1.\" $NetBSD: getpeername.2,v 1.21 2011/06/03 08:07:48 wiz 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 June 3, 2011 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 \ 44"int s" "struct sockaddr * restrict name" "socklen_t * restrict namelen" 45.Sh DESCRIPTION 46The 47.Fn getpeername 48function returns the name of the peer connected to the socket 49.Fa s . 50One common use occurs when a process inherits an open socket, such as 51TCP servers forked from 52.Xr inetd 8 . 53In this scenario, 54.Fn getpeername 55is used to determine the connecting client's IP address. 56.Pp 57The function takes three parameters: 58.Bl -tag -width namelen -offset indent 59.It Fa s 60contains the file descriptor of the socket whose peer should be looked up. 61.It 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.It Fa namelen 80indicates the amount of space pointed to by 81.Fa name , 82in bytes. 83.El 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 104The call succeeds unless: 105.Bl -tag -width Er 106.It Bq Er EBADF 107The argument 108.Fa s 109is not a valid descriptor. 110.It Bq Er EFAULT 111The 112.Fa name 113parameter points to memory not in a valid part of the 114process address space. 115.It Bq Er ENOBUFS 116Insufficient resources were available in the system 117to perform the operation. 118.It Bq Er ENOTCONN 119The socket is not connected. 120.It Bq Er ENOTSOCK 121The argument 122.Fa s 123is a file, not a socket. 124.El 125.Sh SEE ALSO 126.Xr accept 2 , 127.Xr bind 2 , 128.Xr getsockname 2 , 129.Xr socket 2 130.Sh STANDARDS 131The function conforms to 132.St -p1003.1-2008 . 133.Sh HISTORY 134The 135.Fn getpeername 136function call appeared in 137.Bx 4.2 . 138