1BABELD(8) System Manager's Manual BABELD(8)
2
6 babeld - ad-hoc network routing daemon
7
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 re‐
14 distribution 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 de‐
28 fault 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 ev‐
85 ery iteration through the daemon's main loop. A value of 2 ad‐
86 ditionally 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 ba‐
102 beld.
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 in‐
199 serted 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 re‐
204 distributed by babeld, and can be specified multiple times with
205 a cumulative effect. This is equivalent to the command-line op‐
206 tion -T.
207 link-detect {true|false}
209 This specifies whether to use carrier sense for determining in‐
210 terface availability, and is equivalent to the command-line op‐
211 tion -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, and it is assumed that enabling forwarding, disabling
235 redirects and disabling the reverse-path filter is performed by
236 other means. This can be useful when running in environments
237 where system permissions prevent setting kernel parameters, for
238 instance without root permissions or inside a Linux container.
239 router-id id
241 Specify the router-id explicitly, as a modified EUI-64 or a
242 MAC-48 address. If two nodes have the same router-id, bad
243 things will happen. Don't use this option unless you know what
244 you are doing.
245 state-file filename
247 This specifies the name of the file used for preserving long-
248 term information between invocations of the babeld daemon, and
249 is equivalent to the command-line option -S.
250 log-file filename
252 This specifies the name of the file used to log random messages
253 to, and is equivalent to the command-line option -L.
254 pid-file filename
256 This specifies the name of the file to which babeld writes out
257 its process id, and is equivalent to the command-line option -I.
258 first-rule-priority priority
260 This specifies smallest (highest) rule priority used with
261 source-specific routes. The default is 100.
262 key id id type {hmac-sha256|blake2s128} value value
264 Configure a key for use with the key interface option. The type
265 is one of hmac-sha256 or blake2s128. The value is a hexadecimal
266 string (up to 64 bytes for hmac-sha256, up to 32 bytes for
267 blake2s128).
268 Interface configuration
270 An interface is configured by a line with the following format:
271 interface name [parameter...]
273 where name is the name of the interface (something like eth0). The de‐
275 fault value of an interface parameter can be specified changed by a
276 line of the form
277 default [parameter...]
279 Each parameter can be one of:
281 type {auto|wired|wireless|tunnel}
283 The default is auto unless the -w command-line flag was speci‐
285 fied.
286 link-quality {true|false|auto}
288 This specifies whether link quality estimation should be per‐
289 formed on this interface. The default is to perform link qual‐
290 ity estimation on wireless interfaces only.
291 split-horizon {true|false|auto}
293 This specifies whether to perform split-horizon processing on
294 this interface. The default is to perform split-horizon pro‐
295 cessing on on wired interfaces, unless the -s flag was set.
296 rxcost cost
298 This defines the cost of receiving frames on the given interface
299 under ideal conditions (no packet loss); how this relates to the
300 actual cost used for computing metrics of routes going through
301 this interface depends on whether link quality estimation is be‐
302 ing done. The default is 256 if the interface is wireless, and
303 96 otherwise.
304 channel channel
306 Sets the channel for this interface. The value channel can be
307 either an integer, or one of the strings interfering or nonin‐
308 terfering. The default is to autodetect the channel number for
309 wireless interfaces, and noninterfering for other interfaces.
310 faraway {true|false}
312 This specifies whether the network is "far away", in the sense
313 that networks behind it don't interfere with networks in front
314 of it. By default, networks are not far away.
315 hello-interval interval
317 This defines the interval between hello packets sent on this in‐
318 terface. The default is specified with the -h and -H command-
319 line flags.
320 update-interval interval
322 This defines the interval between full routing table dumps sent
323 on this interface; since Babel uses triggered updates and
324 doesn't count to infinity, this can be set to a fairly large
325 value, unless significant packet loss is expected. The default
326 is four times the hello interval.
327 enable-timestamps {true|false}
329 Enable sending timestamps with each Hello and IHU message in or‐
330 der to compute RTT values. The default is true for tunnel in‐
331 terfaces, and false otherwise.
332 unicast {true|false}
334 Send multiple copies of TLVs other than Hellos to all neighbours
335 rather than sending a single multicast packet. The default is
336 false.
337 rfc6126-compatible {true|false}
339 Disable some features that are incompatible with RFC 6126 (the
340 older version of the Babel protocol), such as source-specific
341 routing and RTT estimation over unicast. The default is false.
342 rtt-decay decay
344 This specifies the decay factor for the exponential moving aver‐
345 age of RTT samples, in units of 1/256. Must be between 1 and
346 256, inclusive. Higher values discard old samples faster. The
347 default is 42.
348 rtt-min rtt
350 This specifies the minimum RTT, in milliseconds, starting from
351 which we increase the cost to a neighbour. The additional cost
352 is linear in (rtt - rtt-min). The default is 10 ms.
353 rtt-max rtt
355 This specifies the maximum RTT, in milliseconds, above which we
356 don't increase the cost to a neighbour. The default is 120 ms.
357 max-rtt-penalty cost
359 This specifies the maximum cost added to a neighbour because of
360 RTT, i.e. when the RTT is higher or equal than rtt-max. The de‐
361 fault is 96 if the interface is of type tunnel, and 0 otherwise.
362 Whether to announce IPv4 routes through this interface even when there
364 is
365 no IPv4 address. The default depends on the kernel version.
366 key id Enable HMAC security on this interface, and use the key id.
368 accept-bad-signatures {true|false}
370 Accept packets with no signature or an incorrect signature.
371 This only has an effect if a key was configured on an interface.
372 The default is false.
373 Filtering rules
376 A filtering rule is defined by a single line with the following
377 format:
378 filter selector... action
380 Filter specifies the filter to which this entry will be added, and can
382 be one of in (applied to routes learned from Babel neighbours), out
383 (applied to routes announced to Babel neighbours), redistribute (ap‐
384 plied to routes redistributed from the kernel), or install (applied to
385 routes installed into the kernel).
386 Each selector specifies the conditions under which the given statement
388 matches. It can be one of
389 ip prefix
391 This entry only applies to routes in the given prefix.
392 eq plen
394 This entry only applies to routes with a prefix length equal to
395 plen.
396 le plen
398 This entry only applies to routes with a prefix length less or
399 equal to plen.
400 ge plen
402 This entry only applies to routes with a prefix length greater
403 or equal to plen.
404 src-ip prefix
406 This entry only applies to routes with a source prefix in the
407 given prefix.
408 src-eq plen
410 This entry only applies to routes with a source prefix length
411 equal to plen.
412 src-le plen
414 This entry only applies to routes with a source prefix length
415 less or equal to plen.
416 src-ge plen
418 This entry only applies to routes with a source prefix length
419 greater or equal to plen.
420 neigh address
422 This entry only applies to routes learned from a neighbour with
423 link-local address address.
424 id id This entry only applies to routes originated by a router with
426 router-id id.
427 proto p
429 This entry only applies to kernel routes with kernel protocol
430 number p. If neither proto nor local is specified, this entry
431 applies to all non-local kernel routes with a protocol different
432 from "boot".
433 local This entry only applies to local addresses.
435 if interface
437 For an input filter, this specifies the interface over which the
438 route is learned. For an output filter, this specifies the in‐
439 terface over which this route is advertised. For a redistribute
440 statement, this specifies the interface over which the route
441 forwards packets.
442 Action specifies the action to be taken when this entry matches. It
444 can have one of the following values:
445 allow Allow this route, without changing its metric (or setting its
447 metric to 0 in case of a redistribute filter).
448 deny Ignore this route.
450 metric value
452 For an input or output filter, allow this route after increasing
453 its metric by value. For a redistribute filter, redistribute
454 this route with metric value.
455 src-prefix prefix
457 For a redistribute filter, set the source prefix of this route
458 to prefix.
459 table table
461 In an install filter, specify the kernel routing table to use.
462 For source-specific routes, this only works reliably for IPv6,
463 and only when ipv6-subtrees is true.
464 pref-src ip
466 Specify the preferred source address to use with this route.
467 Only useful in an install filter.
468 If action is not specified, it defaults to allow.
470 By default, babeld redistributes all local addresses, and no other
472 routes. In order to make sure that only the routes you specify are re‐
473 distributed, you should include the line
474 redistribute local deny
476 as the last line in your configuration file.
478
480 If babeld is invoked with the flag -g, it accepts TCP connections from
481 local clients on the given port and address ::1 (the IPv6 localhost ad‐
482 dress), or on the given UNIX-domain socket path if the argument starts
483 with ‘/’. When a client connects, babeld replies with BABEL followed
484 with the supported version of the local configuration protocol (cur‐
485 rently 1.0). This is followed with a number of informational lines
486 (version etc.), terminated by ok. The client can then send requests,
487 one per line. To each request, babeld replies with one or more lines
488 of data terminated by one of ok, no, or bad.
489 The following requests are currently defined:
491 • any configuration file directive, including interface;
493 • flush interface;
495 • dump;
497 • monitor and unmonitor;
499 • quit.
501
503 You can participate in a Babel network by simply running
504 # babeld wlan0
506 where wlan0 is the name of your wireless interface.
508 In order to gateway between multiple interfaces, just list them all on
510 the command line:
511 # babeld wlan0 eth0 sit1
513 On an access point, you'll probably want to redistribute some external
515 routes into Babel:
516 # babeld \
518 -C 'redistribute metric 256' \
519 wlan0
520 or, if you want to constrain the routes that you redistribute,
522 # babeld \
524 -C 'redistribute proto 11 ip ::/0 le 64 metric 256' \
525 -C 'redistribute proto 11 ip 0.0.0.0/0 le 24 metric 256' \
526 wlan0
527 Source-specific routing
529 If your want to redistribute kernel routes as source-specific to the
530 network, with the 2001:DB8:0:1::/64 prefix:
531 redistribute src-prefix 2001:DB8:0:1::/64
533 For more information about source-specific routing, please see
535 Matthieu Boutier and Juliusz Chroboczek. Source-sensitive rout‐
537 ing. In Proc. IFIP Networking 2015. 2015.
538 available online at
540 http://arxiv.org/pdf/1403.0445v4.pdf
542
544 /etc/babeld.conf
545 The default location of the configuration file.
546 /var/lib/babel-state
548 The default location of the file storing long-term state.
549 /var/run/babeld.pid
551 The default location of the pid file.
552 /var/log/babeld.log
554 The default location of the log file.
555
557 SIGUSR1
558 Dump Babel's routing tables to standard output or to the log
559 file.
560 SIGUSR2
562 Check interfaces and kernel routes right now, then reopen the
563 log file.
564
566 Babel is a completely insecure protocol: any attacker able to inject IP
567 packets with a link-local source address can disrupt the protocol's op‐
568 eration. This is no different from unsecured neighbour discovery or
569 ARP.
570 Usage of the -G flag allows any user logged on the local host to change
572 babeld's configuration.
573 Since Babel uses link-local IPv6 packets only, there is no need to up‐
575 date firewalls to allow forwarding of Babel protocol packets. If local
576 filtering is being done, UDP datagrams to the port used by the protocol
577 should be allowed. As Babel uses unicast packets in some cases, it is
578 not enough to just allow packets destined to Babel's multicast address.
579
581 routed(8), route6d(8), zebra(8), ahcpd(8).
582
584 Juliusz Chroboczek.
585 BABELD(8)