netdev - Re: [PATCH net-next] ipv6: Initial skb->dev and skb->protocol in ip6

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Date:   Sat, 10 Jun 2017 07:54:21 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Chenbo Feng <chenbofeng.kernel@...il.com>
Cc:     David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        lorenzo@...gle.com, edumazet@...gle.com, fengc@...gle.com
Subject: Re: [PATCH net-next] ipv6: Initial skb->dev and skb->protocol in
 ip6_output

On Fri, 2017-06-09 at 16:12 -0700, Chenbo Feng wrote:
> 
> On 06/09/2017 12:39 PM, David Miller wrote:
> > From: Chenbo Feng <chenbofeng.kernel@...il.com>
> > Date: Fri, 9 Jun 2017 12:13:57 -0700
> >
> >>
> >> On 06/09/2017 12:08 PM, David Miller wrote:
> >>> From: Chenbo Feng <chenbofeng.kernel@...il.com>
> >>> Date: Fri,  9 Jun 2017 12:06:07 -0700
> >>>
> >>>> From: Chenbo Feng <fengc@...gle.com>
> >>>>
> >>>> Move the initialization of skb->dev and skb->protocol from
> >>>> ip6_finish_output2 to ip6_output. This can make the skb->dev and
> >>>> skb->protocol information avalaible to the CGROUP eBPF filter.
> >>>>
> >>>> Signed-off-by: Chenbo Feng <fengc@...gle.com>
> >>>> Acked-by: Eric Dumazet <edumazet@...gle.com>
> >>> Applied, thanks.
> >>>
> >>> This makes ipv6 consistent with ipv4.
> >>>
> >>> I am surprised this wasn't noticed, for example, in netfilter.
> >>> .
> >>>
> >> Hi David,
> >>
> >> This patch is still under working since it may have problem with
> >> ip_fragment() call, did you applied it already? Should I send a revert
> >> patch to you then?
> > A revert is necessary or a relative fixup.
> >
> > Thank you.
> >
> Hi David,
> 
> The revert is uploaded here: http://patchwork.ozlabs.org/patch/774136/
> 
> Thanks and sorry for the trouble caused
> 
> Chenbo Feng

No worries !

It seems the revert is not needed, after further analysis.

One of the point I raised was this no longer needed chunk, that can be
added as a separate patch :

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 02cd44f0953900108701895108b2fdaa9f9980e5..0d6f3b6345de26c329ae1d6f25dde652a5452d4b 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -869,7 +869,6 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 	if (skb->sk && dst_allfrag(skb_dst(skb)))
 		sk_nocaps_add(skb->sk, NETIF_F_GSO_MASK);
 
-	skb->dev = skb_dst(skb)->dev;
 	icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
 	err = -EMSGSIZE;