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Date: Sat, 17 Oct 2020 01:59:31 +0100 From: Vadim Fedorenko <vfedorenko@...ek.ru> To: Willem de Bruijn <willemdebruijn.kernel@...il.com>, Alexander Ovechkin <ovov@...dex-team.ru> Cc: Network Development <netdev@...r.kernel.org> Subject: Re: [PATCH net] ip6_tunnel: set inner ipproto before ip6_tnl_encap. On 16.10.2020 18:55, Willem de Bruijn wrote: > On Fri, Oct 16, 2020 at 7:14 AM Alexander Ovechkin <ovov@...dex-team.ru> wrote: >> ip6_tnl_encap assigns to proto transport protocol which >> encapsulates inner packet, but we must pass to set_inner_ipproto >> protocol of that inner packet. >> >> Calling set_inner_ipproto after ip6_tnl_encap might break gso. >> For example, in case of encapsulating ipv6 packet in fou6 packet, inner_ipproto >> would be set to IPPROTO_UDP instead of IPPROTO_IPV6. This would lead to >> incorrect calling sequence of gso functions: >> ipv6_gso_segment -> udp6_ufo_fragment -> skb_udp_tunnel_segment -> udp6_ufo_fragment >> instead of: >> ipv6_gso_segment -> udp6_ufo_fragment -> skb_udp_tunnel_segment -> ip6ip6_gso_segment >> >> Signed-off-by: Alexander Ovechkin <ovov@...dex-team.ru> > Commit 6c11fbf97e69 ("ip6_tunnel: add MPLS transmit support") moved > the call from ip6_tnl_encap's caller to inside ip6_tnl_encap. > > It makes sense that that likely broke this behavior for UDP (L4) tunnels. > > But it was moved on purpose to avoid setting the inner protocol to > IPPROTO_MPLS. That needs to use skb->inner_protocol to further > segment. > > I suspect we need to set this before or after conditionally to avoid > breaking that use case. I hope it could be fixed with something like this: diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c index a0217e5..87368b0 100644 --- a/net/ipv6/ip6_tunnel.c +++ b/net/ipv6/ip6_tunnel.c @@ -1121,6 +1121,7 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield, bool use_cache = false; u8 hop_limit; int err = -1; + __u8 pproto = proto; if (t->parms.collect_md) { hop_limit = skb_tunnel_info(skb)->key.ttl; @@ -1280,7 +1281,7 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield, ipv6_push_frag_opts(skb, &opt.ops, &proto); } - skb_set_inner_ipproto(skb, proto); + skb_set_inner_ipproto(skb, pproto == IPPROTO_MPLS ? proto : pproto); skb_push(skb, sizeof(struct ipv6hdr)); skb_reset_network_header(skb);
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