On Fri, Oct 16, 2020 at 7:14 AM Alexander Ovechkin <[email protected]> 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 <[email protected]>
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.
