NAME
guessnet - guess which LAN a network interface is connected to
SYNOPSIS
guessnet [options] [network_interface]
DESCRIPTION
Guessnet guesses which LAN a network interface is connected to. Given
a list of candidate profiles each of which includes a test description,
guessnet runs all the tests in parallel and prints the name of the
profile whose test was the first one to succeed. If no test succeeds
within a certain timeout period then a default profile name is printed.
After printing a profile name, guessnet immediately kills any tests
that are still running and exits.
Candidate profiles are read either from a test description file or, in
ifupdown mode, from /etc/network/interfaces.
OPTIONS
Options follow the usual GNU conventions. In ifupdown mode, options
can also be specified on the standard input in the form
"<long-option-name>: <value>".
-C, --config-file=filename
Name of the configuration file to use if not specified on
command line. Default: standard input or
/etc/network/interfaces in ifupdown mode.
--autofilter
Only useful when operating in ifupdown mode (see below).
Instructs guessnet to only consider logical interface names that
start with physical interface name being mapped. (ie: eth0-home
only matches when mapping eth0) Default: false.
--debug
Print debugging messages.
-d, --default=string
Interface name to print if no known networks are found.
Default: none.
--help Show a brief summary of command line options.
-i, --ifupdown-mode
Operate in ifupdown mode: parse the input as if it is in the
format of /etc/network/interfaces and read from
/etc/network/interfaces instead of the standard input if the
configuration filename is not specified. See the ifupdown mode
section below for details.
--init-time=int
Time in seconds to wait for the interface to initialize when it
is not found already up at program startup. Default: 3 seconds.
--init-delay=int
Sleep a given number of seconds before starting operations. May
be useful in case interface driver needs a little time to settle
before reacting to commands. Default: 0 seconds.
--iwscan-tries=int
Retry wireless network scanning a given amount. Useful if your
driver needs some attempts to return a network list. Default:
1.
--syslog
Send messages to syslog facility DAEMON, in addition to stderr.
-t, --timeout=int
Timeout in seconds used to wait for tests to terminate.
Default: 5 seconds.
-v, --verbose
Operate verbosely.
--version
Show the version number of the program.
TEST DESCRIPTION FILE
guessnet takes as input a description of the tests it should perform.
The test description file looks like this:
# Empty lines and lines starting with ’#’ are ignored.
# Other lines contain:
# <profile-name> <test-method> <parameters>
# At home, look for a host with the given IP and MAC address
home peer 192.168.1.1 00:01:02:03:04:05
# At the university, check for the presence of at least one
# of the following hosts
university peer 130.136.1.1 05:06:03:02:01:0A
university peer 130.136.1.2 15:13:B3:A2:2F:CD
# If the peer doesn’t reply to ARP packets coming from 0.0.0.0
# then you can additionally specify a source address to use
university peer 130.136.1.2 15:13:B3:A2:2F:CD 130.136.1.250
# For the work network use a custom script
work command /usr/local/bin/check_work
# Commands are executed by "sh -c" so shell syntax can be used
john-irda command grep -q ‘cat ~enrico/john-irda-id‘ /proc/net/irda/discovery
# Location name and interface name are exported in NAME and IFACE
weirdnet command /usr/local/bin/weirddetect "$NAME" "$IFACE"
# Profile "none" is selected if no network signal is detected
# (i.e. there is no cable plugged into the socket)
no-net missing-cable
# Match a wireless network with the given essid
home wireless essid Home
# You can also match the mac address of the access point
home wireless mac 01:02:03:04:0A:0B
# Or both
home wireless essid Home mac 01:02:03:04:0A:0B
# You can also match any open network
anyopen wireless open
Every non-comment line represents a test to perform.
The first word in the line is the name that will be printed if the test
succeeds.
The second word is the test type.
The remainder of the line contains parameters for the selected test;
these vary depending on the test type.
IFUPDOWN MODE
ifupdown, Debian’s standard network configuration system, permits one
to define different "logical interfaces" (ifupdown’s name for
configuration profiles) and to choose among them when one configures a
network interface. The choice can be delegated to an external
"mapping" program. guessnet can be used as such a program if it is run
in "ifupdown mode". guessnet runs in ifupdown mode if it is invoked as
guessnet-ifupdown or if it is given the --ifupdown-mode option.
In ifupdown mode guessnet reads test data directly from the logical
interface definitions in /etc/network/interfaces rather than from a
separate test description file.
In ifupdown mode if names are passed to guessnet on its standard input
then guessnet considers only those logical interface definitions;
otherwise it considers them all. You can have ifupdown deliver data to
guessnet’s standard input using the map directive. See interfaces(5)
for more information. If names are preceded with "!" character then
match is inverted, meaning that all logical interfaces will be
processed except for the ones specified in standard input. You cannot
mix normal and negated interface names in the same mapping directive.
Note: when using autofilter option (see above) you can broaden or
tighten the automatic matching by specifying interface names as
descripted.
In ifupdown mode options are selected by passing "<long-option-name>:
<value>" on guessnet’s standard input. This feature is provided
because ifupdown cannot pass command line arguments to mapping scripts.
If you prefer you can precede the test keyword in
/etc/network/interfaces with the word guessnet.
ifupdown does not allow two option lines in /etc/network/interfaces to
start with the same word. To work around this limitation, multiple
test (or guessnet) lines can have different numerals suffixed to their
initial keywords (test1, test2, or guessnet1, guessnet2, and so on).
Here’s an example of an /etc/network/interfaces file that has been set
up for guessnet:
auto lo eth0
iface lo inet loopback
mapping eth0
script guessnet-ifupdown
# Scan all logical interfaces
# More options can be given here, such as:
# map timeout: 10
# map verbose: true
# map debug: true
# map iwscan-tries: 23
map default: none
mapping eth1
script guessnet-ifupdown
# Disable open net checking, just comment out if you are
# desperate enough :) (see relative stanza below)
map !eth1-anyopen
# Scan only logical interfaces named eth1-*
autofilter: true
iface home inet static
address 192.168.1.2
netmask 255.255.255.0
broadcast 192.168.1.255
gateway 192.168.1.1
# Lines for resolvconf (if you use it: see apt-cache show resolvconf)
# dns-search casa
# dns-nameservers 192.168.1.1 192.168.2.1
# Two tests, in case one of the two machines is down when we test
test1 peer address 192.168.1.1 mac 00:01:02:03:04:05
test2 peer address 192.168.1.3 mac 00:01:02:03:04:06
iface work inet static
address 10.1.1.42
netmask 255.255.255.0
broadcast 10.1.1.255
gateway 10.1.1.1
test command /usr/local/bin/check_work
iface work2 inet static
address 192.168.2.23
netmask 255.255.255.0
broadcast 192.168.2.255
gateway 192.168.2.1
# A source address has to be specified in case the peer
# doesn’t reply to ARP packets coming from 0.0.0.0
test peer address 192.168.2.1 mac 00:01:02:03:04:05 source 192.168.2.23
iface eth1-home inet static
wireless-essid Home
wireless-key s:myverysecret
address 192.168.1.5
netmask 255.255.255.0
gateway 192.168.1.1
dns-nameservers 192.168.1.1
# Match a wireless network with the given essid
test wireless essid Home
# You can also match the mac address of the access point
#test wireless mac 01:02:03:04:0A:0B
# Or both
#test wireless essid Home mac 01:02:03:04:0A:0B
iface eth1-work inet dhcp
wireless-essid Work
wireless-key s:myverysecretkey
# Match a wireless network with the given essid
# If you have spaces in the essid, use double quotes
test wireless essid "Work place"
iface eth1-anyopen inet dhcp
# You can also match any open network, if you are desperate :)
wireless-essid any
wireless-mode auto
test wireless open
# If nothing else is found, try DHCP
iface none inet dhcp
Supported tests
peer
Test description file syntax:
profile peer IP-address [MAC-address] [IP-address]
Ifupdown mode syntax:
test peer address IP-address [mac MAC-address] [source
IP-address]
Description:
Look for peer using ARP. The test will succeed if a network
interface with the specified IP address (and MAC address if
specified) is connected to the local network.
One can omit the MAC address, in which case guessnet only tests
for the presence of a host with the specified IP address.
If the peer whose presence you want to test for refuses to reply
to ARP packets coming from 0.0.0.0 then specify some source IP
address from which the peer will accept requests.
Multiple peers can be specified (on multiple lines) but each
peer must have a different IP address. This restriction may be
eliminated in the future.
You can also omit the IP address and only use the MAC: that is
useful to test for the existance of physical interfaces with
changing IP addresses. This kind of scan uses an ICMP ping
packet requires a source address in most cases, as hosts tend
not to reply to pings coming from nowhere.
wireless
Test description file syntax:
profile wireless [essid essid] [mac MAC-address] [open|closed]
Ifupdown mode syntax:
test wireless [essid essid] [mac MAC-address] [open|closed]
Description:
Perform a wireless scan like iwlist scan does, and match the
results.
The test succeeds if the scan reports at least one network for
which all the tests (essid, mac of the access point, network is
open or closed) match.
In case more than one profile matches a network, only the first
one, as found in the configuration file, will succeed. This
allows to prioritise profiles: for example, you can prefer your
home access point to an open network by listing it first in the
configuration file.
missing-cable
Test description file syntax:
profile missing-cable
Ifupdown mode syntax:
test missing-cable
Description:
Check for link beat. The test is successful if link beat is not
detected.
This feature allows guessnet to detect the case where there is
no cable plugged into a network socket; in this case it makes no
sense to go through other detection phases.
This test can be used in ifupdown mode too if a dummy logical
interface is defined that includes the test missing-cable
option. Bear in mind that when the cable is unplugged, ifupdown
will consider the interface to be configured as this dummy
logical interface. That is somewhat counterintuitive; one might
prefer the interface to be deconfigured in that case.
Unfortunately, guessnet is not currently able to tell ifup to
refrain from configuring an interface. The problem can be
solved, however, by means of the ifplugd(8) program.
Link beat detection is not supported on all network hardware.
If the interface or its driver does not support link beat
detection then this test does not succeed.
command
Test description file syntax:
profile command command
Ifupdown mode syntax:
test command command
Description:
Test using an arbitrary command. The test is considered
successful if the command terminates with exit status 0.
Location name and interface name are exported to the script via
the NAME and IFACE environment variables.
For backward compatibility, script can be used instead of
command.
Experimental tests
pppoe
Test description file syntax:
profile pppoe
Ifupdown mode syntax:
test pppoe
Description:
Use the pppoe program to send PADI packets in order to look for
access concentrators. The test should succeed if a PPPOE modem
is present on the given interface.
Using this test requires that pppoe be installed on the system.
wireless
Test description file syntax:
profile wireless [mac MAC-address] [essid ESSID]
Ifupdown mode syntax:
test wireless [mac MAC-address] [essid ESSID]
Description:
Test certain properties of the wireless interface. More
specifically, test the MAC address and/or the ESSID of the
associated access point. If both are given then MAC-address
must precede ESSID.
Blanks may be included in the ESSID. For example,
prof1 wireless essid My LAN
tests for an ESSID of "My LAN".
Note that the wireless test does not attempt to change these
properties; it only examines them. This test is designed to
work with programs such as waproamd which independently and
dynamically manage the wireless network adapter to keep it
associated to an access point.
Note that the wireless test is not yet implemented cleanly.
Note that if one of several tests terminates successfully then any
other tests still running will be terminated with the KILL signal.
Therefore, test programs should not need to do any special cleanup on
exit.
NOTES
Getting remote host MAC addresses
When you prepare the test data for guessnet you may need to know the
MAC address of a remote interface in the local network. There are
various ways to obtain this. The easiest is to use the arping utility
by doing "arping [hostname]". If you don’t have arping installed on
your system then try the command "arp -a [hostname]" which will display
the MAC address if it is in the ARP cache of your machine. You might
want to ping the remote interface first to make sure that you have the
information in the cache. You can also take a look at the
/usr/share/doc/guessnet/examples/getmac script.
Multiple tests
Currently guessnet only supports specifying one kind of test per
profile.
SEE ALSO
ifup(8), interfaces(5), arping(8), sh(1), pppoe(8), ifplugd(8).
AUTHOR
Guessnet was written by Enrico Zini <enrico@debian.org> with
contributions from Thomas Hood. The ARP network detection code was
taken from laptop-netconf by Matt Kern <matt@debian.org>, which in turn
in based on divine by Felix von Leitner <felix@fefe.de>.
The Guessnet webpage is at http://guessnet.alioth.debian.org .
4 November 2007