450 lines
13 KiB
Groff
450 lines
13 KiB
Groff
.\" Copyright (c) 1985, 1991, 1993, 1994
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" from: @(#)inetd.8 8.3 (Berkeley) 4/13/94
|
|
.\" $Id: inetd.8,v 1.6 1995/10/12 16:43:25 wollman Exp $
|
|
.\"
|
|
.Dd April 13, 1994
|
|
.Dt INETD 8
|
|
.Os BSD 4.4
|
|
.Sh NAME
|
|
.Nm inetd
|
|
.Nd internet
|
|
.Dq super-server
|
|
.Sh SYNOPSIS
|
|
.Nm inetd
|
|
.Op Fl d
|
|
.Op Fl l
|
|
.Op Fl R Ar rate
|
|
.Op Ar configuration file
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm inetd
|
|
program
|
|
should be run at boot time by
|
|
.Pa /etc/rc
|
|
(see
|
|
.Xr rc 8 ) .
|
|
It then listens for connections on certain
|
|
internet sockets. When a connection is found on one
|
|
of its sockets, it decides what service the socket
|
|
corresponds to, and invokes a program to service the request.
|
|
The server program is invoked with the service socket
|
|
as its standard input, output and error descriptors.
|
|
After the program is
|
|
finished,
|
|
.Nm inetd
|
|
continues to listen on the socket (except in some cases which
|
|
will be described below). Essentially,
|
|
.Nm inetd
|
|
allows running one daemon to invoke several others,
|
|
reducing load on the system.
|
|
.Pp
|
|
The options available for
|
|
.Nm inetd:
|
|
.Bl -tag -width Ds
|
|
.It Fl d
|
|
Turns on debugging.
|
|
.It Fl l
|
|
Turns on logging.
|
|
.It Fl R Ar rate
|
|
Specifies the maximum number of times a service can be invoked
|
|
in one minute; the default is 256.
|
|
.El
|
|
.Pp
|
|
Upon execution,
|
|
.Nm inetd
|
|
reads its configuration information from a configuration
|
|
file which, by default, is
|
|
.Pa /etc/inetd.conf .
|
|
There must be an entry for each field of the configuration
|
|
file, with entries for each field separated by a tab or
|
|
a space. Comments are denoted by a ``#'' at the beginning
|
|
of a line. There must be an entry for each field. The
|
|
fields of the configuration file are as follows:
|
|
.Pp
|
|
.Bd -unfilled -offset indent -compact
|
|
service name
|
|
socket type
|
|
protocol
|
|
wait/nowait
|
|
user
|
|
server program
|
|
server program arguments
|
|
.Ed
|
|
.Pp
|
|
To specify a
|
|
.Em Sun-RPC
|
|
based service, the entry would contain these fields:
|
|
.Pp
|
|
.Bd -unfilled -offset indent -compact
|
|
service name/version
|
|
socket type
|
|
rpc/protocol
|
|
user
|
|
server program
|
|
server program arguments
|
|
.Ed
|
|
.Pp
|
|
There are two types of services that
|
|
.Nm inetd
|
|
can start: standard and TCPMUX.
|
|
A standard service has a well-known port assigned to it;
|
|
it may be a service that implements an official Internet standard or is a
|
|
BSD-specific service.
|
|
As described in
|
|
.Tn RFC 1078 ,
|
|
TCPMUX services are nonstandard services that do not have a
|
|
well-known port assigned to them.
|
|
They are invoked from
|
|
.Nm inetd
|
|
when a program connects to the
|
|
.Dq tcpmux
|
|
well-known port and specifies
|
|
the service name.
|
|
This feature is useful for adding locally-developed servers.
|
|
.Pp
|
|
The
|
|
.Em service-name
|
|
entry is the name of a valid service in
|
|
the file
|
|
.Pa /etc/services .
|
|
For
|
|
.Dq internal
|
|
services (discussed below), the service
|
|
name
|
|
.Em must
|
|
be the official name of the service (that is, the first entry in
|
|
.Pa /etc/services ) .
|
|
When used to specify a
|
|
.Em Sun-RPC
|
|
based service, this field is a valid RPC service name in
|
|
the file
|
|
.Pa /etc/rpc .
|
|
The part on the right of the
|
|
.Dq /
|
|
is the RPC version number. This
|
|
can simply be a single numeric argument or a range of versions.
|
|
A range is bounded by the low version to the high version -
|
|
.Dq rusers/1-3 .
|
|
For TCPMUX services, the value of the
|
|
.Em service-name
|
|
field consists of the string
|
|
.Dq tcpmux
|
|
followed by a slash and the
|
|
locally-chosen service name.
|
|
The service names listed in
|
|
.Pa /etc/services
|
|
and the name
|
|
.Dq help
|
|
are reserved.
|
|
Try to choose unique names for your TCPMUX services by prefixing them with
|
|
your organization's name and suffixing them with a version number.
|
|
.Pp
|
|
The
|
|
.Em socket-type
|
|
should be one of
|
|
.Dq stream ,
|
|
.Dq dgram ,
|
|
.Dq raw ,
|
|
.Dq rdm ,
|
|
or
|
|
.Dq seqpacket ,
|
|
depending on whether the socket is a stream, datagram, raw,
|
|
reliably delivered message, or sequenced packet socket.
|
|
TCPMUX services must use
|
|
.Dq stream .
|
|
.Pp
|
|
The
|
|
.Em protocol
|
|
must be a valid protocol as given in
|
|
.Pa /etc/protocols .
|
|
Examples might be
|
|
.Dq tcp
|
|
or
|
|
.Dq udp .
|
|
Rpc based services are specified with the
|
|
.Dq rpc/tcp
|
|
or
|
|
.Dq rpc/udp
|
|
service type.
|
|
TCPMUX services must use
|
|
.Dq tcp .
|
|
.Pp
|
|
The
|
|
.Em wait/nowait
|
|
entry specifies whether the server that is invoked by inetd will take over
|
|
the socket associated with the service access point, and thus whether
|
|
.Nm inetd
|
|
should wait for the server to exit before listening for new service
|
|
requests.
|
|
Datagram servers must use
|
|
.Dq wait ,
|
|
as they are always invoked with the original datagram socket bound
|
|
to the specified service address.
|
|
These servers must read at least one datagram from the socket
|
|
before exiting.
|
|
If a datagram server connects
|
|
to its peer, freeing the socket so
|
|
.Nm inetd
|
|
can received further messages on the socket, it is said to be
|
|
a
|
|
.Dq multi-threaded
|
|
server;
|
|
it should read one datagram from the socket and create a new socket
|
|
connected to the peer.
|
|
It should fork, and the parent should then exit
|
|
to allow
|
|
.Nm inetd
|
|
to check for new service requests to spawn new servers.
|
|
Datagram servers which process all incoming datagrams
|
|
on a socket and eventually time out are said to be
|
|
.Dq single-threaded .
|
|
.Xr Comsat 8 ,
|
|
.Pq Xr biff 1
|
|
and
|
|
.Xr talkd 8
|
|
are both examples of the latter type of
|
|
datagram server.
|
|
.Xr Tftpd 8
|
|
is an example of a multi-threaded datagram server.
|
|
.Pp
|
|
Servers using stream sockets generally are multi-threaded and
|
|
use the
|
|
.Dq nowait
|
|
entry.
|
|
Connection requests for these services are accepted by
|
|
.Nm inetd ,
|
|
and the server is given only the newly-accepted socket connected
|
|
to a client of the service.
|
|
Most stream-based services operate in this manner.
|
|
Stream-based servers that use
|
|
.Dq wait
|
|
are started with the listening service socket, and must accept
|
|
at least one connection request before exiting.
|
|
Such a server would normally accept and process incoming connection
|
|
requests until a timeout.
|
|
TCPMUX services must use
|
|
.Dq nowait .
|
|
.Pp
|
|
The
|
|
.Em user
|
|
entry should contain the user name of the user as whom the server
|
|
should run. This allows for servers to be given less permission
|
|
than root.
|
|
.Pp
|
|
The
|
|
.Em server-program
|
|
entry should contain the pathname of the program which is to be
|
|
executed by
|
|
.Nm inetd
|
|
when a request is found on its socket. If
|
|
.Nm inetd
|
|
provides this service internally, this entry should
|
|
be
|
|
.Dq internal .
|
|
.Pp
|
|
The
|
|
.Em server program arguments
|
|
should be just as arguments
|
|
normally are, starting with argv[0], which is the name of
|
|
the program. If the service is provided internally, the
|
|
word
|
|
.Dq internal
|
|
should take the place of this entry.
|
|
.Pp
|
|
The
|
|
.Nm inetd
|
|
program
|
|
provides several
|
|
.Dq trivial
|
|
services internally by use of
|
|
routines within itself. These services are
|
|
.Dq echo ,
|
|
.Dq discard ,
|
|
.Dq chargen
|
|
(character generator),
|
|
.Dq daytime
|
|
(human readable time), and
|
|
.Dq time
|
|
(machine readable time, in the form of the number of seconds since
|
|
midnight, January 1, 1900). All of these services are available in
|
|
both TCP and UDP versions; the UDP versions will refuse service if the
|
|
request specifies a reply port corresponding to any internal service.
|
|
(This is done as a defense against looping attacks; the remote IP address
|
|
is logged.)
|
|
For details of these services, consult the
|
|
appropriate
|
|
.Tn RFC
|
|
document.
|
|
.Pp
|
|
When given the
|
|
.Fl l
|
|
option
|
|
.Nm Inetd
|
|
will log an entry to syslog each time an
|
|
.Xr accept 2
|
|
is made, which notes the
|
|
service selected and the IP-number of the remote requestor.
|
|
.Pp
|
|
The
|
|
.Nm inetd
|
|
program
|
|
rereads its configuration file when it receives a hangup signal,
|
|
.Dv SIGHUP .
|
|
Services may be added, deleted or modified when the configuration file
|
|
is reread.
|
|
Except when started in debugging mode,
|
|
.Nm
|
|
records its process ID in the file
|
|
.Pa /var/run/inetd.pid
|
|
to assist in reconfiguration.
|
|
.Sh TCPMUX
|
|
.Pp
|
|
.Tn RFC 1078
|
|
describes the TCPMUX protocol:
|
|
``A TCP client connects to a foreign host on TCP port 1. It sends the
|
|
service name followed by a carriage-return line-feed <CRLF>. The
|
|
service name is never case sensitive. The server replies with a
|
|
single character indicating positive (+) or negative (\-)
|
|
acknowledgment, immediately followed by an optional message of
|
|
explanation, terminated with a <CRLF>. If the reply was positive,
|
|
the selected protocol begins; otherwise the connection is closed.''
|
|
The program is passed the TCP connection as file descriptors 0 and 1.
|
|
.Pp
|
|
If the TCPMUX service name begins with a ``+'',
|
|
.Nm inetd
|
|
returns the positive reply for the program.
|
|
This allows you to invoke programs that use stdin/stdout
|
|
without putting any special server code in them.
|
|
.Pp
|
|
The special service name
|
|
.Dq help
|
|
causes
|
|
.Nm inetd
|
|
to list TCPMUX services in
|
|
.Pa inetd.conf .
|
|
.Sh "FILES"
|
|
.Bl -tag -width /var/run/inetd.pid -compact
|
|
.It Pa /etc/inetd.conf
|
|
configuration file.
|
|
.It Pa /etc/rpc
|
|
translation of service names to RPC program numbers.
|
|
.It Pa /etc/services
|
|
translation of service names to port numbers.
|
|
.It Pa /var/run/inetd.pid
|
|
the pid of the currently running
|
|
.Nm inetd .
|
|
.El
|
|
.Sh "EXAMPLES"
|
|
.Pp
|
|
Here are several example service entries for the various types of services:
|
|
.Bd -literal
|
|
ftp stream tcp nowait root /usr/libexec/ftpd ftpd -l
|
|
ntalk dgram udp wait root /usr/libexec/ntalkd ntalkd
|
|
tcpmux/+date stream tcp nowait guest /bin/date date
|
|
tcpmux/phonebook stream tcp nowait guest /usr/local/bin/phonebook phonebook
|
|
rstatd/1-3 dgram rpc/udp wait root /usr/libexec/rpc.rstatd rpc.rstatd
|
|
.Ed
|
|
.Sh "ERROR MESSAGES"
|
|
The
|
|
.Nm inetd
|
|
server
|
|
logs error messages using
|
|
.Xr syslog 3 .
|
|
Important error messages and their explanations are:
|
|
.Bd -literal
|
|
\fIservice\fP/\fIprotocol\fP server failing (looping), service terminated.
|
|
.Ed
|
|
The number of requests for the specified service in the past minute
|
|
exceeded the limit. The limit exists to prevent a broken program
|
|
or a malicious user from swamping the system.
|
|
This message may occur for several reasons:
|
|
1) there are lots of hosts requesting the service within a short time period,
|
|
2) a 'broken' client program is requesting the service too frequently,
|
|
3) a malicious user is running a program to invoke the service in
|
|
a 'denial of service' attack, or
|
|
4) the invoked service program has an error that causes clients
|
|
to retry quickly.
|
|
Use the
|
|
.Op Fl R
|
|
option,
|
|
as described above, to change the rate limit.
|
|
Once the limit is reached, the service will be
|
|
reenabled automatically in 10 minutes.
|
|
.sp
|
|
.Bd -literal
|
|
\fIservice\fP/\fIprotocol\fP: No such user '\fIuser\fP', service ignored
|
|
\fIservice\fP/\fIprotocol\fP: getpwnam: \fIuser\fP: No such user
|
|
.Ed
|
|
No entry for
|
|
.Em user
|
|
exists in the
|
|
.Pa passwd
|
|
file. The first message
|
|
occurs when
|
|
.Nm inetd
|
|
(re)reads the configuration file. The second message occurs when the
|
|
service is invoked.
|
|
.sp
|
|
.Bd -literal
|
|
\fIservice\fP: can't set uid \fInumber\fP
|
|
\fIservice\fP: can't set gid \fInumber\fP
|
|
.Ed
|
|
The user or group ID for the entry's
|
|
.Em user
|
|
is invalid.
|
|
.Sh SEE ALSO
|
|
.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 ,
|
|
.Xr portmap 8 ,
|
|
.Xr rpc 5
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
command appeared in
|
|
.Bx 4.3 .
|
|
TCPMUX is based on code and documentation by Mark Lottor.
|
|
Support for
|
|
.Tn "ONC RPC"
|
|
based services is modeled after that
|
|
provided by
|
|
.Tn SunOS
|
|
4.1.
|