Re: [PATCH net] bareudp: set the inner protocol to the protocol of the packet

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Haishuang Yan wrote:
> bareudp_xmit_skb() sets the inner protocol of the skb to the configured
> ethertype, and bareudp6_xmit_skb() does not set it at all. The inner
> protocol is used by skb_udp_tunnel_segment() to segment the inner packet
> when GSO has to be done in software, for instance when the lower device
> does not offload the checksum.
> 
> With multiproto, an IPv4 device also carries IPv6, so the IPv6 header
> is parsed as an IPv4 one. With IPv6 underlay, the inner protocol is
> whatever the skb had before. In both cases segmentation fails and the
> packets are dropped. With veth tx checksum offload disabled, iperf3 TCP
> over bareudp gets about 10 Mbit/s with thousands of retransmits instead
> of about 700 Mbit/s for IPv6 over IPv4 and for both families over IPv6,
> while IPv4 over IPv4 works.

(not for this fix patch)

optionally tools/testing/selftests/net/bareudp.sh could run a stream
test besides/alongside the ping test, to exercise this path (with
segmentation offload disabled).

> At this point skb->protocol is the protocol of the inner packet, which
> bareudp_xmit() has already checked against the configuration, so use it
> on both paths.
> 
> Fixes: 571912c69f0e ("net: UDP tunnel encapsulation module for tunnelling different protocols like MPLS, IP, NSH etc.")
> Fixes: 4b5f67232d95 ("net: Special handling for IP & MPLS.")
> Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>

Reviewed-by: Willem de Bruijn <willemb@google.com>