lkml.org 
[lkml]   [2016]   [Jun]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: IP ID check (flush id) in inet gro receive is necessary or not?
From
Date
On 2016/6/28 12:57, Eric Dumazet wrote:
> On Tue, 2016-06-28 at 12:40 +0800, Tan Xiaojun wrote:
>> Hi everyone,
>>
>> I'm sorry to bother you. But I was confused.
>>
>> The IP ID check (flush_id) in inet_gro_receive is only used by
>> tcp_gro_receive, and in tcp_gro_receive we have tcphdr check to ensure
>> the order of skbs,
>> like below:
>>
>> flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
>> flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
>>
>> So if I remove the IP ID check in inet_gro_receive, there will be a
>> problem ? And under what circumstances ?
>
> You probably missed a recent patch ?
>

Thank you very much.

Is this patch means forcing the IP ID to be incrementing by 1 is necessary in the
case of using tunnel (if the IP_DF is not set in frag_off).

I have not used the tunneled frames. Do you have some examples for that ?

Xiaojun.

> commit 1530545ed64b42e87acb43c0c16401bd1ebae6bf
> Author: Alexander Duyck <aduyck@mirantis.com>
> Date: Sun Apr 10 21:44:57 2016 -0400
>
> GRO: Add support for TCP with fixed IPv4 ID field, limit tunnel IP ID values
>
> This patch does two things.
>
> First it allows TCP to aggregate TCP frames with a fixed IPv4 ID field. As
> a result we should now be able to aggregate flows that were converted from
> IPv6 to IPv4. In addition this allows us more flexibility for future
> implementations of segmentation as we may be able to use a fixed IP ID when
> segmenting the flow.
>
> The second thing this does is that it places limitations on the outer IPv4
> ID header in the case of tunneled frames. Specifically it forces the IP ID
> to be incrementing by 1 unless the DF bit is set in the outer IPv4 header.
> This way we can avoid creating overlapping series of IP IDs that could
> possibly be fragmented if the frame goes through GRO and is then
> resegmented via GSO.
>
> Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
>
>
>
> .
>


\
 
 \ /
  Last update: 2016-06-28 10:21    [W:0.038 / U:1.252 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site