netdev - [PATCH net v3 0/3] Don't take HW USO path when packets can't be checksummed by device

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Message-Id: <20240807-udp-gso-egress-from-tunnel-v3-0-8828d93c5b45@cloudflare.com>
Date: Wed, 07 Aug 2024 19:55:02 +0200
From: Jakub Sitnicki <jakub@...udflare.com>
To: netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, 
 Willem de Bruijn <willemdebruijn.kernel@...il.com>, 
 kernel-team@...udflare.com, Jakub Sitnicki <jakub@...udflare.com>, 
 syzbot+e15b7e15b8a751a91d9a@...kaller.appspotmail.com
Subject: [PATCH net v3 0/3] 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

Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
---
Changes in v3:
- Make USO depend on checksum offload (Willem)
- Contain the bad offload warning fix within the USO callback (Willem)
- Link to v2: https://lore.kernel.org/r/20240801-udp-gso-egress-from-tunnel-v2-0-9a2af2f15d8d@cloudflare.com

Changes in v2:
- Contain the fix inside the GSO stack after discussing with Willem
- Rework tests after realizing the regression has nothing to do with tunnels
- Link to v1: https://lore.kernel.org/r/20240725-udp-gso-egress-from-tunnel-v1-0-5e5530ead524@cloudflare.com

---
Jakub Sitnicki (3):
      net: Make USO depend on CSUM offload
      udp: Fall back to software USO if IPv6 extension headers are present
      selftests/net: Add coverage for UDP GSO with IPv6 extension headers

 net/core/dev.c                       | 27 ++++++++++++++++++---------
 net/ipv4/udp_offload.c               |  6 ++++++
 tools/testing/selftests/net/udpgso.c | 25 ++++++++++++++++++++++++-
 3 files changed, 48 insertions(+), 10 deletions(-)