1BABELD(8) System Manager's Manual BABELD(8)
2
6 babeld - ad-hoc network routing daemon
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9 babeld option... [ -- ] interface...
10
12 Babel is a loop-avoiding distance-vector routing protocol roughly based
13 on DSDV and AODV, but with provisions for link cost estimation and
14 redistribution of routes from other routing protocols.
15 While it is optimised for wireless mesh networks, Babel will also work
17 efficiently on wired networks.
18
20 -V Display babeld's version and quit.
21 -m multicast-address
23 Specify the link-local multicast address to be used by the pro‐
24 tocol. The default is ff02:0:0:0:0:0:1:6.
25 -p port
27 Specify the UDP port number to be used by the protocol. The
28 default is 6696.
29 -S state-file
31 Set the name of the file used for preserving long-term informa‐
32 tion between invocations of the babeld daemon. If this file is
33 deleted, the daemon will run in passive mode for 3 minutes when
34 it is next started, and other hosts might initially ignore it.
35 The default is /var/lib/babel-state.
36 -h hello-interval
38 Specify the interval in seconds at which scheduled hello packets
39 are sent on wireless interfaces. The default is 4 seconds.
40 -H wired-hello-interval
42 Specify the interval in seconds at which scheduled hello packets
43 are sent on wired interfaces. The default is 4 seconds.
44 -z kind [,factor]
46 Enable diversity-sensitive routing. The value kind defines the
47 diversity algorithm used, and can be one of 0 (no diversity), 1
48 (per-interface diversity with no memory), 2 (per-channel diver‐
49 sity with no memory), or 3 (per-channel diversity with memory).
50 The value factor specifies by how much the cost of non-interfer‐
51 ing routes is multiplied, in units of 1/256; the default is 128
52 (i.e. division by 2).
53 -M half-time
55 Specify the half-time in seconds of the exponential decay used
56 for smoothing metrics for performing route selection; the value
57 0 disables smoothing. The default is 4s.
58 -k priority
60 Specify the priority value used when installing routes into the
61 kernel. The default is 0.
62 -A priority
64 Allow duplicating external routes when their kernel priority is
65 at least priority. Do not use this option unless you know what
66 you are doing, as it can cause persistent route flapping.
67 -l Use IFF_RUNNING (carrier sense) when determining interface
69 availability.
70 -w Don't optimise wired links, assume all interfaces are wireless
72 unless explicitly overridden in the configuration file.
73 -s Do not perform split-horizon processing on wired interfaces.
75 Split-horizon is not performed on wireless interfaces.
76 -r Use a random router-id. The default is to use persistent
78 router-ids derived from the MAC address of the first interface,
79 which is easier to debug and more reliably prevents routing
80 loops but may sometimes cause a node to be unreachable for 120
81 seconds just after boot.
82 -u Do not flush unfeasible (useless) routes. This is useful in
84 order to announce more information to a front-end (see -g).
85 -d level
87 Debug level. A value of 1 requests a routing table dump at
88 every iteration through the daemon's main loop. A value of 2
89 additionally requests tracing every message sent or received. A
90 value of 3 additionally dumps all interactions with the OS ker‐
91 nel. The default is 0.
92 -g port, -g path
94 Set up a local configuration server on port port or at path in
95 read-only mode. The protocol is described in the section Local
96 Configuration Protocol below.
97 -G port, -G path
99 Set up a local configuration server on port port or at path in
100 read-write mode. This allows any local user to change babeld's
101 configuration, and may therefore be a security issue.
102 -t table
104 Use the given kernel routing table for routes inserted by
105 babeld.
106 -T table
108 Export routes from the given kernel routing table. This can be
109 specified multiple times in order to export routes from more
110 than one table.
111 -c filename
113 Specify the name of the configuration file. This flag can be
114 repeated multiple times. The default is /etc/babeld.conf.
115 -C statement
117 Specify a configuration statement directly on the command line.
118 -D Daemonise at startup.
120 -L logfile
122 Specify a file to log random ``how do you do?'' messages to.
123 This defaults to standard error if not daemonising, and to
124 /var/log/babeld.log otherwise.
125 -I pidfile
127 Specify a file to write our process id to, use no pidfile if set
128 to the empty string. The default is /var/run/babeld.pid.
129 interface...
131 The list of interfaces on which the protocol should operate.
132
134 The configuration file is a sequence of lines each of which specifies a
135 global option, an interface specification or a filtering rule. Com‐
136 ments are introduced by an octothorp ``#'' and terminate at the end of
137 the line.
138 Global options
140 protocol-group group
141 This specifies the link-local multicast address to be used by
142 the protocol, and is equivalent to the command-line option -m.
143 protocol-port port
145 This specifies the UDP port number to be used by the protocol,
146 and is equivalent to the command-line option -p.
147 kernel-priority priority
149 This specifies the priority value used when installing routes
150 into the kernel, and is equivalent to the command-line option
151 -k.
152 reflect-kernel-metric {true|false}
154 Reflect route metrics as kernel priorities. The priority effec‐
155 tively used is kernel-priority + metric.
156 allow-duplicates priority
158 This allows duplicating external routes when their kernel prior‐
159 ity is at least priority. Do not use this option unless you
160 know what you are doing, as it can cause persistent route flap‐
161 ping.
162 random-id {true|false}
164 This specifies whether to use a random router-id, and is equiva‐
165 lent to the command-line option -r.
166 ipv6-subtrees {true|false}
168 This specifies whether to use native source-specific IPv6 for‐
169 warding rather than multiple routing tables. The default is
170 chosen automatically depending on the kernel version.
171 debug level
173 This specifies the debugging level, and is equivalent to the
174 command-line option -d.
175 local-port port
177 This specifies the TCP port on which babeld will listen for con‐
178 nections from a configuration client in read-only mode, and is
179 equivalent to the command-line option -g.
180 local-port-readwrite port
182 This specifies the TCP port on which babeld will listen for con‐
183 nections from a configuration client in read-write mode, and is
184 equivalent to the command-line option -G. This allows any local
185 user to change babeld's configuration, and may therefore be a
186 security issue.
187 local-path path
189 This specifies the filesystem path to a socket on which babeld
190 will listen for connections from a configuration client in read-
191 only mode, and is equivalent to the command-line option -g.
192 local-path-readwrite path
194 This specifies the filesystem path to a socket on which babeld
195 will listen for connections from a configuration client in read-
196 write mode, and is equivalent to the command-line option -G.
197 Any user with write access to that socket will be able to change
198 babeld's configuration.
199 export-table table
201 This specifies the kernel routing table to use for routes
202 inserted by babeld, and is equivalent to the command-line option
203 -t.
204 import-table table
206 This specifies a kernel routing table from which routes are
207 redistributed by babeld, and can be specified multiple times
208 with a cumulative effect. This is equivalent to the command-
209 line option -T.
210 link-detect {true|false}
212 This specifies whether to use carrier sense for determining
213 interface availability, and is equivalent to the command-line
214 option -l.
215 diversity {true|false|kind}
217 This specifies the diversity algorithm to use; true is equiva‐
218 lent to kind 3. The default is false (do not use any diversity
219 algorithm).
220 diversity-factor factor
222 This specifies by how much the cost of non-interfering routes
223 should be multiplied, in units of 1/256. The default is 128
224 (division by 2).
225 smoothing-half-life seconds
227 This specifies the half-life in seconds of the exponential decay
228 used for smoothing metrics for performing route selection, and
229 is equivalent to the command-line option -M.
230 daemonise {true|false}
232 This specifies whether to daemonize at startup, and is equiva‐
233 lent to the command-line option -D.
234 skip-kernel-setup {true|false}
236 If this flag is set, no kernel (sysctl) setup is performed on
237 startup. This can be useful when running in environments where
238 system permissions prevent setting kernel parameters, for
239 instance inside a Linux container.
240 router-id id
242 Specify the router-id explicitly, as a modified EUI-64 or a
243 MAC-48 address. If two nodes have the same router-id, bad
244 things will happen. Don't use this option unless you know what
245 you are doing.
246 state-file filename
248 This specifies the name of the file used for preserving long-
249 term information between invocations of the babeld daemon, and
250 is equivalent to the command-line option -S.
251 log-file filename
253 This specifies the name of the file used to log random messages
254 to, and is equivalent to the command-line option -L.
255 pid-file filename
257 This specifies the name of the file to which babeld writes out
258 its process id, and is equivalent to the command-line option -I.
259 first-table-number table
261 This specifies the index of the first routing table to use for
262 source-specific routes. The default is 10.
263 first-rule-priority priority
265 This specifies smallest (highest) rule priority used with
266 source-specific routes. The default is 100.
267 Interface configuration
269 An interface is configured by a line with the following format:
270 interface name [parameter...]
272 where name is the name of the interface (something like eth0). The
274 default value of an interface parameter can be specified changed by a
275 line of the form
276 default [parameter...]
278 Each parameter can be one of:
280 type {auto|wired|wireless|tunnel}
282 The default is auto unless the -w command-line flag was speci‐
284 fied.
285 link-quality {true|false|auto}
287 This specifies whether link quality estimation should be per‐
288 formed on this interface. The default is to perform link qual‐
289 ity estimation on wireless interfaces only.
290 split-horizon {true|false|auto}
292 This specifies whether to perform split-horizon processing on
293 this interface. The default is to perform split-horizon pro‐
294 cessing on on wired interfaces, unless the -s flag was set.
295 rxcost cost
297 This defines the cost of receiving frames on the given interface
298 under ideal conditions (no packet loss); how this relates to the
299 actual cost used for computing metrics of routes going through
300 this interface depends on whether link quality estimation is
301 being done. The default is 256 if the interface is wireless,
302 and 96 otherwise.
303 channel channel
305 Sets the channel for this interface. The value channel can be
306 either an integer, or one of the strings interfering or nonin‐
307 terfering. The default is to autodetect the channel number for
308 wireless interfaces, and noninterfering for other interfaces.
309 faraway {true|false}
311 This specifies whether the network is "far away", in the sense
312 that networks behind it don't interfere with networks in front
313 of it. By default, networks are not far away.
314 hello-interval interval
316 This defines the interval between hello packets sent on this
317 interface. The default is specified with the -h and -H command-
318 line flags.
319 update-interval interval
321 This defines the interval between full routing table dumps sent
322 on this interface; since Babel uses triggered updates and
323 doesn't count to infinity, this can be set to a fairly large
324 value, unless significant packet loss is expected. The default
325 is four times the hello interval.
326 enable-timestamps {true|false}
328 Enable sending timestamps with each Hello and IHU message in
329 order to compute RTT values. The default is true for tunnel
330 interfaces, and false otherwise.
331 unicast {true|false}
333 Send multiple copies of TLVs other than Hellos to all neighbours
334 rather than sending a single multicast packet. The default is
335 false.
336 rfc6126-compatible {true|false}
338 Disable some features that are incompatible with RFC 6126 (the
339 older version of the Babel protocol), such as source-specific
340 routing and RTT estimation over unicast. The default is false.
341 rtt-decay decay
343 This specifies the decay factor for the exponential moving aver‐
344 age of RTT samples, in units of 1/256. Must be between 1 and
345 256, inclusive. Higher values discard old samples faster. The
346 default is 42.
347 rtt-min rtt
349 This specifies the minimum RTT, in milliseconds, starting from
350 which we increase the cost to a neighbour. The additional cost
351 is linear in (rtt - rtt-min). The default is 10 ms.
352 rtt-max rtt
354 This specifies the maximum RTT, in milliseconds, above which we
355 don't increase the cost to a neighbour. The default is 120 ms.
356 max-rtt-penalty cost
358 This specifies the maximum cost added to a neighbour because of
359 RTT, i.e. when the RTT is higher or equal than rtt-max. The
360 default is 96 if the interface is of type tunnel, and 0 other‐
361 wise.
362 Filtering rules
364 A filtering rule is defined by a single line with the following format:
365 filter selector... action
367 Filter specifies the filter to which this entry will be added, and can
369 be one of in (applied to routes learned from Babel neighbours), out
370 (applied to routes announced to Babel neighbours), redistribute
371 (applied to routes redistributed from the kernel), or install (applied
372 to routes installed into the kernel).
373 Each selector specifies the conditions under which the given statement
375 matches. It can be one of
376 ip prefix
378 This entry only applies to routes in the given prefix.
379 eq plen
381 This entry only applies to routes with a prefix length equal to
382 plen.
383 le plen
385 This entry only applies to routes with a prefix length less or
386 equal to plen.
387 ge plen
389 This entry only applies to routes with a prefix length greater
390 or equal to plen.
391 src-ip prefix
393 This entry only applies to routes with a source prefix in the
394 given prefix.
395 src-eq plen
397 This entry only applies to routes with a source prefix length
398 equal to plen.
399 src-le plen
401 This entry only applies to routes with a source prefix length
402 less or equal to plen.
403 src-ge plen
405 This entry only applies to routes with a source prefix length
406 greater or equal to plen.
407 neigh address
409 This entry only applies to routes learned from a neighbour with
410 link-local address address.
411 id id This entry only applies to routes originated by a router with
413 router-id id.
414 proto p
416 This entry only applies to kernel routes with kernel protocol
417 number p. If neither proto nor local is specified, this entry
418 applies to all non-local kernel routes with a protocol different
419 from "boot".
420 local This entry only applies to local addresses.
422 if interface
424 For an input filter, this specifies the interface over which the
425 route is learned. For an output filter, this specifies the
426 interface over which this route is advertised. For a redis‐
427 tribute statement, this specifies the interface over which the
428 route forwards packets.
429 Action specifies the action to be taken when this entry matches. It
431 can have one of the following values:
432 allow Allow this route, without changing its metric (or setting its
434 metric to 0 in case of a redistribute filter).
435 deny Ignore this route.
437 metric value
439 For an input or output filter, allow this route after increasing
440 its metric by value. For a redistribute filter, redistribute
441 this route with metric value.
442 src-prefix prefix
444 For a redistribute filter, set the source prefix of this route
445 to prefix.
446 table table
448 In an install filter, specify the kernel routing table to use.
449 For source-specific routes, this only works reliably for IPv6,
450 and only when ipv6-subtrees is true.
451 pref-src ip
453 Specify the preferred source address to use with this route.
454 Only useful in an install filter.
455 If action is not specified, it defaults to allow.
457 By default, babeld redistributes all local addresses, and no other
459 routes. In order to make sure that only the routes you specify are
460 redistributed, you should include the line
461 redistribute local deny
463 as the last line in your configuration file.
465
467 If babeld is invoked with the flag -g, it accepts TCP connections from
468 local clients on the given port and address ::1 (the IPv6 localhost
469 address), or on the given UNIX-domain socket path if the argument
470 starts with ‘/’. When a client connects, babeld replies with BABEL
471 followed with the supported version of the local configuration protocol
472 (currently 1.0). This is followed with a number of informational lines
473 (version etc.), terminated by ok. The client can then send requests,
474 one per line. To each request, babeld replies with one or more lines
475 of data terminated by one of ok, no, or bad.
476 The following requests are currently defined:
478 · any configuration file directive, including interface;
480 · flush interface;
482 · dump;
484 · monitor and unmonitor;
486 · quit.
488
490 You can participate in a Babel network by simply running
491 # babeld wlan0
493 where wlan0 is the name of your wireless interface.
495 In order to gateway between multiple interfaces, just list them all on
497 the command line:
498 # babeld wlan0 eth0 sit1
500 On an access point, you'll probably want to redistribute some external
502 routes into Babel:
503 # babeld \
505 -C 'redistribute metric 256' \
506 wlan0
507 or, if you want to constrain the routes that you redistribute,
509 # babeld \
511 -C 'redistribute proto 11 ip ::/0 le 64 metric 256' \
512 -C 'redistribute proto 11 ip 0.0.0.0/0 le 24 metric 256' \
513 wlan0
514 Source-specific routing
516 If your want to redistribute kernel routes as source-specific to the
517 network, with the 2001:DB8:0:1::/64 prefix:
518 redistribute src-prefix 2001:DB8:0:1::/64
520 For more information about source-specific routing, please see
522 Matthieu Boutier and Juliusz Chroboczek. Source-sensitive rout‐
524 ing. In Proc. IFIP Networking 2015. 2015.
525 available online at
527 http://arxiv.org/pdf/1403.0445v4.pdf
529
531 /etc/babeld.conf
532 The default location of the configuration file.
533 /var/lib/babel-state
535 The default location of the file storing long-term state.
536 /var/run/babeld.pid
538 The default location of the pid file.
539 /var/log/babeld.log
541 The default location of the log file.
542
544 SIGUSR1
545 Dump Babel's routing tables to standard output or to the log
546 file.
547 SIGUSR2
549 Check interfaces and kernel routes right now, then reopen the
550 log file.
551
553 Babel is a completely insecure protocol: any attacker able to inject IP
554 packets with a link-local source address can disrupt the protocol's
555 operation. This is no different from unsecured neighbour discovery or
556 ARP.
557 Usage of the -G flag allows any user logged on the local host to change
559 babeld's configuration.
560 Since Babel uses link-local IPv6 packets only, there is no need to
562 update firewalls to allow forwarding of Babel protocol packets. If
563 local filtering is being done, UDP datagrams to the port used by the
564 protocol should be allowed. As Babel uses unicast packets in some
565 cases, it is not enough to just allow packets destined to Babel's mul‐
566 ticast address.
567
569 routed(8), route6d(8), zebra(8), ahcpd(8).
570
572 Juliusz Chroboczek.
573 BABELD(8)