NAME¶
babeld - ad-hoc network routing daemon
SYNOPSIS¶
babeld option... [
-- ]
interface...
DESCRIPTION¶
Babel is a loop-avoiding distance-vector routing protocol roughly based on DSDV
and AODV, but with provisions for link cost estimation and redistribution of
routes from other routing protocols.
While it is optimised for wireless mesh networks, Babel will also work
efficiently on wired networks.
OPTIONS¶
- -m multicast-address
- Specify the link-local multicast address to be used by the
protocol. The default is ff02:0:0:0:0:0:1:6.
- -p port
- Specify the UDP port number to be used by the protocol. The
default is 6696.
- -S state-file
- Set the name of the file used for preserving long-term
information between invocations of the babeld daemon. If this file
is deleted, the daemon will run in passive mode for 3 minutes when it is
next started (see -P below), and other hosts might initially ignore
it. The default is /var/lib/babel-state.
- -h hello-interval
- Specify the interval in seconds at which scheduled hello
packets are sent on wireless interfaces. The default is 4 seconds.
- -H wired-hello-interval
- Specify the interval in seconds at which scheduled hello
packets are sent on wired interfaces. The default is 4 seconds.
- -z kind
[,factor]
- Enable diversity-sensitive routing. The value kind
defines the diversity algorithm used, and can be one of 0 (no
diversity), 1 (per-interface diversity with no memory), 2
(per-channel diversity with no memory), or 3 (per-channel diversity
with memory). The value factor specifies by how much the cost of
non-interfering routes is multiplied, in units of 1/256; the default is
128 (i.e. division by 2).
- -k priority
- Specify the priority value used when installing routes into
the kernel. The default is 0.
- -A priority
- Allow duplicating external routes when their kernel
priority is at least priority. Do not use this option unless you
know what you are doing, as it can cause persistent route flapping.
- -l
- Use IFF_RUNNING (carrier sense) when determining interface
availability.
- -w
- Don't optimise wired links, assume all interfaces are
wireless unless explicitly overridden in the configuration file.
- -s
- Do not perform split-horizon processing on wired
interfaces. Split-horizon is not performed on wireless interfaces.
- -u
- Do not flush unfeasible (useless) routes. This is useful in
order to announce more information to a front-end (see -g).
- -P
- Run in parasitic (passive) mode. The daemon will only
announce redistributed routes.
- -d level
- Debug level. A value of 1 requests a routing table dump at
every iteration through the daemon's main loop. A value of 2 additionally
requests tracing every message sent or received. A value of 3 additionally
dumps all interactions with the OS kernel. The default is 0.
- -g port
- Listen for connections from a front-end on port
port.
- -t table
- Use the given kernel routing table for routes inserted by
babeld.
- -T table
- Export routes from the given kernel routing table.
- -c filename
- Specify the name of the configuration file. The default is
/etc/babeld.conf.
- -C statement
- Specify a configuration statement directly on the command
line.
- -D
- Daemonise at startup.
- -L logfile
- Specify a file to log random ``how do you do?'' messages
to. This defaults to standard error if not daemonising, and to
/var/log/babeld.log otherwise.
- -I pidfile
- Specify a file to write our process id to. The default is
/var/run/babeld.pid.
- interface...
- The list of interfaces on which the protocol should
operate.
The configuration file is a sequence of lines each of which specifies either an
interface or a filtering rule. Blank lines are ignored. Comments are
introduced with an octothorp ``
#'' and terminate at the end of the
line.
Interface configuration¶
An interface is configured by a single line with the following format:
- interface name [parameter...]
Name is the name of the interface (something like
eth0).
Each
parameter specifies a parameter of the given interface. It can be
one of:
- wired {true|false|auto}
- This specifies whether to enable optimisations specific to
wired interfaces. By default, this is determined automatically unless the
-w command-line flag was specified.
- link-quality
{true|false|auto}
- This specifies whether link quality estimation should be
performed on this interface. The default is to perform link quality
estimation on wireless interfaces but not on wired interfaces.
- split-horizon
{true|false|auto}
- This specifies whether to perform split-horizon processing
on this interface. The default is to never perform split-horizon
processing on wireless interfaces; on wired interfaces, the default
depends on the -s flag.
- rxcost cost
- This defines the cost of receiving frames on the given
interface under ideal conditions (no packet loss); how this relates to the
actual cost used for computing metrics of routes going through this
interface depends on whether link quality estimation is being done. The
default is 96 for wired interfaces, and 256 for wireless ones.
- channel channel
- Sets the channel for this interface. The value
channel can be either an integer, or one of the strings
interfering or noninterfering. The default is to autodetect
the channel number for wireless interfaces, and noninterfering for
wired interfaces.
- faraway {true|false}
- This specifies whether the network is "far away",
in the sense that networks behind it don't interfere with networks in
front of it. By default, networks are not far away.
- hello-interval interval
- This defines the interval between hello packets sent on
this interface. The default is specified with the -h and -H
command-line flags.
- update-interval interval
- This defines the interval between full routing table dumps
sent on this interface; since Babel uses triggered updates and doesn't
count to infinity, this can be set to a fairly large value, unless
significant packet loss is expected. The default is four times the hello
interval.
Filtering rules¶
A filtering rule is defined by a single line with the following format:
- filter selector... action
Filter specifies the filter to which this entry will be added, and can be
one of
in,
out, or
redistribute.
Each
selector specifies the conditions under which the given statement
matches. It can be one of
- ip prefix
- This entry only applies to routes in the given prefix.
- eq plen
- This entry only applies to routes with a prefix length
equal to plen.
- le plen
- This entry only applies to routes with a prefix length less
or equal to plen.
- ge plen
- This entry only applies to routes with a prefix length
greater or equal to plen.
- neigh address
- This entry only applies to routes learned from a neighbour
with link-local address address.
- id id
- This entry only applies to routes originated by a router
with router-id id.
- proto p
- This entry only applies to kernel routes with kernel
protocol number p. If neither proto nor local is
specified, this entry applies to all non-local kernel routes with a
protocol different from "boot".
- local
- This entry only applies to local addresses.
- if interface
- For an input filter, this specifies the interface over
which the route is learned. For an output filter, this specifies the
interface over which this route is advertised. For a redistribute
statement, this specifies the interface over which the route forwards
packets.
Action specifies the action to be taken when this entry matches. It can
have one of the following values:
- allow
- Allow this route, without changing its metric (or setting
its metric to 0 in case of a redistribute filter).
- deny
- Ignore this route.
- metric value
- For an input or output filter, allow this route after
increasing its metric by value. For a redistribute filter,
redistribute this route with metric value.
If
action is not specified, it defaults to
allow.
By default,
babeld redistributes all local addresses, and no other
routes. In order to make sure that only the routes you specify are
redistributed, you should include the line
- redistribute local deny
as the last line in your configuration file.
EXAMPLES¶
You can participate in a Babel network by simply running
- # babeld wlan0
where
wlan0 is the name of your wireless interface.
In order to gateway between multiple interfaces, just list them all on the
command line:
- # babeld wlan0 eth0 sit1
On an access point, you'll probably want to redistribute some external routes
into Babel:
- # babeld \
-C 'redistribute metric 256' \
wlan0
or, if you want to constrain the routes that you redistribute,
- # babeld \
-C 'redistribute proto 11 ip ::/0 le 64 metric 256' \
-C 'redistribute proto 11 ip 0.0.0.0/0 le 24 metric 256' \
wlan0
FILES¶
- /etc/babeld.conf
- The default location of the configuration file.
- /var/lib/babel-state
- The default location of the file storing long-term
state.
- /var/run/babeld.pid
- The default location of the pid file.
- /var/log/babeld.log
- The default location of the log file.
SIGNALS¶
- SIGUSR1
- Dump Babel's routing tables to standard output or to the
log file.
- SIGUSR2
- Check interfaces and kernel routes right now, then reopen
the log file.
SECURITY¶
Babel is a completely insecure protocol: any attacker able to inject IP packets
with a link-local source address can disrupt the protocol's operation. This is
no different from unsecured neighbour discovery or ARP.
Since Babel uses link-local IPv6 packets only, there is no need to update
firewalls to allow forwarding of Babel protocol packets. If local filtering is
being done, UDP datagrams to the port used by the protocol should be allowed.
As Babel uses unicast packets in some cases, it is not enough to just allow
packets destined to Babel's multicast address.
BUGS¶
Plenty. This is experimental software, run at your own risk.
SEE ALSO¶
routed(8),
route6d(8),
zebra(8),
ahcpd(8).
AUTHOR¶
Juliusz Chroboczek.
