netdev - Re: [PATCH net-next 0/3] net: Eliminate gso_send

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Date:	Sat, 20 Sep 2014 18:04:00 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 0/3] net: Eliminate gso_send_check

On Sat, 2014-09-20 at 14:52 -0700, Tom Herbert wrote:
> gso_send_check presents a lot of complexity for what it is being used
> for. It seems that there are only two cases where it might be effective:
> TCP and UFO paths. In these cases, the gso_send_check function
> initializes the TCP or UDP checksum respectively to the pseudo header
> checksum so that the checksum computation is appropriately offloaded or
> computed in the gso_segment functions. The gso_send_check functions
> are only called from dev.c in skb_mac_gso_segment when ip_summed !=
> CHECKSUM_PARTIAL (which seems very unlikely in TCP case). We can move
> the logic of this into the respective gso_segment functions where the
> checksum is initialized if ip_summed != CHECKSUM_PARTIAL.
> 
> With the above cases handled, gso_send_check is no longer needed, so
> we can remove all uses of it and the fields in the offload callbacks.
> With this change, ip_summed in the skb should be preserved though all
> the layers of gso_segment calls.
> 
> In follow-on patches, we may be able to remove the check setup code in
> tcp_gso_segment if we can guarantee that ip_summed will always be
> CHECKSUM_PARTIAL (verify all paths and probably add an assert in
> tcp_gro_segment).
> 
> Tested these patches by:
>   - netperf TCP_STREAM test with GSO enabled
>   - Forced ip_summed != CHECKSUM_PARTIAL with above
>   - Ran UDP_RR with 10000 request size over GRE tunnel. This exercised
>     UFO path.
> 
> Tom Herbert (3):
>   tcp: move logic out of tcp_v[64]_gso_send_check
>   udp: move logic out of udp[46]_ufo_send_check
>   net: Remove gso_send_check as an offload callback

Very very nice !

Acked-by: Eric Dumazet <edumazet@...gle.com>


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