the other side of the
PPP link), enter the following command:
PPP ON awfulhak> add default HISADDR
The string "HISADDR" represents the IP address of the connected peer. If
the add command fails due to an existing route, you can overwrite the ex-
isting route using add!:
PPP ON awfulhak> add! default HISADDR
This command can also be executed before actually making the connection.
If a new IP address is negotiated at connection time, ppp will update
your default route accordingly.
You can now use your network applications (ping, telnet, ftp, etc.) in
other windows or terminals on your machine. If you wish to reuse the
current terminal, you can put ppp into the background using your standard
shell suspend and background commands (usually '^Z' followed by 'bg').
Refer to the PPP COMMAND LIST section for details on all available com-
mands.
AUTOMATIC DIALING
To use automatic dialing, you must prepare some Dial and Login chat
scripts. See the example definitions in /etc/ppp/ppp.conf.sample (the
format of /etc/ppp/ppp.conf is pretty simple). Each line contains one
comment, inclusion, label, or command:
+ A line starting with a '#' character is treated as a comment line.
Leading whitespace is ignored when identifying comment lines.
+ An inclusion is a line beginning with the word "!include". It must
have one argument - the file to include. You may wish to "!include
~/.ppp.conf" for compatibility with older versions of ppp.
+ A label name starts in the first column and is followed by a ':'
character.
+ A command line must contain a space or tab in the first column.
+ A string starting with a '$' character is substituted with the value
of the environment variable by the same name. Likewise, a string
starting with a '~' character is substituted with the full path to
the home directory of the user account by the same name, and the '~'
character by itself is substituted with the full path to the home
directory of the current user. Any characters following a '#' charac-
ter are ignored. To include a literal '$', '~', or '#' character in a
command or argument, escape it with a '\' character or quote the
command/argument using the '"' character. For example:
set password pa\$ss\~word
set password "user#1234@example.net"
The /etc/ppp/ppp.conf file should consist of at least a "default" sec-
tion. This section is always executed. It should also contain one or more
sections, named according to their purpose, for example, "MyISP" would
represent your ISP, and "ppp-in" would represent an incoming ppp confi-
guration. You can now specify the destination label name when you invoke
ppp. Commands associated with the "default" label are executed, followed
by those associated with the destination label provided. When ppp is
started with no arguments, the "default" section is still executed. The
load command can be used to manually load a section from the
/etc/ppp/ppp.conf file:
ppp ON awfulhak> load MyISP
Note, no action is taken by ppp after a section is loaded, whether it's
the result of passing a label on the command line or using the load com-
mand. Only the commands specified for that label in the configuration
file are executed. However, when invoking ppp with the -background,
-ddial, or -dedicated switches, the link mode tells ppp to establish a
connection. Refer to the set mode command below for further details.
Once the connection is made, the "ppp" portion of the prompt will change
to "PPP":
# ppp MyISP
...
ppp ON awfulhak> dial
Ppp ON awfulhak>
PPp ON awfulhak>
PPP ON awfulhak>
The Ppp prompt indicates that ppp has entered the authentication phase.
The PPp prompt indicates that ppp has entered the network phase. The PPP
prompt indicates that ppp has successfully negotiated a network layer
protocol and is in a usable state.
If the /etc/ppp/ppp.linkup file is available, its contents are executed
when the PPP connection is established. See the provided "pmdemand" exam-
ple in /etc/ppp/ppp.conf.sample which runs a script in the background
after the connection is established (refer to the shell and bg commands
below for a description of possible substitution strings). Similarly,
when a connection is closed, the contents of the /etc/ppp/ppp.linkdown
file are executed. Both of these files have the same format as
/etc/ppp/ppp.conf.
In previous versions of ppp, it was necessary to re-add routes such as
the default route in the ppp.linkup file. ppp supports 'sticky routes',
where all routes that contain the HISADDR, MYADDR, HISADDR6, or MYADDR6
literals will automatically be updated when the values of these variables
change.
BACKGROUND DIALING
If you want to establish a connection using ppp non-interactively (such
as from a crontab(5) entry or an at(1) job), you should use the
-background option. When -background is specified, ppp attempts to estab-
lish the connection immediately. If multiple phone numbers are specified,
each phone number will be tried once. If the attempt fails, ppp exits im-
mediately with a non-zero exit code. If it succeeds, then ppp becomes a
daemon, and returns an exit status of zero to its caller. The daemon ex-
its automatically if the connection is dropped by the remote system, or
it receives a TERM signal.
DIAL ON DEMAND
Demand dialing is enabled with the -auto or -ddial options. You must also
specify the destination label in /etc/ppp/ppp.conf to use. It must con-
tain the set ifaddr command to define the remote peer's IP address (refer
to /etc/ppp/ppp.conf.sample).
# ppp-auto pmdemand
When -auto or -ddial is specified, ppp runs as a daemon but you can still
configure or examine its configuration by using the set server command in
/etc/ppp/ppp.conf (for example, "set server +3000 mypasswd") and connect-
ing to the diagnostic port as follows:
# pppctl 3000 (assuming tun0)
Password:
PPP ON awfulhak> show who
tcp (127.0.0.1:1028) *
The show who command lists users that are currently connected to ppp it-
self. If the diagnostic socket is closed or changed to a different sock-
et, all connections are immediately dropped.
In -auto mode, when an outgoing packet is detected, ppp will perform the
dialing action (chat script) and try to connect with the peer. In -ddial
mode, the dialing action is performed any time the line is found to be
down. If the connect fails, the default behaviour is to wait 30 seconds
and then attempt to connect when another outgoing packet is detected.
This behaviour can be changed using the set redial command:
set redial secs[+inc[-max]][.next] [attempts]
secs The number of seconds to wait before attempting to connect
again. If the argument is the literal string 'random', the de-
lay period is a random value between 1 and 30 seconds in-
clusive.
inc The number of seconds that secs should be incremented each time
a new dial attempt is made. The timeout reverts to secs only
after a successful connection is established. The default value
for inc is zero.
max The maximum number of times ppp should increment secs. The de-
fault value for max is 10.
next The number of seconds to wait before attempting to dial the
next number in a list of numbers (see the set phone command).
The default is 3 seconds. Again, if the argument is the literal
string 'random', the delay period is a random value between 1
and 30 seconds.
attempts The maximum number of times to try to connect for each outgoing
packet that triggers a dial. The previous value is unchanged if
this parameter is omitted. If a value of zero is specified for
attempts, ppp will keep trying until a connection is made.
So, for example:
set redial 10.3 4
...will attempt to connect 4 times for each outgoing packet that causes a
dial attempt with a 3 second delay between each number and a 10 second
delay after all numbers have been tried. If multiple phone numbers are
specified, the total number of attempts is still 4 (it does not attempt
each number 4 times).
Alternatively,
set redial 10+10-5.3 20
...tells ppp to attempt to connect 20 times. After the first attempt, ppp
pauses for 10 seconds. After the next attempt it pauses for 20 seconds
and so on until after the sixth attempt it pauses for 1 minute. The next
14 pauses will also have a duration of one minute. If ppp connects,
disconnects, and fails to connect again, the timeout starts again at 10
seconds.
Modifying the dial delay is very useful when running ppp in -auto mode on
both ends of the link. If each end has the same timeout, both ends wind
up calling each other at the same time if the link drops and both ends
have packets queued. At some locations, the serial link may not be reli-
able, and carrier may be lost at inappropriate times. It is possible to
have ppp redial should carrier be unexpectedly lost during a session.
set reconnect timeout ntries
This command tells ppp to re-establish the connection ntries times on
loss of carrier with a pause of timeout seconds before each try. For ex-
ample,
set reconnect 3 5
...tells ppp that on an unexpected loss of carrier, it should wait 3
seconds before attempting to reconnect. This may happen up to 5 times be-
fore ppp gives up. The default value of ntries is zero (no reconnect).
Care should be taken with this option. If the local timeout is slightly
longer than the remote timeout, the reconnect feature will always be
triggered (up to the given number of times) after the remote side times
out and hangs up. NOTE: In this context, losing too many LQRs constitutes
a loss of carrier and will trigger a reconnect. If the -background flag
is specified, all phone numbers are dialed at most once until a connec-
tion is made. The next number redial period specified with the set redial
command is honoured, as is the reconnect tries value. If your redial
value is less than the number of phone numbers specified, not all the
specified numbers will be tried. To terminate the program, type:
PPP ON awfulhak> close
ppp ON awfulhak> quit all
A simple quit command will terminate the pppctl(8) or telnet(1) connec-
tion but not the ppp program itself. You must use quit all to terminate
ppp as well.
RECEIVING INCOMING PPP CONNECTIONS (Method 1)
To handle an incoming PPP connection request, follow these steps:
1. Make sure the modem is configured correctly:
+ Use Hardware Handshake (CTS/RTS) for flow control.
+ Modem should be set to NO echo back (ATE0) and NO results string
(ATQ1).
2. Edit /etc/ttys to enable a getty(8) on the port where the modem is
attached. For example:
ttyd1 "/usr/libexec/getty std.38400" dialup on secure
Don't forget to send a HUP signal to the init(8) process to start
the getty(8):
# kill -HUP 1
It is usually also necessary to train your modem to the same DTR
speed as the getty:
# ppp
ppp ON awfulhak> set device /dev/cua01
ppp ON awfulhak> set speed 38400
ppp ON awfulhak> term
deflink: Entering terminal mode on /dev/cua01
Type `~?' for help
at
OK
at
OK
atz
OK
at
OK
~.
ppp ON awfulhak> quit
3. Create a /usr/local/bin/ppplogin file with the following contents:
#!/bin/mksh
exec /usr/sbin/ppp -direct incoming
Direct mode (-direct) lets ppp work with stdin and stdout. You can
also use pppctl(8) to connect to a configured diagnostic port, in
the same manner as with client-side ppp.
Here, the incoming section must be set up in /etc/ppp/ppp.conf.
Make sure that the incoming section contains the "allow users" com-
mand as appropriate.
4. Prepare an account for the incoming user.
ppp:xxxx:66:66:PPP Login User:/home/ppp:/usr/local/bin/ppplogin
Refer to the manual entries for adduser(8) and vipw(8) for details.
5. Support for IPCP Domain Name Server and NetBIOS Name Server negotia-
tion can be enabled using the accept dns and set nbns commands.
Refer to their descriptions below.
RECEIVING INCOMING PPP CONNECTIONS (Method 2)
This method differs in that we use ppp to authenticate the connection
rather than login(1):
1. Configure your default section in /etc/gettytab with automatic ppp
recognition by specifying the 'pp' capability:
default:\
:pp=/usr/local/bin/ppplogin:\
.....
2. Configure your serial device(s), enable a getty(8), and create
/usr/local/bin/ppplogin as in the first three steps for method 1
above.
3. Add either "enable chap" or "enable pap" (or both) to
/etc/ppp/ppp.conf under the "incoming" label (or whatever label
ppplogin uses).
4. Create an entry in /etc/ppp/ppp.secret for each incoming user:
Pfred<TAB>xxxx
Pgeorge<TAB>yyyy
Now, as soon as getty(8) detects a ppp connection (by recognising the
HDLC frame headers), it runs /usr/local/bin/ppplogin.
It is VITAL that either PAP or CHAP are enabled as above. If they are
not, you are allowing anybody to establish a ppp session with your
machine without a password, opening yourself up to all sorts of potential
attacks.
AUTHENTICATING INCOMING CONNECTIONS
Normally, the receiver of a connection requires that the peer authenti-
cates itself. This may be done using login(1), but alternatively, you can
use PAP or CHAP. CHAP is the more secure of the two, but some clients may
not support it. Once you decide which you wish to use, add the command
"enable chap" or "enable pap" to the relevant section of ppp.conf.
You must then configure the /etc/ppp/ppp.secret file. This file contains
one line per possible client, each line containing up to five fields:
name key [hisaddr [label [callback-number]]]
The name and key specify the client username and password. If key is '*'
and PAP is being used, ppp will look up the password database (passwd(5))
when authenticating. If the client does not offer a suitable response
based on any name/key combination in ppp.secret, authentication fails.
If authentication is successful, hisaddr (if specified) is used when
negotiating IP numbers. See the set ifaddr command for details.
If authentication is successful and label is specified, the current sys-
tem label is changed to match the given label. This will change the sub-
sequent parsing of the ppp.linkup and ppp.linkdown files.
If authentication is successful and callback-number is specified and "set
callback" has been used in ppp.conf, the client will be called back on
the given number. If CBCP is being used, callback-number may also contain
a list of numbers or a '*', as if passed to the "set cbcp" command. The
value will be used in ppp's subsequent CBCP phase.
PPP OVER TCP and UDP (a.k.a. Tunnelling)
Instead of running ppp over a serial link, it is possible to use a TCP
connection instead by specifying the host, port, and protocol as the dev-
ice:
set device ui-gate:6669/tcp
Instead of opening a serial device, ppp will open a TCP connection to the
given machine on the given socket. It should be noted however that ppp
doesn't use the telnet protocol and will be unable to negotiate with a
telnet server. You should set up a port for receiving this PPP connection
on the receiving machine (ui-gate). This is done by first updating
/etc/services to name the service:
ppp-in 6669/tcp # Incoming PPP connections over TCP
and updating /etc/inetd.conf to tell inetd(8) how to deal with incoming
connections on that port:
ppp-in stream tcp nowait root /usr/sbin/ppp ppp-direct ppp-in
Don't forget to send a HUP signal to inetd(8) after you've updated
/etc/inetd.conf. Here, we use a label named "ppp-in". The entry in
/etc/ppp/ppp.conf on ui-gate (the receiver) should contain the following:
ppp-in:
set timeout 0
set ifaddr 10.0.4.1 10.0.4.2
and the entry in /etc/ppp/ppp.linkup should contain:
ppp-in:
add 10.0.1.0/24 HISADDR
It is necessary to put the "add" command in ppp.linkup to ensure that the
route is only added after ppp has negotiated and assigned addresses to
its interface.
You may also want to enable PAP or CHAP for security. To enable PAP, add
the following line:
enable PAP
You'll also need to create the following entry in /etc/ppp/ppp.secret:
MyAuthName MyAuthPasswd
If MyAuthPasswd is a '*', the password is looked up in the passwd(5) da-
tabase.
The entry in /etc/ppp/ppp.conf on awfulhak (the initiator) should contain
the following:
ui-gate:
set escape 0xff
set device ui-gate:ppp-in/tcp
set dial
set timeout 30
set log Phase Chat Connect hdlc LCP IPCP IPV6CP CCP tun
set ifaddr 10.0.4.2 10.0.4.1
...with the route set up in /etc/ppp/ppp.linkup:
ui-gate:
add 10.0.2.0/24 HISADDR
Again, if you're enabling PAP, you'll also need this in the
/etc/ppp/ppp.conf profile:
set authname MyAuthName
set authkey MyAuthKey
We're assigning the address of 10.0.4.1 to ui-gate, and the address
10.0.4.2 to awfulhak. To open the connection, just type
awfulhak # ppp-background ui-gate
The result will be an additional "route" on awfulhak to the 10.0.2.0/24
network via the TCP connection, and an additional "route" on ui-gate to
the 10.0.1.0/24 network. The networks are effectively bridged - the
underlying TCP connection may be across a public network (such as the In-
ternet), and the PPP traffic is conceptually encapsulated (although not
packet by packet) inside the TCP stream between the two gateways.
The major disadvantage of this mechanism is that there are two
"guaranteed delivery" mechanisms in place - the underlying TCP stream and
whatever protocol is used over the PPP link - probably TCP again. If
packets are lost, both levels will get in each others way trying to nego-
tiate sending of the missing packet.
To avoid this overhead, it is also possible to do all this using UDP in-
stead of TCP as the transport by simply changing the protocol from "tcp"
to "udp". When using UDP as a transport, ppp will operate in synchronous
mode. This is another gain as the incoming data does not have to be rear-
ranged into packets.
Care should be taken when adding a default route through a tunnelled set-
up like this. It is quite common for the default route (added in
/etc/ppp/ppp.linkup) to end up routing the link's TCP connection through
the tunnel, effectively garrotting the connection. To avoid this, make
sure you add a static route for the benefit of the link:
ui-gate:
set escape 0xff
set device ui-gate:ppp-in/tcp
add ui-gate x.x.x.x
.....
where "x.x.x.x" is the IP number that your route to "ui-gate" would nor-
mally use.
When routing your connection across a public network such as the Inter-
net, it is preferable to encrypt the data. This can be done with the help
of the MPPE protocol, although currently this means that you will not be
able to also compress the traffic as MPPE is implemented as a compression
layer (thank Microsoft for this). To enable MPPE encryption, add the fol-
lowing lines to /etc/ppp/ppp.conf on the server:
enable MSCHAPv2
disable deflate pred1
deny deflate pred1
Ensure that you've put the requisite entry in /etc/ppp/ppp.secret
(MSCHAPv2 is challenge based, so passwd(5) cannot be used).
MSCHAPv2 and MPPE are accepted by default, so the client end should work
without any additional changes (although ensure you have "set authname"
and "set authkey" in your profile).
NETWORK ADDRESS TRANSLATION (PACKET ALIASING)
The -nat command line option enables network address translation (a.k.a.
packet aliasing). This allows the ppp host to act as a masquerading gate-
way for other computers over a local area network. Outgoing IP packets
are NAT'd so that they appear to come from the ppp host, and incoming
packets are de-NAT'd so that they are routed to the correct machine on
the local area network. NAT allows computers on private, unregistered
subnets to have Internet access, although they are invisible from the
outside world. In general, correct ppp operation should first be verified
with network address translation disabled. Then, the -nat option should
be switched on, and network applications (web browser, telnet(1), ftp(1),
ping(8), traceroute(8), etc.) should be checked on the ppp host. Finally,
the same or similar applications should be checked on other computers in
the LAN. If network applications work correctly on the ppp host, but not
on other machines in the LAN, then the masquerading software is working
properly, but the host is either not forwarding or possibly receiving IP
packets. Check that IP forwarding is enabled in /etc/sysctl.conf and that
other machines have designated the ppp host as the gateway for the LAN.
PACKET FILTERING
This implementation supports packet filtering. There are four kinds of
filters: the in filter, the out filter, the dial filter, and the alive
filter. Here are the basics:
+ A filter definition has the following syntax:
set filter name rule-no action [!]
[[host] src_addr[/width] [dst_addr[/width]]] [proto [src cmp port]
[dst cmp port] [estab] [syn] [finrst] [timeout secs]]
1. Name should be one of "in", "out", "dial", or "alive".
2. Rule-no is a numeric value between 0 and 39 specifying the rule
number. Rules are specified in numeric order according to rule-
no, but only if rule 0 is defined.
3. Action may be specified as "permit" or "deny", in which case if
a given packet matches the rule, the associated action is taken
immediately. Action can also be specified as "clear" to clear
the action associated with that particular rule, or as a new
rule number greater than the current rule. In this case, if a
given packet matches the current rule, the packet will next be
matched against the new rule number (rather than the next rule
number).
The action may optionally be followed with an exclamation mark
('!'), telling ppp to reverse the sense of the following match.
4. [src_addr[/width]] and [dst_addr[/width]] are the source and
destination IP number specifications. If [/width] is specified,
it gives the number of relevant netmask bits, allowing the
specification of an address range.
Either src_addr or dst_addr may be given the values MYADDR,
HISADDR, MYADDR6, or HISADDR6 (refer to the description of the
bg command for a description of these values). When these values
are used, the filters will be updated any time the values
change. This is similar to the behaviour of the add command
below.
5. Proto may be any protocol from protocols(5).
6. Cmp is one of 'lt', 'eq', or 'gt', meaning less-than, equal, and
greater-than, respectively. Port can be specified as a numeric
port or by a service name from /etc/services.
7. The 'estab', 'syn', and 'finrst' flags are only allowed when
proto is set to 'tcp', and represent the TH_ACK, TH_SYN, and
TH_FIN or TH_RST TCP flags, respectively.
8. The timeout value adjusts the current idle timeout to at least
secs seconds. If a timeout is given in the alive filter as well
as in the in/out filter, the in/out value is used. If no timeout
is given, the default timeout (set using set timeout and de-
faulting to 180 seconds) is used.
+ Each filter can hold up to 40 rules, starting from rule 0. The entire
rule set is not effective until rule 0 is defined, i.e., the default
is to allow everything through.
+ If no rule in a defined set of rules matches a packet, that packet
will be discarded (blocked). If there are no rules in a given filter,
the packet will be permitted.
+ It's possible to filter based on the payload of UDP frames where
those frames contain a PROTO_IP PPP frame header. See the filter-
decapsulation option below for further details.
+ Use "set filter name -1" to flush all rules.
See /etc/ppp/ppp.conf.sample.
SETTING THE IDLE TIMER
To check/set the idle timer, use the show bundle and set timeout com-
mands:
ppp ON awfulhak> set timeout 600
The timeout period is measured in seconds, the default value for which is
180 seconds (or 3 min). To disable the idle timer function, use the fol-
lowing command:
ppp ON awfulhak> set timeout 0
In -ddial and -dedicated modes, the idle timeout is ignored. In -auto
mode, when the idle timeout causes the PPP session to be closed, the ppp
program itself remains running. Another trigger packet will cause it to
attempt to re-establish the link.
PREDICTOR-1 and DEFLATE COMPRESSION
ppp supports both Predictor type 1 and deflate compression. By default,
ppp will attempt to use (or be willing to accept) both compression proto-
cols when the peer agrees (or requests them). The deflate protocol is
preferred by ppp. Refer to the disable and deny commands if you wish to
disable this functionality.
It is possible to use a different compression algorithm in each direction
by using only one of "disable deflate" and "deny deflate" (assuming that
the peer supports both algorithms).
By default, when negotiating DEFLATE, ppp will use a window size of 15.
Refer to the set deflate command if you wish to change this behaviour.
A special algorithm called DEFLATE24 is also available, and is disabled
and denied by default. This is exactly the same as DEFLATE except that it
uses CCP ID 24 to negotiate. This allows ppp to successfully negotiate
DEFLATE with pppd version 2.3.*.
CONTROLLING IP ADDRESS
For IPv4, ppp uses IPCP to negotiate IP addresses. Each side of the con-
nection specifies the IP address that it's willing to use, and if the re-
quested IP address is acceptable then ppp returns an ACK to the reques-
ter. Otherwise, ppp returns NAK to suggest that the peer use a different
IP address. When both sides of the connection agree to accept the re-
ceived request (and send an ACK), IPCP is set to the open state and a
network level connection is established. To control this IPCP behaviour,
this implementation has the set ifaddr command for defining the local and
remote IP address:
set ifaddr [src_addr[/nn] [dst_addr[/nn] [netmask [trigger_addr]]]]
src_addr is the IP address that the local side is willing to use,
dst_addr is the IP address which the remote side should use, and netmask
is the netmask that should be used. src_addr defaults to the current
hostname(1), dst_addr defaults to 0.0.0.0, and netmask defaults to what-
ever mask is appropriate for src_addr. It is only possible to make
netmask smaller than the default. The usual value is 255.255.255.255, as
most kernels ignore the netmask of a POINTOPOINT interface.
Some incorrect PPP implementations require that the peer negotiates a
specific IP address instead of src_addr. If this is the case,
trigger_addr may be used to specify this IP number. This will not affect
the routing table unless the other side agrees with this proposed number.
set ifaddr 192.244.177.38 192.244.177.2 255.255.255.255 0.0.0.0
The above specification means:
+ I will first suggest that my IP address should be 0.0.0.0, but I will
only accept an address of 192.244.177.38.
+ I strongly insist that the peer uses 192.244.177.2 as his own address
and won't permit the use of any IP address but 192.244.177.2. When
the peer requests another IP address, I will always suggest that it
uses 192.244.177.2.
+ The routing table entry will have a netmask of 0xffffffff.
This is all fine when each side has a pre-determined IP address, however
it is often the case that one side is acting as a server which controls
all IP addresses and the other side should go along with it. In order to
allow more flexible behaviour, the set ifaddr command allows the user to
specify IP addresses more loosely:
set ifaddr 192.244.177.38/24 192.244.177.2/20
A number followed by a slash ('/') represents the number of bits signifi-
cant in the IP address. The above example means:
+ I'd like to use 192.244.177.38 as my address if it is possible, but
I'll also accept any IP address between 192.244.177.0 and
192.244.177.255.
+ I'd like to make him use 192.244.177.2 as his own address, but I'll
also permit him to use any IP address between 192.244.176.0 and
192.244.191.255.
+ As you may have already noticed, 192.244.177.2 is equivalent to say-
ing 192.244.177.2/32.
+ As an exception, 0 is equivalent to 0.0.0.0/0, meaning that I have no
preferred IP address and will obey the remote peer's selection. When
using zero, no routing table entries will be made until a connection
is established.
+ 192.244.177.2/0 means that I'll accept/permit any IP address but I'll
suggest that 192.244.177.2 be used first.
When negotiating IPv6 addresses, no control is given to the user. IPV6CP
negotiation is fully automatic.
CONNECTING WITH YOUR INTERNET SERVICE PROVIDER
The following steps should be taken when connecting to your ISP:
1. Describe your providers phone number(s) in the dial script using the
set phone command. This command allows you to set multiple phone
numbers for dialing and redialing separated by either a pipe ('|')
or a colon (':'):
set phone telno[|backupnumber]...[:nextnumber]...
Numbers after the first in a pipe-separated list are only used if
the previous number was used in a failed dial or login script.
Numbers separated by a colon are used sequentially, irrespective of
what happened as a result of using the previous number. For example:
set phone "1234567|2345678:3456789|4567890"
Here, the 1234567 number is attempted. If the dial or login script
fails, the 2345678 number is used next time, but *only* if the dial
or login script fails. On the dial after this, the 3456789 number is
used. The 4567890 number is only used if the dial or login script
using the 3456789 fails. Irrespective of whether the login script of
the 2345678 number succeeds or fails, the next number is still the
3456789 number.
As many pipes and colons can be used as are necessary (although a
given site would usually prefer to use either the pipe or the colon,
but not both). The next number redial timeout is used between all
numbers. When the end of the list is reached, the normal redial
period is used before starting at the beginning again. The selected
phone number is substituted for the \\T string in the set dial com-
mand (see below).
2. Set up your redial requirements using set redial. For example, if
you have a bad telephone line or your provider is usually engaged
(not so common these days), you may want to specify the following:
set redial 10 4
This says that up to 4 phone calls should be attempted with a pause
of 10 seconds before dialing the first number again.
3. Describe your login procedure using the set dial and set login com-
mands. The set dial command is used to talk to your modem and estab-
lish a link with your ISP, for example:
set dial "ABORT BUSY ABORT NO\\sCARRIER TIMEOUT 4 \"\" \
ATZ OK-ATZ-OK ATDT\\T TIMEOUT 60 CONNECT"
This modem "chat" string means:
+ Abort if the string "BUSY" or "NO CARRIER" is received.
+ Set the timeout to 4 seconds.
+ Expect nothing.
+ Send ATZ.
+ Expect OK. If that's not received within the 4 second timeout,
send ATZ and expect OK.
+ Send ATDTxxxxxxx where xxxxxxx is the next number in the phone
list from above.
+ Set the timeout to 60.
+ Wait for the CONNECT string.
Once the connection is established, the login script is executed.
This script is written in the same style as the dial script, but
care should be taken to avoid having your password logged:
set authkey MySecret
set login "TIMEOUT 15 login:-\\r-login: awfulhak \
word: \\P ocol: PPP HELLO"
This login "chat" string means:
+ Set the timeout to 15 seconds.
+ Expect "login:". If it's not received, send a carriage return
and expect "login:" again.
+ Send "awfulhak".
+ Expect "word:" (the tail end of a "Password:" prompt).
+ Send whatever our current authkey value is set to.
+ Expect "ocol:" (the tail end of a "Protocol:" prompt).
+ Send "PPP".
+ Expect "HELLO".
The set authkey command is logged specially. When command or chat
logging is enabled, the actual password is not logged; '********' is
logged instead.
Login scripts vary greatly between ISPs. If you're setting one up
for the first time, ENABLE CHAT LOGGING so that you can see if your
script is behaving as you expect.
4. Use set device and set speed to specify your serial line and speed,
for example:
set device /dev/cua00
set speed 115200
The first serial port is cua00. The modem will attach at either
com(4), pccom(4), or ucom(4). So, for example, if the modem attaches
at "pccom3", device should be set to /dev/cua03.
A speed of 115200 should be specified if you have a modem capable of
bit rates of 28800 or more. In general, the serial speed should be
about four times the modem speed.
5. Use the set ifaddr command to define the IP address.
+ If you know what IP address your provider uses, then use it as
the remote address (dst_addr), otherwise choose something like
10.0.0.2/0 (see below).
+ If your provider has assigned a particular IP address to you,
then use it as your address (src_addr).
+ If your provider assigns your address dynamically, choose a
suitably unobtrusive and unspecific IP number as your address.
10.0.0.1/0 would be appropriate. The bit after the / specifies
how many bits of the address you consider to be important, so if
you wanted to insist on something in the class C network
1.2.3.0, you could specify 1.2.3.1/24.
+ If you find that your ISP accepts the first IP number that you
suggest, specify third and forth arguments of "0.0.0.0". This
will force your ISP to assign a number (the third argument will
be ignored as it is less restrictive than the default mask for
your 'src_addr').
An example for a connection where you don't know your IP number or
your ISP's IP number would be:
set ifaddr 10.0.0.1/0 10.0.0.2/0 0.0.0.0 0.0.0.0
6. In most cases, your ISP will also be your default router. If this is
the case, add the following line to /etc/ppp/ppp.conf (or to
/etc/ppp/ppp.linkup for setups that don't use -auto mode):
add default HISADDR
This tells ppp to add a default route to whatever the peer address
is (10.0.0.2 in this example). This route is "sticky", meaning that
should the value of HISADDR change, the route will be updated ac-
cordingly.
7. If your provider requests that you use PAP/CHAP authentication
methods, add the next lines to your /etc/ppp/ppp.conf file:
set authname MyName
set authkey MyPassword
Both are accepted by default, so ppp will provide whatever your ISP
requires.
It should be noted that a login script is rarely (if ever) required
when PAP or CHAP are in use.
8. Ask your ISP to authenticate your nameserver address(es) with the
following line:
enable dns
Do NOT do this if you are running a local DNS unless you also either
use "resolv readonly" or have "resolv restore" in
/etc/ppp/ppp.linkdown, as ppp will simply circumvent its use by
entering some nameserver lines in /etc/resolv.conf.
Please refer to /etc/ppp/ppp.conf.sample and /etc/ppp/ppp.linkup.sample
for some real examples. The pmdemand label should be appropriate for most
ISPs.
LOGGING FACILITYppp is able to generate the following log info either via syslog(3) or
directly to the screen:
All Enable all logging facilities. This generates a lot of
log. The most common use of "all" is as a basis, where
you remove some facilities after enabling "all" ("debug"
and "timer" are usually best disabled).
Async Dump async level packet in hex.
CBCP Generate CBCP (CallBack Control Protocol) logs.
CCP Generate a CCP packet trace.
Chat Generate "dial", "login", "logout", and "hangup" chat
script trace logs.
Command Log commands executed either from the command line or
any of the configuration files.
Connect Log Chat lines containing the string "CONNECT".
Debug Log debug information.
DNS Log DNS QUERY packets.
Filter Log packets permitted by the dial filter and denied by
any filter.
HDLC Dump HDLC packet in hex.
ID0 Log all function calls specifically made as user ID 0.
IPCP Generate an IPCP packet trace.
LCP Generate an LCP packet trace.
LQM Generate LQR reports.
Phase Phase transition log output.
Physical Dump physical level packet in hex.
Sync Dump sync level packet in hex.
TCP/IP Dump all TCP/IP packets.
Timer Log timer manipulation.
TUN Include the tun(4) device on each log line.
Warning Output to the terminal device. If there is currently no
terminal, output is sent to the log file using syslog's
LOG_WARNING.
Error Output to both the terminal device and the log file us-
ing syslog's LOG_ERROR.
Alert Output to the log file using LOG_ALERT.
The set log command allows you to set the logging output level. Multiple
levels can be specified on a single command line. The default is
equivalent to "set log Phase".
It is also possible to log directly to the screen. The syntax is the same
except that the word "local" should immediately follow "set log". The de-
fault is "set log local" (i.e., only the un-maskable warning, error, and
alert output).
If the first argument to "set log [local]" begins with a '+' or a '-'
character, the current log levels are not cleared, for example:
PPP ON awfulhak> set log phase
PPP ON awfulhak> show log
Log: Phase Warning Error Alert
Local: Warning Error Alert
PPP ON awfulhak> set log +tcp/ip -warning
PPP ON awfulhak> set log local +command
PPP ON awfulhak> show log
Log: Phase TCP/IP Warning Error Alert
Local: Command Warning Error Alert
Log messages of level Warning, Error, and Alert are not controllable us-
ing "set log [local]".
The Warning level is special in that it will not be logged if it can be
displayed locally.
SIGNAL HANDLINGppp deals with the following signals:
INT Receipt of this signal causes the termination of the current con-
nection (if any). This will cause ppp to exit unless it is in -auto
or -ddial mode.
HUP, TERM, & QUIT
These signals tell ppp to exit.
USR1 This signal tells ppp to re-open any existing server socket, drop-
ping all existing diagnostic connections. Sockets that couldn't
previously be opened will be retried.
USR2 This signal tells ppp to close any existing server socket, dropping
all existing diagnostic connections. SIGUSR1 can still be used to
re-open the socket.
MULTI-LINK PPP
If you wish to use more than one physical link to connect to a PPP peer,
that peer must also understand the MULTI-LINK PPP protocol. Refer to RFC
1990 for specification details.
The peer is identified using a combination of his "endpoint
discriminator" and his "authentication ID". Either or both of these may
be specified. It is recommended that at least one is specified, otherwise
there is no way of ensuring that all links are actually connected to the
same peer program, and some confusing lock-ups may result. Locally, these
identification variables are specified using the set enddisc and set
authname commands. The 'authname' (and 'authkey') must be agreed in ad-
vance with the peer.
Multi-link capabilities are enabled using the set mrru command (set max-
imum reconstructed receive unit). Once multi-link is enabled, ppp will
attempt to negotiate a multi-link connection with the peer.
By default, only one "link" is available (called "deflink"). To create
more links, the clone command is used. This command will clone existing
links, where all characteristics are the same except:
1. The new link has its own name as specified on the clone command
line.
2. The new link is an "interactive" link. Its mode may subsequently be
changed using the set mode command.
3. The new link is in a "closed" state.
A summary of all available links can be seen using the show links com-
mand.
Once a new link has been created, command usage varies. All link specific
commands must be prefixed with the "link name" command, specifying on
which link the command is to be applied. When only a single link is
available, ppp is smart enough not to require the "link name" prefix.
Some commands can still be used without specifying a link - resulting in
an operation at the "bundle" level. For example, once two or more links
are available, the command "show ccp" will show CCP configuration and
statistics at the multi-link level, and "link deflink show ccp" will show
the same information at the "deflink" link level.
Armed with this information, the following configuration might be used:
mp:
set timeout 0
set log phase chat
set device /dev/cua00 /dev/cua01 /dev/cua02
set phone "123456789"
set dial "ABORT BUSY ABORT NO\sCARRIER TIMEOUT 5 \"\" ATZ \
OK-AT-OK \\dATDT\\T TIMEOUT 45 CONNECT"
set login
set ifaddr 10.0.0.1/0 10.0.0.2/0 0.0.0.0 0.0.0.0
set authname ppp
set authkey ppppassword
set mrru 1500
clone 1,2,3 # Create 3 new links - duplicates of the default
link deflink remove # Delete the default link (called ``deflink'')
Note how all cloning is done at the end of the configuration. Usually the
link will be configured first, then cloned. If you wish all links to be
up all the time, you can add the following line to the end of your confi-
guration:
link 1,2,3 set mode ddial
If you want the links to dial on demand, this command could be used:
link * set mode auto
Links may be tied to specific names by removing the "set device" line
above, and specifying the following after the "clone" command:
link 1 set device /dev/cua00
link 2 set device /dev/cua01
link 3 set device /dev/cua02
Use the help command to see which commands require context (using the
link command), which have optional context, and which should not have any
context.
When ppp has negotiated MULTI-LINK mode with the peer, it creates a local
domain socket in the /var/run directory. This socket is used to pass link
information (including the actual link file descriptor) between different
ppp invocations. This facilitates ppp's ability to be run from a getty(8)
or directly from /etc/gettydefs (using the 'pp=' capability), without
needing to have initial control of the serial line. Once ppp negotiates
multi-link mode, it will pass its open link to any already running pro-
cess. If there is no already running process, ppp will act as the master,
creating the socket and listening for new connections.
PPP COMMAND LIST
This section lists the available commands and their effect. They are us-
able either from an interactive ppp session, from a configuration file or
from a pppctl(8) or telnet(1) session.
accept | deny | enable | disable option....
These directives tell ppp how to negotiate the initial connection
with the peer. Each option has a default of either accept or deny and
enable or disable. "Accept" means that the option will be ACK'd if
the peer asks for it. "Deny" means that the option will be NAK'd if
the peer asks for it. "Enable" means that the option will be request-
ed by us. "Disable" means that the option will not be requested by
us.
option may be one of the following:
acfcomp
Default: Enabled and Accepted. ACFComp stands for Address and
Control Field Compression. Non LCP packets will usually have an
address field of 0xff (the All-Stations address) and a control
field of 0x03 (the Unnumbered Information command). If this op-
tion is negotiated, these two bytes are simply not sent, thus
minimising traffic.
See RFC 1662 for details.
chap[05]
Default: Disabled and Accepted. CHAP stands for Challenge
Handshake Authentication Protocol. Only one of CHAP and PAP
(below) may be negotiated. With CHAP, the authenticator sends a
"challenge" message to its peer. The peer uses a one-way hash
function to encrypt the challenge and sends the result back. The
authenticator does the same, and compares the results. The advan-
tage of this mechanism is that no passwords are sent across the
connection. A challenge is made when the connection is first
made. Subsequent challenges may occur. If you want to have your
peer authenticate itself, you must "enable chap" in
/etc/ppp/ppp.conf, and have an entry in /etc/ppp/ppp.secret for
the peer.
When using CHAP as the client, you need only specify "AuthName"
and "AuthKey" in /etc/ppp/ppp.conf. CHAP is accepted by default.
Some PPP implementations use "MS-CHAP" rather than MD5 when en-
crypting the challenge. MS-CHAP is a combination of MD4 and DES.
If ppp was built on a machine with DES libraries available, it
will respond to MS-CHAP authentication requests, but will never
request them.
deflate
Default: Enabled and Accepted. This option decides if deflate
compression will be used by the Compression Control Protocol
(CCP). This is the same algorithm as used by the gzip(1) program.
Note: There is a problem negotiating deflate capabilities with
pppd(8) - a PPP implementation available under many operating
systems. pppd (version 2.3.1) incorrectly attempts to negotiate
deflate compression using type 24 as the CCP configuration type
rather than type 26 as specified in RFC 1979. Type 24 is actually
specified as "PPP Magna-link Variable Resource Compression" in
RFC 1975! ppp is capable of negotiating with pppd, but only if
"deflate24" is enabled and accepted.
deflate24
Default: Disabled and Denied. This is a variance of the deflate
option, allowing negotiation with the pppd(8) program. Refer to
the deflate section above for details. It is disabled by default
as it violates RFC 1975.
dns
Default: Disabled and Denied. This option allows DNS negotiation.
If enabled, ppp will request that the peer confirms the entries
in /etc/resolv.conf. If the peer NAKs our request (suggesting new
IP numbers), /etc/resolv.conf is updated and another request is
sent to confirm the new entries.
If accepted, ppp will answer any DNS queries requested by the
peer rather than rejecting them. The answer is taken from
/etc/resolv.conf unless the set dns command is used as an over-
ride.
enddisc
Default: Enabled and Accepted. This option allows control over
whether we negotiate an endpoint discriminator. We only send our
discriminator if set enddisc is used and enddisc is enabled. We
reject the peer's discriminator if enddisc is denied.
LANMan|chap80lm
Default: Disabled and Accepted. The use of this authentication
protocol is discouraged as it partially violates the authentica-
tion protocol by implementing two different mechanisms (LANMan &
NT) under the guise of a single CHAP type (0x80). "LANMan" uses a
simple DES encryption mechanism and is the least secure of the
CHAP alternatives (although still more secure than PAP).
Refer to the "MSChap" description below for more details.
lqr
Default: Disabled and Accepted. This option decides if Link Qual-
ity Requests will be sent or accepted. LQR is a protocol that al-
lows ppp to determine that the link is down without relying on
the modem's carrier detect. When LQR is enabled, ppp sends the
QUALPROTO option (see "set lqrperiod" below) as part of the LCP
request. If the peer agrees, both sides will exchange LQR packets
at the agreed frequency, allowing detailed link quality monitor-
ing by enabling LQM logging. If the peer doesn't agree, and if
the "echo" option is enabled, ppp will send LCP ECHO requests in-
stead. These packets pass no information of interest, but they
MUST be replied to by the peer.
Whether using LQR or LCP ECHO, ppp will abruptly drop the connec-
tion if 5 unacknowledged packets have been sent rather than send-
ing a 6th. A message is logged at the PHASE level, and any ap-
propriate "reconnect" values are honoured as if the peer were
responsible for dropping the connection.
Refer to the "enable echo" command description for differences in
behaviour prior to ppp version 3.4.2.
mppe
Default: Enabled and Accepted. This is Microsoft Point to Point
Encryption scheme. MPPE key size can be 40-, 56-, and 128-bits.
Refer to the set mppe command.
MSChapV2|chap81
Default: Disabled and Accepted. It is very similar to standard
CHAP (type 0x05) except that it issues challenges of a fixed 16
bytes in length and uses a combination of MD4, SHA-1, and DES to
encrypt the challenge rather than using the standard MD5 mechan-
ism.
MSChap|chap80nt
Default: Disabled and Accepted. The use of this authentication
protocol is discouraged as it partially violates the authentica-
tion protocol by implementing two different mechanisms (LANMan &
NT) under the guise of a single CHAP type (0x80). It is very
similar to standard CHAP (type 0x05) except that it issues chal-
lenges of a fixed 8 bytes in length and uses a combination of MD4
and DES to encrypt the challenge rather than using the standard
MD5 mechanism. CHAP type 0x80 for LANMan is also supported - see
"enable LANMan" for details.
Because both "LANMan" and 'NT' use CHAP type 0x80, when acting as
authenticator with both enabled, ppp will rechallenge the peer up
to three times if it responds using the wrong one of the two pro-
tocols. This gives the peer a chance to attempt using both proto-
cols.
Conversely, when ppp acts as the authenticatee with both proto-
cols accepted, the protocols are used alternately in response to
challenges.
Note: If only LANMan is enabled, pppd(8) (version 2.3.5) mis-
behaves when acting as authenticatee. It provides both the NT and
the LANMan answers, but also suggests that only the NT answer
should be used.
pap
Default: Disabled and Accepted. PAP stands for Password Authenti-
cation Protocol. Only one of PAP and CHAP (above) may be nego-
tiated. With PAP, the ID and Password are sent repeatedly to the
peer until authentication is acknowledged or the connection is
terminated. This is a rather poor security mechanism. It is only
performed when the connection is first established. If you want
to have your peer authenticate itself, you must "enable pap" in
/etc/ppp/ppp.conf, and have an entry in /etc/ppp/ppp.secret for
the peer (although see the passwdauth and set radius options
below).
When using PAP as the client, you need only specify "AuthName"
and "AuthKey" in /etc/ppp/ppp.conf. PAP is accepted by default.
pred1
Default: Enabled and Accepted. This option decides if Predictor 1
compression will be used by the Compression Control Protocol
(CCP).
protocomp
Default: Enabled and Accepted. This option is used to negotiate
PFC (Protocol Field Compression), a mechanism where the protocol
field number is reduced to one octet rather than two.
shortseq
Default: Enabled and Accepted. This option determines if ppp will
request and accept requests for short (12-bit) sequence numbers
when negotiating multi-link mode. This is only applicable if our
MRRU is set (thus enabling multi-link).
vjcomp
Default: Enabled and Accepted. This option determines if Van
Jacobson header compression will be used.
The following options are not actually negotiated with the peer.
Therefore, accepting or denying them makes no sense.
echo
Default: Disabled. When this option is enabled, ppp will send LCP
ECHO requests to the peer at the frequency defined by
"echoperiod". Note, LQR requests will supersede LCP ECHO requests
if enabled and negotiated. See "set lqrperiod" below for details.
Prior to ppp version 3.4.2, "echo" was considered enabled if lqr
was enabled and negotiated, otherwise it was considered disabled.
For the same behaviour, it is now necessary to "enable lqr echo"
rather than just "enable lqr".
filter-decapsulation
Default: Disabled. When this option is enabled, ppp will examine
UDP frames to see if they actually contain a PPP frame as their
payload. If this is the case, all filters will operate on the
payload rather than the actual packet.
This is useful if you want to send PPPoUDP traffic over a PPP
link, but want that link to do smart things with the real data
rather than the UDP wrapper.
The UDP frame payload must not be compressed in any way, other-
wise ppp will not be able to interpret it. It's therefore recom-
mended that you disable vj pred1 deflate and deny vj pred1
deflate in the configuration for the ppp invocation with the udp
link.
force-scripts
Default: Disabled. Forces execution of the configured chat
scripts in direct and dedicated modes.
idcheck
Default: Enabled. When ppp exchanges low-level LCP, CCP, and IPCP
configuration traffic, the Identifier field of any replies is ex-
pected to be the same as that of the request. By default, ppp
drops any reply packets that do not contain the expected identif-
ier field, reporting the fact at the respective log level. If
idcheck is disabled, ppp will ignore the identifier field.
iface-alias
Default: Enabled if -nat is specified. This option simply tells
ppp to add new interface addresses to the interface rather than
replacing them. The option can only be enabled if network address
translation is enabled ("nat enable yes").
With this option enabled, ppp will pass traffic for old interface
addresses through the NAT engine, resulting in the ability (in
-auto mode) to properly connect the process that caused the PPP
link to come up in the first place.
Disabling NAT with "nat enable no" will also disable "iface-
alias".
ipcp
Default: Enabled. This option allows ppp to attempt to negotiate
IP control protocol capabilities and if successful to exchange IP
datagrams with the peer.
ipv6cp
Default: Enabled. This option allows ppp to attempt to negotiate
IPv6 control protocol capabilities and if successful to exchange
IPv6 datagrams with the peer.
keep-session
Default: Disabled. When ppp runs as a Multi-link server, a dif-
ferent ppp instance initially receives each connection. After
determining that the link belongs to an already existing bundle
(controlled by another ppp invocation), ppp will transfer the
link to that process.
If the link is a tty device or if this option is enabled, ppp
will not exit, but will change its process name to "session
owner" and wait for the controlling ppp to finish with the link
and deliver a signal back to the idle process. This prevents the
confusion that results from ppp's parent considering the link
resource available again.
For tty devices that have entries in /etc/ttys, this is necessary
to prevent another getty(8) from being started, and for program
links such as sshd(8), it prevents sshd(8) from exiting due to
the death of its child. As ppp cannot determine its parents re-
quirements (except for the tty case), this option must be enabled
manually depending on the circumstances.
loopback
Default: Enabled. When loopback is enabled, ppp will automatical-
ly loop back packets being sent out with a destination address
equal to that of the PPP interface. If disabled, ppp will send
the packet, probably resulting in an ICMP redirect from the other
end. It is convenient to have this option enabled when the inter-
face is also the default route as it avoids the necessity of a
loopback route.
passwdauth
Default: Disabled. Enabling this option will tell the PAP authen-
tication code to use the password database (see passwd(5)) to au-
thenticate the caller if they cannot be found in the
/etc/ppp/ppp.secret file. /etc/ppp/ppp.secret is always checked
first. If you wish to use passwords from passwd(5), but also to
specify an IP number or label for a given client, use '*' as the
client password in /etc/ppp/ppp.secret.
proxy
Default: Disabled. Enabling this option will tell ppp to proxy
ARP for the peer. This means that ppp will make an entry in the
ARP table using HISADDR and the MAC address of the local network
in which HISADDR appears. This allows other machines connected to
the LAN to talk to the peer as if the peer itself was connected
to the LAN. The proxy entry cannot be made unless HISADDR is an
address from a LAN.
proxyall
Default: Disabled. Enabling this will tell ppp to add proxy arp
entries for every IP address in all class C or smaller subnets
routed via the tun interface.
Proxy arp entries are only made for sticky routes that are added
using the add command. No proxy arp entries are made for the in-
terface address itself (as created by the set ifaddr command).
sroutes
Default: Enabled. When the add command is used with the HISADDR,
MYADDR, HISADDR6, or MYADDR6 values, entries are stored in the
"sticky route" list. Each time these variables change, this list
is re-applied to the routing table.
Disabling this option will prevent the re-application of sticky
routes, although the "sticky route" list will still be main-
tained.
[tcp]mssfixup
Default: Enabled. This option tells ppp to adjust TCP SYN packets
so that the maximum receive segment size is not greater than the
amount allowed by the interface MTU.
throughput
Default: Enabled. This option tells ppp to gather throughput
statistics. Input and output is sampled over a rolling 5 second
window, and current, best, and total figures are retained. This
data is output when the relevant PPP layer shuts down, and is
also available using the show command. Throughput statistics are
available at the "IPCP" and "physical" levels.
utmp
Default: Enabled. Normally, when a user is authenticated using
PAP or CHAP, and when ppp is running in -direct mode, an entry is
made in the utmp and wtmp files for that user. Disabling this op-
tion will tell ppp not to make any utmp or wtmp entries. This is
usually only necessary if you require the user to both login and
authenticate themselves.
add[!] dest[/nn] [mask] [gateway]
Dest is the destination IP address. The netmask is specified either
as a number of bits with /nn or as an IP number using mask. 0 0 or
simply 0 with no mask refers to the default route. It is also possi-
ble to use the literal name "default" instead of 0. Gateway is the
next hop gateway to get to the given dest machine/network. Refer to
the route(8) command for further details.
It is possible to use the symbolic names "MYADDR", "HISADDR",
"MYADDR6", or "HISADDR6" as the destination, and "HISADDR" or
"HISADDR6" as the gateway. "MYADDR" is replaced with the interface IP
address, "HISADDR" is replaced with the interface IP destination
(peer) address, "MYADDR6" is replaced with the interface IPv6 ad-
dress, and "HISADDR6" is replaced with the interface IPv6 destination
address.
If the add! command is used (note the trailing '!'), then if the
route already exists, it will be updated as with the route change
command (see route(8) for further details).
Routes that contain the "HISADDR", "MYADDR", "HISADDR6", "MYADDR6",
"DNS0", or "DNS1" constants are considered "sticky". They are stored
in a list (use show ncp to see the list), and each time the value of
one of these variables changes, the appropriate routing table entries
are updated. This facility may be disabled using disable sroutes.
allow command [args]
This command controls access to ppp and its configuration files. It
is possible to allow user-level access, depending on the configura-
tion file label and on the mode that ppp is being run in. For exam-
ple, you may wish to configure ppp so that only user "fred" may ac-
cess label "fredlabel" in -background mode.
User ID 0 is immune to these commands.
allow user[s] logname ...
By default, only user ID 0 is allowed access to ppp. If this com-
mand is used, all of the listed users are allowed access to the
section in which the allow users command is found. The "default"
section is always checked first (even though it is only ever au-
tomatically loaded at startup). allow users commands are cumula-
tive in a given section, but users allowed in any given section
override users allowed in the default section, so it's possible
to allow users access to everything except a given label by
specifying default users in the "default" section, and then
specifying a new user list for that label.
If user '*' is specified, access is allowed to all users. If
logname is omitted, the user access list is emptied (i.e. only
root will have access). There is no difference between the forms
allow user and allow users.
allow mode[s] mode ...
By default, access using any ppp mode is possible. If this com-
mand is used, it restricts the access modes allowed to load the
label under which this command is specified. Again, as with the
allow users command, each allow modes command overrides any pre-
vious settings, and the "default" section is always checked
first.
Possible modes are: "interactive", "auto", "direct", "dedicated",
"ddial", "background", and '*'. There is no difference between
the forms allow mode and allow modes.
When running in multi-link mode, a section can be loaded if it
allows any of the currently existing line modes.
[!]bg command
The given command is executed in the background with the following
words replaced:
AUTHNAME This is replaced with the local authname value. See
the set authname command below.
DNS0 & DNS1 These are replaced with the primary and secondary
nameserver IP numbers. If nameservers are negotiated
by IPCP, the values of these macros will change.
ENDDISC This is replaced with the local endpoint discrimina-
tor value. See the set enddisc command below.
HISADDR This is replaced with the peer's IP number.
HISADDR6 This is replaced with the peer's IPv6 number.
INTERFACE This is replaced with the name of the interface
that's in use.
IPOCTETSIN This is replaced with the number of IP bytes received
since the connection was established.
IPOCTETSOUT This is replaced with the number of IP bytes sent
since the connection was established.
IPPACKETSIN This is replaced with the number of IP packets re-
ceived since the connection was established.
IPPACKETSOUT This is replaced with the number of IP packets sent
since the connection was established.
IPV6OCTETSIN This is replaced with the number of IPv6 bytes re-
ceived since the connection was established.
IPV6OCTETSOUT This is replaced with the number of IPv6 bytes sent
since the connection was established.
IPV6PACKETSIN This is replaced with the number of IPv6 packets re-
ceived since the connection was established.
IPV6PACKETSOUT This is replaced with the number of IPv6 packets sent
since the connection was established.
LABEL This is replaced with the last label name used. A la-
bel may be specified on the ppp command line, via the
load or dial commands and in the ppp.secret file.
MYADDR This is replaced with the IP number assigned to the
local interface.
MYADDR6 This is replaced with the IPv6 number assigned to the
local interface.
OCTETSIN This is replaced with the number of bytes received
since the connection was established.
OCTETSOUT This is replaced with the number of bytes sent since
the connection was established.
PACKETSIN This is replaced with the number of packets received
since the connection was established.
PACKETSOUT This is replaced with the number of packets sent
since the connection was established.
PEER_ENDDISC This is replaced with the value of the peer's end-
point discriminator.
PROCESSID This is replaced with the current process ID.
SOCKNAME This is replaced with the name of the diagnostic
socket.
UPTIME This is replaced with the bundle uptime in HH:MM:SS
format.
USER This is replaced with the username that has been au-
thenticated with PAP or CHAP. Normally, this variable
is assigned only in -direct mode. This value is
available irrespective of whether utmp logging is en-
abled.
VERSION This is replaced with the current version number of
ppp.
These substitutions are also done by the set proctitle, ident, and
log commands.
If you wish to pause ppp while the command executes, use the shell
command instead.
clear physical | ipcp | ipv6 [current | overall | peak ...]
Clear the specified throughput values at either the "physical",
"ipcp", or "ipv6cp" level. If "physical" is specified, context must
be given (see the link command below). If no second argument is
given, all values are cleared.
clone name[,name]...
Clone the specified link, creating one or more new links according to
the name argument(s). This command must be used from the "link" com-
mand below unless you've only got a single link (in which case that
link becomes the default). Links may be removed using the remove com-
mand (see below).
The default link name is "deflink".
close [lcp[!] | ccp[!]]
If no arguments are given, the relevant protocol layers will be
brought down and the link will be closed. If "lcp" is specified, the
LCP layer is brought down, but ppp will not bring the link offline.
It is subsequently possible to use "term" (see below) to talk to the
peer machine if, for example, something like "slirp" is being used.
If "ccp" is specified, only the relevant compression layer is closed.
If the '!' is used, the compression layer will remain in the closed
state, otherwise it will re-enter the STOPPED state, waiting for the
peer to initiate further CCP negotiation. In any event, this command
does not disconnect the user from ppp or exit ppp. See the quit com-
mand below.
delete[!] dest
This command deletes the route with the given dest IP address. If
dest is specified as "ALL", all non-direct entries in the routing
table for the current interface, and all "sticky route" entries are
deleted. If dest is specified as "default", the default route is
deleted.
If the delete! command is used (note the trailing '!'), ppp will not
complain if the route does not already exist.
dial | call [label ...]
This command is the equivalent of "load label" followed by "open",
and is provided for backwards compatibility.
down [lcp | ccp]
Bring the relevant layer down ungracefully, as if the underlying
layer had become unavailable. It's not considered polite to use this
command on a Finite State Machine that's in the OPEN state. If no ar-
guments are supplied, the entire link is closed (or if no context is
given, all links are terminated). If "lcp" is specified, the LCP
layer is terminated but the device is not brought offline and the
link is not closed. If "ccp" is specified, only the relevant compres-
sion layer(s) are terminated.
help | ? [command]
Show a list of available commands. If command is specified, show the
usage string for that command.
ident [text ...]
Identify the link to the peer using text. If text is empty, link
identification is disabled. It is possible to use any of the words
described for the bg command above. Refer to the sendident command
for details of when ppp identifies itself to the peer.
iface command [args]
This command is used to control the interface used by ppp. Command
may be one of the following:
iface add[!] addr[/bits] [peer]
iface add[!] addr mask peer
Add the given addr mask peer combination to the interface. In-
stead of specifying mask, /bits can be used (with no space
between it and addr). If the given address already exists, the
command fails unless the '!' is used - in which case the previous
interface address entry is overwritten with the new one, allowing
a change of netmask or peer address.
If only addr is specified, bits defaults to 32 and peer defaults
to 255.255.255.255. This address (the broadcast address) is the
only duplicate peer address that ppp allows.
iface clear [INET | INET6]
If this command is used while ppp is in the OPENED state or while
in -auto mode, all addresses except for the NCP negotiated ad-
dress are deleted from the interface. If ppp is not in the OPENED
state and is not in -auto mode, all interface addresses are
deleted.
If the INET or INET6 arguments are used, only addresses for that
address family are cleared.
iface delete[!] | rm[!] addr
This command deletes the given addr from the interface. If the
'!' is used, no error is given if the address isn't currently as-
signed to the interface (and no deletion takes place).
iface show
Shows the current state and current addresses for the interface.
It is much the same as running "ifconfig INTERFACE".
iface help [sub-command]
This command, when invoked without sub-command, will show a list
of possible "iface" sub-commands and a brief synopsis for each.
When invoked with sub-command, only the synopsis for the given
sub-command is shown.
[data]link name[,name]... command [args]
This command may prefix any other command if the user wishes to
specify which link the command should affect. This is only applicable
after multiple links have been created in Multi-link mode using the
clone command.
Name specifies the name of an existing link. If name is a comma
separated list, command is executed on each link. If name is '*',
command is executed on all links.
load [label]...
Load the given label(s) from the ppp.conf file. If label is not
given, the default label is used.
Unless the label section uses the set mode, open, or dial commands,
ppp will not attempt to make an immediate connection.
log word...
Send the given word(s) to the log file with the prefix "LOG:". Word
substitutions are done as explained under the !bg command above.
nat command [args]
This command allows the control of the network address translation
(also known as masquerading or IP aliasing) facilities that are built
into ppp. NAT is done on the external interface only, and is unlikely
to make sense if used with the -direct flag.
If nat is enabled on your system (it may be omitted at compile time),
the following commands are possible:
nat enable yes | no
This command either switches network address translation on or
turns it off. The -nat command line flag is synonymous with "nat
enable yes".
nat addr [addr_local addr_alias]
This command allows data for addr_alias to be redirected to
addr_local. It is useful if you own a small number of real IP
numbers that you wish to map to specific machines behind your
gateway.
nat deny_incoming yes | no
If set to yes, this command will refuse all incoming packets
where an aliasing link doesn't already exist.
It should be noted under what circumstances an aliasing link is
created. It may be necessary to further protect your network from
outside connections using the set filter or nat target commands.
nat help | ?
This command gives a summary of available nat commands.
nat log yes | no
This option causes various NAT statistics and information to be
logged to the file /var/log/alias.log.
nat port proto targetIP:targetPort[-targetPort] aliasPort[-aliasPort]
[remoteIP:remotePort[-remotePort]]
This command causes incoming proto connections to aliasPort to be
redirected to targetPort on targetIP. proto is either "tcp" or
"udp".
A range of port numbers may be specified as shown above. The
ranges must be of the same size.
If remoteIP is specified, only data coming from that IP number is
redirected. remotePort must either be 0 (indicating any source
port) or a range of ports the same size as the other ranges.
This option is useful if you wish to run things like an Internet
phone on machines behind your gateway, but it is limited in that
connections to only one interior machine per source machine and
target port are possible.
nat proto proto localIP [publicIP [remoteIP]]
This command tells ppp to redirect packets of protocol type proto
(see protocols(5)) to the internal address localIP.
If publicIP is specified, only packets destined for that address
are matched, otherwise the default alias address is used.
If remoteIP is specified, only packets matching that source ad-
dress are matched.
This command is useful for redirecting tunnel endpoints to an
internal machine, for example:
nat proto ipencap 10.0.0.1
nat proxy cmd arg ...
This command tells ppp to proxy certain connections, redirecting
them to a given server.
nat punch_fw [base count]
This command tells ppp to punch holes in the firewall for FTP or
IRC DCC connections. This is done dynamically by installing tem-
porary firewall rules which allow a particular connection (and
only that connection) to go through the firewall. The rules are
removed once the corresponding connection terminates.
A maximum of count rules starting from rule number base will be
used for punching firewall holes. The range will be cleared when
the nat punch_fw command is run.
If no arguments are given, firewall punching is disabled.
nat same_ports yes | no
When enabled, this command tells the network address translation
engine to attempt to avoid changing the port number on outgoing
packets. This is useful if you want to support protocols such as
RPC and LPD which require connections to come from a well known
port.
nat target [address]
Set the given target address or clear it if no address is given.
The target address is used to specify how to NAT incoming packets
by default. If a target address is not set or if "default" is
given, packets are not altered and are allowed to route to the
internal network.
The target address may be set to "MYADDR", in which case all
packets will be redirected to the interface address.
nat use_sockets yes | no
When enabled, this option tells the network address translation
engine to create a socket so that it can guarantee a correct in-
coming FTP data or IRC connection.
nat unregistered_only yes | no
Only alter outgoing packets with an unregistered source address.
According to RFC 1918, unregistered source addresses are
10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16.
These commands are also discussed in the file README.nat which comes
with the source distribution.
open [lcp | ccp | ipcp]
This is the opposite of the close command. All closed links are im-
mediately brought up apart from second and subsequent demand-dial
links - these will come up based on the set autoload command that has
been used.
If the "lcp" argument is used while the LCP layer is already open,
LCP will be renegotiated. This allows various LCP options to be
changed, after which "open lcp" can be used to put them into effect.
After renegotiating LCP, any agreed authentication will also take
place.
If the "ccp" argument is used, the relevant compression layer is
opened. Again, if it is already open, it will be renegotiated.
If the "ipcp" argument is used, the link will be brought up as nor-
mal, but if IPCP is already open, it will be renegotiated and the
network interface will be reconfigured.
It is probably not good practice to re-open the PPP state machines
like this as it's possible that the peer will not behave correctly.
It is however useful as a way of forcing the CCP or VJ dictionaries
to be reset.
passwd pass
Specify the password required for access to the full ppp command set.
This password is required when connecting to the diagnostic port (see
the set server command). Pass is specified on the set server command
line. The value of pass is not logged when command logging is active,
instead, the literal string "********" is logged.
quit | bye [all]
If quit is executed from the controlling connection or from a command
file, ppp will exit after closing all connections. Otherwise, if the
user is connected to a diagnostic socket, the connection is simply
dropped.
If the all keyword is given, ppp will exit despite the source of the
command after closing all existing connections.
remove | rm
This command removes the given link. It is only really useful in
multi-link mode. A link must be in the CLOSED state before it is re-
moved.
rename | mv name
This command renames the given link to name. It will fail if name is
already used by another link.
The default link name is "deflink". Renaming it to "modem", "cua00",
or "USR" may make the log file more readable.
resolv command
This command controls ppp's manipulation of the resolv.conf(5) file.
When ppp starts up, it loads the contents of this file into memory
and retains this image for future use. command is one of the follow-
ing:
readonly Treat /etc/resolv.conf as read only. If "dns" is enabled,
ppp will still attempt to negotiate nameservers with the
peer, making the results available via the DNS0 and DNS1
macros. This is the opposite of the resolv writable com-
mand.
reload Reload /etc/resolv.conf into memory. This may be necessary
if, for example, a DHCP client overwrote /etc/resolv.conf.
restore Replace /etc/resolv.conf with the version originally read
at startup or with the last resolv reload command. This is
sometimes a useful command to put in the
/etc/ppp/ppp.linkdown file.
rewrite Rewrite the /etc/resolv.conf file. This command will work
even if the resolv readonly command has been used. It may
be useful as a command in the /etc/ppp/ppp.linkup file if
you wish to defer updating /etc/resolv.conf until after
other commands have finished.
writable Allow ppp to update /etc/resolv.conf if "dns" is enabled
and ppp successfully negotiates a DNS. This is the opposite
of the resolv readonly command.
sendident
This command tells ppp to identify itself to the peer. The link must
be in LCP state or higher. If no identity has been set (via the ident
command), sendident will fail.
When an identity has been set, ppp will automatically identify itself
when it sends or receives a configure reject, when negotiation fails,
or when LCP reaches the opened state.
Received identification packets are logged to the LCP log (see set
log for details) and are never responded to.
set[up] var value
This option allows the setting of any of the following variables:
set accmap hex-value
ACCMap stands for Asynchronous Control Character Map. This is al-
ways negotiated with the peer, and defaults to a value of
00000000 in hex. This protocol is required to defeat hardware
that depends on passing certain characters from end to end (such
as XON/XOFF etc).
For the XON/XOFF scenario, use "set accmap 000a0000".
set [auth]key value
This sets the authentication key (or password) used in client
mode PAP or CHAP negotiation to the given value. It also speci-
fies the password to be used in the dial or login scripts in
place of the '\P' sequence, preventing the actual password from
being logged. If command or chat logging is in effect, value is
logged as "********" for security reasons.
If the first character of value is an exclamation mark ('!'), ppp
treats the remainder of the string as a program that must be exe-
cuted to determine the "authname" and "authkey" values.
If the '!' is doubled up (to '!!'), it is treated as a single
literal '!', otherwise, ignoring the '!', value is parsed as a
program to execute in the same was as the !bg command above, sub-
stituting special names in the same manner. Once executed, ppp
will feed the program three lines of input, each terminated by a
newline character:
+ The host name as sent in the CHAP challenge.
+ The challenge string as sent in the CHAP challenge.
+ The locally defined "authname".
Two lines of output are expected:
+ The "authname" to be sent with the CHAP response.
+ The "authkey", which is encrypted with the challenge and re-
quest ID, the answer being sent in the CHAP response packet.
When configuring ppp in this manner, it's expected that the host
challenge is a series of ASCII digits or characters. An encryp-
tion device or Secure ID card is usually required to calculate
the secret appropriate for the given challenge.
set authname ID
This sets the authentication ID used in client mode PAP or CHAP
negotiation.
If used in -direct mode with CHAP enabled, ID is used in the ini-
tial authentication challenge and should normally be set to the
local machine name.
set autoload min-percent max-percent period
These settings apply only in multi-link mode and default to zero,
zero, and five, respectively. When more than one demand-dial
(also known as -auto) mode link is available, only the first link
is made active when ppp first reads data from the tun device. The
next demand-dial link will be opened only when the current bundle
throughput is at least max-percent percent of the total bundle
bandwidth for period seconds. When the current bundle throughput
decreases to min-percent percent or less of the total bundle
bandwidth for period seconds, a demand-dial link will be brought
down as long as it's not the last active link.
Bundle throughput is measured as the maximum of inbound and out-
bound traffic.
The default values cause demand-dial links to simply come up one
at a time.
Certain devices cannot determine their physical bandwidth, so it
is sometimes necessary to use the set bandwidth command
(described below) to make set autoload work correctly.
set bandwidth value
This command sets the connection bandwidth in bits per second.
value must be greater than zero. It is currently only used by the
set autoload command above.
set callback option ...
If no arguments are given, callback is disabled, otherwise, ppp
will request (or in -direct mode, will accept) one of the given
options. In client mode, if an option is NAK'd ppp will request a
different option, until no options remain; at which point ppp
will terminate negotiations (unless "none" is one of the speci-
fied options). In server mode, ppp will accept any of the given
protocols - but the client must request one of them. If you wish
callback to be optional, you must include none as an option.
The options are as follows (in this order of preference):
auth The callee is expected to decide the callback number
based on authentication. If ppp is the callee, the number
should be specified as the fifth field of the peer's en-
try in /etc/ppp/ppp.secret.
cbcp Microsoft's callback control protocol is used. See set
cbcp below.
If you wish to negotiate cbcp in client mode but also
wish to allow the server to request no callback at CBCP
negotiation time, you must specify both cbcp and none as
callback options.
E.164 *|number[,number]...
The caller specifies the number. If ppp is the callee,
number should be either a comma separated list of allow-
able numbers or a '*', meaning any number is permitted.
If ppp is the caller, only a single number should be
specified.
Note, this option is very unsafe when used with a '*' as
a malicious caller can tell ppp to call any (possibly
international) number without first authenticating them-
selves.
none If the peer does not wish to do callback at all, ppp will
accept the fact and continue without callback rather than
terminating the connection. This is required (in addition
to one or more other callback options) if you wish call-
back to be optional.
set cbcp [*|number[,number...] [delay [retry]]]
If no arguments are given, CBCP (Microsoft's CallBack Control
Protocol) is disabled - i.e., configuring CBCP in the "set
callback" command will result in ppp requesting no callback in
the CBCP phase. Otherwise, ppp attempts to use the given phone
number(s).
In server mode (-direct), ppp will insist that the client uses
one of these numbers, unless '*' is used in which case the client
is expected to specify the number.
In client mode, ppp will attempt to use one of the given numbers
(whichever it finds to be agreeable with the peer), or if '*' is
specified, ppp will expect the peer to specify the number.
set cd [off|seconds[!]]
Normally, ppp checks for the existence of carrier depending on
the type of device that has been opened:
Terminal Devices
Carrier is checked one second after the login script is
complete. If it's not set, ppp assumes that this is be-
cause the device doesn't support carrier (which is true
for most "laplink" NULL-modem cables), logs the fact, and
stops checking for carrier.
As ptys don't support the TIOCMGET ioctl, the tty device
will switch all carrier detection off when it detects
that the device is a pty.
ISDN (i4b) Devices
Carrier is checked once per second for 6 seconds. If it's
not set after the sixth second, the connection attempt is
considered to have failed and the device is closed. Car-
rier is always required for i4b devices.
PPPoE (netgraph) Devices
Carrier is checked once per second for 5 seconds. If it's
not set after the fifth second, the connection attempt is
considered to have failed and the device is closed. Car-
rier is always required for PPPoE devices.
All other device types don't support carrier. Setting a carrier
value will result in a warning when the device is opened.
Some modems take more than one second after connecting to assert
the carrier signal. If this delay isn't increased, this will
result in ppp's inability to detect when the link is dropped, as
ppp assumes that the device isn't asserting carrier.
The set cd command overrides the default carrier behaviour.
seconds specifies the maximum number of seconds that ppp should
wait after the dial script has finished before deciding if car-
rier is available or not.
If "off" is specified, ppp will not check for carrier on the dev-
ice, otherwise ppp will not proceed to the login script until ei-
ther carrier is detected or until seconds has elapsed, at which
point ppp assumes that the device will not set carrier.
If no arguments are given, carrier settings will go back to their
default values.
If seconds is followed immediately by an exclamation mark ('!'),
ppp will require carrier. If carrier is not detected after
seconds seconds, the link will be disconnected.
set choked [timeout]
This sets the number of seconds that ppp will keep a choked out-
put queue before dropping all pending output packets. If timeout
is less than or equal to zero or if timeout isn't specified, it
is set to the default value of 120 seconds.
A choked output queue occurs when ppp has read a certain number
of packets from the local network for transmission, but cannot
send the data due to link failure (the peer is busy etc.). ppp
will not read packets indefinitely. Instead, it reads up to 30
packets (or 30 + nlinks * 2 packets in multi-link mode), then
stops reading the network interface until either timeout seconds
have passed or at least one packet has been sent.
If timeout seconds pass, all pending output packets are dropped.
set ctsrts|crtscts on|off
This sets hardware flow control. Hardware flow control is on by
default.
set deflate out-winsize [in-winsize]
This sets the DEFLATE algorithm's default outgoing and incoming
window sizes. Both out-winsize and in-winsize must be values
between 8 and 15. If in-winsize is specified, ppp will insist
that this window size is used and will not accept any other
values from the peer.
set device | line value ...
This sets the device(s) to which ppp will talk to the given
value.
All serial device names are expected to begin with /dev/. Serial
devices are usually called cuaXX.
If value does not begin with /dev/, it must either begin with an
exclamation mark ('!') or be of the format host:port[/tcp|udp].
If it begins with an exclamation mark, the rest of the device
name is treated as a program name, and that program is executed
when the device is opened. Standard input, output, and error are
fed back to ppp and are read and written as if they were a regu-
lar device.
If a host:port[/tcp|udp] specification is given, ppp will attempt
to connect to the given host on the given port. If a "/tcp" or
"/udp" suffix is not provided, the default is "/tcp". Refer to
the section on PPP OVER TCP and UDP above for further details.
If multiple values are specified, ppp will attempt to open each
one in turn until it succeeds or runs out of devices.
set dial chat-script
This specifies the chat script that will be used to dial the oth-
er side. See also the set login command below. Refer to chat(8)
and to the example configuration files for details of the chat
script format. It is possible to specify some special "values" in
your chat script as follows:
\c When used as the last character in a "send" string, this in-
dicates that a newline should not be appended.
\d When the chat script encounters this sequence, it delays two
seconds.
\n This is replaced with a newline character.
\p When the chat script encounters this sequence, it delays for
one quarter of a second.
\r This is replaced with a carriage return character.
\s This is replaced with a space character.
\t This is replaced with a tab character.
\T This is replaced by the current phone number (see set phone
below).
\P This is replaced by the current authkey value (see set
authkey above).
\U This is replaced by the current authname value (see set
authname above).
Note that two parsers will examine these escape sequences, so in
order to have the "chat parser" see the escape character, it is
necessary to escape it from the "command parser". This means that
in practice you should use two escapes, for example:
set dial "... ATDT\\T CONNECT"
It is also possible to execute external commands from the chat
script. To do this, the first character of the expect or send
string is an exclamation mark ('!'). If a literal exclamation
mark is required, double it up to '!!' and it will be treated as
a single literal '!'. When the command is executed, standard in-
put and standard output are directed to the open device (see the
set device command), and standard error is read by ppp and sub-
stituted as the expect or send string. If ppp is running in in-
teractive mode, file descriptor 3 is attached to /dev/tty.
For example (wrapped for readability):
set login "TIMEOUT 5 \"\" \"\" login:--login: ppp \
word: ppp \"!sh \\-c \\\"echo \\-n label: >&2\\\"\" \
\"!/bin/echo in\" HELLO"
would result in the following chat sequence (output using the
"set log local chat" command before dialing):
Dial attempt 1 of 1
dial OK!
Chat: Expecting:
Chat: Sending:
Chat: Expecting: login:--login:
Chat: Wait for (5): login:
Chat: Sending: ppp
Chat: Expecting: word:
Chat: Wait for (5): word:
Chat: Sending: ppp
Chat: Expecting: !sh \-c "echo \-n label: >&2"
Chat: Exec: sh -c "echo -n label: >&2"
Chat: Wait for (5): !sh \-c "echo \-n label: >&2" --> label:
Chat: Exec: /bin/echo in
Chat: Sending:
Chat: Expecting: HELLO
Chat: Wait for (5): HELLO
login OK!
Note (again) the use of the escape character, allowing many lev-
els of nesting. Here there are four parsers at work. The first
parses the original line, reading it as three arguments. The
second parses the third argument, reading it as 11 arguments. At
this point, it is important that the '-' signs are escaped, oth-
erwise this parser will see them as constituting an expect-send-
expect sequence. When the '!' character is seen, the execution
parser reads the first command as three arguments, and then sh(1)
itself expands the argument after the -c. As we wish to send the
output back to the modem, in the first example we redirect our
output to file descriptor 2 (stderr) so that ppp itself sends and
logs it, and in the second example we just output to stdout,
which is attached directly to the modem.
This, of course means that it is possible to execute an entirely
external "chat" command rather than using the internal one. See
chat(8) for a good alternative.
The external command that is executed is subjected to the same
special word expansions as the !bg command.
set dns [primary [secondary]]
This command specifies DNS overrides for the accept dns command.
Refer to the accept command description above for details. This
command does not affect the IP numbers requested using enable
dns.
set enddisc [label|IP|MAC|magic|psn value]
This command sets our local endpoint discriminator. If set prior
to LCP negotiation, and if no disable enddisc command has been
used, ppp will send the information to the peer using the LCP
endpoint discriminator option. The following discriminators may
be set:
label The current label is used.
IP Our local IP number is used. As LCP is negotiated prior
to IPCP, it is possible that the IPCP layer will subse-
quently change this value. If it does, the endpoint
discriminator stays at the old value unless manually
reset.
MAC This is similar to the IP option above, except that the
MAC address associated with the local IP number is used.
If the local IP number is not resident on any Ethernet
interface, the command will fail.
As the local IP number defaults to whatever the machine
host name is, "set enddisc mac" is usually done prior to
any "set ifaddr" commands.
magic A 20-digit random number is used. Care should be taken
when using magic numbers as restarting ppp or creating a
link using a different ppp invocation will also use a
different magic number and will therefore not be recog-
nised by the peer as belonging to the same bundle. This
makes it unsuitable for -direct connections.
psn value
The given value is used. Value should be set to an abso-
lute public switched network number with the country code
first.
If no arguments are given, the endpoint discriminator is reset.
set escape value...
This option is similar to the set accmap option above. It allows
the user to specify a set of characters that will be "escaped" as
they travel across the link.
set filter dial|alive|in|out rule-no permit|deny|clear|rule-no [!]
[[host] src_addr[/width] [dst_addr[/width]]] [proto [src lt|eq|gt
port] [dst lt|eq|gt port] [estab] [syn] [finrst] [timeout secs]]
ppp supports four filter sets. The alive filter specifies packets
that keep the connection alive - resetting the idle timer. The
dial filter specifies packets that cause ppp to dial when in
-auto mode. The in filter specifies packets that are allowed to
travel into the machine and the out filter specifies packets that
are allowed out of the machine.
Filtering is done prior to any IP alterations that might be done
by the NAT engine on outgoing packets and after any IP altera-
tions that might be done by the NAT engine on incoming packets.
By default all empty filter sets allow all packets to pass. Rules
are processed in order according to rule-no (unless skipped by
specifying a rule number as the action). Up to 40 rules may be
given for each set. If a packet doesn't match any of the rules in
a given set, it is discarded. In the case of in and out filters,
this means that the packet is dropped. In the case of alive
filters it means that the packet will not reset the idle timer
(even if the in/out filter has a "timeout" value) and in the case
of dial filters it means that the packet will not trigger a dial.
A packet failing to trigger a dial will be dropped rather than
queued. Refer to the section on PACKET FILTERING above for furth-
er details.
set hangup chat-script
This specifies the chat script that will be used to reset the
device before it is closed. It should not normally be necessary,
but can be used for devices that fail to reset themselves proper-
ly on close.
set help | ? [command]
This command gives a summary of available set commands, or if
command is specified, the command usage is shown.
set ifaddr [myaddr[/nn] [hisaddr[/nn] [netmask [triggeraddr]]]]
This command specifies the IP addresses that will be used during
IPCP negotiation. Addresses are specified using the following
format:
a.b.c.d/nn
...where "a.b.c.d" is the preferred IP, but nn specifies how many
bits of the address we will insist on. If /nn is omitted, it de-
faults to '/32' unless the IP address is 0.0.0.0 in which case it
defaults to '/0'.
If you wish to assign a dynamic IP number to the peer, hisaddr
may also be specified as a range of IP numbers in the following
format:
IP[-IP][,IP[-IP]]...
For example:
set ifaddr 10.0.0.1 10.0.1.2-10.0.1.10,10.0.1.20
...will only negotiate "10.0.0.1" as the local IP number, but may
assign any of the given 10 IP numbers to the peer. If the peer
requests one of these numbers, and that number is not already in
use, ppp will grant the peer's request. This is useful if the
peer wants to re-establish a link using the same IP number as was
previously allocated (thus maintaining any existing TCP or UDP
connections).
If the peer requests an IP number that's either outside of this
range or is already in use, ppp will suggest a random unused IP
number from the range.
If triggeraddr is specified, it is used in place of myaddr in the
initial IPCP negotiation. However, only an address in the myaddr
range will be accepted. This is useful when negotiating with some
PPP implementations that will not assign an IP number unless
their peer requests "0.0.0.0".
It should be noted that in -auto mode, ppp will configure the in-
terface immediately upon reading the "set ifaddr" line in the
config file. In any other mode, these values are just used for
IPCP negotiations, and the interface isn't configured until the
IPCP layer is up.
Note that the HISADDR argument may be overridden by the third
field in the ppp.secret file once the client has authenticated
itself (if PAP or CHAP are "enabled"). Refer to the
AUTHENTICATING INCOMING CONNECTIONS section for details.
In all cases, if the interface is already configured, ppp will
try to maintain the interface IP numbers so that any existing
bound sockets will remain valid.
set ifqueue packets
Set the maximum number of packets that ppp will read from the
tunnel interface while data cannot be sent to any of the avail-
able links. This queue limit is necessary to flow control outgo-
ing data as the tunnel interface is likely to be far faster than
the combined links available to ppp.
If packets is set to a value less than the number of links, ppp
will read up to that value regardless. This prevents any possible
latency problems.
The default value for packets is 30.
set ccpretry | ccpretries [timeout [reqtries [trmtries]]]
set chapretry | chapretries [timeout [reqtries]]
set ipcpretry | ipcpretries [timeout [reqtries [trmtries]]]
set lcpretry | lcpretries [timeout [reqtries [trmtries]]]
set papretry | papretries [timeout [reqtries]]
These commands set the number of seconds that ppp will wait be-
fore resending Finite State Machine (FSM) Request packets. The
default timeout for all FSMs is 3 seconds (which should suffice
in most cases).
If reqtries is specified, it tells ppp how many configuration re-
quest attempts it should make while receiving no reply from the
peer before giving up. The default is 5 attempts for CCP, LCP,
and IPCP, and 3 attempts for PAP and CHAP.
If trmtries is specified, it tells ppp how many terminate re-
quests should be sent before giving up waiting for the peer's
response. The default is 3 attempts. Authentication protocols are
not terminated and it is therefore invalid to specify trmtries
for PAP or CHAP.
In order to avoid negotiations with the peer that will never con-
verge, ppp will only send at most 3 times the configured number
of reqtries in any given negotiation session before giving up and
closing that layer.
set log [local] [+|-]value...
This command allows the adjustment of the current log level.
Refer to the LOGGING FACILITY section above for further details.
set login chat-script
This chat-script compliments the dial-script. If both are speci-
fied, the login script will be executed after the dial script.
Escape sequences available in the dial script are also available
here.
set logout chat-script
This specifies the chat script that will be used to log out be-
fore the hangup script is called. It should not normally be
necessary.
set lqrperiod|echoperiod frequency
This command sets the frequency in seconds at which LQR or LCP
ECHO packets are sent. The default is 30 seconds. You must also
use the enable lqr and/or "enable echo" commands if you wish to
send LQR or LCP ECHO requests to the peer.
set mode interactive | auto | ddial | background
This command allows you to change the "mode" of the specified
link. This is normally only useful in multi-link mode, but may
also be used in uni-link mode.
It is not possible to change a link that is "direct" or
"dedicated".
Note: If you issue the command "set mode auto", and have network
address translation enabled, it may be useful to "enable iface-
alias" afterwards. This will allow ppp to do the necessary ad-
dress translations to enable the process that triggers the con-
nection to connect once the link is up despite the peer assigning
us a new (dynamic) IP address.
set mppe [40|56|128|* [stateless|stateful|*]]
This option selects the encryption parameters used when negotiat-
ing MPPE. MPPE can be disabled entirely with the disable mppe
command. If no arguments are given, ppp will attempt to negotiate
a stateful link with a 128-bit key, but will agree to whatever
the peer requests (including no encryption at all).
If any arguments are given, ppp will insist on using MPPE and
will close the link if it's rejected by the peer. (Note: this
behaviour can be overridden by a configured RADIUS server.)
The first argument specifies the number of bits that ppp should
insist on during negotiations and the second specifies whether
ppp should insist on stateful or stateless mode. In stateless
mode, the encryption dictionary is re-initialised with every
packet according to an encryption key that is changed with every
packet. In stateful mode, the encryption dictionary is re-
initialised every 256 packets or after the loss of any data and
the key is changed every 256 packets. Stateless mode is less ef-
ficient but is better for unreliable transport layers.
set mrru [value]
Setting this option enables Multi-link PPP negotiations, also
known as Multi-link Protocol or MP. There is no default MRRU
(Maximum Reconstructed Receive Unit) value. If no argument is
given, multi-link mode is disabled.
set mru [max[imum]] [value]
The default MRU (Maximum Receive Unit) is 1500. If it is in-
creased, the other side *may* increase its MTU. In theory there
is no point in decreasing the MRU to below the default as the PPP
protocol says implementations *must* be able to accept packets of
at least 1500 octets.
If the maximum keyword is used, ppp will refuse to negotiate a
higher value. The maximum MRU can be set to 2048 at most. Setting
a maximum of less than 1500 violates the PPP RFC, but may some-
times be necessary. For example, PPPoE imposes a maximum of 1492
due to hardware limitations.
If no argument is given, 1500 is assumed. A value must be given
when maximum is specified.
set mtu [max[imum]] [value]
The default MTU is 1500. At negotiation time, ppp will accept
whatever MRU the peer requests (assuming it's not less than 296
bytes or greater than the assigned maximum). If the MTU is set,
ppp will not accept MRU values less than value. When negotiations
are complete, the MTU is used when writing to the interface, even
if the peer requested a higher value MRU. This can be useful for
limiting your packet size (giving better bandwidth sharing at the
expense of more header data).
If the maximum keyword is used, ppp will refuse to negotiate a
higher value. The maximum MTU can be set to 2048 at most.
If no value is given, 1500, or whatever the peer asks for, is
used. A value must be given when maximum is specified.
set nbns [x.x.x.x [y.y.y.y]]
This option allows the setting of the Microsoft NetBIOS name
server values to be returned at the peer's request. If no values
are given, ppp will reject any such requests.
set openmode active|passive [delay]
By default, openmode is always active with a one second delay.
That is, ppp will always initiate LCP/IPCP/CCP negotiation one
second after the line comes up. If you want to wait for the peer
to initiate negotiations, you can use the value passive. If you
want to initiate negotiations immediately or after more than one
second, the appropriate delay may be specified here in seconds.
set parity odd|even|none|mark
This allows the line parity to be set. The default value is none.
set phone telno[|backupnumber]...[:nextnumber]...
This allows the specification of the phone number to be used in
place of the \\T string in the dial and login chat scripts. Mul-
tiple phone numbers may be given separated either by a pipe ('|')
or a colon (':').
Numbers after the pipe are only dialed if the dial or login
script for the previous number failed.
Numbers after the colon are tried sequentially, irrespective of
the reason the line was dropped.
If multiple numbers are given, ppp will dial them according to
these rules until a connection is made, retrying the maximum
number of times specified by set redial below. In -background
mode, each number is attempted at most once.
set [proc]title [value]
The current process title as displayed by ps(1) is changed ac-
cording to value. If value is not specified, the original process
title is restored. All the word replacements done by the shell
commands (see the bg command above) are done here too.
Note, if USER is required in the process title, the set proctitle
command must appear in ppp.linkup, as it is not known when the
commands in ppp.conf are executed.
set radius [config-file]
This command enables RADIUS support (if it's compiled in).
config-file refers to the radius client configuration file. If
PAP, CHAP, MSCHAP, or MSCHAPv2 are enabled, ppp behaves as a
Network Access Server and uses the configured RADIUS server to
authenticate rather than authenticating from the ppp.secret file
or from the passwd database.
If none of PAP, CHAP, MSCHAP, or MSCHAPv2 are enabled, set radius
will do nothing.
ppp uses the following attributes from the RADIUS reply:
RAD_FRAMED_IP_ADDRESS
The peer IP address is set to the given value.
RAD_FRAMED_IP_NETMASK
The tun interface netmask is set to the given value.
RAD_FRAMED_MTU
If the given MTU is less than the peer's MRU as agreed
during LCP negotiation, and it is less that any config-
ured MTU (see the set mru command), the tun interface MTU
is set to the given value.
RAD_FRAMED_COMPRESSION
If the received compression type is '1', ppp will request
VJ compression during IPCP negotiations despite any
"disable vj" configuration command.
RAD_FILTER_ID
If this attribute is supplied, ppp will attempt to use it
as an additional label to load from the ppp.linkup and
ppp.linkdown files. The load will be attempted before
(and in addition to) the normal label search. If the la-
bel doesn't exist, no action is taken and ppp proceeds to
the normal load using the current label.
RAD_FRAMED_ROUTE
The received string is expected to be in the format
dest[/bits] gw [metrics]. Any specified metrics are ig-
nored. MYADDR and HISADDR are understood as valid values
for dest and gw, "default" can be used for dest to sepci-
fy the default route, and "0.0.0.0" is understood to be
the same as "default" for dest and HISADDR for gw.
For example, a returned value of "1.2.3.4/24 0.0.0.0 1 2
-1 3 400" would result in a routing table entry to the
1.2.3.0/24 network via HISADDR and a returned value of
"0.0.0.0 0.0.0.0" or "default HISADDR" would result in a
default route to HISADDR.
All RADIUS routes are applied after any sticky routes are
applied, making RADIUS routes override configured routes.
This also applies for RADIUS routes that don't include
the MYADDR or HISADDR keywords.
RAD_SESSION_TIMEOUT
If supplied, the client connection is closed after the
given number of seconds.
RAD_REPLY_MESSAGE
If supplied, this message is passed back to the peer as
the authentication SUCCESS text.
RAD_MICROSOFT_MS_CHAP_ERROR
If this RAD_VENDOR_MICROSOFT vendor specific attribute is
supplied, it is passed back to the peer as the authenti-
cation FAILURE text.
RAD_MICROSOFT_MS_CHAP2_SUCCESS
If this RAD_VENDOR_MICROSOFT vendor specific attribute is
supplied and if MS-CHAPv2 authentication is being used,
it is passed back to the peer as the authentication SUC-
CESS text.
RAD_MICROSOFT_MS_MPPE_ENCRYPTION_POLICY
If this RAD_VENDOR_MICROSOFT vendor specific attribute is
supplied and has a value of 2 (Required), ppp will insist
that MPPE encryption is used (even if no "set mppe" con-
figuration command has been given with arguments). If it
is supplied with a value of 1 (Allowed), encryption is
made optional (despite any set mppe configuration com-
mands with arguments).
RAD_MICROSOFT_MS_MPPE_ENCRYPTION_TYPES
If this RAD_VENDOR_MICROSOFT vendor specific attribute is
supplied, bits 1 and 2 are examined. If either or both
are set, 40-bit and/or 128-bit (respectively) encryption
options are set, overriding any given first argument to
the set mppe command. Note, it is not currently possible
for the RADIUS server to specify 56-bit encryption.
RAD_MICROSOFT_MS_MPPE_RECV_KEY
If this RAD_VENDOR_MICROSOFT vendor specific attribute is
supplied, its value is used as the master key for decryp-
tion of incoming data. When clients are authenticated us-
ing MSCHAPv2, the RADIUS server MUST provide this attri-
bute if inbound MPPE is to function.
RAD_MICROSOFT_MS_MPPE_SEND_KEY
If this RAD_VENDOR_MICROSOFT vendor specific attribute is
supplied, its value is used as the master key for encryp-
tion of outgoing data. When clients are authenticated us-
ing MSCHAPv2, the RADIUS server MUST provide this attri-
bute if outbound MPPE is to function.
Values received from the RADIUS server may be viewed using show
bundle.
set reconnect timeout ntries
Should the line drop unexpectedly (due to loss of CD or LQR
failure), a connection will be re-established after the given
timeout. The line will be re-connected at most ntries times.
Ntries defaults to zero. A value of random for timeout will
result in a variable pause, somewhere between 1 and 30 seconds.
set recvpipe [value]
This sets the routing table RECVPIPE value. The optimum value is
just over twice the MTU value. If value is unspecified or zero,
the default kernel controlled value is used.
set redial secs[+inc[-max]][.next] [attempts]
ppp can be instructed to attempt to redial attempts times. If
more than one phone number is specified (see set phone above), a
pause of next is taken before dialing each number. A pause of
secs is taken before starting at the first number again. A
literal value of "random" may be used here in place of secs and
next, causing a random delay of between 1 and 30 seconds.
If inc is specified, its value is added onto secs each time ppp
tries a new number. secs will only be incremented at most max
times. max defaults to 10.
Note, the secs delay will be effective, even after attempts has
been exceeded, so an immediate manual dial may appear to have
done nothing. If an immediate dial is required, a '!' should im-
mediately follow the open keyword. See the open description above
for further details.
set sendpipe [value]
This sets the routing table SENDPIPE value. The optimum value is
just over twice the MTU value. If value is unspecified or zero,
the default kernel controlled value is used.
set server|socket TcpPort|LocalName|none|open|closed [password
[mask]]
This command tells ppp to listen on the given socket or
'diagnostic port' for incoming command connections.
The word "none" instructs ppp to close any existing socket and
clear the socket configuration. The word "open" instructs ppp to
attempt to re-open the port. The word "closed" instructs ppp to
close the open port.
If you wish to specify a local domain socket, LocalName must be
specified as an absolute file name, otherwise it is assumed to be
the name or number of a TCP port. You may specify the octal umask
to be used with a local domain socket. Refer to umask(2) for
umask details. Refer to services(5) for details of how to
translate TCP port names.
You must also specify the password that must be entered by the
client (using the "passwd" variable above) when connecting to
this socket. If the password is specified as an empty string, no
password is required for connecting clients.
When specifying a local domain socket, the first '%d' sequence
found in the socket name will be replaced with the current inter-
face unit number. This is useful when you wish to use the same
profile for more than one connection.
In a similar manner TCP sockets may be prefixed with the '+'
character, in which case the current interface unit number is ad-
ded to the port number.
When using ppp with a server socket, the pppctl(8) command is the
preferred mechanism of communication. Currently, telnet(1) can
also be used, but link encryption may be implemented in the fu-
ture, so telnet(1) should be avoided.
Note: SIGUSR1 and SIGUSR2 interact with the diagnostic socket.
set speed value
This sets the speed of the serial device. If speed is specified
as "sync", ppp treats the device as a synchronous device.
Certain device types will know whether they should be specified
as synchronous or asynchronous. These devices will override in-
correct settings and log a warning to this effect.
set stopped [LCPseconds [CCPseconds]]
If this option is set, ppp will time out after the given FSM
(Finite State Machine) has been in the stopped state for the
given number of "seconds". This option may be useful if the peer
sends a terminate request, but never actually closes the connec-
tion despite our sending a terminate acknowledgement. This is
also useful if you wish to "set openmode passive" and time out if
the peer doesn't send a Configure Request within the given time.
Use "set log +lcp +ccp" to make ppp log the appropriate state
transitions.
The default value is zero, where ppp doesn't time out in the
stopped state.
This value should not be set to less than the openmode delay (see
set openmode above).
set timeout idleseconds [mintimeout]
This command allows the setting of the idle timer. Refer to the
section titled SETTING THE IDLE TIMER for further details.
If mintimeout is specified, ppp will never idle out before the
link has been up for at least that number of seconds.
set urgent [tcp|udp|none] [[+|-]port] ...
This command controls the ports that ppp prioritizes when
transmitting data. The default priority TCP ports are ports 21
(ftp control), 22 (ssh), 23 (telnet), 513 (login), 514 (shell),
543 (klogin) and 544 (kshell). There are no priority UDP ports by
default. See services(5) for details.
If neither "tcp" or "udp" are specified, "tcp" is assumed.
If no ports are given, the priority port lists are cleared
(although if "tcp" or "udp" is specified, only that list is
cleared). If the first port argument is prefixed with a plus
('+') or a minus ('-'), the current list is adjusted, otherwise
the list is reassigned. ports prefixed with a plus or not pre-
fixed at all are added to the list and ports prefixed with a
minus are removed from the list.
If "none" is specified, all priority port lists are disabled and
even IPTOS_LOWDELAY packets are not prioritised.
set vj slotcomp on|off
This command tells ppp whether it should attempt to negotiate VJ
slot compression. By default, slot compression is turned on.
set vj slots nslots
This command sets the initial number of slots that ppp will try
to negotiate with the peer when VJ compression is enabled (see
the enable command above). It defaults to a value of 16. Nslots
must be between 4 and 16 inclusive.
shell | ! [command]
If command is not specified, a shell is invoked according to the
SHELL environment variable. Otherwise, the given command is executed.
Word replacement is done in the same way as for the !bg command as
described above.
Use of the '!' character requires a following space as with any of
the other commands. You should note that this command is executed in
the foreground; ppp will not continue running until this process has
exited. Use the bg command if you wish processing to happen in the
background.
show var
This command allows the user to examine the following:
show bundle
Show the current bundle settings.
show ccp
Show the current CCP compression statistics.
show compress
Show the current VJ compression statistics.
show escape
Show the current escape characters.
show filter [name]
List the current rules for the given filter. If name is not
specified, all filters are shown.
show hdlc
Show the current HDLC statistics.
show help | ?
Give a summary of available show commands.
show iface
Show the current interface information (the same as iface show).
show ipcp
Show the current IPCP statistics.
show layers
Show the protocol layers currently in use.
show lcp
Show the current LCP statistics.
show [data]link
Show high level link information.
show links
Show a list of available logical links.
show log
Show the current log values.
show mem
Show current memory statistics.
show ncp
Show the current NCP statistics.
show physical
Show low level link information.
show mp
Show Multi-link information.
show proto
Show current protocol totals.
show route
Show the current routing tables.
show stopped
Show the current stopped timeouts.
show timer
Show the active alarm timers.
show version
Show the current version number of ppp.
term
Go into terminal mode. Characters typed at the keyboard are sent to
the device. Characters read from the device are displayed on the
screen. When a remote PPP peer is detected, ppp automatically enables
Packet Mode and goes back into command mode.
MORE DETAILS
+ Read the example configuration files. They are a good source of in-
formation.
+ Use help, nat ?, enable ?, set ?, and show ? to get online informa-
tion about what's available.
+ The following URLs contain useful information:
+ http://www.FreeBSD.org/doc/en_US.ISO8859-1/books/faq/ppp.html
+ http://www.FreeBSD.org/doc/en_US.ISO8859-
1/books/handbook/userppp.html
FILESppp refers to four files: ppp.conf, ppp.linkup, ppp.linkdown, and
ppp.secret. These files are placed in the /etc/ppp directory.
/etc/ppp/ppp.conf
System default configuration file.
/etc/ppp/ppp.secret
An authorisation file for each system.
/etc/ppp/ppp.linkup
A file to check when ppp establishes a network level connection.
/etc/ppp/ppp.linkdown
A file to check when ppp closes a network level connection.
/var/log/ppp.log
Logging and debugging information file. Note, this name is specified
in /etc/syslog.conf. See syslog.conf(5) for further details.
/var/spool/lock/LCK..*
tty port locking file. Refer to uucplock(3) for further details.
/var/run/tunN.pid
The process ID (PID) of the ppp program connected to the tunN device,
where 'N' is the number of the device.
/var/run/cuaXX.if
The tun interface used by this port. Again, this file is only created
in -background, -auto, and -ddial modes.
/etc/services
Get port number if port number is using service name.
/var/run/ppp-authname-class-value
In multi-link mode, local domain sockets are created using the peer
authentication name ('authname'), the peer endpoint discriminator
class ('class'), and the peer endpoint discriminator value ('value').
As the endpoint discriminator value may be a binary value, it is
turned to HEX to determine the actual file name.
This socket is used to pass links between different instances of ppp.
SEE ALSOat(1), ftp(1), gzip(1), hostname(1), login(1), ps(1), telnet(1),
umask(2), syslog(3), uucplock(3), com(4), pccom(4), tun(4), ucom(4),
crontab(5), group(5), passwd(5), protocols(5), resolv.conf(5),
services(5), syslog.conf(5), adduser(8), chat(8), getty(8), ifconfig(8),
inetd(8), init(8), named(8), ping(8), pppctl(8), pppd(8), pppoe(8),
route(8), sshd(8), syslogd(8), tcpdump(8), traceroute(8), vipw(8)HISTORY
This program was originally written by Toshiharu OHNO <tony-o@iij.ad.jp>,
and was submitted to FreeBSD 2.0.5 by Atsushi Murai <amurai@spec.co.jp>.
It was substantially modified during 1997 by Brian Somers
<brian@Awfulhak.org>, and was ported to OpenBSD in November that year
(just after the 2.2 release).
Most of the code was rewritten by Brian Somers in early 1998 when multi-
link ppp support was added.
MirOS BSD #10-current September 20, 1995 51
