1.\" $NetBSD: getpeername.2,v 1.14 2002/08/11 12:04:25 yamt 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.\" @(#)getpeername.2 8.1 (Berkeley) 6/4/93 35.\" 36.Dd August 11, 2002 37.Dt GETPEERNAME 2 38.Os 39.Sh NAME 40.Nm getpeername 41.Nd get name of connected peer 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.Fd #include \*[Lt]sys/socket.h\*[Gt] 46.Ft int 47.Fn getpeername "int s" "struct sockaddr * restrict name" "socklen_t * restrict namelen" 48.Sh DESCRIPTION 49.Fn getpeername 50returns the name of the peer connected to 51socket 52.Fa s . 53One common use occurs when a process inherits an open socket, such as 54TCP servers forked from 55.Xr inetd 8 . 56In this scenario, 57.Fn getpeername 58is used to determine the connecting client's IP address. 59.Pp 60.Fn getpeername 61takes three parameters: 62.Pp 63.Fa s 64Contains the file descriptor of the socket whose peer should be looked up. 65.Pp 66.Fa name 67Points to a 68.Li sockaddr 69structure that will hold the address information for the connected peer. 70Normal use requires one to use a structure 71specific to the protocol family in use, such as 72.Li sockaddr_in 73(IPv4) or 74.Li sockaddr_in6 75(IPv6), cast to a (struct sockaddr *). 76.Pp 77For greater portability, especially with the newer protocol families, the new 78.Li struct sockaddr_storage 79should be used. 80.Li sockaddr_storage 81is large enough to hold any of the other sockaddr_* variants. 82On return, it can be cast to the correct sockaddr type, 83based the protocol family contained in its ss_family field. 84.Pp 85.Fa namelen 86Indicates the amount of space pointed to by 87.Fa name , 88in bytes. 89.Pp 90If address information for the local end of the socket is required, the 91.Xr getsockname 2 92function should be used instead. 93.Pp 94If 95.Fa name 96does not point to enough space to hold the entire socket address, the 97result will be truncated to 98.Fa namelen 99bytes. 100.Sh RETURN VALUES 101If the call succeeds, a 0 is returned and 102.Fa namelen 103is set to the actual size of the socket address returned in 104.Fa name . 105Otherwise, 106.Va errno 107is set and a value of \-1 is returned. 108.Sh ERRORS 109The call succeeds unless: 110.Bl -tag -width Er 111.It Bq Er EBADF 112The argument 113.Fa s 114is not a valid descriptor. 115.It Bq Er ENOTSOCK 116The argument 117.Fa s 118is a file, not a socket. 119.It Bq Er ENOTCONN 120The socket is not connected. 121.It Bq Er ENOBUFS 122Insufficient resources were available in the system 123to perform the operation. 124.It Bq Er EFAULT 125The 126.Fa name 127parameter points to memory not in a valid part of the 128process address space. 129.El 130.Sh SEE ALSO 131.Xr accept 2 , 132.Xr bind 2 , 133.Xr getsockname 2 , 134.Xr socket 2 135.Sh HISTORY 136The 137.Fn getpeername 138function call appeared in 139.Bx 4.2 . 140