Merge branch 'don-t-take-hw-uso-path-when-packets-can-t-be-checksummed-by-device'

Jakub Sitnicki says:

====================
Don't take HW USO path when packets can't be checksummed by device

This series addresses a recent regression report from syzbot [1].

After enabling UDP_SEGMENT for egress devices which don't support checksum
offload [2], we need to tighten down the checks which let packets take the
HW USO path.

The fix consists of two parts:

1. don't let devices offer USO without checksum offload, and
2. force software USO fallback in presence of IPv6 extension headers.

[1] https://lore.kernel.org/all/000000000000e1609a061d5330ce@google.com/
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=10154dbded6d6a2fecaebdfda206609de0f121a9

v3: https://lore.kernel.org/r/20240807-udp-gso-egress-from-tunnel-v3-0-8828d93c5b45@cloudflare.com
v2: https://lore.kernel.org/r/20240801-udp-gso-egress-from-tunnel-v2-0-9a2af2f15d8d@cloudflare.com
v1: https://lore.kernel.org/r/20240725-udp-gso-egress-from-tunnel-v1-0-5e5530ead524@cloudflare.com
====================

Link: https://patch.msgid.link/20240808-udp-gso-egress-from-tunnel-v4-0-f5c5b4149ab9@cloudflare.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>