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Message-ID: <19f5bdf9-c83b-c9ec-83c3-1e9a88763b30@lab.ntt.co.jp> Date: Thu, 14 Feb 2019 18:16:12 +0900 From: Toshiaki Makita <makita.toshiaki@....ntt.co.jp> To: Zahari Doychev <zahari.doychev@...ux.com>, netdev@...r.kernel.org, bridge@...ts.linux-foundation.org, nikolay@...ulusnetworks.com, roopa@...ulusnetworks.com, jhs@...atatu.com, jiri@...nulli.us, xiyou.wangcong@...il.com Cc: johannes@...solutions.net Subject: Re: [RFC PATCH] net act_vlan: use correct len in skb_pull On 2019/02/14 4:51, Zahari Doychev wrote: > The bridge and VLAN code expects that skb->data points to the start of the > VLAN header instead of the next (network) header. Currently after > tcf_vlan_act() on ingress filter skb->data points to the next network > header. In this case the Linux bridge does not forward correctly double > tagged VLAN packets added using tc vlan action as the outer vlan tag from > the skb is inserted at the wrong offset after the vlan tag in the payload. > Making skb->data to point to the VLAN header in tcf_vlan_act() by using > ETH_HLEN in skb_pull_rcsum() fixes the problem. > > The following commands were used for testing: > > ip link add name br0 type bridge vlan_filtering 1 > ip link set dev br0 up > > ip link set dev net0 up > ip link set dev net0 master br0 > > ip link set dev net1 up > ip link set dev net1 master br0 > > bridge vlan add dev net0 vid 100 master > bridge vlan add dev br0 vid 100 self > bridge vlan add dev net1 vid 100 master > > tc qdisc add dev net0 handle ffff: clsact > tc qdisc add dev net1 handle ffff: clsact > > tc filter add dev net0 ingress pref 1 protocol all flower \ > action vlan push id 10 pipe action vlan push id 100 > > tc filter add dev net0 egress pref 1 protocol 802.1q flower \ > vlan_id 100 vlan_ethtype 802.1q cvlan_id 10 \ > action vlan pop pipe action vlan pop > > Signed-off-by: Zahari Doychev <zahari.doychev@...ux.com> > --- > net/sched/act_vlan.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/sched/act_vlan.c b/net/sched/act_vlan.c > index 93fdaf707313..308d7d89f925 100644 > --- a/net/sched/act_vlan.c > +++ b/net/sched/act_vlan.c > @@ -86,7 +86,7 @@ static int tcf_vlan_act(struct sk_buff *skb, const struct tc_action *a, > > out: > if (skb_at_tc_ingress(skb)) > - skb_pull_rcsum(skb, skb->mac_len); > + skb_pull_rcsum(skb, ETH_HLEN); As I said before, it would be safer to remember mac_len and use it later. __u16 mac_len = skb->mac_len; ... err = skb_vlan_push(...) ... if (skb_at_tc_ingress(skb)) skb_pull_rcsum(skb, mac_len); -- Toshiaki Makita
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