Subject: Re: [PATCH net-next v5 00/11] BIG TCP for UDP tunnels

From: Jakub Kicinski <[email-masked]>
Date: Wed, 27 May 2026 19:13:03 -0700

On Tue, 26 May 2026 18:11:49 +0200 Alice Mikityanska wrote:
> This series is a follow-up to "BIG TCP without HBH in IPv6", and it adds
> support for BIG TCP IPv4/IPv6 workloads in vxlan and geneve. Now that
> IPv6 BIG TCP doesn't require stripping the HBH in all various
> combinations in tunneled traffic, adding BIG TCP becomes feasible.
> 
> Patches 01-02 are small fixups to some related code that I'm changing in
> the series.
> 
> Patch 03 adds accessors for the length field in the UDP header, as
> suggested by Paolo in review. The usage of udp_set_len is then added in
> the following patches that start using length=0 in BIG TCP UDP packets.
> 
> Patches 04-06 close the gaps that prevent BIG TCP packets from going
> through UDP tunnel code.
> 
> Patch 07 re-adds proper validation of malformed packets that arrive with
> length=0 from the wire.
> 
> Patch 08 is for proper formatting in tcpdump (set UDP len to 0 rather
> than a trimmed value on overflow).
> 
> Patches 09-10 bump up tso_max_size for VXLAN and GENEVE.
> 
> Patch 11 adds selftests.

Looks like the selftest fails on debug kernel builds:

# overriding timeout to 7200
# selftests: net: big_tcp_tunnels.sh
# 0.50 [+0.50] Setting up VXLAN over IPv4
# 0.78 [+0.28] Running IPv4 traffic in the tunnel
# 5.93 [+5.14] Captured BIG TCP GRO packets: 18138
# 5.93 [+0.00] Captured BIG TCP GSO packets: 17445
# 6.01 [+0.08] Setting up VXLAN over IPv4
# 6.29 [+0.29] Running IPv6 traffic in the tunnel
# 11.40 [+5.11] Captured BIG TCP GRO packets: 17827
# 11.40 [+0.00] Captured BIG TCP GSO packets: 16964
# 11.49 [+0.08] Setting up VXLAN over IPv6
# 11.78 [+0.29] Running IPv4 traffic in the tunnel
# 16.89 [+5.11] Captured BIG TCP GRO packets: 8951
# 16.89 [+0.00] Captured BIG TCP GSO packets: 9063
not ok 1 selftests: net: big_tcp_tunnels.sh # exit=1

https://netdev-ctrl.bots.linux.dev/logs/vmksft/net-dbg/results/665442/153-big-tcp-tunnels-sh/stdout
https://netdev-ctrl.bots.linux.dev/logs/vmksft/net-dbg/results/665442/153-big-tcp-tunnels-sh-retry/stdout