netdev - Re: [PATCH net-next] ipv6: gro: do not use slow memcmp() in ipv6_gro

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Message-Id: <20181106.145947.2202292638886026880.davem@davemloft.net>
Date:   Tue, 06 Nov 2018 14:59:47 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH net-next] ipv6: gro: do not use slow memcmp() in
 ipv6_gro_receive()

From: Eric Dumazet <edumazet@...gle.com>
Date: Tue, 6 Nov 2018 14:51:15 -0800

> On Tue, Nov 6, 2018 at 2:41 PM David Miller <davem@...emloft.net> wrote:
>>
>> From: Eric Dumazet <edumazet@...gle.com>
>> Date: Tue,  6 Nov 2018 14:25:52 -0800
>>
>> > +             if (unlikely(nlen > sizeof(struct ipv6hdr))) {
>> > +                     if (memcmp(iph + 1, iph2 + 1,
>> > +                                nlen - sizeof(struct ipv6hdr)))
>> > +                             goto not_same_flow;
>> > +             }
>>
>> Is this even possible?
> 
> I believe that nlen can be indeed > sizeof(struct ipv6hdr) in presence
> of exthdrs,
> eg if ipv6_gso_pull_exthdrs() had to be called (line 201)
> 
>  I admit I have not checked if this was actually possible.

Indeed, that does make it possible.

Patch applied, thanks!