On Thu, 2017-01-26 at 07:27 -0800, Eric Dumazet wrote:

                if (!uh->check && !udp_sk(sk)->no_check6_rx) {
                        udp6_csum_zero_error(skb);
                        goto csum_error;
                }

Yeah, I'd found no_check6_rx already, was still trying to figure out this one :)

Looks like we actually check uh->check regardless of anything the
driver said (CHECKSUM_UNNECESSARY, or whatever), so we should be fine
even with the hardware tagging it as good in this case.

johannes