A virtio-net header can supply CHECKSUM_PARTIAL metadata whose checksum
start resolves inside a network header. Software checksum completion can
then modify bytes the stack has already parsed.

Patch 1 checks the data-relative L3 origin in the virtio-net conversion
paths. Patch 2 checks the parsed header length before checksum completion
in IPv4 and IPv6 fragmentation paths.

Changes in v6 address Michael S. Tsirkin's review of v5:
- Name the Ethernet-only L3 parser accordingly.
- Derive the AF_PACKET L3 offset and protocol from the actual Ethernet
  frame, including inline VLAN tags on an ETH_P_IP raw socket.
- Use the IPv6 base-header minimum for IPv6 checksum-only packets,
  including IFF_TUN before skb->protocol is set.
- Restore Assisted-by: LLM on both patches. Patch 2's code is unchanged.

Validation: focused x86 allmodconfig and UML defconfig W=1 object builds,
strict checkpatch, and application of the exact mail series to the stated
base. No runtime regression reproducer was run.

Link: https://lore.kernel.org/netdev/20260921025341.44846-1-habte.yibelo@gmail.com/

Paulos Yibelo (2):
  net: validate virtio checksum start after network header
  ip: reject partial checksums covering network headers

 arch/um/drivers/vector_transports.c        | 13 +++-
 drivers/net/tun_vnet.h                     | 52 ++++++++++++-
 drivers/net/virtio_net.c                   | 10 ++-
 include/linux/virtio_net.h                 | 87 ++++++++++++++++++----
 net/bridge/netfilter/nf_conntrack_bridge.c | 21 ++++--
 net/ipv4/ip_output.c                       | 23 ++++--
 net/ipv6/ip6_output.c                      | 12 ++-
 net/ipv6/netfilter.c                       | 12 ++-
 net/packet/af_packet.c                     | 24 +++++-
 9 files changed, 214 insertions(+), 40 deletions(-)


base-commit: 1e24c4f2ee44be0eee94092b5d13cbdb4bdf0d60
-- 
2.46.0