dhclient assigns all interfaces connected to a bridge addresses

[Thomas Schweikle]

After the bridge is up, dhclient assigns all interfaces connected to the bridge an IP address. This breaks networking: two (or more) default routes, two (or more) interfaces assigned the same address. In some cases: interfaces configured static are assigned dynamic addresses (absolutely unwanted!). After cleaning up the mess, dhclient produced, all is fine again --- until your leases expire ...

dhclient should only assign addresses to interfaces given on commandline!

I found this bug with maverik and lucid (bug report #677152)

Network setup:
manual eth0
iface eth0 inet manual
  pre-up ifconfig eth0 0.0.0.0 promisc up
  ...

auto vb0
iface vb0 inet manual
  pre-up ifup eth0
  pre-up brctl addbr vb0
  pre-up brctl addif vb0 eth0
  pre-up dhclient vb0
  ...

root@ivory:~# dhclient3 -e IF_METRIC=100 -pf /var/run/dhclient.vb0.pid -lf /var/lib/dhcp3/dhclient.vb0.leases vb0
There is already a pid file /var/run/dhclient.vb0.pid with pid 1805
removed stale PID file
Internet Systems Consortium DHCP Client V3.1.3
Copyright 2004-2009 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Listening on LPF/eth0/00:1e:68:06:4b:e9
Sending on LPF/eth0/00:1e:68:06:4b:e9
Listening on LPF/vb0/00:1e:68:06:4b:e9
Sending on LPF/vb0/00:1e:68:06:4b:e9
Sending on Socket/fallback
DHCPREQUEST of 192.168.1.113 on eth0 to 255.255.255.255 port 67
DHCPREQUEST of 192.168.1.113 on vb0 to 255.255.255.255 port 67
DHCPACK of 192.168.1.113 from 192.168.1.1
bound to 192.168.1.113 -- renewal in 1382 seconds.
root@ivory:~# route -n
Kernel-IP-Routentabelle
Ziel Router Genmask Flags Metric Ref Use Iface
172.16.38.0 0.0.0.0 255.255.255.0 U 0 0 0 vmnet8
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 vb0
172.16.31.0 0.0.0.0 255.255.255.0 U 0 0 0 vmnet1
0.0.0.0 192.168.1.1 0.0.0.0 UG 100 0 0 vb0
0.0.0.0 192.168.1.1 0.0.0.0 UG 100 0 0 eth0
root@ivory:~# ifconfig eth0
eth0 Link encap:Ethernet Hardware Adresse 00:1e:68:06:4b:e9
          inet Adresse:192.168.1.113 Bcast:192.168.1.255 Maske:255.255.255.0
          inet6-Adresse: fe80::21e:68ff:fe06:4be9/64 Gültigkeitsbereich:Verbindung
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metrik:1
          RX packets:7865272 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4017664 errors:0 dropped:0 overruns:0 carrier:0
          Kollisionen:0 Sendewarteschlangenlänge:1000
          RX bytes:11925842333 (11.9 GB) TX bytes:287765516 (287.7 MB)
          Interrupt:18

root@ivory:~# ifconfig vb0
vb0 Link encap:Ethernet Hardware Adresse 00:1e:68:06:4b:e9
          inet Adresse:192.168.1.113 Bcast:192.168.1.255 Maske:255.255.255.0
          inet6-Adresse: fe80::21e:68ff:fe06:4be9/64 Gültigkeitsbereich:Verbindung
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metrik:1
          RX packets:7841208 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4018042 errors:0 dropped:0 overruns:0 carrier:0
          Kollisionen:0 Sendewarteschlangenlänge:0
          RX bytes:11784284373 (11.7 GB) TX bytes:271726107 (271.7 MB)

root@ivory:~# brctl show
bridge name bridge id STP enabled interfaces
vb0 8000.001e68064be9 no eth0

ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: dhcp3-client 3.1.3-2ubuntu6
ProcVersionSignature: Error: [Errno 2] No such file or directory: '/proc/version_signature'
Uname: Linux 2.6.35.8 x86_64
Architecture: amd64
Date: Thu Nov 18 20:12:51 2010
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.35.8 root=UUID=e8a84ed2-696e-4c59-b2c6-0df091211846 ro splash
ProcEnviron:
 LANG=de_DE.utf8
 SHELL=/bin/bash
SourcePackage: dhcp3

[Thomas Schweikle (tps)]

dhclient-versions between maverick and lucid match --- looks as if it is the very same bug! I've marked the lucid one as being duplicate (#677152)

[Thomas Schweikle (tps)]

This is a bug, not an "Opinion". Just configure your system this way, wait on dhcp assigning an address and then loose network connectivity. If it where an "Opinion" I'd suspect not to lose network connectivity.

[Thomas Schweikle (tps)]

To avoid this problem: I've switched to pump not having this bug. Only the interface given will be assigned an address. Not all connected interfaces! dhclient is broken if it assigns identical addresses to all connected interfaces. It only has to assign one address to the given interface!