Have had a look on both tcpdump captures.
1. From the OpenWRT domU: nothing special. Lot of STP traffic due to my
network architecture. Don't thing this could be the cause of my problem
since I'm always able to reproduce the failure whatever could be the
order of DNS requests. Don't see "big" DNS answers coming in, see
multiple requests before timeout.
2. From my gateway: nothing special here too. Same STP traffic (have
checked GW network setup as well). See each DNS requests my domU sent
and can see as well answers, which are not received by domU. No strange
ARP traffic.
I wanted to change the network, thinking about a bogus driver (never
know). My Dom0 has crashed during reboot and I've no way to remotely
reboot it (no remote power control and it seems that Magic SysRQ are not
transfered through my Putty/screen connection).
Will reboot it when at home and continue investigation with another
network card and maybe another operating system to check if bad
behaviour is still there.
Regards,
JB
Le 12/01/2011 23:18, Jean Baptiste Favre a écrit :
> Ok, my bad. Screen IS available on OpenWRT.
> I've added it to my disk image and now have a tcpdump capture of network
> traffic of my DomU
>
> Have the same network capture from my GW so I 'll be able to investigate
> deeper.
>
> Let me know if you have specific points you want me to look at.
>
> Regards,
> JB
>
>
> Le 12/01/2011 22:46, Jean Baptiste Favre a écrit :
>> Le 12/01/2011 22:40, Konrad Rzeszutek Wilk a écrit :
>>> On Wed, Jan 12, 2011 at 09:07:30PM +0100, Jean Baptiste Favre wrote:
>>>> Le 12/01/2011 19:32, Konrad Rzeszutek Wilk a écrit :
>>>>>>
>>>>>> Finally, I think that my setup shall not be responsible for the fact
>>>>>> that ping works, small DNS answers are received but not bigger ones
>>>>>
>>>>> Aah, somehow I missed that fact.
>>>>
>>>> Seems yes :)
>>>>
>>>>>> (limit seems to be around 100 bytes).
>>>>>
>>>>> What does wireshark or tcpdump tell you when you send the larger packets?
>>>>
>>>> That's one of my problem: nothing special :(
>>>>
>>>> I can only run tcpdump on my gateway (no SSH available on my OpenWRT
>>>> domU and only xm console access is available).
>>>
>>> You can install (or just compile it statically) tcpdump on your OpenWRT,
>>> or just hook it up to a beffier guest..
>>
>> tcpdump is available on my OpenWRT domU, but I can not perform tcpdump
>> and DNS lookup with only console access and AFAIK screen is not
>> available on OpenWRT
>>
>>>> I see DNS requests comming in, I see DNS answers going out.
>>>> ARP requests are fine.
>>>>
>>>> As an example:
>>>> dig free.fr works
>>>> dig jbfavre.org works
>>>> dig amazon.fr works
>>>> dig amazon.com works (quite long, but works)
>>>> dig google.fr fails
>>>> dig google.com fails
>>>
>>> Fails as in response or fails halfway?
>>
>> Fails as in:
>> # dig google.com
>>
>> ; <<>> DiG 9.7.2-P3 <<>> google.com
>> ;; global options: +cmd
>> ;; connection timed out; no servers could be reached
>>
>>>>
>>>> >From another machine in the same LAN, all requests work fine.
>>>>
>>>> Thought this was due to some ARP restriction setted up by default in
>>>> OpenWRT, but in this case, I can not explain why some DNS lookup do work
>>>> and some don't.
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