| blob | e20ca76e5cac2430dbfd22d824ba6ccdcf27acfb |
1 .\" $NetBSD: inetd.8,v 1.57 2011/04/25 22:12:05 wiz Exp $
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6 .\" This code is derived from software contributed to The NetBSD Foundation
7 .\" by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
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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.
217 In this case
218 .Nm
219 will not see new connections for the specified service until the accept
220 filter decides they are ready to be handled.
221 .Pp
222 The
223 .Em protocol
224 must be a valid protocol as given in
225 .Pa /etc/protocols
226 or the string
227 .Dq unix .
228 Examples might be
229 .Dq tcp
230 and
231 .Dq udp .
232 Rpc based services are specified with the
233 .Dq rpc/tcp
234 or
235 .Dq rpc/udp
236 service type.
237 .Dq tcp
238 and
239 .Dq udp
240 will be recognized as
241 .Dq TCP or UDP over default IP version .
242 It is currently IPv4, but in the future it will be IPv6.
243 If you need to specify IPv4 or IPv6 explicitly, use something like
244 .Dq tcp4
245 or
246 .Dq udp6 .
247 If you would like to enable special support for
248 .Xr faithd 8 ,
249 prepend a keyword
250 .Dq faith
251 into
252 .Em protocol ,
253 like
254 .Dq faith/tcp6 .
255 .Pp
256 In addition to the protocol, the configuration file may specify the
257 send and receive socket buffer sizes for the listening socket.
258 This is especially useful for
259 .Tn TCP
260 as the window scale factor, which is based on the receive socket
261 buffer size, is advertised when the connection handshake occurs,
262 thus the socket buffer size for the server must be set on the listen socket.
263 By increasing the socket buffer sizes, better
264 .Tn TCP
265 performance may be realized in some situations.
266 The socket buffer sizes are specified by appending their values to
267 the protocol specification as follows:
268 .Bd -literal -offset indent
269 tcp,rcvbuf=16384
270 tcp,sndbuf=64k
271 tcp,rcvbuf=64k,sndbuf=1m
272 .Ed
273 .Pp
274 A literal value may be specified, or modified using
275 .Sq k
276 to indicate kilobytes or
277 .Sq m
278 to indicate megabytes.
279 Socket buffer sizes may be specified for all
280 services and protocols except for tcpmux services.
281 .Pp
282 The
283 .Em wait/nowait
284 entry is used to tell
285 .Nm
286 if it should wait for the server program to return,
287 or continue processing connections on the socket.
288 If a datagram server connects
289 to its peer, freeing the socket so
290 .Nm
291 can receive further messages on the socket, it is said to be
292 a
293 .Dq multi-threaded
294 server, and should use the
295 .Dq nowait
296 entry.
297 For datagram servers which process all incoming datagrams
298 on a socket and eventually time out, the server is said to be
299 .Dq single-threaded
300 and should use a
301 .Dq wait
302 entry.
303 .Xr comsat 8
304 .Pq Xr biff 1
305 and
306 .Xr ntalkd 8
307 are both examples of the latter type of
308 datagram server.
309 .Xr tftpd 8
310 is an exception; it is a datagram server that establishes pseudo-connections.
311 It must be listed as
312 .Dq wait
313 in order to avoid a race;
314 the server reads the first packet, creates a new socket,
315 and then forks and exits to allow
316 .Nm
317 to check for new service requests to spawn new servers.
318 The optional
319 .Dq max
320 suffix (separated from
321 .Dq wait
322 or
323 .Dq nowait
324 by a dot or a colon) specifies the maximum number of server instances that may
325 be spawned from
326 .Nm
327 within an interval of 60 seconds.
328 When omitted,
329 .Dq max
330 defaults to 40.
331 If it reaches this maximum spawn rate,
332 .Nm
333 will log the problem (via the syslogger using the
334 .Dv LOG_DAEMON
335 facility and
336 .Dv LOG_ERR
337 level)
338 and stop handling the specific service for ten minutes.
339 .Pp
340 Stream servers are usually marked as
341 .Dq nowait
342 but if a single server process is to handle multiple connections, it may be
343 marked as
344 .Dq wait .
345 The master socket will then be passed as fd 0 to the server, which will then
346 need to accept the incoming connection.
347 The server should eventually time
348 out and exit when no more connections are active.
349 .Nm
350 will continue to
351 listen on the master socket for connections, so the server should not close
352 it when it exits.
353 .Xr identd 8
354 is usually the only stream server marked as wait.
355 .Pp
356 The
357 .Em user
358 entry should contain the user name of the user as whom the server should run.
359 This allows for servers to be given less permission than root.
360 Optionally, a group can be specified by appending a colon to the user name,
361 followed by the group name (it is possible to use a dot (``.'') in lieu of a
362 colon, however this feature is provided only for backward compatibility).
363 This allows for servers to run with a different (primary) group id than
364 specified in the password file.
365 If a group is specified and
366 .Em user
367 is not root, the supplementary groups associated with that user will still be
368 set.
369 .Pp
370 The
371 .Em server-program
372 entry should contain the pathname of the program which is to be
373 executed by
374 .Nm
375 when a request is found on its socket.
376 If
377 .Nm
378 provides this service internally, this entry should
379 be
380 .Dq internal .
381 .Pp
382 The
383 .Em server program arguments
384 should be just as arguments
385 normally are, starting with argv[0], which is the name of
386 the program.
387 If the service is provided internally, the
388 word
389 .Dq internal
390 should take the place of this entry.
391 It is possible to quote an argument using either single or double quotes.
392 This allows you to have, e.g., spaces in paths and parameters.
393 .Ss Internal Services
394 .Nm
395 provides several
396 .Qq trivial
397 services internally by use of routines within itself.
398 These services are
399 .Qq echo ,
400 .Qq discard ,
401 .Qq chargen
402 (character generator),
403 .Qq daytime
404 (human readable time), and
405 .Qq time
406 (machine readable time,
407 in the form of the number of seconds since midnight, January 1, 1900 GMT).
408 For details of these services, consult the appropriate
409 .Tn RFC .
410 .Pp
411 TCP services without official port numbers can be handled with the
412 RFC1078-based tcpmux internal service.
413 TCPmux listens on port 1 for requests.
414 When a connection is made from a foreign host, the service name
415 requested is passed to TCPmux, which performs a lookup in the
416 service name table provided by
417 .Pa /etc/inetd.conf
418 and returns the proper entry for the service.
419 TCPmux returns a negative reply if the service doesn't exist,
420 otherwise the invoked server is expected to return the positive
421 reply if the service type in
422 .Pa /etc/inetd.conf
423 file has the prefix
424 .Qq tcpmux/ .
425 If the service type has the
426 prefix
427 .Qq tcpmux/+ ,
428 TCPmux will return the positive reply for the
429 process; this is for compatibility with older server code, and also
430 allows you to invoke programs that use stdin/stdout without putting any
431 special server code in them.
432 Services that use TCPmux are
433 .Qq nowait
434 because they do not have a well-known port number and hence cannot listen
435 for new requests.
436 .Pp
437 .Nm
438 rereads its configuration file when it receives a hangup signal,
439 .Dv SIGHUP .
440 Services may be added, deleted or modified when the configuration file
441 is reread.
442 .Nm
443 creates a file
444 .Em /var/run/inetd.pid
445 that contains its process identifier.
446 .Ss libwrap
447 Support for
448 .Tn TCP
449 wrappers is included with
450 .Nm
451 to provide internal tcpd-like access control functionality.
452 An external tcpd program is not needed.
453 You do not need to change the
454 .Pa /etc/inetd.conf
455 server-program entry to enable this capability.
456 .Nm
457 uses
458 .Pa /etc/hosts.allow
459 and
460 .Pa /etc/hosts.deny
461 for access control facility configurations, as described in
462 .Xr hosts_access 5 .
463 .Pp
464 .Em Nota Bene :
465 .Tn TCP
466 wrappers do not affect/restrict
467 .Tn UDP
468 or internal services.
469 .Ss IPsec
470 The implementation includes a tiny hack to support IPsec policy settings for
471 each socket.
472 A special form of the comment line, starting with
473 .Dq Li "#@" ,
474 is used as a policy specifier.
475 The content of the above comment line will be treated as a IPsec policy string,
476 as described in
477 .Xr ipsec_set_policy 3 .
478 Multiple IPsec policy strings may be specified by using a semicolon
479 as a separator.
480 If conflicting policy strings are found in a single line,
481 the last string will take effect.
482 A
483 .Li "#@"
484 line affects all of the following lines in
485 .Pa /etc/inetd.conf ,
486 so you may want to reset the IPsec policy by using a comment line containing
487 only
488 .Li "#@"
489 .Pq with no policy string .
490 .Pp
491 If an invalid IPsec policy string appears in
492 .Pa /etc/inetd.conf ,
493 .Nm
494 logs an error message using
495 .Xr syslog 3
496 and terminates itself.
497 .Ss IPv6 TCP/UDP behavior
498 If you wish to run a server for both IPv4 and IPv6 traffic,
499 you will need to run two separate processes for the same server program,
500 specified as two separate lines in
501 .Pa /etc/inetd.conf
502 using
503 .Dq tcp4
504 and
505 .Dq tcp6
506 respectively.
507 Plain
508 .Dq tcp
509 means TCP on top of the current default IP version,
510 which is, at this moment, IPv4.
511 .Pp
512 Under various combination of IPv4/v6 daemon settings,
513 .Nm
514 will behave as follows:
515 .Bl -bullet -compact
516 .It
517 If you have only one server on
518 .Dq tcp4 ,
519 IPv4 traffic will be routed to the server.
520 IPv6 traffic will not be accepted.
521 .It
522 If you have two servers on
523 .Dq tcp4
524 and
525 .Dq tcp6 ,
526 IPv4 traffic will be routed to the server on
527 .Dq tcp4 ,
528 and IPv6 traffic will go to server on
529 .Dq tcp6 .
530 .It
531 If you have only one server on
532 .Dq tcp6 ,
533 only IPv6 traffic will be routed to the server.
534 The kernel may route to the server IPv4 traffic as well,
535 under certain configuration.
536 See
537 .Xr ip6 4
538 for details.
539 .El
540 .Sh FILES
541 .Bl -tag -width /etc/hosts.allow -compact
542 .It Pa /etc/inetd.conf
543 configuration file for all
544 .Nm
545 provided services
546 .It Pa /etc/services
547 service name to protocol and port number mappings.
548 .It Pa /etc/protocols
549 protocol name to protocol number mappings
550 .It Pa /etc/rpc
551 .Tn Sun-RPC
552 service name to service number mappings.
553 .It Pa /etc/hosts.allow
554 explicit remote host access list.
555 .It Pa /etc/hosts.deny
556 explicit remote host denial of service list.
557 .El
558 .Sh SEE ALSO
559 .Xr hosts_access 5 ,
560 .Xr hosts_options 5 ,
561 .Xr protocols 5 ,
562 .Xr rpc 5 ,
563 .Xr services 5 ,
564 .Xr comsat 8 ,
565 .Xr fingerd 8 ,
566 .Xr ftpd 8 ,
567 .Xr rexecd 8 ,
568 .Xr rlogind 8 ,
569 .Xr rshd 8 ,
570 .Xr telnetd 8 ,
571 .Xr tftpd 8
572 .Rs
573 .%A J. Postel
574 .%R RFC
575 .%N 862
576 .%D May 1983
577 .%T "Echo Protocol"
578 .Re
579 .Rs
580 .%A J. Postel
581 .%R RFC
582 .%N 863
583 .%D May 1983
584 .%T "Discard Protocol"
585 .Re
586 .Rs
587 .%A J. Postel
588 .%R RFC
589 .%N 864
590 .%D May 1983
591 .%T "Character Generator Protocol"
592 .Re
593 .Rs
594 .%A J. Postel
595 .%R RFC
596 .%N 867
597 .%D May 1983
598 .%T "Daytime Protocol"
599 .Re
600 .Rs
601 .%A J. Postel
602 .%A K. Harrenstien
603 .%R RFC
604 .%N 868
605 .%D May 1983
606 .%T "Time Protocol"
607 .Re
608 .Rs
609 .%A M. Lottor
610 .%R RFC
611 .%N 1078
612 .%D November 1988
613 .%T "TCP port service Multiplexer (TCPMUX)"
614 .Re
615 .Sh HISTORY
616 The
617 .Nm
618 command appeared in
619 .Bx 4.3 .
620 Support for
621 .Em Sun-RPC
622 based services is modeled after that
623 provided by SunOS 4.1.
624 Support for specifying the socket buffer sizes was added in
625 .Nx 1.4 .
626 In November 1996, libwrap support was added to provide
627 internal tcpd-like access control functionality;
628 libwrap is based on Wietse Venema's tcp_wrappers.
629 IPv6 support and IPsec hack was made by KAME project, in 1999.
630 .Sh BUGS
631 Host address specifiers, while they make conceptual sense for RPC
632 services, do not work entirely correctly.
633 This is largely because the portmapper interface does not provide
634 a way to register different ports for the same service on different
635 local addresses.
636 Provided you never have more than one entry for a given RPC service,
637 everything should work correctly (Note that default host address
638 specifiers do apply to RPC lines with no explicit specifier.)
639 .Pp
640 .Dq tcpmux
641 on IPv6 is not tested enough.
642 .Sh SECURITY CONSIDERATIONS
643 Enabling the
644 .Dq echo ,
645 .Dq discard ,
646 and
647 .Dq chargen
648 built-in trivial services is not recommended because remote
649 users may abuse these to cause a denial of network service to
650 or from the local host.