netdev - Re: [PATCH net] net: gre: recompute gre csum for sctp over gre tunnels

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Message-ID: <20200731220417.GD3398@localhost.localdomain>
Date:   Fri, 31 Jul 2020 19:04:17 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        lorenzo.bianconi@...hat.com, tom@...bertland.com
Subject: Re: [PATCH net] net: gre: recompute gre csum for sctp over gre
 tunnels

On Fri, Jul 31, 2020 at 08:12:05PM +0200, Lorenzo Bianconi wrote:
> The GRE tunnel can be used to transport traffic that does not rely on a
> Internet checksum (e.g. SCTP). The issue can be triggered creating a GRE
> or GRETAP tunnel and transmitting SCTP traffic ontop of it where CRC
> offload has been disabled. In order to fix the issue we need to
> recompute the GRE csum in gre_gso_segment() not relying on the inner
> checksum.
> The issue is still present when we have the CRC offload enabled.
> In this case we need to disable the CRC offload if we require GRE
> checksum since otherwise skb_checksum() will report a wrong value.
> 
> Fixes: 4749c09c37030 ("gre: Call gso_make_checksum")
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>

Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>