selftests/bpf: Add tests to verify the fix of encapsulating VxLAN in lwt

Add two tests to verify the transport header of skb has been set when
encapsulate VxLAN using bpf_lwt_push_encap() helper.

1. VxLAN over IPv4.
2. VxLAN over IPv6.

Without the fix, the tests would fail:

 lwt_ip_encap_vxlan:FAIL:transport_hdr offset unexpected transport_hdr offset: actual 70 != expected 20
 #208     lwt_ip_encap_vxlan_ipv4:FAIL
 lwt_ip_encap_vxlan:FAIL:transport_hdr offset unexpected transport_hdr offset: actual 110 != expected 40
 #209     lwt_ip_encap_vxlan_ipv6:FAIL

The unexpected offsets are: outer encap headers
(IPv4: iphdr+udp+vxlan+eth = 50 bytes, IPv6: ipv6hdr+udp+vxlan+eth = 70 bytes)
plus the inner IP header (20 or 40 bytes), because without the fix
transport_header still points at the inner transport layer instead of the
outer UDP header.

Assisted-by: Claude:claude-sonnet-4-6
Cc: Leon Hwang <leon.huangfu@shopee.com>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260602150931.49629-3-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

0 files changed, 0 insertions, 0 deletions