Re: [PATCH net-next v3 0/5] net: resegment oversized TCP GSO skbs

[Wang Zhan <wang.zhan@smartx.com>]

On Mon, 28 Sep 2026 19:34:21 -0400 Willem de Bruijn wrote:
> If 1/5 fixes a bug that is reachable today (does it?) then it needs to
> go to net on its own.

Before this series, it is reachable when the tag is already in the frame,
for example a stacked VLAN device or an OVS QinQ path.  I reproduced it
with the following script:

  ip netns add g1; ip netns add g2
  ip link add v0 type veth peer name v1
  ip link set v0 netns g1; ip link set v1 netns g2
  for n in g1 g2; do
      r=v0; [ $n = g2 ] && r=v1
      ip -n $n link add link $r name vlan200 type vlan id 200
      ip -n $n link add link vlan200 name vlan100 type vlan id 100
      for d in $r vlan200 vlan100; do
          ip -n $n link set $d gso_max_size 524280
      done
      ip -n $n link set $r up; ip -n $n link set vlan200 up
      ip -n $n link set vlan100 up
  done
  ip -n g1 addr add 2001:db8::1/64 dev vlan100
  ip -n g2 addr add 2001:db8::2/64 dev vlan100
  ip netns exec g2 iperf3 -s -D
  ip -n g1 link set v0 gso_ipv4_max_size 65536
  ip netns exec g1 iperf3 -c 2001:db8::2 -t 6
  ip -n g1 link set v0 gso_ipv4_max_size 524280
  ip netns exec g1 iperf3 -c 2001:db8::2 -t 6

With gso_ipv4_max_size = 65536, iperf3 reports 442 Mbps; with 524280, it
reports 39.4 Gbps.  So gso_ipv4_max_size clearly affects this IPv6 flow.

I will keep 1/5 in the series and drop the Fixes tag, as Paolo suggests.