1BABELD(8) System Manager's Manual BABELD(8)
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6 babeld - ad-hoc network routing daemon
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9 babeld option... [ -- ] interface...
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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 -d level
84 Debug level. A value of 1 requests a routing table dump at
85 every iteration through the daemon's main loop. A value of 2
86 additionally requests tracing every message sent or received. A
87 value of 3 additionally dumps all interactions with the OS ker‐
88 nel. The default is 0.
89 -g port, -g path
91 Set up a local configuration server on port port or at path in
92 read-only mode. The protocol is described in the section Local
93 Configuration Protocol below.
94 -G port, -G path
96 Set up a local configuration server on port port or at path in
97 read-write mode. This allows any local user to change babeld's
98 configuration, and may therefore be a security issue.
99 -t table
101 Use the given kernel routing table for routes inserted by
102 babeld.
103 -T table
105 Export routes from the given kernel routing table. This can be
106 specified multiple times in order to export routes from more
107 than one table.
108 -c filename
110 Specify the name of the configuration file. This flag can be
111 repeated multiple times. The default is /etc/babeld.conf.
112 -C statement
114 Specify a configuration statement directly on the command line.
115 -D Daemonise at startup.
117 -L logfile
119 Specify a file to log random ``how do you do?'' messages to.
120 This defaults to standard error if not daemonising, and to
121 /var/log/babeld.log otherwise.
122 -I pidfile
124 Specify a file to write our process id to, use no pidfile if set
125 to the empty string. The default is /var/run/babeld.pid.
126 interface...
128 The list of interfaces on which the protocol should operate.
129
131 The configuration file is a sequence of lines each of which specifies a
132 global option, an interface specification or a filtering rule. Com‐
133 ments are introduced by an octothorp ``#'' and terminate at the end of
134 the line.
135 Global options
137 protocol-group group
138 This specifies the link-local multicast address to be used by
139 the protocol, and is equivalent to the command-line option -m.
140 protocol-port port
142 This specifies the UDP port number to be used by the protocol,
143 and is equivalent to the command-line option -p.
144 kernel-priority priority
146 This specifies the priority value used when installing routes
147 into the kernel, and is equivalent to the command-line option
148 -k.
149 reflect-kernel-metric {true|false}
151 Reflect route metrics as kernel priorities. The priority effec‐
152 tively used is kernel-priority + metric.
153 allow-duplicates priority
155 This allows duplicating external routes when their kernel prior‐
156 ity is at least priority. Do not use this option unless you
157 know what you are doing, as it can cause persistent route flap‐
158 ping.
159 random-id {true|false}
161 This specifies whether to use a random router-id, and is equiva‐
162 lent to the command-line option -r.
163 ipv6-subtrees {true|false}
165 This specifies whether to use native source-specific IPv6 for‐
166 warding rather than multiple routing tables. The default is
167 chosen automatically depending on the kernel version.
168 debug level
170 This specifies the debugging level, and is equivalent to the
171 command-line option -d.
172 local-port port
174 This specifies the TCP port on which babeld will listen for con‐
175 nections from a configuration client in read-only mode, and is
176 equivalent to the command-line option -g.
177 local-port-readwrite port
179 This specifies the TCP port on which babeld will listen for con‐
180 nections from a configuration client in read-write mode, and is
181 equivalent to the command-line option -G. This allows any local
182 user to change babeld's configuration, and may therefore be a
183 security issue.
184 local-path path
186 This specifies the filesystem path to a socket on which babeld
187 will listen for connections from a configuration client in read-
188 only mode, and is equivalent to the command-line option -g.
189 local-path-readwrite path
191 This specifies the filesystem path to a socket on which babeld
192 will listen for connections from a configuration client in read-
193 write mode, and is equivalent to the command-line option -G.
194 Any user with write access to that socket will be able to change
195 babeld's configuration.
196 export-table table
198 This specifies the kernel routing table to use for routes
199 inserted by babeld, and is equivalent to the command-line option
200 -t.
201 import-table table
203 This specifies a kernel routing table from which routes are
204 redistributed by babeld, and can be specified multiple times
205 with a cumulative effect. This is equivalent to the command-
206 line option -T.
207 link-detect {true|false}
209 This specifies whether to use carrier sense for determining
210 interface availability, and is equivalent to the command-line
211 option -l.
212 diversity {true|false|kind}
214 This specifies the diversity algorithm to use; true is equiva‐
215 lent to kind 3. The default is false (do not use any diversity
216 algorithm).
217 diversity-factor factor
219 This specifies by how much the cost of non-interfering routes
220 should be multiplied, in units of 1/256. The default is 128
221 (division by 2).
222 smoothing-half-life seconds
224 This specifies the half-life in seconds of the exponential decay
225 used for smoothing metrics for performing route selection, and
226 is equivalent to the command-line option -M.
227 daemonise {true|false}
229 This specifies whether to daemonize at startup, and is equiva‐
230 lent to the command-line option -D.
231 skip-kernel-setup {true|false}
233 If this flag is set, no kernel (sysctl) setup is performed on
234 startup. This can be useful when running in environments where
235 system permissions prevent setting kernel parameters, for
236 instance inside a Linux container.
237 router-id id
239 Specify the router-id explicitly, as a modified EUI-64 or a
240 MAC-48 address. If two nodes have the same router-id, bad
241 things will happen. Don't use this option unless you know what
242 you are doing.
243 state-file filename
245 This specifies the name of the file used for preserving long-
246 term information between invocations of the babeld daemon, and
247 is equivalent to the command-line option -S.
248 log-file filename
250 This specifies the name of the file used to log random messages
251 to, and is equivalent to the command-line option -L.
252 pid-file filename
254 This specifies the name of the file to which babeld writes out
255 its process id, and is equivalent to the command-line option -I.
256 first-table-number table
258 This specifies the index of the first routing table to use for
259 source-specific routes. The default is 10.
260 first-rule-priority priority
262 This specifies smallest (highest) rule priority used with
263 source-specific routes. The default is 100.
264 Interface configuration
266 An interface is configured by a line with the following format:
267 interface name [parameter...]
269 where name is the name of the interface (something like eth0). The
271 default value of an interface parameter can be specified changed by a
272 line of the form
273 default [parameter...]
275 Each parameter can be one of:
277 type {auto|wired|wireless|tunnel}
279 The default is auto unless the -w command-line flag was speci‐
281 fied.
282 link-quality {true|false|auto}
284 This specifies whether link quality estimation should be per‐
285 formed on this interface. The default is to perform link qual‐
286 ity estimation on wireless interfaces only.
287 split-horizon {true|false|auto}
289 This specifies whether to perform split-horizon processing on
290 this interface. The default is to perform split-horizon pro‐
291 cessing on on wired interfaces, unless the -s flag was set.
292 rxcost cost
294 This defines the cost of receiving frames on the given interface
295 under ideal conditions (no packet loss); how this relates to the
296 actual cost used for computing metrics of routes going through
297 this interface depends on whether link quality estimation is
298 being done. The default is 256 if the interface is wireless,
299 and 96 otherwise.
300 channel channel
302 Sets the channel for this interface. The value channel can be
303 either an integer, or one of the strings interfering or nonin‐
304 terfering. The default is to autodetect the channel number for
305 wireless interfaces, and noninterfering for other interfaces.
306 faraway {true|false}
308 This specifies whether the network is "far away", in the sense
309 that networks behind it don't interfere with networks in front
310 of it. By default, networks are not far away.
311 hello-interval interval
313 This defines the interval between hello packets sent on this
314 interface. The default is specified with the -h and -H command-
315 line flags.
316 update-interval interval
318 This defines the interval between full routing table dumps sent
319 on this interface; since Babel uses triggered updates and
320 doesn't count to infinity, this can be set to a fairly large
321 value, unless significant packet loss is expected. The default
322 is four times the hello interval.
323 enable-timestamps {true|false}
325 Enable sending timestamps with each Hello and IHU message in
326 order to compute RTT values. The default is true for tunnel
327 interfaces, and false otherwise.
328 unicast {true|false}
330 Send multiple copies of TLVs other than Hellos to all neighbours
331 rather than sending a single multicast packet. The default is
332 false.
333 rfc6126-compatible {true|false}
335 Disable some features that are incompatible with RFC 6126 (the
336 older version of the Babel protocol), such as source-specific
337 routing and RTT estimation over unicast. The default is false.
338 rtt-decay decay
340 This specifies the decay factor for the exponential moving aver‐
341 age of RTT samples, in units of 1/256. Must be between 1 and
342 256, inclusive. Higher values discard old samples faster. The
343 default is 42.
344 rtt-min rtt
346 This specifies the minimum RTT, in milliseconds, starting from
347 which we increase the cost to a neighbour. The additional cost
348 is linear in (rtt - rtt-min). The default is 10 ms.
349 rtt-max rtt
351 This specifies the maximum RTT, in milliseconds, above which we
352 don't increase the cost to a neighbour. The default is 120 ms.
353 max-rtt-penalty cost
355 This specifies the maximum cost added to a neighbour because of
356 RTT, i.e. when the RTT is higher or equal than rtt-max. The
357 default is 96 if the interface is of type tunnel, and 0 other‐
358 wise.
359 Filtering rules
361 A filtering rule is defined by a single line with the following format:
362 filter selector... action
364 Filter specifies the filter to which this entry will be added, and can
366 be one of in (applied to routes learned from Babel neighbours), out
367 (applied to routes announced to Babel neighbours), redistribute
368 (applied to routes redistributed from the kernel), or install (applied
369 to routes installed into the kernel).
370 Each selector specifies the conditions under which the given statement
372 matches. It can be one of
373 ip prefix
375 This entry only applies to routes in the given prefix.
376 eq plen
378 This entry only applies to routes with a prefix length equal to
379 plen.
380 le plen
382 This entry only applies to routes with a prefix length less or
383 equal to plen.
384 ge plen
386 This entry only applies to routes with a prefix length greater
387 or equal to plen.
388 src-ip prefix
390 This entry only applies to routes with a source prefix in the
391 given prefix.
392 src-eq plen
394 This entry only applies to routes with a source prefix length
395 equal to plen.
396 src-le plen
398 This entry only applies to routes with a source prefix length
399 less or equal to plen.
400 src-ge plen
402 This entry only applies to routes with a source prefix length
403 greater or equal to plen.
404 neigh address
406 This entry only applies to routes learned from a neighbour with
407 link-local address address.
408 id id This entry only applies to routes originated by a router with
410 router-id id.
411 proto p
413 This entry only applies to kernel routes with kernel protocol
414 number p. If neither proto nor local is specified, this entry
415 applies to all non-local kernel routes with a protocol different
416 from "boot".
417 local This entry only applies to local addresses.
419 if interface
421 For an input filter, this specifies the interface over which the
422 route is learned. For an output filter, this specifies the
423 interface over which this route is advertised. For a redis‐
424 tribute statement, this specifies the interface over which the
425 route forwards packets.
426 Action specifies the action to be taken when this entry matches. It
428 can have one of the following values:
429 allow Allow this route, without changing its metric (or setting its
431 metric to 0 in case of a redistribute filter).
432 deny Ignore this route.
434 metric value
436 For an input or output filter, allow this route after increasing
437 its metric by value. For a redistribute filter, redistribute
438 this route with metric value.
439 src-prefix prefix
441 For a redistribute filter, set the source prefix of this route
442 to prefix.
443 table table
445 In an install filter, specify the kernel routing table to use.
446 For source-specific routes, this only works reliably for IPv6,
447 and only when ipv6-subtrees is true.
448 pref-src ip
450 Specify the preferred source address to use with this route.
451 Only useful in an install filter.
452 If action is not specified, it defaults to allow.
454 By default, babeld redistributes all local addresses, and no other
456 routes. In order to make sure that only the routes you specify are
457 redistributed, you should include the line
458 redistribute local deny
460 as the last line in your configuration file.
462
464 If babeld is invoked with the flag -g, it accepts TCP connections from
465 local clients on the given port and address ::1 (the IPv6 localhost
466 address), or on the given UNIX-domain socket path if the argument
467 starts with ‘/’. When a client connects, babeld replies with BABEL
468 followed with the supported version of the local configuration protocol
469 (currently 1.0). This is followed with a number of informational lines
470 (version etc.), terminated by ok. The client can then send requests,
471 one per line. To each request, babeld replies with one or more lines
472 of data terminated by one of ok, no, or bad.
473 The following requests are currently defined:
475 · any configuration file directive, including interface;
477 · flush interface;
479 · dump;
481 · monitor and unmonitor;
483 · quit.
485
487 You can participate in a Babel network by simply running
488 # babeld wlan0
490 where wlan0 is the name of your wireless interface.
492 In order to gateway between multiple interfaces, just list them all on
494 the command line:
495 # babeld wlan0 eth0 sit1
497 On an access point, you'll probably want to redistribute some external
499 routes into Babel:
500 # babeld \
502 -C 'redistribute metric 256' \
503 wlan0
504 or, if you want to constrain the routes that you redistribute,
506 # babeld \
508 -C 'redistribute proto 11 ip ::/0 le 64 metric 256' \
509 -C 'redistribute proto 11 ip 0.0.0.0/0 le 24 metric 256' \
510 wlan0
511 Source-specific routing
513 If your want to redistribute kernel routes as source-specific to the
514 network, with the 2001:DB8:0:1::/64 prefix:
515 redistribute src-prefix 2001:DB8:0:1::/64
517 For more information about source-specific routing, please see
519 Matthieu Boutier and Juliusz Chroboczek. Source-sensitive rout‐
521 ing. In Proc. IFIP Networking 2015. 2015.
522 available online at
524 http://arxiv.org/pdf/1403.0445v4.pdf
526
528 /etc/babeld.conf
529 The default location of the configuration file.
530 /var/lib/babel-state
532 The default location of the file storing long-term state.
533 /var/run/babeld.pid
535 The default location of the pid file.
536 /var/log/babeld.log
538 The default location of the log file.
539
541 SIGUSR1
542 Dump Babel's routing tables to standard output or to the log
543 file.
544 SIGUSR2
546 Check interfaces and kernel routes right now, then reopen the
547 log file.
548
550 Babel is a completely insecure protocol: any attacker able to inject IP
551 packets with a link-local source address can disrupt the protocol's
552 operation. This is no different from unsecured neighbour discovery or
553 ARP.
554 Usage of the -G flag allows any user logged on the local host to change
556 babeld's configuration.
557 Since Babel uses link-local IPv6 packets only, there is no need to
559 update firewalls to allow forwarding of Babel protocol packets. If
560 local filtering is being done, UDP datagrams to the port used by the
561 protocol should be allowed. As Babel uses unicast packets in some
562 cases, it is not enough to just allow packets destined to Babel's mul‐
563 ticast address.
564
566 routed(8), route6d(8), zebra(8), ahcpd(8).
567
569 Juliusz Chroboczek.
570 BABELD(8)