Re: [PATCH bpf-next v4 5/6] bpf: clear decap tunnel GSO state in skb_adjust_room

[bot+bpf-ci]

> diff --git a/net/core/filter.c b/net/core/filter.c
> index 1dac64b50de4..4e77e9c46f1a 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -3657,6 +3657,44 @@ static int bpf_skb_net_shrink(struct sk_buff *skb, u32 off, u32 len_diff,
>  		if (!(flags & BPF_F_ADJ_ROOM_FIXED_GSO))
>  			skb_increase_gso_size(shinfo, len_diff);
>
> +		/* Selective GSO flag clearing based on decap type.
> +		 * Only clear the flags for the tunnel layer being removed.
> +		 */
> +		if ((flags & BPF_F_ADJ_ROOM_DECAP_L4_UDP) &&

The symbols BPF_F_ADJ_ROOM_DECAP_L4_UDP, BPF_F_ADJ_ROOM_DECAP_L4_GRE,
BPF_F_ADJ_ROOM_DECAP_IPXIP4, BPF_F_ADJ_ROOM_DECAP_IPXIP6,
BPF_F_ADJ_ROOM_DECAP_L4_MASK, and BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK
are used throughout this hunk but are not defined anywhere in the tree.

The series cover letter lists patch 3/6 "bpf: add
BPF_F_ADJ_ROOM_DECAP_* flags for tunnel decapsulation" which would
add these to include/uapi/linux/bpf.h, but that patch is not present.
Without it, this commit will not compile.

Additionally, even if these symbols were defined, BPF_F_ADJ_ROOM_MASK
and BPF_F_ADJ_ROOM_DECAP_MASK do not include the new flag bits.  Both
bpf_skb_adjust_room():

    if (unlikely(flags & ~BPF_F_ADJ_ROOM_MASK))
        return -EINVAL;

and bpf_skb_net_shrink():

    if (unlikely(flags & ~(BPF_F_ADJ_ROOM_DECAP_MASK |
                           BPF_F_ADJ_ROOM_FIXED_GSO |
                           BPF_F_ADJ_ROOM_NO_CSUM_RESET)))
        return -EINVAL;

would reject any flags value containing these new bits, making the
new code unreachable.  Patch 4/6 "bpf: allow new DECAP flags and add
guard rails" from the series would presumably update these masks, but
it is also not present.

Are patches 3/6 and 4/6 of the series missing from this tree?

> +		    (shinfo->gso_type & (SKB_GSO_UDP_TUNNEL |
> +					 SKB_GSO_UDP_TUNNEL_CSUM)))
> +			shinfo->gso_type &= ~(SKB_GSO_UDP_TUNNEL |
> +					      SKB_GSO_UDP_TUNNEL_CSUM);

[ ... ]

> +		/* Clear encapsulation flag only when no tunnel GSO flags remain */
> +		if (flags & (BPF_F_ADJ_ROOM_DECAP_L4_MASK |
> +			     BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK)) {

[ ... ]

> +			if (flags & BPF_F_ADJ_ROOM_DECAP_L4_UDP) {
> +				skb->encap_hdr_csum = 0;
> +				skb->remcsum_offload = 0;
> +			}
> +		}

This isn't a bug, but the BPF subsystem convention is that multi-line
comments should have the opening /* on its own line:

> +		/* Selective GSO flag clearing based on decap type.
> +		 * Only clear the flags for the tunnel layer being removed.
> +		 */

Should be:

    /*
     * Selective GSO flag clearing based on decap type.
     * Only clear the flags for the tunnel layer being removed.
     */


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/24499314045