1. Let's assume a driver which has a HW csum capability, however it has a
privilege to assign any value for ip_summed.
For example the driver assigns "unnecessary" for most of the packets, however
it fails to verify the packets less than 96 bytes ("checksum_none").
Now, the LRO will aggregate all of them and assign the value "used for all
aggregated packets" - that is wrong,
Of course, it is possible to avoid that situation in driver, however [proposal]
from the point of view of the *generic* LRO it could be better to check each
newly aggregated skb whether it has the same ip_summed as the first one
(preserve coherency). Thus, there is no need to keep ip_summed field in the
struct net_lro_mgr.
2. Now, when a skb could not be aggregated (modes: aggregating SKBs) I think
where's no need to override its original ip_summed (see "out" label of
__lro_proc_skb()) The comment says "Original SKB has to be posted to stack". I
would be wrong, but I don't get the reason to possible change of ip_summed.
Regards,
- Kostya
----------------------------------------
> From: [EMAIL PROTECTED]
> To: [EMAIL PROTECTED]
> Subject: Re: LRO ip_summed
> Date: Mon, 4 Feb 2008 10:14:23 +0100
> CC: netdev@vger.kernel.org
>
> On Sunday 03 February 2008 10:48, Kostya B wrote:
>>
>> Hi,
>>
>> The mail is related to the way LRO manipulates the ip_summed value. Could
>> anybody (author) explain why to overwrite the original value of
>> skb->ip_summed, when it's processing by __lro_proc_skb ?
>> E.g. in out: label
>>
>> Why not to preserve the coherency of csum status of each incoming to LRO
>> packet, the same way the IP defragmentation does? That means - all skb in
>> descriptor have the same value of ip_summed.
>>
>
> Hi,
>
> I'm not sure if I understand your proposal correctly.
> Currently the driver decides via the struct net_lro_mgr
> a) which ip_summed value will be used for all aggregated packets
> b) which one to use for those packets that can not be aggregated
>
> to a) this one should always be the same. The driver knows whether its HW is
> capable of performing ip checksum checking for this kind of traffic
> (TCP)
>
> There are two modes: aggregating SKBs or aggregating fragments.
> When fragments are aggregated, there is no SKB with a filled ip_summed
> available.
>
> Please outline which parts of which mode you suggest to change.
>
> Regards,
> Jan-Bernd
>
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