t_optmgmt(3)t_optmgmt(3)NAMEt_optmgmt - Manage protocol options for a transport endpoint
SYNOPSIS
#include <xti.h>
int t_optmgmt(
int fd,
struct t_optmgmt *req,
struct t_optmgmt *ret );
LIBRARY
XTI Library (libxti.a)
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
t_optmgmt(): XNS4.0, XNS5.0
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
PARAMETERS
The following table summarizes the relevance of input and output param‐
eters before and after t_optmgmt() is called:
───────────────────────────────────────────
Parameter Before Call After Call
───────────────────────────────────────────
fd y n
req->opt.maxlen n n
req->opt.len y n
req->opt.buf y(y) n
req->options y n
ret->opt.maxlen y n
ret->opt.len n y
ret->opt.buf o (o)
ret->options n y
───────────────────────────────────────────
Notes to Table: This a meaningful parameter. The content of the object
pointed to by y is meaningful. This is not a meaningful parameter.
This is an optional parameter. The content of the object pointed to by
o is optional. Specifies a file descriptor returned by t_open() func‐
tion that identifies the local transport endpoint. The argument req is
used to request a specific action of the provider and to send options
to the provider. The argument ret is used by the transport provider to
return options and option values to the user.
Both arguments point to a type t_optmgmt structure. This struc‐
ture is used to reserve space for a transport-user options data
buffer that stores negotiable protocol options. The type t_opt‐
mgmt structure has the following members: Specifies a buffer for
protocol options associated with the referenced transport end‐
point. The type netbuf structure pointed to by this member is
defined in the xti.h include file. This structure, which is
used to define buffer parameters, has the following members: For
the req argument, this has no meaning. For the ret argument, it
specifies the maximum byte length of the options buffer. For
the req argument, this specifies the number of bytes in the
options. For the ret argument, it specifies the number of bytes
of options returned. For the req argument, this points to the
options buffer. For the ret argument, it points to the buffer
where the options are placed.
Each option in the options buffer is of the form struct
t_opthdr, possibly followed by an option value. The t_opthdr
structure, which is defined in the xti.h file, has the following
members: Contains its total length (the length of the option
header t_opthdr plus the length of the option value). Identi‐
fies the XTI level or a protocol of the transport provider.
Identifies the option within the level. If t_optmgmt() is
called with the action T_NEGOTIATE set, the status field of the
returned options contains information about the success or fail‐
ure of the negotiation.
Each option in the input or output option buffer must start at a
longword boundary. The macro OPT_NEXTHDR(pbuf, buflen, poption)
can be used for that purpose. This macro is defined in the xti.h
file.
If the transport user specifies several options on input, all
the options must address the same level. If any option in the
options buffer does not indicate the same level as the first
option, or the level specified is unsupported, the t_optmgmt()
request will fail with the error [TBADOPT]. Some options may
have been successfully negotiated when this error is detected.
The transport user can check the current status by calling
t_optmgmt() with the T_CURRENT option set. A longword (least
significant bit rightmost) that specifies the response action
that must be taken by a transport provider when the t_optmgmt()
function is processed. The symbolic names for indicating vari‐
ous actions are defined in the xti.h include file. The flags
field of req must specify one of the symbolic names shown in the
following table.
──────────────────────────────────────────────────────────
Symbolic Name Meaning
──────────────────────────────────────────────────────────
T_NEGOTIATE The transport user wants to negotiate the
values of the options stored in the
options buffer. In response, the trans‐
port provider evaluates the options and
writes acceptable (negotiated) values to
the data buffer pointed to by
ret->opt.buf.
T_CHECK The transport user wants to verify that
the options specified in the data buffer
pointed to by req->opt.buf are supported
by the transport provider. On return, the
transport provider writes a ret->flags
value, which is either T_SUCCESS or
T_FAILURE.
T_DEFAULT The transport user wants to know what the
default options supported by the trans‐
port provider are. The transport provider
writes default data into the options data
buffer pointed to by ret->opt.buf. The
req->opt.lenparameter must be set to 0
(zero). The req->opt.buf member may be
set to its null value.
T_CURRENT The transport user wants to retrieve the
currently effective option values, for
options specified in req->opt.buf. It is
sufficient to specify only the t_opthdr
part of an option. The currently effec‐
tive values are then returned in
ret->opt.buf.
──────────────────────────────────────────────────────────
The option T_ALLOPT can only be used with t_optmgmt() and the
actions T_NEGOTIATE, T_DEFAULT, and T_CURRENT. It can be used
with any supported level, and it addresses all supported options
of this level. The option has no value; it consists only of a
t_opthdr. In a t_optmgmt() call, only options of one level may
be addressed, so this option should not be requested together
with other options. The function returns as soon as this option
has been processed.
Options are processed independently in the order they appear in
the input option buffer. If an option is input multiple times,
it may be output multiple times or only once, depending on the
implementation.
If the transport provider is not able to provide an interface
that can support the T_NEGOTIATE or T_CHECK functions, the error
[TNOTSUPPORT] is returned.
DESCRIPTION
The t_optmgmt() XTI function is used in connectionless and connection-
oriented transport service. The t_optmgmt() function associates spe‐
cific optional parameters with a bound transport endpoint previously
defined by a file descriptor returned by the t_open() function. The
t_optmgmt() function permits a transport user to retrieve, verify, or
negotiate desired options with a transport provider.
A type t_optmgmt structure defined in the xti.h include file is used to
specify options.
ERRORS
If the t_optmgmt() function fails, t_errno may be set to one of the
following values: File descriptor fd does not refer to a valid trans‐
port endpoint. This function was called in the wrong sequence. The
specified protocol options are either of an incorrect format or contain
illegal information. The specified option is invalid. The transport
user does not have permission to negotiate the specified options. The
number of bytes allowed for an incoming argument is not sufficient to
store the value of that argument. The information intended for the
data buffer pointed to by the ret parameter is discarded. A system
error occurred during execution of the t_optmgmt() function. This
function is not supported by the underlying transport provider. This
error indicates that a communication problem has been detected between
XTI and the transport provider for which there is no other suitable XTI
(t_errno).
XTI-LEVEL OPTIONS
XTI-level options are not specific for a particular transport provider.
This operating system's XTI implementation supports all of the options
defined in this section.
The options described in this section are association-related. They may
be negotiated in all XTI states except T_UNINIT.
The protocol level is XTI_GENERIC. The options defined for this level
are listed in the following table.
───────────────────────────────────────────────────────────────────────
Option Name Type of Option Legal Option Meaning
Value Value
───────────────────────────────────────────────────────────────────────
XTI_DEBUG array of unsigned See text enable debug‐
longs ging
XTI_LINGER struct linger See text linger on close
if data is
present
XTI_RCVBUF unsigned long size in octets receive buffer
size
XTI_RCVLOWAT unsigned long size in octets receive low-
water mark
XTI_SNDBUF unsigned long size in octets send buffer
size
XTI_SNDLOWAT unsigned long size in octets send low-water
mark
───────────────────────────────────────────────────────────────────────
A request for XTI_DEBUG is an absolute requirement. A request to acti‐
vate XTI_LINGER is also an absolute requirement; the timeout value for
this option is not. XTI_RCVBUF, XTI_RCVLOWAT, XTI_SNDBUF, and XTI_SND‐
LOWAT are not absolute requirements. This option controls debugging.
Debugging is disabled if the option is specified with "no value", that
is, with only an option header. Tru64 UNIX accepts a single value for
this option. A non-zero value enables socket level debugging and a
zero value disables it.
The actual effects of the debugging depend upon the underlying
transport provider. For example, you can set the XTI_DEBUG
option for any transport endpoint in the TCP/IP family. How‐
ever, TCP is the only protocol that looks at the option. trpt
can be used to report the trace records for TCP. Other trans‐
port providers may supply utilities to process the traces. The
system supplies utilities to process the traces. Lingers the
execution of a t_close() or close() if send data is still queued
in the send buffer. The option value specifies the linger
period. If a close() or a t_close() is issued and the send buf‐
fer is not empty, the system attempts to send the pending data
within the linger period before closing the endpoint. Data
still pending after the linger period has elapsed is discarded.
Depending on the transport, t_close() or close() either block
for, at maximum, the linger period, or immediately return,
whereupon the system holds the connection in existence for, at
most, the linger period.
The option value consists of a structure t_linger, which is
declared as shown here:
struct t_linger {
long l_onoff; /* switch option on/off */
long l_linger; /* linger period in seconds */ }
The value for l_onoff is an absolute requirement. The legal
values for this field are as follows: switch option off activate
option
The field l_linger determines the linger period in seconds. The
transport user can request the default value by setting the
field to T_UNSPEC. The default timeout value depends on the
underlying transport provider; the value is often T_INFINITE.
Legal values for this field are as follows: T_UNSPEC, T_INFI‐
NITE, and all non-negative numbers.
The l_linger value is not an absolute requirement. The imple‐
mentation may place upper and lower limits on this value.
Requests that fall short of the lower limit are negotiated to
the lower limit.
Note that this option does not linger the execution of t_snd‐
dis(). Adjusts the internal buffer size allocated for the
receive buffer. The buffer size may be increased for high volume
connections or decreased to limit the possible backlog of incom‐
ing data.
This request is not an absolute requirement. The implementation
may place upper and lower limits on the option value. Requests
that fall short of the lower limit are negotiated to the lower
limit. Sets a low-water mark in the receive buffer. The option
value gives the minimal number of bytes that must have accumu‐
lated in the receive buffer before they become visible to the
transport user. If and when the amount of accumulated receive
data exceeds the low-water mark, a T_DATA event is created, an
event mechanism, for example poll() or select(), indicates the
data, and the data can be read by t_rcv() or t_rcvdata().
Legal values for this field are all positive numbers.
This request is not an absolute requirement. The implementation
may place upper and lower limits on the option value. Requests
that fall short of the lower limit are negotiated to the lower
limit. Adjusts the internal buffer size allocated for the send
buffer.
Legal values for this field are all positive numbers.
This request is not an absolute requirement. The implementation
may place upper and lower limits on the option value. Requests
that fall short of the lower limit are negotiated to the lower
limit. Sets a low-water mark in the send buffer. The option
value gives the minimal number of bytes that must have accumu‐
lated in the send buffer before they are sent.
Legal values for this field are all positive numbers.
This request is not an absolute requirement. The implementation
may place upper and lower limits on the option value. Requests
that fall short of the lower limit are negotiated to the lower
limit.
VALID STATES
The t_optmgmt() function can be called in all the transport provider
states, except T_UNINIT.
RETURN VALUE
Upon successful completion, a value of 0 (zero) is returned. Other‐
wise, a value of -1 is returned and t_errno is set to indicate the
error.
SEE ALSO
Functions: t_accept(3), t_alloc(3), t_connect(3), t_getinfo(3), t_lis‐
ten(3), t_open(3), t_rcvconnect(3)
Standards: standards(5)
Network Programmer's Guide
t_optmgmt(3)
