1.\" $OpenBSD: getpeername.2,v 1.20 2003/06/02 20:18:39 millert Exp $ 2.\" $NetBSD: getpeername.2,v 1.6 1995/10/12 15:40:56 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.\" @(#)getpeername.2 8.1 (Berkeley) 6/4/93 32.\" 33.Dd July 17, 1999 34.Dt GETPEERNAME 2 35.Os 36.Sh NAME 37.Nm getpeername 38.Nd get name of connected peer 39.Sh SYNOPSIS 40.Fd #include <sys/types.h> 41.Fd #include <sys/socket.h> 42.Ft int 43.Fn getpeername "int s" "struct sockaddr *name" "socklen_t *namelen" 44.Sh DESCRIPTION 45.Fn getpeername 46returns the address information of the peer connected to socket 47.Fa s . 48One common use occurs when a process inherits an open socket, such as 49TCP servers forked from 50.Xr inetd 8 . 51In this scenario, 52.Fn getpeername 53is used to determine the connecting client's IP address. 54.Pp 55.Fn getpeername 56takes three parameters: 57.Pp 58.Fa s 59contains the file descriptor of the socket whose peer should be looked up. 60.Pp 61.Fa name 62points to a 63.Li sockaddr 64structure that will hold the address information for the connected peer. 65Normal use requires one to use a structure 66specific to the protocol family in use, such as 67.Li sockaddr_in 68(IPv4) or 69.Li sockaddr_in6 70(IPv6), cast to a (struct sockaddr *). 71.Pp 72For greater portability, especially with the newer protocol families, the new 73.Li struct sockaddr_storage 74should be used. 75.Li sockaddr_storage 76is large enough to hold any of the other sockaddr_* variants. 77On return, it can be cast to the correct sockaddr type, 78based on the protocol family contained in its ss_family field. 79.Pp 80.Fa namelen 81indicates the amount of space pointed to by 82.Fa name , 83in bytes. 84.Pp 85If address information for the local end of the socket is required, the 86.Xr getsockname 2 87function should be used instead. 88.Pp 89If 90.Fa name 91does not point to enough space to hold the entire socket address, the 92result will be truncated to 93.Fa namelen 94bytes. 95.Sh RETURN VALUES 96If the call succeeds, a 0 is returned and 97.Fa namelen 98is set to the actual size of the socket address returned in 99.Fa name . 100Otherwise, 101.Va errno 102is set and a value of \-1 is returned. 103.Sh ERRORS 104On failure, 105.Va errno 106is set to one of the following: 107.Bl -tag -width Er 108.It Bq Er EBADF 109The argument 110.Fa s 111is not a valid descriptor. 112.It Bq Er ENOTSOCK 113The argument 114.Fa s 115is a file, not a socket. 116.It Bq Er ENOTCONN 117The socket is not connected. 118.It Bq Er ENOBUFS 119Insufficient resources were available in the system 120to perform the operation. 121.It Bq Er EFAULT 122The 123.Fa name 124parameter points to memory not in a valid part of the 125process address space. 126.El 127.Sh SEE ALSO 128.Xr accept 2 , 129.Xr bind 2 , 130.Xr getpeereid 2 , 131.Xr getsockname 2 , 132.Xr socket 2 133.Sh HISTORY 134The 135.Fn getpeername 136function call appeared in 137.Bx 4.2 . 138