b89e82dd87
return zero on success and an error code otherwise. The possible errors are EADDRNOTAVAIL if an address being checked for doesn't match the prison, and EAFNOSUPPORT if the prison doesn't have any addresses in that address family. For most callers of these functions, use the returned error code instead of e.g. a hard-coded EADDRNOTAVAIL or EINVAL. Always include a jailed() check in these functions, where a non-jailed cred always returns success (and makes no changes). Remove the explicit jailed() checks that preceded many of the function calls. Approved by: bz (mentor)
233 lines
6.5 KiB
Groff
233 lines
6.5 KiB
Groff
.\" 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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.\" 4. 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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.\" From: @(#)send.2 8.2 (Berkeley) 2/21/94
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.\" $FreeBSD$
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.\"
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.Dd February 5, 2009
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.Dt SEND 2
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.Os
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.Sh NAME
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.Nm send ,
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.Nm sendto ,
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.Nm sendmsg
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.Nd send a message from a socket
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/socket.h
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.Ft ssize_t
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.Fn send "int s" "const void *msg" "size_t len" "int flags"
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.Ft ssize_t
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.Fn sendto "int s" "const void *msg" "size_t len" "int flags" "const struct sockaddr *to" "socklen_t tolen"
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.Ft ssize_t
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.Fn sendmsg "int s" "const struct msghdr *msg" "int flags"
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.Sh DESCRIPTION
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The
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.Fn send
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function,
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and
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.Fn sendto
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and
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.Fn sendmsg
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system calls
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are used to transmit a message to another socket.
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The
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.Fn send
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function
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may be used only when the socket is in a
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.Em connected
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state, while
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.Fn sendto
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and
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.Fn sendmsg
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may be used at any time.
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.Pp
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The address of the target is given by
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.Fa to
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with
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.Fa tolen
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specifying its size.
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The length of the message is given by
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.Fa len .
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If the message is too long to pass atomically through the
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underlying protocol, the error
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.Er EMSGSIZE
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is returned, and
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the message is not transmitted.
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.Pp
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No indication of failure to deliver is implicit in a
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.Fn send .
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Locally detected errors are indicated by a return value of -1.
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.Pp
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If no messages space is available at the socket to hold
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the message to be transmitted, then
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.Fn send
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normally blocks, unless the socket has been placed in
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non-blocking I/O mode.
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The
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.Xr select 2
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system call may be used to determine when it is possible to
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send more data.
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.Pp
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The
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.Fa flags
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argument may include one or more of the following:
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.Bd -literal
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#define MSG_OOB 0x00001 /* process out-of-band data */
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#define MSG_DONTROUTE 0x00004 /* bypass routing, use direct interface */
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#define MSG_EOR 0x00008 /* data completes record */
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#define MSG_EOF 0x00100 /* data completes transaction */
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#define MSG_NOSIGNAL 0x20000 /* do not generate SIGPIPE on EOF */
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.Ed
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.Pp
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The flag
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.Dv MSG_OOB
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is used to send
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.Dq out-of-band
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data on sockets that support this notion (e.g.\&
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.Dv SOCK_STREAM ) ;
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the underlying protocol must also support
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.Dq out-of-band
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data.
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.Dv MSG_EOR
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is used to indicate a record mark for protocols which support the
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concept.
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.Dv MSG_EOF
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requests that the sender side of a socket be shut down, and that an
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appropriate indication be sent at the end of the specified data;
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this flag is only implemented for
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.Dv SOCK_STREAM
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sockets in the
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.Dv PF_INET
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protocol family.
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.Dv MSG_DONTROUTE
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is usually used only by diagnostic or routing programs.
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.Dv MSG_NOSIGNAL
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is used to prevent
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.Dv SIGPIPE
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generation when writing a socket that
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may be closed.
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.Pp
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See
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.Xr recv 2
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for a description of the
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.Fa msghdr
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structure.
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.Sh RETURN VALUES
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The call returns the number of characters sent, or -1
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if an error occurred.
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.Sh ERRORS
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The
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.Fn send
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function and
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.Fn sendto
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and
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.Fn sendmsg
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system calls
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fail if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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An invalid descriptor was specified.
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.It Bq Er EACCES
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The destination address is a broadcast address, and
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.Dv SO_BROADCAST
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has not been set on the socket.
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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 not a socket.
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.It Bq Er EFAULT
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An invalid user space address was specified for an argument.
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.It Bq Er EMSGSIZE
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The socket requires that message be sent atomically,
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and the size of the message to be sent made this impossible.
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.It Bq Er EAGAIN
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The socket is marked non-blocking and the requested operation
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would block.
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.It Bq Er ENOBUFS
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The system was unable to allocate an internal buffer.
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The operation may succeed when buffers become available.
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.It Bq Er ENOBUFS
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The output queue for a network interface was full.
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This generally indicates that the interface has stopped sending,
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but may be caused by transient congestion.
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.It Bq Er EHOSTUNREACH
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The remote host was unreachable.
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.It Bq Er EISCONN
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A destination address was specified and the socket is already connected.
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.It Bq Er ECONNREFUSED
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The socket received an ICMP destination unreachable message
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from the last message sent.
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This typically means that the
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receiver is not listening on the remote port.
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.It Bq Er EHOSTDOWN
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The remote host was down.
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.It Bq Er ENETDOWN
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The remote network was down.
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.It Bq Er EADDRNOTAVAIL
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The process using a
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.Dv SOCK_RAW
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socket was jailed and the source
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address specified in the IP header did not match the IP
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address bound to the prison.
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.It Bq Er EPIPE
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The socket is unable to send anymore data
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.Dv ( SBS_CANTSENDMORE
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has been set on the socket).
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This typically means that the socket
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is not connected.
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.El
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.Sh SEE ALSO
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.Xr fcntl 2 ,
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.Xr getsockopt 2 ,
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.Xr recv 2 ,
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.Xr select 2 ,
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.Xr socket 2 ,
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.Xr write 2
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.Sh HISTORY
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The
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.Fn send
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function appeared in
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.Bx 4.2 .
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.Sh BUGS
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Because
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.Fn sendmsg
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does not necessarily block until the data has been transferred, it
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is possible to transfer an open file descriptor across an
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.Dv AF_UNIX
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domain socket
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(see
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.Xr recv 2 ) ,
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then
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.Fn close
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it before it has actually been sent, the result being that the receiver
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gets a closed file descriptor.
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It is left to the application to
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implement an acknowledgment mechanism to prevent this from happening.
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