Re: [PATCH bpf v2] lwt_bpf: restore reserved headroom after xmit program

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <[email protected]>:

On Tue, 11 Aug 2026 13:41:49 +0900 you wrote:
> ip_finish_output2() expands an skb to LL_RESERVED_SPACE(dev) before LWT
> xmit. An LWT_XMIT BPF program can then modify the skb head and still
> return BPF_OK, so bpf_xmit() rechecks the remaining headroom before the
> skb continues to neighbour output.
> 
> That recheck uses dst->dev->hard_header_len. This is not enough for the
> neighbour cached-header path: neigh_hh_output() copies the cached hardware
> header using the aligned hh_cache size, HH_DATA_MOD for short headers or
> HH_DATA_ALIGN(hh_len) otherwise.
> 
> [...]

Here is the summary with links:
  - [bpf,v2] lwt_bpf: restore reserved headroom after xmit program
    https://git.kernel.org/bpf/bpf-next/c/5fe7007aed9a

You are awesome, thank you!
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