[Bug 684424] [NEW] Bridges are not transparent for packets

[Thomas Schweikle]

Public bug reported:

Setup:

maverick (latest updates applied), libvirtd, kvm.

Host network setup:
br0, bridge-port eth0, ip assigned to br0.
eth0 up, promisc-mode.

br0-address: 192.168.1.4
br0-default gw: 192.168.1.1
br0-netmask: 255.255.255.192
br0-broadcast: 192.168.1.63

kvm added interface:
vnc0 up (this interface is not in promisc mode).

from the host:
ping 192.168.1.1 succeeds.

protocols using only mac (like NetBIOS) work. Devices connected to the
host are usable.

-----

Within the virtual machine:
br0, bridge-port eth0, ip assigned to br0.
eth0 up, promiscuous-mode.

br0-address: 192.168.1.46
br0-default gw: 192.168.1.1
br0-netmask: 255.255.255.192
br0-broadcast: 192.168.1.63

within the virtual machine:
ping 192.168.1.4 succeeds.
ping 192.168.1.1 fails.

protocols using only mac (like NetBIOS) do not reach any device
connected to the host via Ethernet.

-----

various further testing gave:
mac broadcasts from the guest are seen by the host, but not by any device connected to the host.
The bridge is not transparent to mac broadcasts. But this is something a bridge *has* to be!!
A bridge is defined to be transparent. Packets are transparently passed, regardless of where they come from or they go to.

ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: libvirt-bin 0.8.3-1ubuntu14
Uname: Linux 2.6.35.9 x86_64
Architecture: amd64
Date: Thu Dec  2 21:17:02 2010
ProcEnviron:
 PATH=(custom, user)
 LANG=de_DE.utf8
 SHELL=/bin/bash
SourcePackage: libvirt

** Affects: libvirt (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug maverick

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https://bugs.launchpad.net/bugs/684424

Title:
  Bridges are not transparent for packets