1.\" $NetBSD: getpeername.2,v 1.19 2006/03/05 22:06:08 agc 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. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)getpeername.2 8.1 (Berkeley) 6/4/93 31.\" 32.Dd March 5, 2006 33.Dt GETPEERNAME 2 34.Os 35.Sh NAME 36.Nm getpeername 37.Nd get name of connected peer 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In sys/socket.h 42.Ft int 43.Fn getpeername "int s" "struct sockaddr * restrict name" "socklen_t * restrict namelen" 44.Sh DESCRIPTION 45.Fn getpeername 46returns the name of the peer connected to 47socket 48.Fa s . 49One common use occurs when a process inherits an open socket, such as 50TCP servers forked from 51.Xr inetd 8 . 52In this scenario, 53.Fn getpeername 54is used to determine the connecting client's IP address. 55.Pp 56.Fn getpeername 57takes three parameters: 58.Pp 59.Fa s 60contains the file descriptor of the socket whose peer should be looked up. 61.Pp 62.Fa name 63points to a 64.Li sockaddr 65structure that will hold the address information for the connected peer. 66Normal use requires one to use a structure 67specific to the protocol family in use, such as 68.Li sockaddr_in 69(IPv4) or 70.Li sockaddr_in6 71(IPv6), cast to a (struct sockaddr *). 72.Pp 73For greater portability, especially with the newer protocol families, the new 74.Li struct sockaddr_storage 75should be used. 76.Li sockaddr_storage 77is large enough to hold any of the other sockaddr_* variants. 78On return, it can be cast to the correct sockaddr type, 79based on the protocol family contained in its ss_family field. 80.Pp 81.Fa namelen 82indicates the amount of space pointed to by 83.Fa name , 84in bytes. 85.Pp 86If address information for the local end of the socket is required, the 87.Xr getsockname 2 88function should be used instead. 89.Pp 90If 91.Fa name 92does not point to enough space to hold the entire socket address, the 93result will be truncated to 94.Fa namelen 95bytes. 96.Sh RETURN VALUES 97If the call succeeds, a 0 is returned and 98.Fa namelen 99is set to the actual size of the socket address returned in 100.Fa name . 101Otherwise, 102.Va errno 103is set and a value of \-1 is returned. 104.Sh ERRORS 105The call succeeds unless: 106.Bl -tag -width Er 107.It Bq Er EBADF 108The argument 109.Fa s 110is not a valid descriptor. 111.It Bq Er ENOTSOCK 112The argument 113.Fa s 114is a file, not a socket. 115.It Bq Er ENOTCONN 116The socket is not connected. 117.It Bq Er ENOBUFS 118Insufficient resources were available in the system 119to perform the operation. 120.It Bq Er EFAULT 121The 122.Fa name 123parameter points to memory not in a valid part of the 124process address space. 125.El 126.Sh SEE ALSO 127.Xr accept 2 , 128.Xr bind 2 , 129.Xr getsockname 2 , 130.Xr socket 2 131.Sh HISTORY 132The 133.Fn getpeername 134function call appeared in 135.Bx 4.2 . 136