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t_optmgmt(3)
NAME
t_optmgmt - Manages protocol options for a transport endpoint
LIBRARY
XTI Library (libxti.a)
SYNOPSIS
#include <xti.h>
int t_optmgmt(
int fd,
struct t_optmgmt *req,
struct t_optmgmt *ret) ;
STANDARDS
Interfaces documented on this reference page conform to industry standards
as follows:
t_optmgmt(): XNS4.0
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 parameters
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->flags y n
ret->opt.maxlen y n
ret->opt.len n y
ret->opt.buf o (o)
ret->flags n y
__________________________________________
Table Notes:
y This a meaningful parameter.
(y) The content of the object pointed to by y is meaningful.
n This is not a meaningful parameter.
o This is an optional parameter.
(o) The content of the object pointed to by o is optional.
fd Specifies a file descriptor returned by t_open() function that
identifies the local transport endpoint.
req and ret
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 flag values to the user.
Both arguments point to a type t_optmgmt structure. This structure is
used to reserve space for a transport-user options data buffer that
stores negotiable protocol options. The type t_optmgmt structure has
the following members:
struct netbuf opt
Specifies a buffer for protocol options associated with the
referenced transport endpoint. 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:
unsigned int maxlen
For the req argument, this has no meaning. For the ret argument, it
specifies the maximum byte length of the options buffer.
unsigned int len
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.
char *buf
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:
unsigned long len
Contains its total length (the length of the option header t_opthdr
plus the length of the option value).
unsigned long level
Identifies the XTI level or a protocol of the transport provider.
unsigned long name
Identifies the option within the level.
unsigned long status
If t_optmgmt() is called with the action T_NEGOTIATE set, the
status field of the returned options contains information about the
success or failure 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 flag set.
flags
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
various 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
transport 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 transport
provider are. The transport
provider writes default data
into the options data buffer
pointed to by ret->opt.buf.
The req->opt.len parameter
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 effective 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.
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
Value
Legal Option
Value
Meaning
_______________________________________________________________________
XTI_DEBUG See text enable debugging
array of
unsigned longs
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 activate
XTI_LINGER is also an absolute requirement; the timeout value for this
option is not. XTI_RCVBUF, XTI_RCVLOWAT, XTI_SNDBUF, and XTI_SNDLOWAT are
not absolute requirements.
XTI_DEBUG 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. However,
TCP is the only protocol that looks at the option. trpt can be
used to report the trace records for TCP. Other transport
providers may supply utilities to process the traces. The system
supplies utilities to process the traces.
XTI_LINGER
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
buffer 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:
T_NO
switch option off
T_YES
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_INFINITE, and all
non-negative numbers.
The l_linger value is not an absolute requirement. The
implementation 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_snddis().
XTI_RCVBUF
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
incoming 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.
XTI_RCVLOWAT
Sets a low-water mark in the receive buffer. The option value
gives the minimal number of bytes that must have accumulated 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.
XTI_SNDBUF
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.
XTI_SNDLOWWAT
Sets a low-water mark in the send buffer. The option value gives
the minimal number of bytes that must have accumulated 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.
DESCRIPTION
The t_optmgmt() XTI function is used in connectionless and connection-
oriented transport service. The t_optmgmt() function associates specific
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.
RETURN VALUE
Upon successful completion, a value of 0 (zero) is returned. Otherwise, a
value of -1 is returned and t_errno is set to indicate the error.
ERRORS
If the t_optmgmt() function fails, t_errno may be set to one of the
following values:
[TBADF]
File descriptor fd does not refer to a valid transport endpoint.
[TOUTSTATE]
This function was called in the wrong sequence.
[TBADOPT]
The specified protocol options are either of an incorrect format or
contain illegal information.
[TBADFLAG]
The specified flag is invalid.
[TACCES]
The transport user does not have permission to negotiate the specified
options.
[TBUFOVFLW]
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.
[TSYSERR]
A system error occurred during execution of the t_optmgmt() function.
[TNOTSUPPORT]
This function is not supported by the underlying transport provider.
[TPROTO]
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).
RELATED INFORMATION
Functions: t_accept(3), t_alloc(3), t_connect(3), t_getinfo(3),
t_listen(3), t_open(3), t_rcvconnect(3)
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