.\" $NetBSD: inetd.8,v 1.27 2000/01/31 14:28:17 itojun Exp $ .\" .\" Copyright (c) 1998 The NetBSD Foundation, Inc. .\" All rights reserved. .\" .\" This code is derived from software contributed to The NetBSD Foundation .\" by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, .\" NASA Ames Research Center. .\" .\" 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. 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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 8.4 (Berkeley) 6/1/94 .\" .Dd March 16, 1991 .Dt INETD 8 .Os .Sh NAME .Nm inetd , .Nm inetd.conf .Nd internet .Dq super-server .Sh SYNOPSIS .Nm .Op Fl d .Op Fl l .Op Ar configuration file .Sh DESCRIPTION .Nm 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. After the program is finished, it continues to listen on the socket (except in some cases which will be described below). Essentially, .Nm allows running one daemon to invoke several others, reducing load on the system. .Pp The options available for .\" Why doesn't just `.Nm :' work? .Nm "" : .Bl -tag -width Ds .It Fl d Turns on debugging. .El .Pp .Bl -tag -width Ds .It Fl l Turns on libwrap connection logging. .El .Pp Upon execution, .Nm 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 (except for one special case, described below). The fields of the configuration file are as follows: .Pp .Bd -unfilled -offset indent -compact [addr:]service-name socket-type protocol[,sndbuf=size][,rcvbuf=size] wait/nowait[:max] user[:group] server-program server program arguments .Ed .Pp To specify an .Em Sun-RPC based service, the entry would contain these fields. .Pp .Bd -unfilled -offset indent -compact service-name/version socket-type rpc/protocol[,sndbuf=size][,rcvbuf=size] wait/nowait[:max] user[:group] server-program server program arguments .Ed .Pp For Internet services, the first field of the line may also have a host address specifier prefixed to it, separated from the service name by a colon. If this is done, the string before the colon in the first field indicates what local address .Nm should use when listening for that service, or the single character .Dq \&* to indicate .Dv INADDR_ANY , meaning .Sq all local addresses . To avoid repeating an address that occurs frequently, a line with a host address specifier and colon, but no further fields, causes the host address specifier to be remembered and used for all further lines with no explicit host specifier (until another such line or the end of the file). A line .Dl *: is implicitly provided at the top of the file; thus, traditional configuration files (which have no host address specifiers) will be interpreted in the traditional manner, with all services listened for on all local addresses. .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 . .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. .Pp The .Em protocol must be a valid protocol as given in .Pa /etc/protocols . Examples might be .Dq tcp and .Dq udp . Rpc based services are specified with the .Dq rpc/tcp or .Dq rpc/udp service type. .Dq tcp and .Dq udp will be recognized as .Dq TCP or UDP over default IP version . It is currently IPv4, but in the future it will be IPv6. If you need to specify IPv4 or IPv6 explicitly, use something like .Dq tcp4 or .Dq udp6 . .Pp In addition to the protocol, the configuration file may specify the send and receive socket buffer sizes for the listening socket. This is especially useful for TCP as the window scale factor, which is based on the receive socket buffer size, is advertised when the connection handshake occurs, thus the socket buffer size for the server must be set on the listen socket. By increasing the socket buffer sizes, better TCP performance may be realized in some situations. The socket buffer sizes are specified by appending their values to the protocol specification as follows: .Bd -literal -offset indent tcp,rcvbuf=16384 tcp,sndbuf=64k tcp,rcvbuf=64k,sndbuf=1m .Ed .Pp A literal value may be specified, or modified using .Sq k to indicate kilobytes or .Sq m to indicate megabytes. Socket buffer sizes may be specified for all services and protocols except for tcpmux services. .Pp The .Em wait/nowait entry is used to tell .Nm if it should wait for the server program to return, or continue processing connections on the socket. If a datagram server connects to its peer, freeing the socket so .Nm can receive further messages on the socket, it is said to be a .Dq multi-threaded server, and should use the .Dq nowait entry. For datagram servers which process all incoming datagrams on a socket and eventually time out, the server is said to be .Dq single-threaded and should use a .Dq wait entry. .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 exception; it is a datagram server that establishes pseudo-connections. It must be listed as .Dq wait in order to avoid a race; the server reads the first packet, creates a new socket, and then forks and exits to allow .Nm to check for new service requests to spawn new servers. The optional .Dq max suffix (separated from .Dq wait or .Dq nowait by a dot or a colon) specifies the maximum number of server instances that may be spawned from .Nm within an interval of 60 seconds. When omitted, .Dq max defaults to 40. .Pp Stream servers are usually marked as .Dq nowait but if a single server process is to handle multiple connections, it may be marked as .Dq wait . The master socket will then be passed as fd 0 to the server, which will then need to accept the incoming connection. The server should eventually time out and exit when no more connections are active. .Nm will continue to listen on the master socket for connections, so the server should not close it when it exits. .Xr identd 8 is usually the only stream server marked as wait. .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. An optional group name can be specified by appending a colon to the user name followed by the group name (it is possible to use a dot in lieu of a colon, however this feature is provided only for backward compatibility). This allows for servers to run with a different (primary) group id than specified in the password file. If a group is specified and user is not root, the supplementary groups associated with that user will still be set. .Pp The .Em server-program entry should contain the pathname of the program which is to be executed by .Nm when a request is found on its socket. If .Nm 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 .Nm 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). For details of these services, consult the appropriate .Tn RFC from the Network Information Center. .Pp .Nm 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. .Nm creates a file .Em /var/run/inetd.pid that contains its process identifier. .Ss IPsec The implementation includes tiny hack to support IPsec policy setting for each of the socket. A special form of comment line, starting with .Dq Li "#@" , will work as policy specifier. The content of the above comment line will be treated as IPsec policy string, as described in .Xr ipsec_set_policy 3 . You can specify multiple IPsec policy string by using semicolon as separator. If conflicting strings are found in a single line, the last string will take effect. A .Li "#@" line will affect all the following lines in .Pa inetd.conf , so you may want to reset IPsec policy by using a comment line with .Li "#@" only .Pq with no policy string . .Pp If invalid IPsec policy string appears on .Pa inetd.conf , .Nm will leave error message using .Xr syslog 3 , and terminates itself. .Ss IPv6 TCP/UDP behavior If you run servers for IPv4 and IPv6 traffic, you'll need to specify .Dq tcp4 and .Dq tcp6 properly on the .Pa inetd.conf lines. For safety reasons the author recommends you to run two separate process for the same server program, specified as two separate lines on .Pa inetd.conf , for .Dq tcp6 and .Dq tcp4 . For detailed description please read on. .Pp The behavior of .Dv AF_INET6 socket is documented in RFC2553. Basically, it says as follows: .Bl -bullet -compact .It Specific bind on .Dv AF_INET6 socket .Po .Xr bind 2 with address specified .Pc should accept IPv6 traffic to that address only. .It If you perform wildcard bind on .Dv AF_INET6 socket .Po .Xr bind 2 to IPv6 address .Li :: .Pc , and there is no wildcard bind .Dv AF_INET socket on that TCP/UDP port, IPv6 traffic as well as IPv4 traffic should be routed to that .Dv AF_INET6 socket. IPv4 traffic should be seen as if it came from IPv6 address like .Li ::ffff:10.1.1.1 . This is called IPv4 mapped address. .It If there are both wildcard bind .Dv AF_INET socket and wildcard bind .Dv AF_INET6 socket on one TCP/UDP port, they should behave separately. IPv4 traffic should be routed to .Dv AF_INET socket and IPv6 should be routed to .Dv AF_INET6 socket. .El .Pp Because of this, .Nm will behave as follows. .Bl -bullet -compact .It If you have only one server on .Dq tcp4 , IPv4 traffic will be routed to the server. IPv6 traffic will not be accepted. .It If you have two servers on .Dq tcp4 and .Dq tcp6 , IPv4 traffic will be routed to the server on .Dq tcp4, and IPv6 traffic will go to server on .Dq tcp6 . .It If you have only one server on .Dq tcp6 , Both IPv4 and IPv6 traffic will be routed to the server. .El .Pp The author do not recommend the third option on the above bullets. RFC2553 does not define the constraint between the order of .Xr bind 2 , nor how IPv4 TCP/UDP port number and IPv6 TCP/UDP port number relate each other .Po should they be integrated or separated .Pc . Implemented behavior is very different across kernel to kernel. Many of the servers do not properly handle IPv4 mapped address. Therefore, it is unwise to rely too much upon the behavior of .Dv AF_INET6 wildcard bind socket. .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 rpc or .Dq tcpmux on IPv6 is not tested enough. .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 , .Xr hosts_access 5 , .Xr hosts_options 5 .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 . IPv6 support and IPsec hack was made by KAME project, in 1999. .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.