From: Ben Greear <greearb@candelatech•com>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: netdev <netdev@vger•kernel.org>
Subject: Re: More details on why received UDP packets are treated as errors?
Date: Wed, 07 Aug 2013 17:10:35 -0700 [thread overview]
Message-ID: <5202E1FB.8020405@candelatech.com> (raw)
In-Reply-To: <1375129292.10515.21.camel@edumazet-glaptop>
On 07/29/2013 01:21 PM, Eric Dumazet wrote:
> On Mon, 2013-07-29 at 11:21 -0700, Ben Greear wrote:
>> We have a test case on 3.9.9+ (local patches applied) where sending from
>> VETH interface, through peer VETH bridged (with our own emulator bridge module)
>> to physical interface, which is then looped to another physical interface (B).
>> The VETH and the wired B interface are sending UDP traffic to each other.
>> Routing rules should be configured such that this all works appropriately.
>>
>> Replacing our bridging module with a user-space bridge has same behaviour.
>>
>> This setup works on the 3.7.y kernel, but we only get one-way traffic
>> (B to VETH) on 3.9.9+.
>>
>> I sniffed the B port, and traffic appears to be sent and received
>> properly (ie, no checksum errors, etc). But, our user-space app
>> shows no received UDP frames on B, and netstat -s gives the
>> output below.
>>
>> Is there any way to get more details about what these 'packet receive errors'
>> are caused by using normal-ish tools?
>
> You could try dropwatch for this kind of obscure drops
>
> https://fedorahosted.org/dropwatch/
I had a chance to crank this up today.
dropwatch is pretty sweet...turns out it's dropping due to bad UDP checksums,
due to the VETH bug/issue where it claims to calculate HW checksum but appearantly does
not actually do so (see previous email in another thread).
Thanks,
Ben
--
Ben Greear <greearb@candelatech•com>
Candela Technologies Inc http://www.candelatech.com
prev parent reply other threads:[~2013-08-08 0:10 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-29 18:21 More details on why received UDP packets are treated as errors? Ben Greear
2013-07-29 20:21 ` Eric Dumazet
2013-07-30 20:38 ` Benjamin Poirier
2013-08-08 0:10 ` Ben Greear [this message]
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