643 lines
18 KiB
Groff
643 lines
18 KiB
Groff
.\" $NetBSD: inetd.8,v 1.61 2017/07/20 07:42:54 wiz Exp $
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.\"
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.\" Copyright (c) 1998 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
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.\" NASA Ames Research Center.
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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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" Copyright (c) 1985, 1991 The Regents of the University of California.
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.\" 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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.\" from: @(#)inetd.8 8.4 (Berkeley) 6/1/94
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.\"
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.Dd July 19, 2017
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.Dt INETD 8
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.Os
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.Sh NAME
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.Nm inetd ,
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.Nm inetd.conf
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.Nd internet
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.Dq super-server
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.Sh SYNOPSIS
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.Nm
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.Op Fl d
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.Op Fl l
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.Op Ar configuration file
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.Sh DESCRIPTION
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.Nm
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should be run at boot time by
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.Pa /etc/rc
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(see
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.Xr rc 8 ) .
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It then opens sockets according to its configuration and listens
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for connections.
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When a connection is found on one of its sockets, it decides what
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service the socket corresponds to, and invokes a program to service
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the request.
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After the program is finished, it continues to listen on the socket
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(except in some cases which will be described below).
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Essentially,
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.Nm
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allows running one daemon to invoke several others,
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reducing load on the system.
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.Pp
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The options available for
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.Nm :
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.Bl -tag -width Ds
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.It Fl d
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Turns on debugging.
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.It Fl l
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Turns on libwrap connection logging.
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.El
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.Pp
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Upon execution,
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.Nm
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reads its configuration information from a configuration
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file which, by default, is
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.Pa /etc/inetd.conf .
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The path given for this configuration file must be absolute, unless
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the
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.Fl d
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option is also given on the command line.
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There must be an entry for each field of the configuration
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file, with entries for each field separated by a tab or
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a space.
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Comments are denoted by a ``#'' at the beginning of a line.
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There must be an entry for each field (except for one
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special case, described below).
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The fields of the configuration file are as follows:
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.Pp
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.Bd -unfilled -offset indent -compact
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[listen-addr:]service-spec
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socket-type[:accept-filter]
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protocol[,sndbuf=size][,rcvbuf=size]
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wait/nowait[:max]
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user[:group]
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server-program
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server program arguments
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.Ed
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.Pp
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The
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.Em listen-addr
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specifies the local address
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.Nm
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should use when listening.
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The single character
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.Dq \&*
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means
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.Dv INADDR_ANY :
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all local addresses.
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To avoid the need to repeat listen addresses over and over again,
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listen addresses are inherited from line to line, and the listen
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address can be changed without defining a service by including a line
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containing just
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a
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.Em listen-addr
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followed by a colon.
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The default (compatible with historical configuration files) is \&*.
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To return to this behavior after configuring some services with
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specific listen addresses, give \&* explicitly.
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.Pp
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Note that restricted listen addresses are meaningless and ignored for
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UNIX-domain services, and are not supported for
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.Em Sun-RPC
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services.
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All
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.Em Sun-RPC
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services always listen on all interfaces.
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.Pp
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The form of the
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.Em service-spec
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varies with the service type.
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For Internet services, the
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.Em service-spec
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can be either the name of a service from
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.Pa /etc/services
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or a decimal port number.
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For
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.Dq internal
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services (discussed below), the service name
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.Em must
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be the official name of the service (that is, the first entry in
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.Pa /etc/services )
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and not an alias for it.
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.Pp
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For
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.Em Sun-RPC
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based services, the
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.Em service-spec
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has the form
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.Em service-name Ns Li / Ns Em version .
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The service name must be a valid RPC service name from
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the file
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.Pa /etc/rpc .
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The
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.Em version
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on the right of the
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.Dq /
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is the RPC version number.
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This can simply be a single numeric argument or a range of versions.
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A range is bounded by the low version to the high version \- e.g.
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.Dq rusers/1-3 .
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.Pp
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For UNIX-domain (local) services, the
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.Em service-spec
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is the path name to listen on.
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.Pp
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The
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.Em socket-type
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should be one of
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.Dq stream ,
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.Dq dgram ,
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.Dq raw ,
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.Dq rdm ,
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or
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.Dq seqpacket ,
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depending on whether the socket is a stream, datagram, raw,
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reliably delivered message, or sequenced packet socket.
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.Pp
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Optionally, for Internet services, an accept filter
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(see
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.Xr accept_filter 9 )
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can be specified by appending a colon to
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.Em socket-type ,
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followed by
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the name of the desired accept filter.
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In this case
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.Nm
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will not see new connections for the specified service until the accept
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filter decides they are ready to be handled.
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.\" XXX: do accept filters work for AF_UNIX sockets? nobody probably
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.\" cares, but...
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.Pp
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The
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.Em protocol
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must be a valid protocol as given in
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.Pa /etc/protocols
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or (for UNIX-domain services) the string
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.Dq unix .
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The most common are
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.Dq tcp
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and
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.Dq udp .
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For TCP and UDP, the IP version (4 or 6) may be specified explicitly
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by appending 4 or 6 to the protocol name.
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Otherwise the default version (IPv4) is used.
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For
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.Em Sun-RPC
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the string
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.Dq rpc
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and a slash should be prepended:
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.Dq rpc/tcp
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or
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.Dq rpc/udp .
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If you would like to enable special support for
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.Xr faithd 8 ,
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prepend the string
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.Dq faith
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and a slash:
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.Dq faith/tcp6 .
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.Pp
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In addition to the protocol, the configuration file may specify the
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send and receive socket buffer sizes for the listening socket.
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This is especially useful for
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.Tn TCP :
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the window scale factor, which is based on the receive socket
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buffer size, is advertised when the connection handshake occurs
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and thus the socket buffer size must be set on the listen socket.
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By increasing the socket buffer sizes, better
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.Tn TCP
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performance may be realized in some situations.
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The socket buffer sizes are specified by appending their values to
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the protocol specification as follows:
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.Bd -literal -offset indent
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tcp,rcvbuf=16384
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tcp,sndbuf=64k
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tcp,rcvbuf=64k,sndbuf=1m
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.Ed
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.Pp
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A literal value may be specified, or modified using
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.Sq k
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to indicate kilobytes or
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.Sq m
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to indicate megabytes.
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Socket buffer sizes may be specified for all
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services and protocols except for tcpmux services.
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.Pp
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The
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.Em wait/nowait
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entry is used to tell
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.Nm
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if it should wait for the server program to return,
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or continue processing connections on the socket.
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If a datagram server connects
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to its peer, freeing the socket so
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.Nm
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can receive further messages on the socket, it is said to be
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a
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.Dq multi-threaded
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server, and should use the
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.Dq nowait
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entry.
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For datagram servers which process all incoming datagrams
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on a socket and eventually time out, the server is said to be
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.Dq single-threaded
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and should use a
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.Dq wait
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entry.
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.Xr comsat 8
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.Pq Xr biff 1
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and
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.Xr ntalkd 8
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are both examples of the latter type of
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datagram server.
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.Xr tftpd 8
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is an exception; it is a datagram server that establishes pseudo-connections.
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It must be listed as
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.Dq wait
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in order to avoid a race;
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the server reads the first packet, creates a new socket,
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and then forks and exits to allow
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.Nm
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to check for new service requests to spawn new servers.
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The optional
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.Dq max
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suffix (separated from
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.Dq wait
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or
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.Dq nowait
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by a dot or a colon) specifies the maximum number of server instances that may
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be spawned from
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.Nm
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within an interval of 60 seconds.
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When omitted,
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.Dq max
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defaults to 40.
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If it reaches this maximum spawn rate,
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.Nm
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will log the problem (via the syslogger using the
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.Dv LOG_DAEMON
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facility and
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.Dv LOG_ERR
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level)
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and stop handling the specific service for ten minutes.
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.Pp
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Stream servers are usually marked as
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.Dq nowait
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but if a single server process is to handle multiple connections, it may be
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marked as
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.Dq wait .
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The master socket will then be passed as fd 0 to the server, which will then
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need to accept the incoming connection.
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The server should eventually time
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out and exit when no more connections are active.
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.Nm
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will continue to
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listen on the master socket for connections, so the server should not close
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it when it exits.
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.Xr identd 8
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is usually the only stream server marked as wait.
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.Pp
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The
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.Em user
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entry should contain the user name of the user as whom the server should run.
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This allows for servers to be given less permission than root.
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Optionally, a group can be specified by appending a colon to the user name,
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followed by the group name (it is possible to use a dot (``.'') in lieu of a
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colon, however this feature is provided only for backward compatibility).
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This allows for servers to run with a different (primary) group id than
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specified in the password file.
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If a group is specified and
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.Em user
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is not root, the supplementary groups associated with that user will still be
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set.
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.Pp
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The
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.Em server-program
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entry should contain the pathname of the program which is to be
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executed by
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.Nm
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when a request is found on its socket.
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If
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.Nm
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provides this service internally, this entry should
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be
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.Dq internal .
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.Pp
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The
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.Em server program arguments
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should be just as arguments
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normally are, starting with argv[0], which is the name of
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the program.
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If the service is provided internally, the
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word
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.Dq internal
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should take the place of this entry.
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It is possible to quote an argument using either single or double quotes.
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This allows you to have, e.g., spaces in paths and parameters.
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.Ss Internal Services
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.Nm
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provides several
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.Qq trivial
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services internally by use of routines within itself.
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These services are
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.Qq echo ,
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.Qq discard ,
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.Qq chargen
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(character generator),
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.Qq daytime
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(human readable time), and
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.Qq time
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(machine readable time,
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in the form of the number of seconds since midnight, January 1, 1900 GMT).
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For details of these services, consult the appropriate
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.Tn RFC .
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.Pp
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TCP services without official port numbers can be handled with the
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RFC1078-based tcpmux internal service.
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TCPmux listens on port 1 for requests.
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When a connection is made from a foreign host, the service name
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requested is passed to TCPmux, which performs a lookup in the
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service name table provided by
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.Pa /etc/inetd.conf
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and returns the proper entry for the service.
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TCPmux returns a negative reply if the service doesn't exist,
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otherwise the invoked server is expected to return the positive
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reply if the service type in
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.Pa /etc/inetd.conf
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file has the prefix
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.Qq tcpmux/ .
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If the service type has the
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prefix
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.Qq tcpmux/+ ,
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TCPmux will return the positive reply for the
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process; this is for compatibility with older server code, and also
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allows you to invoke programs that use stdin/stdout without putting any
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special server code in them.
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Services that use TCPmux are
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.Qq nowait
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because they do not have a well-known port number and hence cannot listen
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for new requests.
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.Pp
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.Nm
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rereads its configuration file when it receives a hangup signal,
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.Dv SIGHUP .
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Services may be added, deleted or modified when the configuration file
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is reread.
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.Nm
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creates a file
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.Em /var/run/inetd.pid
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that contains its process identifier.
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.Ss libwrap
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Support for
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.Tn TCP
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wrappers is included with
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.Nm
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to provide internal tcpd-like access control functionality.
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An external tcpd program is not needed.
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You do not need to change the
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.Pa /etc/inetd.conf
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server-program entry to enable this capability.
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.Nm
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uses
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.Pa /etc/hosts.allow
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and
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.Pa /etc/hosts.deny
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for access control facility configurations, as described in
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.Xr hosts_access 5 .
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.Pp
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.Em Nota Bene :
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.Tn TCP
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wrappers do not affect/restrict
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.Tn UDP
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or internal services.
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.Ss IPsec
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|
The implementation includes a tiny hack to support IPsec policy settings for
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each socket.
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A special form of the comment line, starting with
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.Dq Li "#@" ,
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is used as a policy specifier.
|
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The content of the above comment line will be treated as a IPsec policy string,
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as described in
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.Xr ipsec_set_policy 3 .
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Multiple IPsec policy strings may be specified by using a semicolon
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as a separator.
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|
If conflicting policy strings are found in a single line,
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the last string will take effect.
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A
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.Li "#@"
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line affects all of the following lines in
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.Pa /etc/inetd.conf ,
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so you may want to reset the IPsec policy by using a comment line containing
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only
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.Li "#@"
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.Pq with no policy string .
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.Pp
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If an invalid IPsec policy string appears in
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.Pa /etc/inetd.conf ,
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.Nm
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logs an error message using
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.Xr syslog 3
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and terminates itself.
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.Ss IPv6 TCP/UDP behavior
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|
If you wish to run a server for both IPv4 and IPv6 traffic,
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|
you will need to run two separate processes for the same server program,
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|
specified as two separate lines in
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.Pa /etc/inetd.conf
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|
using
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.Dq tcp4
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|
and
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|
.Dq tcp6
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|
respectively.
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|
Plain
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.Dq tcp
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|
means TCP on top of the current default IP version,
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which is, at this moment, IPv4.
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.Pp
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Under various combination of IPv4/v6 daemon settings,
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.Nm
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will behave as follows:
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.Bl -bullet -compact
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.It
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If you have only one server on
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.Dq tcp4 ,
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IPv4 traffic will be routed to the server.
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|
IPv6 traffic will not be accepted.
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.It
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If you have two servers on
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.Dq tcp4
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and
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.Dq tcp6 ,
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IPv4 traffic will be routed to the server on
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.Dq tcp4 ,
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and IPv6 traffic will go to server on
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.Dq tcp6 .
|
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.It
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|
If you have only one server on
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.Dq tcp6 ,
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only IPv6 traffic will be routed to the server.
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|
The kernel may route to the server IPv4 traffic as well,
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under certain configuration.
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|
See
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.Xr ip6 4
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for details.
|
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.El
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|
.Sh FILES
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|
.Bl -tag -width /etc/hosts.allow -compact
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.It Pa /etc/inetd.conf
|
|
configuration file for all
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.Nm
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|
provided services
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.It Pa /etc/services
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|
service name to protocol and port number mappings.
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.It Pa /etc/protocols
|
|
protocol name to protocol number mappings
|
|
.It Pa /etc/rpc
|
|
.Tn Sun-RPC
|
|
service name to service number mappings.
|
|
.It Pa /etc/hosts.allow
|
|
explicit remote host access list.
|
|
.It Pa /etc/hosts.deny
|
|
explicit remote host denial of service list.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr hosts_access 5 ,
|
|
.Xr hosts_options 5 ,
|
|
.Xr protocols 5 ,
|
|
.Xr rpc 5 ,
|
|
.Xr services 5 ,
|
|
.Xr comsat 8 ,
|
|
.Xr fingerd 8 ,
|
|
.Xr ftpd 8 ,
|
|
.Xr rexecd 8 ,
|
|
.Xr rlogind 8 ,
|
|
.Xr rshd 8 ,
|
|
.Xr telnetd 8 ,
|
|
.Xr tftpd 8
|
|
.Rs
|
|
.%A J. Postel
|
|
.%R RFC
|
|
.%N 862
|
|
.%D May 1983
|
|
.%T "Echo Protocol"
|
|
.Re
|
|
.Rs
|
|
.%A J. Postel
|
|
.%R RFC
|
|
.%N 863
|
|
.%D May 1983
|
|
.%T "Discard Protocol"
|
|
.Re
|
|
.Rs
|
|
.%A J. Postel
|
|
.%R RFC
|
|
.%N 864
|
|
.%D May 1983
|
|
.%T "Character Generator Protocol"
|
|
.Re
|
|
.Rs
|
|
.%A J. Postel
|
|
.%R RFC
|
|
.%N 867
|
|
.%D May 1983
|
|
.%T "Daytime Protocol"
|
|
.Re
|
|
.Rs
|
|
.%A J. Postel
|
|
.%A K. Harrenstien
|
|
.%R RFC
|
|
.%N 868
|
|
.%D May 1983
|
|
.%T "Time Protocol"
|
|
.Re
|
|
.Rs
|
|
.%A M. Lottor
|
|
.%R RFC
|
|
.%N 1078
|
|
.%D November 1988
|
|
.%T "TCP port service Multiplexer (TCPMUX)"
|
|
.Re
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
command appeared in
|
|
.Bx 4.3 .
|
|
Support for
|
|
.Em Sun-RPC
|
|
based services is modeled after that
|
|
provided by SunOS 4.1.
|
|
Support for specifying the socket buffer sizes was added in
|
|
.Nx 1.4 .
|
|
In November 1996, libwrap support was added to provide
|
|
internal tcpd-like access control functionality;
|
|
libwrap is based on Wietse Venema's tcp_wrappers.
|
|
IPv6 support and IPsec hack was made by KAME project, in 1999.
|
|
.Sh BUGS
|
|
Host address specifiers, while they make conceptual sense for RPC
|
|
services, do not work entirely correctly.
|
|
This is largely because the portmapper interface does not provide
|
|
a way to register different ports for the same service on different
|
|
local addresses.
|
|
Provided you never have more than one entry for a given RPC service,
|
|
everything should work correctly (Note that default host address
|
|
specifiers do apply to RPC lines with no explicit specifier.)
|
|
.Pp
|
|
.Dq tcpmux
|
|
on IPv6 is not tested enough.
|
|
.Sh SECURITY CONSIDERATIONS
|
|
Enabling the
|
|
.Dq echo ,
|
|
.Dq discard ,
|
|
and
|
|
.Dq chargen
|
|
built-in trivial services is not recommended because remote
|
|
users may abuse these to cause a denial of network service to
|
|
or from the local host.
|