selftests: net: tun: add test for VLAN-tagged GSO without NEEDS_CSUM

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Add selftests in tun.c verifying that a VLAN-tagged (802.1Q) TCPv4 GSO
packet without VIRTIO_NET_HDR_F_NEEDS_CSUM (both flags = 0 and
flags = VIRTIO_NET_HDR_F_DATA_VALID) is accepted when written to a TAP
device (/dev/net/tun with IFF_TAP | IFF_NO_PI | IFF_VNET_HDR).

Also verify that the following are rejected with -EINVAL:
- a mismatched GSO type (VIRTIO_NET_HDR_GSO_TCPV6 on a VLAN-tagged IPv4
  packet).
- a frame whose TCP header is truncated after 10 bytes. Pulling only
  sizeof(struct iphdr) + sizeof(struct tcphdr) bytes would accept it,
  so this requires the transport offset found by flow dissection.

Finally, verify that a 65540-byte frame is accepted. Its skb->len is
above U16_MAX while it is flow-dissected, before eth_type_trans() pulls
the Ethernet header.

Based on a reproducer by Michael S. Tsirkin <mst@redhat.com>.

Signed-off-by: Eric Dumazet <edumazet@kernel.org>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20261001191140.2818991-4-edumazet@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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Eric Dumazet 2026-10-01 19:11:40 +00:00 • committed by Jakub Kicinski

parent 44378d02c5

commit ee2d4c2d7c

1 changed files with 136 additions and 0 deletions

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tools/testing/selftests/net/tun.c

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