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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. .\" .\" @(#)inetd.8 8.4 (Berkeley) 6/1/94 .\" .Dd June 1, 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 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 R Ar rate Specifies the maximum number of times a service can be invoked in one minute; the default is 1000. .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 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 ) . 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 . 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 tcp based. For details of these services, consult the appropriate .Tn RFC from the Network Information Center. .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 . .ne 1i .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 .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 comsat 8 , .Xr fingerd 8 , .Xr ftpd 8 , .Xr rexecd 8 , .Xr rlogind 8 , .Xr rshd 8 , .Xr telnetd 8 , .Xr tftpd 8 .Sh HISTORY The .Nm command appeared in .Bx 4.3 . TCPMUX is based on code and documentation by Mark Lottor.