307 lines
8.1 KiB
Groff
307 lines
8.1 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: @(#)rcmd.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd March 3, 2000
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.Dt RCMD 3
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.Os
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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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.Nm rcmd_af ,
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.Nm rresvport_af ,
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.Nm iruserok_sa
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.Nd routines for returning a stream to a remote command
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In 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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.Ft int
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.Fn rcmd_af "char **ahost" "int inport" "const char *locuser" "const char *remuser" "const char *cmd" "int *fd2p" "int af"
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.Ft int
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.Fn rresvport_af "int *port" "int af"
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.Ft int
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.Fn iruserok_sa "const void *addr" "int addrlen" "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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.Dv stdin
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and
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.Dv 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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.Ux
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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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.Dv 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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.Dv 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 to which an address with a Privileged
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Internet port is bound.
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This socket is suitable for use by
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.Fn rcmd
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and several other functions.
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Privileged Internet ports are those in the range 0 to 1023.
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Only the super-user is allowed to bind an address of this sort
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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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.Pp
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The functions with an
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.Dq Li _af
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or
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.Dq Li _sa
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suffix, i.e.,
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.Fn rcmd_af ,
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.Fn rresvport_af
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and
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.Fn iruserok_sa ,
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work the same as the corresponding functions without a
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suffix, except that they are capable of handling both IPv6 and IPv4 ports.
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.Pp
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The
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.Dq Li _af
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suffix means that the function has an additional
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.Fa af
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argument which is used to specify the address family,
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(see below).
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The
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.Fa af
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argument extension is implemented for functions
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that have no binary address argument.
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Instead, the
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.Fa af
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argument specifies which address family is desired.
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.Pp
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The
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.Dq Li _sa
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suffix means that the function has general socket address and
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length arguments.
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As the socket address is a protocol independent data structure,
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IPv4 and IPv6 socket address can be passed as desired.
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The
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.Fa sa
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argument extension is implemented for functions
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that pass a protocol dependent binary address argument.
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The argument needs to be replaced with a more general address structure
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to support multiple address families in a general way.
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.Pp
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The functions with neither an
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.Dq Li _af
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suffix nor an
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.Dq Li _sa
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suffix work for IPv4 only, except for
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.Fn ruserok
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which can handle both IPv6 and IPv4.
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To switch the address family, the
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.Fa af
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argument must be filled with
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.Dv AF_INET ,
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or
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.Dv AF_INET6 .
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For
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.Fn rcmd_af ,
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.Dv PF_UNSPEC
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is also allowed.
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.Sh ENVIRONMENT
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.Bl -tag -width RSH
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.It Ev RSH
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When using the
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.Fn rcmd
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function, this variable is used as the program to run instead of
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.Xr rsh 1 .
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.El
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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
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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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.Er 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 rlogind 8 ,
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.Xr rshd 8
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.Pp
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.Rs
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.%A W. Stevens
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.%A M. Thomas
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.%T "Advanced Socket API for IPv6"
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.%O RFC2292
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.Re
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.Rs
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.%A W. Stevens
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.%A M. Thomas
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.%A E. Nordmark
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.%T "Advanced Socket API for IPv6"
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.%O RFC3542
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.Re
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.Sh HISTORY
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Most of these
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functions appeared in
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.Bx 4.2 .
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The
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.Fn rresvport_af
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function
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appeared in RFC2292, and was implemented by the WIDE project
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for the Hydrangea IPv6 protocol stack kit.
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The
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.Fn rcmd_af
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function
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appeared in draft-ietf-ipngwg-rfc2292bis-01.txt,
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and was implemented in the WIDE/KAME IPv6 protocol stack kit.
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The
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.Fn iruserok_sa
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function
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appeared in discussion on the IETF ipngwg mailing list,
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and was implemented in
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.Fx 4.0 .
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