netdev - Re: [PATCH net] sit: Set skb->protocol properly in ipip6_tunnel

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Message-ID: <1480357043.18162.70.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 28 Nov 2016 10:17:23 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     alexander.duyck@...il.com, sfr@...b.auug.org.au, elicooper@....com,
        netdev@...r.kernel.org
Subject: Re: [PATCH net] sit: Set skb->protocol properly in
 ipip6_tunnel_xmit()

On Mon, 2016-11-28 at 13:01 -0500, David Miller wrote:

> Hmmm, ip6_finish_output2() also does a proper assignment of skb->protocol,
> therefore why was commit ae148b085876fa771d9ef2c05f85d4b4bf09ce0d
> ("ip6_tunnel: Update skb->protocol to ETH_P_IPV6 in ip6_tnl_xmit()")
> necessary at all?
I was referring to Stephen bug report.

It appears that Eli changelog was not very precise, because his bug was
because of XFRM being involved.

xfrm_output() -> xfrm_output_gso() -> skb_gso_segment()

So XFRM calls skb_gso_segment() before ip_output() or
ip6_finish_output2() had a chance to change skb->protocol