netdev - Re: problems with SCTP GSO

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Date:   Tue, 12 Jun 2018 14:05:06 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     lucien.xin@...il.com, edumazet@...gle.com, netdev@...r.kernel.org
Subject: Re: problems with SCTP GSO

On Mon, Jun 11, 2018 at 08:29:05PM -0700, David Miller wrote:
> 
> I would like to bring up some problems with the current GSO
> implementation in SCTP.
> 
> The most important for me right now is that SCTP uses
> "skb_gro_receive()" to build "GSO" frames :-(
> 
> Really it just ends up using the slow path (basically, label 'merge'
> and onwards).
> 
> So, using a GRO helper to build GSO packets is not great.

Okay.

> 
> I want to make major surgery here and the only way I can is if
> it is exactly the GRO demuxing path that uses skb_gro_receive().
> 
> Those paths pass in the list head from the NAPI struct that initiated
> the GRO code paths.  That makes it easy for me to change this to use a
> list_head or a hash chain.
> 
> Probably in the short term SCTP should just have a private helper that
> builds the frag list, appending 'skb' to 'head'.
> 
> In the long term, SCTP should use the page frags just like TCP to
> append the data when building GSO frames.  Then it could actually be
> offloaded and passed into drivers without linearizing.

Sounds like a plan. Shouldn't be too hard to do it.
(I'm out on PTO, btw)

Thanks,
Marcelo