On Tue, 10 Mar 2026 11:05:33 +0100, Paolo Abeni <[email protected]> wrote: > On 3/5/26 4:19 AM, Xuan Zhuo wrote: > > The commit a2fb4bc4e2a6a03 ("net: implement virtio helpers to handle UDP > > GSO tunneling.") introduces support for the UDP GSO tunnel feature in > > virtio-net. > > > > The virtio spec says: > > > > If the \field{gso_type} has the VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IPV4 bit > > or > > VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IPV6 bit set, \field{hdr_len} accounts for > > all the headers up to and including the inner transport. > > > > The commit did not update the hdr_len to include the inner transport. > > > > I observed that the "hdr_len" is 116 for this packet: > > > > 17:36:18.241105 52:55:00:d1:27:0a > 2e:2c:df:46:a9:e1, ethertype IPv4 > > (0x0800), length 2912: (tos 0x0, ttl 64, id 45197, offset 0, flags [none], > > proto UDP (17), length 2898) > > 192.168.122.100.50613 > 192.168.122.1.4789: [bad udp cksum 0x8106 > > -> 0x26a0!] VXLAN, flags [I] (0x08), vni 1 > > fa:c3:ba:82:05:ee > ce:85:0c:31:77:e5, ethertype IPv4 (0x0800), length > > 2862: (tos 0x0, ttl 64, id 14678, offset 0, flags [DF], proto TCP (6), > > length 2848) > > 192.168.3.1.49880 > 192.168.3.2.9898: Flags [P.], cksum 0x9266 > > (incorrect -> 0xaa20), seq 515667:518463, ack 1, win 64, options > > [nop,nop,TS val 2990048824 ecr 2798801412], length 2796 > > > > 116 = 14(mac) + 20(ip) + 8(udp) + 8(vxlan) + 14(inner mac) + 20(inner ip) + > > 32(innner tcp) > > > > Fixes: a2fb4bc4e2a6a03 ("net: implement virtio helpers to handle UDP GSO > > tunneling.") > > Signed-off-by: Xuan Zhuo <[email protected]> > > --- > > include/linux/virtio_net.h | 31 ++++++++++++++++++++----------- > > 1 file changed, 20 insertions(+), 11 deletions(-) > > > > diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h > > index 23f42bb8ece0..906157779955 100644 > > --- a/include/linux/virtio_net.h > > +++ b/include/linux/virtio_net.h > > @@ -209,18 +209,29 @@ static inline int virtio_net_hdr_to_skb(struct > > sk_buff *skb, > > > > static inline void virtio_net_set_hdrlen(const struct sk_buff *skb, > > struct virtio_net_hdr *hdr, > > + struct skb_shared_info *sinfo, > > bool little_endian, > > bool feature_hdrlen) > > { > > u16 hdr_len; > > > > if (feature_hdrlen) { > > - hdr_len = skb_transport_offset(skb); > > - > > - if (hdr->gso_type == VIRTIO_NET_HDR_GSO_UDP_L4) > > - hdr_len += sizeof(struct udphdr); > > - else > > - hdr_len += tcp_hdrlen(skb); > > + if (sinfo->gso_type & (SKB_GSO_UDP_TUNNEL | > > + SKB_GSO_UDP_TUNNEL_CSUM)) { > > + hdr_len = skb_inner_transport_offset(skb); > > + > > + if (hdr->gso_type == VIRTIO_NET_HDR_GSO_UDP_L4) > > + hdr_len += sizeof(struct udphdr); > > + else > > + hdr_len += inner_tcp_hdrlen(skb); > > + } else { > > + hdr_len = skb_transport_offset(skb); > > + > > + if (hdr->gso_type == VIRTIO_NET_HDR_GSO_UDP_L4) > > + hdr_len += sizeof(struct udphdr); > > + else > > + hdr_len += tcp_hdrlen(skb); > > + } > > I already mentioned the following a couple of times, with no replies... > perhaps the 3rd attempt will be more successful. > > I think it's a bad adding tunnel specific check here. It sounds like > layering violation. Instead you could have tunnel-specific variant, say > virtio_net_set_tnl_hdrlen(), and use it in virtio_net_hdr_tnl_from_skb(). > > Or you could try what i suggested in: > > https://lore.kernel.org/netdev/CAF6piCLkv6kFqoq7OQfJ=su9avhsq9j7dzaumosf5xuf9w-...@mail.gmail.com/#t
I saw your suggestions, though I didn't reply directly. I proceeded to adjust the code based on my understanding of your feedback, but it appears my understanding was incorrect. After re-reading your suggestions, I think virtio_net_hdr_from_skb does not need to be changed. Instead, within virtio_net_hdr_tnl_from_skb, we should directly call the device header length function based on whether the feature is negotiated. Thanks. > > Thanks, > > Paolo >
