Package: ifupdown
Version: 0.6.4-4
ifup has a subtle but annoying problem when used with dhclient3. The
problem is to do with environment variable setting.
The version of DHCP I have tested this with is:
Source: dhcp3
Version: 3.0+3.0.1rc9-2.2
When the dhcp method is used ifup passes IF_xxx environment variables
representing the configuration stanzas to the dhcp program, eg:
iface eth1 inet dhcp
metric 10
results in /sbin/dhclient3 being called with this in the environment:
IF_METRIC=10
However, dhclient3 does not pass arbritary environment variables on to
the client configuration script. Instead it has some command line
syntax to allow you to specify env vars and their values:
dhclient3 -e IF_METRIC=10 eth1
Without the argument the env var is not passed through and
consequently the dhclient-script does not get a chance to use stanzas
from the interfaces definition, eg: IF_METRIC.
I think that ifup, for the dhclient3 case, should work out what env
vars it has set on the environment and then do this:
dhclient3 -e IF_xxx=$IF_xxx -e ... ethX
where IF_xxx is one of the env vars ifup has set.
I think this would work because the following manual config of ifup
works:
iface eth1 inet manual
metric 10
up dhclient3 -e IF_METRIC=$IF_METRIC \
-pf /var/run/dhclient.eth1.pid \
-lf /var/run/dhclient.eth1.leases eth1
But the fact that ifup works via a config file (I mean inet.dfn) looks
like it might present a real problem in getting this right (because
code to work out the env vars might be hard to add for just
dhclient3).
The only solution I can think of is changing the inet.dfn for
dhclient3 to provide the env vars. I'm not sure of the syntax
limitations of the file... maybe this would be ok:
up
[[ifconfig %iface% hw %hwaddress%]]
dhclient3 $(set | awk '/IF_/ { print "-e " $1 "=$" $1 " " }') \
-pf /var/run/dhclient.%iface%.pid -lf /var/run/dhclient.%iface%.leases
%iface% \
if (execable("/sbin/dhclient3"))
.
.
.
If that's not possible then an ifupdown package supplied shell script
could call dhclient3 with the correct -e ... statements.
I mean a script like this:
#!/bin/sh
ENVVARS=$(set | awk '/IF_/ { print "-e " $1 "=$" $1 " " }')
dhclient3 $ENVVARS $*
# End.
Nic Ferrier
http://www.tapsellferrier.co.uk
PS I've taken a look at the ifup source code and it is way too
complicated for me to change. A large part of the reason for that is
the documentation system (a neat idea but it stops idle patches from
people like me).
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