Re: [Bridge] 802.1q tagging broken when used with bridging in 2.6.38

[Jiri Pirko <jpirko@redhat.com>]

Tue, Mar 29, 2011 at 09:18:44PM CEST, andy@greyhouse.net wrote:
>On Tue, Mar 29, 2011 at 2:36 PM, Jiri Pirko <jpirko@redhat.com> wrote:
>> Tue, Mar 29, 2011 at 06:54:58PM CEST, andy@greyhouse.net wrote:
>>>On Mon, Mar 28, 2011 at 1:54 PM, igor serebryany <igor47@moomers.org> wrote:
>>>> it appears that 802.1q tagging is broken in 2.6.38 when combined with bridging.
>>>> here is how to reproduce the problem:
>>>>
>>>> i set up an interface for the machine running 2.6.38 on my cisco router, and
>>>> assign a subnet to that interface. i am using ping from the router to do the
>>>> testing. i am getting all the data here with 'tcpdump -e -n' from the machine.
>>>>
>>>> i ping the machine from the router, and i see properly-tagged ARP requests
>>>> coming in on eth0:
>>>>
>>>> 12:12:05.052465 00:11:20:dd:81:00 > ff:ff:ff:ff:ff:ff, ethertype 802.1Q
>>>> (0x8100), length 64: vlan 234, p 0, ethertype ARP, Request who-has 10.0.0.206
>>>> tell 10.0.0.205, length 46
>>>>
>>>> i then create a vlan interface on the machine:
>>>>
>>>> vconfig add eth0 234
>>>> ifconfig eth0.234 up
>>>>
>>>> i tcpdump the newly-created interface, and i see the arp packets appearing on
>>>> it, now properly untagged
>>>>
>>>> 12:14:33.549939 00:11:20:dd:81:00 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806),
>>>> length 60: Request who-has 10.0.0.206 tell 10.0.0.205, length 46
>>>>
>>>> if i assign an ip to this interface, i can see pings being exchanged on eth0.234
>>>>
>>>> 12:17:12.681079 00:11:20:dd:81:00 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806),
>>>> length 60: Request who-has 10.0.0.206 tell 10.0.0.205, length 46
>>>> 12:17:12.681090 00:30:48:fd:98:d8 > 00:11:20:dd:81:00, ethertype ARP (0x0806),
>>>> length 42: Reply 10.0.0.206 is-at 00:30:48:fd:98:d8, length 28
>>>> 12:17:14.682076 00:11:20:dd:81:00 > 00:30:48:fd:98:d8, ethertype IPv4 (0x0800),
>>>> length 114: 10.0.0.205 > 10.0.0.206: ICMP echo request, id 24, seq 1, length 80
>>>> 12:17:14.682088 00:30:48:fd:98:d8 > 00:11:20:dd:81:00, ethertype IPv4 (0x0800),
>>>> length 114: 10.0.0.206 > 10.0.0.205: ICMP echo reply, id 24, seq 1, length 80
>>>>
>>>> now, i want to assign eth0 to a bridge
>>>>
>>>> brctl addbr xenbr0
>>>> ifconfig xenbr0 up
>>>> brctl addif xenbr0 eth0
>>>>
>>>> i now attempt to ping the machine again. watching tcpdump on eth0.234, i don't
>>>> see any of my packets anymore!
>>>>
>>>> instead, if i watch xenbr0 with tcpdump, i can see the tagged packets being
>>>> dumped straight into xenbr0, without the vlan tags stripped out!
>>
>> Yep, that seems expected. rx_handler for bridge is earlier in rx path
>> than vlan processing. This is was not changed in 2.6.38. This is with us
>> for a long time. I plan to refuse this topo in future (not sure yet
>> thought)
>>
>
>I have no idea what version Igor was using before.  Even if Igor's
>upgrade as not from 2.6.37, this sounds like a regression.

Well, one commit I'm thinking of which might cause this "regression"
(athought I do not see that as one) is this:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=3701e51382a026cba10c60b03efabe534fba4ca4

cc'ing Jesse.

Anyway. I think that on non-hw-accel vlans this is the same all the
time as it is now.


Jirka