Re: [PATCH v2 3/5] bpf: add helper masks for ADJ_ROOM flags and encap validation

Nick Hudson wrote:

Introduce helper masks for bpf_skb_adjust_room() flags to simplify
validation logic:

- BPF_F_ADJ_ROOM_DECAP_L4_MASK
- BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK
- BPF_F_ADJ_ROOM_ENCAP_MASK
- BPF_F_ADJ_ROOM_DECAP_MASK

Add flag validation to bpf_skb_net_grow() to reject invalid encap
flags early. Refactor existing validation checks in bpf_skb_net_shrink()
and bpf_skb_adjust_room() to use the new masks (no behavior change).

Co-developed-by: Max Tottenham <redacted>
Signed-off-by: Max Tottenham <redacted>
Co-developed-by: Anna Glasgall <redacted>
Signed-off-by: Anna Glasgall <redacted>
Signed-off-by: Nick Hudson <redacted>

Reviewed-by: Willem de Bruijn <willemb@google.com>