136 lines
4 KiB
Groff
136 lines
4 KiB
Groff
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.\" $NetBSD: getpeername.2,v 1.19 2006/03/05 22:06:08 agc Exp $
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.\"
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.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)getpeername.2 8.1 (Berkeley) 6/4/93
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.\"
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.Dd March 5, 2006
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.Dt GETPEERNAME 2
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.Os
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.Sh NAME
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.Nm getpeername
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.Nd get name of connected peer
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/socket.h
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.Ft int
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.Fn getpeername "int s" "struct sockaddr * restrict name" "socklen_t * restrict namelen"
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.Sh DESCRIPTION
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.Fn getpeername
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returns the name of the peer connected to
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socket
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.Fa s .
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One common use occurs when a process inherits an open socket, such as
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TCP servers forked from
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.Xr inetd 8 .
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In this scenario,
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.Fn getpeername
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is used to determine the connecting client's IP address.
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.Pp
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.Fn getpeername
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takes three parameters:
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.Pp
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.Fa s
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contains the file descriptor of the socket whose peer should be looked up.
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.Pp
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.Fa name
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points to a
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.Li sockaddr
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structure that will hold the address information for the connected peer.
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Normal use requires one to use a structure
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specific to the protocol family in use, such as
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.Li sockaddr_in
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(IPv4) or
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.Li sockaddr_in6
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(IPv6), cast to a (struct sockaddr *).
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.Pp
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For greater portability, especially with the newer protocol families, the new
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.Li struct sockaddr_storage
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should be used.
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.Li sockaddr_storage
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is large enough to hold any of the other sockaddr_* variants.
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On return, it can be cast to the correct sockaddr type,
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based on the protocol family contained in its ss_family field.
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.Pp
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.Fa namelen
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indicates the amount of space pointed to by
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.Fa name ,
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in bytes.
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.Pp
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If address information for the local end of the socket is required, the
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.Xr getsockname 2
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function should be used instead.
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.Pp
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If
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.Fa name
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does not point to enough space to hold the entire socket address, the
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result will be truncated to
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.Fa namelen
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bytes.
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.Sh RETURN VALUES
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If the call succeeds, a 0 is returned and
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.Fa namelen
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is set to the actual size of the socket address returned in
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.Fa name .
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Otherwise,
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.Va errno
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is set and a value of \-1 is returned.
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.Sh ERRORS
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The call succeeds unless:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The argument
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.Fa s
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is not a valid descriptor.
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.It Bq Er ENOTSOCK
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The argument
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.Fa s
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is a file, not a socket.
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.It Bq Er ENOTCONN
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The socket is not connected.
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.It Bq Er ENOBUFS
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Insufficient resources were available in the system
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to perform the operation.
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.It Bq Er EFAULT
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The
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.Fa name
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parameter points to memory not in a valid part of the
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process address space.
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.El
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.Sh SEE ALSO
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.Xr accept 2 ,
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.Xr bind 2 ,
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.Xr getsockname 2 ,
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.Xr socket 2
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.Sh HISTORY
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The
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.Fn getpeername
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function call appeared in
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.Bx 4.2 .
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