| blob | 9247b8e90422bb24b9635287305d134fed1b9ac0 |
1 .\" $NetBSD: inetd.8,v 1.49 2008/08/27 19:55:20 elric Exp $
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6 .\" This code is derived from software contributed to The NetBSD Foundation
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58 .\" from: @(#)inetd.8 8.4 (Berkeley) 6/1/94
59 .\"
60 .Dd August 27, 2008
61 .Dt INETD 8
62 .Os
63 .Sh NAME
64 .Nm inetd ,
65 .Nm inetd.conf
66 .Nd internet
67 .Dq super-server
68 .Sh SYNOPSIS
69 .Nm
70 .Op Fl d
71 .Op Fl l
72 .Op Ar configuration file
73 .Sh DESCRIPTION
74 .Nm
75 should be run at boot time by
76 .Pa /etc/rc
77 (see
78 .Xr rc 8 ) .
79 It then opens sockets according to its configuration and listens
80 for connections.
81 When a connection is found on one of its sockets, it decides what
82 service the socket corresponds to, and invokes a program to service
83 the request.
84 After the program is finished, it continues to listen on the socket
85 (except in some cases which will be described below).
86 Essentially,
87 .Nm
88 allows running one daemon to invoke several others,
89 reducing load on the system.
90 .Pp
91 The options available for
92 .Nm :
93 .Bl -tag -width Ds
94 .It Fl d
95 Turns on debugging.
96 .It Fl l
97 Turns on libwrap connection logging.
98 .El
99 .Pp
100 Upon execution,
101 .Nm
102 reads its configuration information from a configuration
103 file which, by default, is
104 .Pa /etc/inetd.conf .
105 The path given for this configuration file must be absolute, unless
106 the
107 .Fl d
108 option is also given on the command line.
109 There must be an entry for each field of the configuration
110 file, with entries for each field separated by a tab or
111 a space.
112 Comments are denoted by a ``#'' at the beginning of a line.
113 There must be an entry for each field (except for one
114 special case, described below).
115 The fields of the configuration file are as follows:
116 .Pp
117 .Bd -unfilled -offset indent -compact
118 [addr:]service-name
119 socket-type[:accept_filter]
120 protocol[,sndbuf=size][,rcvbuf=size]
121 wait/nowait[:max]
122 user[:group]
123 server-program
124 server program arguments
125 .Ed
126 .Pp
127 To specify an
128 .Em Sun-RPC
129 based service, the entry would contain these fields:
130 .Pp
131 .Bd -unfilled -offset indent -compact
132 service-name/version
133 socket-type
134 rpc/protocol[,sndbuf=size][,rcvbuf=size]
135 wait/nowait[:max]
136 user[:group]
137 server-program
138 server program arguments
139 .Ed
140 .Pp
141 To specify a UNIX-domain (local) socket, the entry would contain
142 these fields:
143 .Pp
144 .Bd -unfilled -offset indent -compact
145 path
146 socket-type
147 unix[,sndbuf=size][,rcvbuf=size]
148 wait/nowait[:max]
149 user[:group]
150 server-program
151 server program arguments
152 .Ed
153 .Pp
154 For Internet services, the first field of the line may also have a host
155 address specifier prefixed to it, separated from the service name by a colon.
156 If this is done, the string before the colon in the first field
157 indicates what local address
158 .Nm
159 should use when listening for that service, or the single character
160 .Dq \&*
161 to indicate
162 .Dv INADDR_ANY ,
163 meaning
164 .Sq all local addresses .
165 To avoid repeating an address that occurs frequently, a line with a
166 host address specifier and colon, but no further fields, causes the
167 host address specifier to be remembered and used for all further lines
168 with no explicit host specifier (until another such line or the end of
169 the file).
170 A line
171 .Dl *:
172 is implicitly provided at the top of the file; thus, traditional
173 configuration files (which have no host address specifiers) will be
174 interpreted in the traditional manner, with all services listened for
175 on all local addresses.
176 .Pp
177 The
178 .Em service-name
179 entry is the name of a valid service in
180 the file
181 .Pa /etc/services .
182 For
183 .Dq internal
184 services (discussed below), the service
185 name
186 .Em must
187 be the official name of the service (that is, the first entry in
188 .Pa /etc/services ) .
189 When used to specify a
190 .Em Sun-RPC
191 based service, this field is a valid RPC service name in
192 the file
193 .Pa /etc/rpc .
194 The part on the right of the
195 .Dq /
196 is the RPC version number.
197 This can simply be a single numeric argument or a range of versions.
198 A range is bounded by the low version to the high version \-
199 .Dq rusers/1-3 .
200 .Pp
201 The
202 .Em socket-type
203 should be one of
204 .Dq stream ,
205 .Dq dgram ,
206 .Dq raw ,
207 .Dq rdm ,
208 or
209 .Dq seqpacket ,
210 depending on whether the socket is a stream, datagram, raw,
211 reliably delivered message, or sequenced packet socket.
212 .Pp
213 Optionally, an
214 .Xr accept_filter 9
215 can be specified by appending a colon to the socket-type, followed by
216 the name of the desired accept filter. In this case
217 .Nm
218 will not see new connections for the specified service until the accept
219 filter decides they are ready to be handled.
220 .Pp
221 The
222 .Em protocol
223 must be a valid protocol as given in
224 .Pa /etc/protocols
225 or the string
226 .Dq unix .
227 Examples might be
228 .Dq tcp
229 and
230 .Dq udp .
231 Rpc based services are specified with the
232 .Dq rpc/tcp
233 or
234 .Dq rpc/udp
235 service type.
236 .Dq tcp
237 and
238 .Dq udp
239 will be recognized as
240 .Dq TCP or UDP over default IP version .
241 It is currently IPv4, but in the future it will be IPv6.
242 If you need to specify IPv4 or IPv6 explicitly, use something like
243 .Dq tcp4
244 or
245 .Dq udp6 .
246 If you would like to enable special support for
247 .Xr faithd 8 ,
248 prepend a keyword
249 .Dq faith
250 into
251 .Em protocol ,
252 like
253 .Dq faith/tcp6 .
254 .Pp
255 In addition to the protocol, the configuration file may specify the
256 send and receive socket buffer sizes for the listening socket.
257 This is especially useful for
258 .Tn TCP
259 as the window scale factor, which is based on the receive socket
260 buffer size, is advertised when the connection handshake occurs,
261 thus the socket buffer size for the server must be set on the listen socket.
262 By increasing the socket buffer sizes, better
263 .Tn TCP
264 performance may be realized in some situations.
265 The socket buffer sizes are specified by appending their values to
266 the protocol specification as follows:
267 .Bd -literal -offset indent
268 tcp,rcvbuf=16384
269 tcp,sndbuf=64k
270 tcp,rcvbuf=64k,sndbuf=1m
271 .Ed
272 .Pp
273 A literal value may be specified, or modified using
274 .Sq k
275 to indicate kilobytes or
276 .Sq m
277 to indicate megabytes.
278 Socket buffer sizes may be specified for all
279 services and protocols except for tcpmux services.
280 .Pp
281 The
282 .Em wait/nowait
283 entry is used to tell
284 .Nm
285 if it should wait for the server program to return,
286 or continue processing connections on the socket.
287 If a datagram server connects
288 to its peer, freeing the socket so
289 .Nm
290 can receive further messages on the socket, it is said to be
291 a
292 .Dq multi-threaded
293 server, and should use the
294 .Dq nowait
295 entry.
296 For datagram servers which process all incoming datagrams
297 on a socket and eventually time out, the server is said to be
298 .Dq single-threaded
299 and should use a
300 .Dq wait
301 entry.
302 .Xr comsat 8
303 .Pq Xr biff 1
304 and
305 .Xr talkd 8
306 are both examples of the latter type of
307 datagram server.
308 .Xr tftpd 8
309 is an exception; it is a datagram server that establishes pseudo-connections.
310 It must be listed as
311 .Dq wait
312 in order to avoid a race;
313 the server reads the first packet, creates a new socket,
314 and then forks and exits to allow
315 .Nm
316 to check for new service requests to spawn new servers.
317 The optional
318 .Dq max
319 suffix (separated from
320 .Dq wait
321 or
322 .Dq nowait
323 by a dot or a colon) specifies the maximum number of server instances that may
324 be spawned from
325 .Nm
326 within an interval of 60 seconds.
327 When omitted,
328 .Dq max
329 defaults to 40.
330 If it reaches this maximum spawn rate,
331 .Nm
332 will log the problem (via the syslogger using the LOG_DAEMON
333 facility and LOG_ERR level)
334 and stop handling the specific service for ten minutes.
335 .Pp
336 Stream servers are usually marked as
337 .Dq nowait
338 but if a single server process is to handle multiple connections, it may be
339 marked as
340 .Dq wait .
341 The master socket will then be passed as fd 0 to the server, which will then
342 need to accept the incoming connection.
343 The server should eventually time
344 out and exit when no more connections are active.
345 .Nm
346 will continue to
347 listen on the master socket for connections, so the server should not close
348 it when it exits.
349 .Xr identd 8
350 is usually the only stream server marked as wait.
351 .Pp
352 The
353 .Em user
354 entry should contain the user name of the user as whom the server should run.
355 This allows for servers to be given less permission than root.
356 Optionally, a group can be specified by appending a colon to the user name,
357 followed by the group name (it is possible to use a dot (``.'') in lieu of a
358 colon, however this feature is provided only for backward compatibility).
359 This allows for servers to run with a different (primary) group id than
360 specified in the password file.
361 If a group is specified and
362 .Em user
363 is not root, the supplementary groups associated with that user will still be
364 set.
365 .Pp
366 The
367 .Em server-program
368 entry should contain the pathname of the program which is to be
369 executed by
370 .Nm
371 when a request is found on its socket.
372 If
373 .Nm
374 provides this service internally, this entry should
375 be
376 .Dq internal .
377 .Pp
378 The
379 .Em server program arguments
380 should be just as arguments
381 normally are, starting with argv[0], which is the name of
382 the program.
383 If the service is provided internally, the
384 word
385 .Dq internal
386 should take the place of this entry.
387 It is possible to quote an argument using either single or double quotes.
388 This allows you to have, e.g., spaces in paths and parameters.
389 .Ss Internal Services
390 .Nm
391 provides several
392 .Qq trivial
393 services internally by use of routines within itself.
394 These services are
395 .Qq echo ,
396 .Qq discard ,
397 .Qq chargen
398 (character generator),
399 .Qq daytime
400 (human readable time), and
401 .Qq time
402 (machine readable time,
403 in the form of the number of seconds since midnight, January 1, 1900 GMT).
404 For details of these services, consult the appropriate
405 .Tn RFC .
406 .Pp
407 TCP services without official port numbers can be handled with the
408 RFC1078-based tcpmux internal service.
409 TCPmux listens on port 1 for requests.
410 When a connection is made from a foreign host, the service name
411 requested is passed to TCPmux, which performs a lookup in the
412 service name table provided by
413 .Pa /etc/inetd.conf
414 and returns the proper entry for the service.
415 TCPmux returns a negative reply if the service doesn't exist,
416 otherwise the invoked server is expected to return the positive
417 reply if the service type in
418 .Pa /etc/inetd.conf
419 file has the prefix
420 .Qq tcpmux/ .
421 If the service type has the
422 prefix
423 .Qq tcpmux/+ ,
424 TCPmux will return the positive reply for the
425 process; this is for compatibility with older server code, and also
426 allows you to invoke programs that use stdin/stdout without putting any
427 special server code in them.
428 Services that use TCPmux are
429 .Qq nowait
430 because they do not have a well-known port number and hence cannot listen
431 for new requests.
432 .Pp
433 .Nm
434 rereads its configuration file when it receives a hangup signal,
435 .Dv SIGHUP .
436 Services may be added, deleted or modified when the configuration file
437 is reread.
438 .Nm
439 creates a file
440 .Em /var/run/inetd.pid
441 that contains its process identifier.
442 .Ss libwrap
443 Support for
444 .Tn TCP
445 wrappers is included with
446 .Nm
447 to provide internal tcpd-like access control functionality.
448 An external tcpd program is not needed.
449 You do not need to change the
450 .Pa /etc/inetd.conf
451 server-program entry to enable this capability.
452 .Nm
453 uses
454 .Pa /etc/hosts.allow
455 and
456 .Pa /etc/hosts.deny
457 for access control facility configurations, as described in
458 .Xr hosts_access 5 .
459 .Pp
460 .Em Nota Bene :
461 .Tn TCP
462 wrappers do not affect/restrict
463 .Tn UDP
464 or internal services.
465 .Ss IPsec
466 The implementation includes a tiny hack to support IPsec policy settings for
467 each socket.
468 A special form of the comment line, starting with
469 .Dq Li "#@" ,
470 is used as a policy specifier.
471 The content of the above comment line will be treated as a IPsec policy string,
472 as described in
473 .Xr ipsec_set_policy 3 .
474 Multiple IPsec policy strings may be specified by using a semicolon
475 as a separator.
476 If conflicting policy strings are found in a single line,
477 the last string will take effect.
478 A
479 .Li "#@"
480 line affects all of the following lines in
481 .Pa /etc/inetd.conf ,
482 so you may want to reset the IPsec policy by using a comment line containing
483 only
484 .Li "#@"
485 .Pq with no policy string .
486 .Pp
487 If an invalid IPsec policy string appears in
488 .Pa /etc/inetd.conf ,
489 .Nm
490 logs an error message using
491 .Xr syslog 3
492 and terminates itself.
493 .Ss IPv6 TCP/UDP behavior
494 If you wish to run a server for IPv4 and IPv6 traffic,
495 you'll need to run two separate process for the same server program,
496 specified as two separate lines on
497 .Pa /etc/inetd.conf ,
498 for
499 .Dq tcp4
500 and
501 .Dq tcp6 .
502 .Dq tcp
503 means TCP on top of currently-default IP version,
504 which is, at this moment, IPv4.
505 .Pp
506 Under various combination of IPv4/v6 daemon settings,
507 .Nm
508 will behave as follows:
509 .Bl -bullet -compact
510 .It
511 If you have only one server on
512 .Dq tcp4 ,
513 IPv4 traffic will be routed to the server.
514 IPv6 traffic will not be accepted.
515 .It
516 If you have two servers on
517 .Dq tcp4
518 and
519 .Dq tcp6 ,
520 IPv4 traffic will be routed to the server on
521 .Dq tcp4 ,
522 and IPv6 traffic will go to server on
523 .Dq tcp6 .
524 .It
525 If you have only one server on
526 .Dq tcp6 ,
527 only IPv6 traffic will be routed to the server.
528 The kernel may route to the server IPv4 traffic as well,
529 under certain configuration.
530 See
531 .Xr ip6 4
532 for details.
533 .El
534 .Sh FILES
535 .Bl -tag -width /etc/hosts.allow -compact
536 .It Pa /etc/inetd.conf
537 configuration file for all
538 .Nm
539 provided services
540 .It Pa /etc/services
541 service name to protocol and port number mappings.
542 .It Pa /etc/protocols
543 protocol name to protocol number mappings
544 .It Pa /etc/rpc
545 .Tn Sun-RPC
546 service name to service number mappings.
547 .It Pa /etc/hosts.allow
548 explicit remote host access list.
549 .It Pa /etc/hosts.deny
550 explicit remote host denial of service list.
551 .El
552 .Sh SEE ALSO
553 .Xr hosts_access 5 ,
554 .Xr hosts_options 5 ,
555 .Xr protocols 5 ,
556 .Xr rpc 5 ,
557 .Xr services 5 ,
558 .Xr comsat 8 ,
559 .Xr fingerd 8 ,
560 .Xr ftpd 8 ,
561 .Xr rexecd 8 ,
562 .Xr rlogind 8 ,
563 .Xr rshd 8 ,
564 .Xr telnetd 8 ,
565 .Xr tftpd 8
566 .Rs
567 .%A J. Postel
568 .%R RFC
569 .%N 862
570 .%D May 1983
571 .%T "Echo Protocol"
572 .Re
573 .Rs
574 .%A J. Postel
575 .%R RFC
576 .%N 863
577 .%D May 1983
578 .%T "Discard Protocol"
579 .Re
580 .Rs
581 .%A J. Postel
582 .%R RFC
583 .%N 864
584 .%D May 1983
585 .%T "Character Generator Protocol"
586 .Re
587 .Rs
588 .%A J. Postel
589 .%R RFC
590 .%N 867
591 .%D May 1983
592 .%T "Daytime Protocol"
593 .Re
594 .Rs
595 .%A J. Postel
596 .%A K. Harrenstien
597 .%R RFC
598 .%N 868
599 .%D May 1983
600 .%T "Time Protocol"
601 .Re
602 .Rs
603 .%A M. Lottor
604 .%R RFC
605 .%N 1078
606 .%D November 1988
607 .%T "TCP port service Multiplexer (TCPMUX)"
608 .Re
609 .Sh HISTORY
610 The
611 .Nm
612 command appeared in
613 .Bx 4.3 .
614 Support for
615 .Em Sun-RPC
616 based services is modeled after that
617 provided by SunOS 4.1.
618 Support for specifying the socket buffer sizes was added in
619 .Nx 1.4 .
620 In November 1996, libwrap support was added to provide
621 internal tcpd-like access control functionality;
622 libwrap is based on Wietse Venema's tcp_wrappers.
623 IPv6 support and IPsec hack was made by KAME project, in 1999.
624 .Sh BUGS
625 Host address specifiers, while they make conceptual sense for RPC
626 services, do not work entirely correctly.
627 This is largely because the portmapper interface does not provide
628 a way to register different ports for the same service on different
629 local addresses.
630 Provided you never have more than one entry for a given RPC service,
631 everything should work correctly (Note that default host address
632 specifiers do apply to RPC lines with no explicit specifier.)
633 .Pp
634 .Dq tcpmux
635 on IPv6 is not tested enough.
636 .Sh SECURITY CONSIDERATIONS
637 Enabling the
638 .Dq echo ,
639 .Dq discard ,
640 and
641 .Dq chargen
642 built-in trivial services is not recommended because remote
643 users may abuse these to cause a denial of network service to
644 or from the local host.