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Subject: Re: [Cake] [PATCH net-next 1/5] sch_cake: fix IP protocol handling
 in the presence of VLAN tags
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From: Toke H=F8iland-J=F8rgensen <toke@redhat.com>
Date: Thu, 25 Jun 2020 13:55:03 +0200

> From: Ilya Ponetayev <i.ponetaev@ndmsystems.com>
> =

> CAKE was using the return value of tc_skb_protocol() and expecting it=
 to be
> the IP protocol type. This can fail in the presence of QinQ VLAN tags=
,
> making CAKE unable to handle ECN marking and diffserv parsing in this=
 case.
> Fix this by implementing our own version of tc_skb_protocol(), which =
will
> use skb->protocol directly, but also parse and skip over any VLAN tag=
s and
> return the inner protocol number instead.
> =

> Also fix CE marking by implementing a version of INET_ECN_set_ce() th=
at
> uses the same parsing routine.
> =

> Fixes: ea82511518f4 ("sch_cake: Add NAT awareness to packet classifie=
r")
> Fixes: b2100cc56fca ("sch_cake: Use tc_skb_protocol() helper for gett=
ing packet protocol")
> Fixes: 046f6fd5daef ("sched: Add Common Applications Kept Enhanced (c=
ake) qdisc")
> Signed-off-by: Ilya Ponetayev <i.ponetaev@ndmsystems.com>
> [ squash original two patches, rewrite commit message ]
> Signed-off-by: Toke H=F8iland-J=F8rgensen <toke@redhat.com>

First, this is a bug fix and should probably be steered to 'net'.

Also, other users of tc_skb_protocol() are almost certainly hitting a
similar problem aren't they?  Maybe fix this generically.