1.\" $OpenBSD: getsockname.2,v 1.30 2015/09/10 17:55:21 schwarze Exp $ 2.\" $NetBSD: getsockname.2,v 1.6 1995/10/12 15:41:00 jtc Exp $ 3.\" 4.\" Copyright (c) 1983, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)getsockname.2 8.1 (Berkeley) 6/4/93 32.\" 33.Dd $Mdocdate: September 10 2015 $ 34.Dt GETSOCKNAME 2 35.Os 36.Sh NAME 37.Nm getsockname 38.Nd get socket name 39.Sh SYNOPSIS 40.In sys/socket.h 41.Ft int 42.Fn getsockname "int s" "struct sockaddr *name" "socklen_t *namelen" 43.Sh DESCRIPTION 44.Fn getsockname 45returns the locally bound address information for a specified socket. 46.Pp 47Common uses of this function are as follows: 48.Bl -bullet 49.It 50When 51.Xr bind 2 52is called with a port number of 0 (indicating the kernel should pick 53an ephemeral port) 54.Fn getsockname 55is used to retrieve the kernel-assigned port number. 56.It 57When a process calls 58.Xr bind 2 59on a wildcard IP address, 60.Fn getsockname 61is used to retrieve the local IP address for the connection. 62.It 63When a function wishes to know the address family of a socket, 64.Fn getsockname 65can be used. 66.El 67.Pp 68.Fn getsockname 69takes three parameters: 70.Pp 71.Fa s 72contains the file descriptor for the socket to be looked up. 73.Pp 74.Fa name 75points to a 76.Li sockaddr 77structure which will hold the resulting address information. 78Normal use requires one to use a structure 79specific to the protocol family in use, such as 80.Li sockaddr_in 81(IPv4) or 82.Li sockaddr_in6 83(IPv6), cast to a (struct sockaddr *). 84.Pp 85For greater portability (such as newer protocol families) the new 86structure sockaddr_storage exists. 87.Li sockaddr_storage 88is large enough to hold any of the other sockaddr_* variants. 89On return, it should be cast to the correct sockaddr type, 90according to the current protocol family. 91.Pp 92.Fa namelen 93indicates the amount of space pointed to by 94.Fa name , 95in bytes. 96Upon return, 97.Fa namelen 98is set to the actual size of the returned address information. 99.Pp 100If the address of the destination socket for a given socket connection is 101needed, the 102.Xr getpeername 2 103function should be used instead. 104.Pp 105If 106.Fa name 107does not point to enough space to hold the entire socket address, the 108result will be truncated to 109.Fa namelen 110bytes. 111.Sh RETURN VALUES 112On success, 113.Fn getsockname 114returns a 0, and 115.Fa namelen 116is set to the actual size of the socket address returned in 117.Fa name . 118Otherwise, 119.Va errno 120is set, and a value of \-1 is returned. 121.Sh ERRORS 122If 123.Fn getsockname 124fails, 125.Va errno 126is set to one of the following: 127.Bl -tag -width Er 128.It Bq Er EBADF 129The argument 130.Fa s 131is not a valid descriptor. 132.It Bq Er ENOTSOCK 133The argument 134.Fa s 135is a file, not a socket. 136.It Bq Er ENOBUFS 137Insufficient resources were available in the system 138to perform the operation. 139.It Bq Er EFAULT 140The 141.Fa name 142or 143.Fa namelen 144parameter points to memory not in a valid part of the 145process address space. 146.El 147.Sh SEE ALSO 148.Xr accept 2 , 149.Xr bind 2 , 150.Xr getpeername 2 , 151.Xr socket 2 , 152.Xr getpeereid 3 153.Sh STANDARDS 154The 155.Fn getsockname 156function conforms to 157.St -p1003.1-2008 . 158.Sh HISTORY 159The 160.Fn getsockname 161function call appeared in 162.Bx 4.2 . 163