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Date: Tue, 27 Oct 2020 21:53:43 -0400 From: Willem de Bruijn <willemdebruijn.kernel@...il.com> To: Alexander Ovechkin <ovov@...dex-team.ru> Cc: Willem de Bruijn <willemdebruijn.kernel@...il.com>, vfedorenko@...ek.ru, Network Development <netdev@...r.kernel.org>, Tom Herbert <tom@...bertland.com> Subject: Re: [PATCH net] ip6_tunnel: set inner ipproto before ip6_tnl_encap. On Tue, Oct 27, 2020 at 5:52 PM Alexander Ovechkin <ovov@...dex-team.ru> wrote: > > > 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. > And why do we need to avoid setting the inner protocol to IPPROTO_MPLS? Currently skb->inner_protocol is used before call of ip6_tnl_xmit. > Can you please give example when this patch breaks MPLS segmentation? mpls_gso_segment calls skb_mac_gso_segment on the inner packet. After setting skb->protocol based on skb->inner_protocol. perhaps mpls encap gso and udp tunnel gso simply cannot be enabled together, because both use skb->inner_(ipproto|protocol) to demultiplex: 18 163 net/ipv4/udp_offload.c <<skb_udp_tunnel_segment>> protocol = skb->inner_protocol; 19 35 net/mpls/mpls_gso.c <<mpls_gso_segment>> skb->protocol = skb->inner_protocol; 3 168 net/ipv4/udp_offload.c <<skb_udp_tunnel_segment>> ops = rcu_dereference(offloads[skb->inner_ipproto]); Please don't top post, btw. > > On 16 Oct 2020, at 20:55, Willem de Bruijn <willemdebruijn.kernel@...il.com> 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. >
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