View Source: setsockopt(2) - Waikato Linux Users Group

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!!!GETSOCKOPT
!!NAME

getsockopt, setsockopt - get and set options on sockets
!!SYNOPSIS
 __#include <sys/types.h>__
 __#include <sys/socket.h>__

 __int getsockopt(int__ ''s''__, int__ ''level''__, int__ ''optname''__, void *__''optval''__, socklen_t *__''optlen''__);__

 __int setsockopt(int__ ''s''__, int__ ''level''__, int__ ''optname''__, const void *__''optval''__, socklen_t__ ''optlen''__);__

!!DESCRIPTION


__Getsockopt__ and __setsockopt__ manipulate the
''options'' associated with a socket. Options may exist
at multiple protocol levels; they are always present at the
uppermost __socket__ level.


When manipulating socket options the level at which the
option resides and the name of the option must be specified.
To manipulate options at the socket level, ''level'' is
specified as __SOL_SOCKET__. To manipulate options at any
other level the protocol number of the appropriate protocol
controlling the option is supplied. For example, to indicate
that an option is to be interpreted by the __TCP__
protocol, ''level'' should be set to the protocol number
of __TCP__; see getprotoent(3).


The parameters ''optval'' and ''optlen'' are used to
access option values for __setsockopt__. For
__getsockopt__ they identify a buffer in which the value
for the requested option(s) are to be returned. For
__getsockopt__, ''optlen'' is a value-result
parameter, initially containing the size of the buffer
pointed to by ''optval'', and modified on return to
indicate the actual size of the value returned. If no option
value is to be supplied or returned, ''optval'' may be
NULL.


''Optname'' and any specified options are passed
uninterpreted to the appropriate protocol module for
interpretation. The include file ''''
contains definitions for socket level options, described
below. Options at other protocol levels vary in format and
name; consult the appropriate entries in section 4 of the
manual.


Most socket-level options utilize an ''int'' parameter
for ''optval''. For __setsockopt__, the parameter
should be non-zero to enable a boolean option, or zero if
the option is to be disabled.


For a description of the available socket options see
socket(7) and the appropriate protocol man
pages.
!!RETURN VALUE

On success, zero is returned. On error, -1 is returned, and
''errno'' is set appropriately.

!!ERRORS
;[EBADF]: The argument ''s'' is not a valid descriptor.
;[ENOTSOCK]: The argument ''s'' is a file, not a socket.
;[ENOPROTOOPT]: The option is unknown at the level indicated.
;[EFAULT]: The address pointed to by ''optval'' is not in a valid part of the process address space. For getsockopt(2), this error may also be returned if ''optlen'' is not in a valid part of the process address space.
;[EINVAL]: The optlen or the option you are trying to set is invalid.
;[EADDRNOTAVAIL]: The level isn't applicable for this option.

!!CONFORMING TO
SVr4, 4.4BSD (these system calls first appeared in 4.2BSD). SVr4 documents additional [ENOMEM] and [ENOSR] error codes, but does not document the __SO_SNDLOWAT__, __SO_RCVLOWAT__, __SO_SNDTIMEO__, __SO_RCVTIMEO__ options

!!NOTE
The fifth argument of getsockopt(2) and setsockopt(2) is in reality an int [[*] (and this is what BSD 4.* and libc4 and libc5 have). Some [POSIX] confusion
resulted in the present socklen_t. The draft standard has not been adopted yet, but glibc2 already follows it and also has socklen_t [[*]. See also accept(2).

!!BUGS
Several of the socket options should be handled at lower levels of the system.

!!SEE ALSO
ioctl(2), socket(2), getprotoent(3), protocols(5), socket(7), unix(7), tcp(7)
15 pages link to setsockopt(2):
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Last edited on Thursday, December 1, 2005 10:54:53 am by PerryLorier
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