[ovs-discuss] Arp problem on vlan

[Jesse Gross]

On Tue, Oct 25, 2011 at 10:25 AM, olivier Blanc <
olivier.blanc at dgfip.finances.gouv.fr> wrote:

> **
> I am trying to setup a simple test case with openvswitch but im having
> trouble with arp reply.
> Here is my configuration
> On host A I have a bridge hosting vm interface tagged on vlan 2
> ovs-vsctl add-port br0 vif1.0 tag=2
>
> On host B i have a simple bridge hosting an internal interface tagged on
> vlan 2 and configured with IP on same network than my vm interface.
> The interface was added whith the following command :
> ovs-vsctl add-port br0 vlan2 tag=2 -- set Interface vlan2 type=internal
>
> when trying to ping my VM interface from host B, I have no answer from my
> VM.
>

The packet captures that you're giving don't make a lot of sense because
they don't correspond to the same packet.


> while dumping network on my VM, I can see the the arp request and the arp
> reply :
> 19:11:13.504167 arp who-has 172.3.0.2 tell 172.3.0.1
> 19:11:13.504925 arp reply 172.3.0.2 is-at 00:16:3e:68:3c:96 (oui Unknown)
>

This looks somewhat right except that the MAC address doesn't correspond to
the one below and an incorrectly transmitted packet should not be received
correctly.


> On host B, tcpdump gives me the following errors :
> On the ethernet driver eth1, here is the dump
> 19:12:25.332533 arp who-has 172.3.0.2 tell 172.3.0.1
> 19:12:25.332947 IP0 bad-len 2
>
> Extract from wireshark : Byte offset hex dump
> 0000  00 23 20 d9 d2 d9 00 16  3e 68 00 01 08 00 06 04   .# ..... >h......
> 0010  00 02 00 16 3e 68 81 00  00 02 3c 96 ac 03 00 02   ....>h.. ..<.....
> 0020  00 23 20 d9 d2 d9 ac 03  00 01 00 00 00 00 00 00   .# ..... ........
> 0030  00 00 00 00 00 00 00 00
>
> decoded as
> 40 1079.705000 Xensourc_68:00:01 NiciraNe_d9:d2:d9 IP Bogus IP length (2,
> less than header length 24)
>

According to your capture above this should be an ARP response but it's not
because it's IP based.


> On the bridge br0 on Host B, here is the error :
> 19:13:22.173626 arp who-has 172.3.0.2 tell 172.3.0.1
> 19:13:22.174523 20:d9:d2:d9:00:16 (oui Unknown) > ff:ff:00:23:00:23 (oui
> Unknown), ethertype Unknown (0x3e68), length 60:
> 0x0000:  0001 0800 0604 0002 0016 3e68 8100 0002  ..........>h....
> 0x0010:  3c96 ac03 0002 0023 20d9 d2d9 ac03 0001  <......#........
> 0x0020:  0000 0000 0000 0000 0000 0000 0000       ..............
>

This is offset from the correct start of the packet, which is why it appears
wrong.  However, this is captured before the packet actually ingresses into
Open vSwitch.

I think you need to actually look at a single packet in all places and see
where it goes bad.
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