1.\" $NetBSD: getsockname.2,v 1.22 2003/05/01 08:45:20 gmcgarry Exp $ 2.\" 3.\" Copyright (c) 1983, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)getsockname.2 8.1 (Berkeley) 6/4/93 35.\" 36.Dd August 11, 2002 37.Dt GETSOCKNAME 2 38.Os 39.Sh NAME 40.Nm getsockname 41.Nd get socket name 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In sys/socket.h 46.Ft int 47.Fn getsockname "int s" "struct sockaddr * restrict name" "socklen_t * restrict namelen" 48.Sh DESCRIPTION 49.Fn getsockname 50returns the locally bound address information for a specified socket. 51.Pp 52Common uses of this function are as follows: 53.Bl -bullet 54.It 55When 56.Xr bind 2 57is called with a port number of 0 (indicating the kernel should pick 58an ephemeral port) 59.Fn getsockname 60is used to retrieve the kernel-assigned port number. 61.It 62When a process calls 63.Xr bind 2 64on a wildcard IP address, 65.Fn getsockname 66is used to retrieve the local IP address for the connection. 67.It 68When a function wishes to know the address family of a socket, 69.Fn getsockname 70can be used. 71.El 72.Pp 73.Fn getsockname 74takes three parameters: 75.Pp 76.Fa s , 77Contains the file descriptor for the socket to be looked up. 78.Pp 79.Fa name 80points to a 81.Li sockaddr 82structure which will hold the resulting address information. 83Normal use requires one to use a structure 84specific to the protocol family in use, such as 85.Li sockaddr_in 86(IPv4) or 87.Li sockaddr_in6 88(IPv6), cast to a (struct sockaddr *). 89.Pp 90For greater portability (such as newer protocol families) the new 91structure sockaddr_storage exists. 92.Li sockaddr_storage 93is large enough to hold any of the other sockaddr_* variants. 94On return, it should be cast to the correct sockaddr type, 95according to the current protocol family. 96.Pp 97.Fa namelen 98indicates the amount of space pointed to by 99.Fa name , 100in bytes. 101Upon return, 102.Fa namelen 103is set to the actual size of the returned address information. 104.Pp 105If the address of the destination socket for a given socket connection is 106needed, the 107.Xr getpeername 2 108function should be used instead. 109.Pp 110If 111.Fa name 112does not point to enough space to hold the entire socket address, the 113result will be truncated to 114.Fa namelen 115bytes. 116.Sh RETURN VALUES 117On success, 118.Fn getsockname 119returns a 0, and 120.Fa namelen 121is set to the actual size of the socket address returned in 122.Fa name . 123Otherwise, 124.Va errno 125is set, and a value of \-1 is returned. 126.Sh ERRORS 127The call succeeds unless: 128.Bl -tag -width Er 129.It Bq Er EBADF 130The argument 131.Fa s 132is not a valid descriptor. 133.It Bq Er ENOTSOCK 134The argument 135.Fa s 136is a file, not a socket. 137.It Bq Er EINVAL 138The socket has been shut down. 139.It Bq Er ENOBUFS 140Insufficient resources were available in the system to perform the operation. 141.It Bq Er EFAULT 142The 143.Fa name 144parameter points to memory not in a valid part of the process address space. 145.El 146.Sh SEE ALSO 147.Xr bind 2 , 148.Xr socket 2 149.Sh HISTORY 150The 151.Fn getsockname 152function call appeared in 153.Bx 4.2 . 154.Sh BUGS 155Names bound to sockets in the 156.Ux 157domain are inaccessible; 158.Fn getsockname 159returns a zero length name. 160