Re: [PATCH v2 0/5] bpf: skb_adjust_room helper refactor and tunnel decap flags

Nick Hudson wrote:

This series refactors the bpf_skb_adjust_room() helper to support tunnel
decapsulation with L4 and IPXIP modes, in addition to the existing L3
decapsulation support.

The changes are structured as follows:
1. Name the enum for BPF_FUNC_skb_adjust_room flags
2. Add new BPF_F_ADJ_ROOM_DECAP_* flags for L4 and IPXIP decap modes
3. Introduce helper masks to simplify validation logic
4. Enable the new decap flags and add guard rails for invalid combinations
5. Clear tunnel GSO state when decapsulating in skb_adjust_room

These patches enable BPF programs to efficiently decapsulate various tunnel
encapsulation formats and properly handle GSO state transitions.

Consider expanding the existing BPF tunneling tests. Similar to
commit 166b5a7f2ca3 ("selftests_bpf: extend test_tc_tunnel for UDP
encap"). Given how far along this series is fine to do separately.