1130b656e5
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
205 lines
6.0 KiB
Groff
205 lines
6.0 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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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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: @(#)rcmd.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd February 15, 1996
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.Dt RCMD 3
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.Os BSD 4.2
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.Sh NAME
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.Nm rcmd ,
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.Nm rresvport ,
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.Nm iruserok ,
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.Nm ruserok
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.Nd routines for returning a stream to a remote command
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.Sh SYNOPSIS
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.Fd #include <unistd.h>
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.Ft int
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.Fn rcmd "char **ahost" "int inport" "const char *locuser" "const char *remuser" "const char *cmd" "int *fd2p"
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.Ft int
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.Fn rresvport "int *port"
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.Ft int
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.Fn iruserok "u_long raddr" "int superuser" "const char *ruser" "const char *luser"
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.Ft int
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.Fn ruserok "const char *rhost" "int superuser" "const char *ruser" "const char *luser"
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.Sh DESCRIPTION
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The
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.Fn rcmd
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function
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is used by the super-user to execute a command on
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a remote machine using an authentication scheme based
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on reserved port numbers.
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The
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.Fn rresvport
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function
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returns a descriptor to a socket
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with an address in the privileged port space.
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The
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.Fn ruserok
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function
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is used by servers
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to authenticate clients requesting service with
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.Fn rcmd .
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All three functions are present in the same file and are used
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by the
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.Xr rshd 8
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server (among others).
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.Pp
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The
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.Fn rcmd
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function
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looks up the host
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.Fa *ahost
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using
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.Xr gethostbyname 3 ,
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returning \-1 if the host does not exist.
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Otherwise
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.Fa *ahost
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is set to the standard name of the host
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and a connection is established to a server
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residing at the well-known Internet port
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.Fa inport .
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.Pp
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If the connection succeeds,
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a socket in the Internet domain of type
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.Dv SOCK_STREAM
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is returned to the caller, and given to the remote
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command as
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.Em stdin
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and
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.Em stdout .
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If
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.Fa fd2p
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is non-zero, then an auxiliary channel to a control
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process will be set up, and a descriptor for it will be placed
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in
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.Fa *fd2p .
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The control process will return diagnostic
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output from the command (unit 2) on this channel, and will also
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accept bytes on this channel as being
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.Tn UNIX
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signal numbers, to be
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forwarded to the process group of the command.
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If
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.Fa fd2p
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is 0, then the
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.Em stderr
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(unit 2 of the remote
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command) will be made the same as the
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.Em stdout
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and no
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provision is made for sending arbitrary signals to the remote process,
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although you may be able to get its attention by using out-of-band data.
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.Pp
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The protocol is described in detail in
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.Xr rshd 8 .
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.Pp
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The
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.Fn rresvport
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function is used to obtain a socket with a privileged
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address bound to it. This socket is suitable for use
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by
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.Fn rcmd
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and several other functions. Privileged Internet ports are those
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in the range 0 to 1023. Only the super-user
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is allowed to bind an address of this sort to a socket.
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.Pp
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The
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.Fn iruserok
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and
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.Fn ruserok
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functions take a remote host's IP address or name, as returned by the
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.Xr gethostbyname 3
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routines, two user names and a flag indicating whether the local user's
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name is that of the super-user.
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Then, if the user is
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.Em NOT
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the super-user, it checks the
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.Pa /etc/hosts.equiv
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file.
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If that lookup is not done, or is unsuccessful, the
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.Pa .rhosts
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in the local user's home directory is checked to see if the request for
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service is allowed.
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.Pp
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If this file does not exist, is not a regular file, is owned by anyone
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other than the user or the super-user, or is writable by anyone other
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than the owner, the check automatically fails.
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Zero is returned if the machine name is listed in the
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.Dq Pa hosts.equiv
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file, or the host and remote user name are found in the
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.Dq Pa .rhosts
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file; otherwise
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.Fn iruserok
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and
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.Fn ruserok
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return \-1.
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If the local domain (as obtained from
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.Xr gethostname 3 )
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is the same as the remote domain, only the machine name need be specified.
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.Pp
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The
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.Fn iruserok
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function is strongly preferred for security reasons.
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It requires trusting the local DNS at most, while the
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.Fn ruserok
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function requires trusting the entire DNS, which can be spoofed.
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.Sh DIAGNOSTICS
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The
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.Fn rcmd
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function
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returns a valid socket descriptor on success.
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It returns \-1 on error and prints a diagnostic message on the standard error.
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.Pp
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The
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.Fn rresvport
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function
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returns a valid, bound socket descriptor on success.
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It returns \-1 on error with the global value
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.Va errno
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set according to the reason for failure.
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The error code
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.Dv EAGAIN
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is overloaded to mean ``All network ports in use.''
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.Sh SEE ALSO
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.Xr rlogin 1 ,
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.Xr rsh 1 ,
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.Xr intro 2 ,
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.Xr rexec 3 ,
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.Xr rexecd 8 ,
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.Xr rlogind 8 ,
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.Xr rshd 8
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.Sh HISTORY
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These
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functions appeared in
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.Bx 4.2 .
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