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34 .Dd March 13, 2000
35 .Dt IP6FW 8
36 .Os
37 .Sh NAME
38 .Nm ip6fw
39 .Nd controlling utility for IPv6 firewall
40 .Sh SYNOPSIS
41 .Nm
42 .Op Fl q
43 .Oo
44 .Fl p Ar preproc
45 .Oo Fl D
46 .Ar macro Ns Op = Ns Ar value
47 .Oc
48 .Op Fl U Ar macro
49 .Oc
50 .Ar pathname
51 .Nm
52 .Op Fl f | Fl q
53 flush
54 .Nm
55 .Op Fl q
56 zero
57 .Op Ar number ...
58 .Nm
59 delete
60 .Ar number ...
61 .Nm
62 .Op Fl aftN
63 list
64 .Op Ar number ...
65 .Nm
66 .Op Fl ftN
67 show
68 .Op Ar number ...
69 .Nm
70 .Op Fl q
71 add
72 .Op Ar number
73 .Ar action
74 .Op log
75 .Ar proto
76 from
77 .Ar src
78 to
79 .Ar dst
80 .Op via Ar name | ipv6no
81 .Op Ar options
82 .Sh DESCRIPTION
83 To ease configuration, rules can be put into a file which is
84 processed using
85 .Nm
86 as shown in the first synopsis line.
87 An absolute
88 .Ar pathname
89 must be used.
90 The file
91 will be read line by line and applied as arguments to the
92 .Nm
93 utility.
94 .Pp
95 Optionally, a preprocessor can be specified using
96 .Fl p Ar preproc
97 where
98 .Ar pathname
99 is to be piped through.
100 Useful preprocessors include
101 .Xr cpp 1
102 and
103 .Xr m4 1 .
104 If
105 .Ar preproc
106 doesn't start with a slash
107 .Pq Ql /
108 as its first character, the usual
109 .Ev PATH
110 name search is performed.
111 Care should be taken with this in environments where not all
112 file systems are mounted (yet) by the time
113 .Nm
114 is being run (e.g. when they are mounted over NFS).
115 Once
116 .Fl p
117 has been specified, optional
118 .Fl D
119 and
120 .Fl U
121 specifications can follow and will be passed on to the preprocessor.
122 This allows for flexible configuration files (like conditionalizing
123 them on the local hostname) and the use of macros to centralize
124 frequently required arguments like IP addresses.
125 .Pp
126 The
127 .Nm
128 code works by going through the rule-list for each packet,
129 until a match is found.
130 All rules have two associated counters, a packet count and
131 a byte count.
132 These counters are updated when a packet matches the rule.
133 .Pp
134 The rules are ordered by a
135 .Dq line-number
136 from 1 to 65534 that is used
137 to order and delete rules.
138 Rules are tried in increasing order, and the
139 first rule that matches a packet applies.
140 Multiple rules may share the same number and apply in
141 the order in which they were added.
142 .Pp
143 If a rule is added without a number, it is numbered 100 higher
144 than the previous rule.
145 If the highest defined rule number is
146 greater than 65434, new rules are appended to the last rule.
147 .Pp
148 The delete operation deletes the first rule with number
149 .Ar number ,
150 if any.
151 .Pp
152 The list command prints out the current rule set.
153 .Pp
154 The show command is equivalent to `ip6fw -a list'.
155 .Pp
156 The zero operation zeroes the counters associated with rule number
157 .Ar number .
158 .Pp
159 The flush operation removes all rules.
160 .Pp
161 Any command beginning with a
162 .Sq # ,
163 or being all blank, is ignored.
164 .Pp
165 One rule is always present:
166 .Bd -literal -offset center
167 65535 deny all from any to any
168 .Ed
169 .Pp
170 This rule is the default policy, i.e., don't allow anything at all.
171 Your job in setting up rules is to modify this policy to match your
172 needs.
173 .Pp
174 The following options are available:
175 .Bl -tag -width flag
176 .It Fl a
177 While listing, show counter values. See also
178 .Dq show
179 command.
180 .It Fl f
181 Don't ask for confirmation for commands that can cause problems if misused
182 (ie; flush).
183 .Ar Note ,
184 if there is no tty associated with the process, this is implied.
185 .It Fl q
186 While adding, zeroing or flushing, be quiet about actions (implies '-f').
187 This is useful for adjusting rules by executing multiple ip6fw commands in a
188 script (e.g. sh /etc/rc.firewall), or by processing a file of many ip6fw rules,
189 across a remote login session. If a flush is performed in normal
190 (verbose) mode, it prints a message. Because all rules are flushed, the
191 message cannot be delivered to the login session, the login session is
192 closed and the remainder of the ruleset is not processed. Access to the
193 console is required to recover.
194 .It Fl t
195 While listing, show last match timestamp.
196 .It Fl N
197 Try to resolve addresses and service names in output.
198 .El
199 .Pp
200 .Ar action :
201 .Bl -hang -offset flag -width 16n
202 .It Ar allow
203 Allow packets that match rule.
204 The search terminates.
205 Aliases are
206 .Ar pass ,
207 .Ar permit ,
208 and
209 .Ar accept .
210 .It Ar deny
211 Discard packets that match this rule.
212 The search terminates.
213 .Ar Drop
214 is an alias for
215 .Ar deny .
216 .It Ar reject
217 (Deprecated.) Discard packets that match this rule, and try to send an ICMPv6
218 host unreachable notice.
219 The search terminates.
220 .It Ar unreach code
221 Discard packets that match this rule, and try to send an ICMPv6
222 unreachable notice with code
223 .Ar code ,
224 where
225 .Ar code
226 is a number from zero to 255, or one of these aliases:
227 .Ar noroute ,
228 .Ar admin ,
229 .Ar notneighbor ,
230 .Ar addr ,
231 or
232 .Ar noport ,
233 The search terminates.
234 .It Ar reset
235 TCP packets only.
236 Discard packets that match this rule,
237 and try to send a TCP reset (RST) notice.
238 The search terminates
239 .Em ( "not working yet" ) .
240 .It Ar count
241 Update counters for all packets that match rule.
242 The search continues with the next rule.
243 .It Ar skipto number
244 Skip all subsequent rules numbered less than
245 .Ar number .
246 The search continues with the first rule numbered
247 .Ar number
248 or higher.
249 .El
250 .Pp
251 If the kernel was compiled with
252 .Dv IPV6FIREWALL_VERBOSE ,
253 then when a packet matches a rule with the
254 .Dq log
255 keyword or a clear/resetlog is performed, a message will be logged to
256 .Xr syslogd 8 ,
257 or, if that fails, to the console. If the kernel was compiled with the
258 .Dv IPV6FIREWALL_VERBOSE_LIMIT
259 option, then logging will cease after the number of packets
260 specified by the option are received for that particular
261 chain entry.
262 When this limit is reached, the limit and rule number will be logged.
263 Logging may then be re-enabled by clearing
264 the packet counter for that entry.
265 .Pp
266 The
267 .Xr syslogd 8
268 logging and the default log limit are adjustable dynamically through the
269 .Xr sysctl 8
270 interface.
271 .Pp
272 .Ar proto :
273 .Bl -hang -offset flag -width 16n
274 .It Ar ipv6
275 All packets match.
276 The alias
277 .Ar all
278 has the same effect.
279 .It Ar tcp
280 Only TCP packets match.
281 .It Ar udp
282 Only UDP packets match.
283 .It Ar ipv6-icmp
284 Only ICMPv6 packets match.
285 .It Ar <number|name>
286 Only packets for the specified protocol matches (see
287 .Pa /etc/protocols
288 for a complete list).
289 .El
290 .Pp
291 .Ar src
292 and
293 .Ar dst :
294 .Bl -hang -offset flag
295 .It Ar <address/prefixlen>
296 .Op Ar ports
297 .El
298 .Pp
299 The
300 .Em <address/prefixlen>
301 may be specified as:
302 .Bl -hang -offset flag -width 16n
303 .It Ar ipv6no
304 An ipv6number of the form
305 .Li fec0::1:2:3:4 .
306 .It Ar ipv6no/prefixlen
307 An ipv6number with a prefix length of the form
308 .Li fec0::1:2:3:4/112 .
309 .El
310 .Pp
311 The sense of the match can be inverted by preceding an address with the
312 .Dq not
313 modifier, causing all other addresses to be matched instead.
314 This
315 does not affect the selection of port numbers.
316 .Pp
317 With the TCP and UDP protocols, optional
318 .Em ports
319 may be specified as:
320 .Pp
321 .Bl -hang -offset flag
322 .It Ns {port|port-port} Ns Op ,port Ns Op ,...
323 .El
324 .Pp
325 Service names (from
326 .Pa /etc/services )
327 may be used instead of numeric port values.
328 A range may only be specified as the first value,
329 and the length of the port list is limited to
330 .Dv IPV6_FW_MAX_PORTS
331 (as defined in
332 .In net/ip6fw/ip6_fw.h )
333 ports.
334 .Pp
335 Fragmented packets which have a non-zero offset (i.e. not the first
336 fragment) will never match a rule which has one or more port
337 specifications. See the
338 .Ar frag
339 option for details on matching fragmented packets.
340 .Pp
341 Rules can apply to packets when they are incoming, or outgoing, or both.
342 The
343 .Ar in
344 keyword indicates the rule should only match incoming packets.
345 The
346 .Ar out
347 keyword indicates the rule should only match outgoing packets.
348 .Pp
349 To match packets going through a certain interface, specify
350 the interface using
351 .Ar via :
352 .Bl -hang -offset flag -width 16n
353 .It Ar via ifX
354 Packet must be going through interface
355 .Ar ifX .
356 .It Ar via if*
357 Packet must be going through interface
358 .Ar ifX ,
359 where X is any unit number.
360 .It Ar via any
361 Packet must be going through
362 .Em some
363 interface.
364 .It Ar via ipv6no
365 Packet must be going through the interface having IPv6 address
366 .Ar ipv6no .
367 .El
368 .Pp
369 The
370 .Ar via
371 keyword causes the interface to always be checked.
372 If
373 .Ar recv
374 or
375 .Ar xmit
376 is used instead of
377 .Ar via ,
378 then the only receive or transmit interface (respectively) is checked.
379 By specifying both, it is possible to match packets based on both receive
380 and transmit interface, e.g.:
381 .Pp
382 .Dl "ip6fw add 100 deny ip from any to any out recv ed0 xmit ed1"
383 .Pp
384 The
385 .Ar recv
386 interface can be tested on either incoming or outgoing packets, while the
387 .Ar xmit
388 interface can only be tested on outgoing packets.
389 So
390 .Ar out
391 is required (and
392 .Ar in
393 invalid) whenever
394 .Ar xmit
395 is used.
396 Specifying
397 .Ar via
398 together with
399 .Ar xmit
400 or
401 .Ar recv
402 is invalid.
403 .Pp
404 A packet may not have a receive or transmit interface: packets originating
405 from the local host have no receive interface. while packets destined for
406 the local host have no transmit interface.
407 .Pp
408 Additional
409 .Ar options :
410 .Bl -hang -offset flag -width 16n
411 .It frag
412 Matches if the packet is a fragment and this is not the first fragment
413 of the datagram.
414 .Ar frag
415 may not be used in conjunction with either
416 .Ar tcpflags
417 or TCP/UDP port specifications.
418 .It in
419 Matches if this packet was on the way in.
420 .It out
421 Matches if this packet was on the way out.
422 .It ipv6options Ar spec
423 Matches if the IPv6 header contains the comma separated list of
424 options specified in
425 .Ar spec .
426 The supported IPv6 options are:
427 .Ar hopopt
428 (hop-by-hop options header),
429 .Ar route
430 (routing header),
431 .Ar frag
432 (fragment header),
433 .Ar esp
434 (encapsulating security payload),
435 .Ar ah
436 (authentication header),
437 .Ar nonxt
438 (no next header), and
439 .Ar opts
440 (destination options header).
441 The absence of a particular option may be denoted
442 with a
443 .Dq \&!
444 .Em ( "not working yet" ) .
445 .It established
446 Matches packets that have the RST or ACK bits set.
447 TCP packets only.
448 .It setup
449 Matches packets that have the SYN bit set but no ACK bit.
450 TCP packets only.
451 .It tcpflags Ar spec
452 Matches if the TCP header contains the comma separated list of
453 flags specified in
454 .Ar spec .
455 The supported TCP flags are:
456 .Ar fin ,
457 .Ar syn ,
458 .Ar rst ,
459 .Ar psh ,
460 .Ar ack ,
461 and
462 .Ar urg .
463 The absence of a particular flag may be denoted
464 with a
465 .Dq \&! .
466 A rule which contains a
467 .Ar tcpflags
468 specification can never match a fragmented packet which has
469 a non-zero offset. See the
470 .Ar frag
471 option for details on matching fragmented packets.
472 .It icmptypes Ar types
473 Matches if the ICMPv6 type is in the list
474 .Ar types .
475 The list may be specified as any combination of ranges
476 or individual types separated by commas.
477 .El
478 .Sh CHECKLIST
479 Here are some important points to consider when designing your
480 rules:
481 .Bl -bullet -offset flag
482 .It
483 Remember that you filter both packets going in and out.
484 Most connections need packets going in both directions.
485 .It
486 Remember to test very carefully.
487 It is a good idea to be near the console when doing this.
488 .It
489 Don't forget the loopback interface.
490 .El
491 .Sh FINE POINTS
492 There is one kind of packet that the firewall will always discard,
493 that is an IPv6 fragment with a fragment offset of one.
494 This is a valid packet, but it only has one use, to try to circumvent
495 firewalls.
496 .Pp
497 If you are logged in over a network, loading the KLD version of
498 .Nm
499 is probably not as straightforward as you would think
500 .Em ( "not supported" ) .
501 I recommend this command line:
502 .Bd -literal -offset center
503 kldload /modules/ip6fw_mod.o && \e
504 ip6fw add 32000 allow all from any to any
505 .Ed
506 .Pp
507 Along the same lines, doing an
508 .Bd -literal -offset center
509 ip6fw flush
510 .Ed
511 .Pp
512 in similar surroundings is also a bad idea.
513 .Sh PACKET DIVERSION
514 not supported.
515 .Sh EXAMPLES
516 This command adds an entry which denies all tcp packets from
517 .Em hacker.evil.org
518 to the telnet port of
519 .Em wolf.tambov.su
520 from being forwarded by the host:
521 .Pp
522 .Dl ip6fw add deny tcp from hacker.evil.org to wolf.tambov.su 23
523 .Pp
524 This one disallows any connection from the entire hackers network to
525 my host:
526 .Pp
527 .Dl ip6fw add deny all from fec0::123:45:67:0/112 to my.host.org
528 .Pp
529 Here is a good usage of the list command to see accounting records
530 and timestamp information:
531 .Pp
532 .Dl ip6fw -at l
533 .Pp
534 or in short form without timestamps:
535 .Pp
536 .Dl ip6fw -a l
537 .Sh SEE ALSO
538 .Xr ip 4 ,
539 .Xr ipfirewall 4 ,
540 .Xr protocols 5 ,
541 .Xr services 5 ,
542 .Xr reboot 8 ,
543 .Xr sysctl 8 ,
544 .Xr syslogd 8
545 .Sh HISTORY
546 A
547 .Nm
548 utility first appeared in
549 .Fx 4.0 .
550 .Sh AUTHORS
551 .An Ugen J. S. Antsilevich ,
552 .An Poul-Henning Kamp ,
553 .An Alex Nash ,
554 .An Archie Cobbs .
555 .Pp
556 .An -nosplit
557 API based upon code written by
558 .An Daniel Boulet
559 for BSDI.
560 .Sh BUGS
561 .Em WARNING!!WARNING!!WARNING!!WARNING!!WARNING!!WARNING!!WARNING!!
562 .Pp
563 This program can put your computer in rather unusable state.
564 When
565 using it for the first time, work on the console of the computer, and
566 do
567 .Em NOT
568 do anything you don't understand.
569 .Pp
570 When manipulating/adding chain entries, service and protocol names are
571 not accepted.