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Diffstat (limited to 'man2/getsockopt.2')
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diff --git a/man2/getsockopt.2 b/man2/getsockopt.2 new file mode 100644 index 0000000..f80900a --- /dev/null +++ b/man2/getsockopt.2 @@ -0,0 +1,172 @@ +.\" Copyright (c) 1983, 1991 The Regents of the University of California. +.\" All rights reserved. +.\" +.\" SPDX-License-Identifier: BSD-4-Clause-UC +.\" +.\" $Id: getsockopt.2,v 1.1 1999/05/24 14:57:04 freitag Exp $ +.\" +.\" Modified Sat Jul 24 16:19:32 1993 by Rik Faith (faith@cs.unc.edu) +.\" Modified Mon Apr 22 02:29:06 1996 by Martin Schulze (joey@infodrom.north.de) +.\" Modified Tue Aug 27 10:52:51 1996 by Andries Brouwer (aeb@cwi.nl) +.\" Modified Thu Jan 23 13:29:34 1997 by Andries Brouwer (aeb@cwi.nl) +.\" Modified Sun Mar 28 21:26:46 1999 by Andries Brouwer (aeb@cwi.nl) +.\" Modified 1999 by Andi Kleen <ak@muc.de>. +.\" Removed most stuff because it is in socket.7 now. +.\" +.TH getsockopt 2 2023-04-03 "Linux man-pages 6.05.01" +.SH NAME +getsockopt, setsockopt \- get and set options on sockets +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <sys/socket.h> +.PP +.BI "int getsockopt(int " sockfd ", int " level ", int " optname , +.BI " void " optval "[restrict *." optlen ], +.BI " socklen_t *restrict " optlen ); +.BI "int setsockopt(int " sockfd ", int " level ", int " optname , +.BI " const void " optval [. optlen ], +.BI " socklen_t " optlen ); +.fi +.SH DESCRIPTION +.BR getsockopt () +and +.BR setsockopt () +manipulate options for the socket referred to by the file descriptor +.IR sockfd . +Options may exist at multiple +protocol levels; they are always present at the uppermost +socket level. +.PP +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 sockets API level, +.I level +is specified as +.BR 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 +.B TCP +protocol, +.I level +should be set to the protocol number of +.BR TCP ; +see +.BR getprotoent (3). +.PP +The arguments +.I optval +and +.I optlen +are used to access option values for +.BR setsockopt (). +For +.BR getsockopt () +they identify a buffer in which the value for the +requested option(s) are to be returned. +For +.BR getsockopt (), +.I optlen +is a value-result argument, initially containing the +size of the buffer pointed to by +.IR optval , +and modified on return to indicate the actual size of +the value returned. +If no option value is to be supplied or returned, +.I optval +may be NULL. +.PP +.I Optname +and any specified options are passed uninterpreted to the appropriate +protocol module for interpretation. +The include file +.I <sys/socket.h> +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. +.PP +Most socket-level options utilize an +.I int +argument for +.IR optval . +For +.BR setsockopt (), +the argument should be nonzero to enable a boolean option, or zero if the +option is to be disabled. +.PP +For a description of the available socket options see +.BR socket (7) +and the appropriate protocol man pages. +.SH RETURN VALUE +On success, zero is returned for the standard options. +On error, \-1 is returned, and +.I errno +is set to indicate the error. +.PP +Netfilter allows the programmer +to define custom socket options with associated handlers; for such +options, the return value on success is the value returned by the handler. +.SH ERRORS +.TP +.B EBADF +The argument +.I sockfd +is not a valid file descriptor. +.TP +.B EFAULT +The address pointed to by +.I optval +is not in a valid part of the process address space. +For +.BR getsockopt (), +this error may also be returned if +.I optlen +is not in a valid part of the process address space. +.TP +.B EINVAL +.I optlen +invalid in +.BR setsockopt (). +In some cases this error can also occur for an invalid value in +.I optval +(e.g., for the +.B IP_ADD_MEMBERSHIP +option described in +.BR ip (7)). +.TP +.B ENOPROTOOPT +The option is unknown at the level indicated. +.TP +.B ENOTSOCK +The file descriptor +.I sockfd +does not refer to a socket. +.SH STANDARDS +POSIX.1-2008. +.SH HISTORY +POSIX.1-2001, +SVr4, 4.4BSD (first appeared in 4.2BSD). +.\" SVr4 documents additional ENOMEM and ENOSR error codes, but does +.\" not document the +.\" .BR SO_SNDLOWAT ", " SO_RCVLOWAT ", " SO_SNDTIMEO ", " SO_RCVTIMEO +.\" options +.SH BUGS +Several of the socket options should be handled at lower levels of the +system. +.SH SEE ALSO +.BR ioctl (2), +.BR socket (2), +.BR getprotoent (3), +.BR protocols (5), +.BR ip (7), +.BR packet (7), +.BR socket (7), +.BR tcp (7), +.BR udp (7), +.BR unix (7) |