Subject: Re: [PATCH bpf-next v3] bpf: check for BPF_F_ADJ_ROOM_FIXED_GSO when bpf_skb_change_proto

From: [email-masked]
Date: Tue, 18 May 2021 20:10:09 +0000

Hello:

This patch was applied to bpf/bpf-next.git (refs/heads/master):

On Wed, 12 May 2021 16:27:33 +0900 you wrote:
> In the forwarding path GRO -> BPF 6 to 4 -> GSO for TCP traffic, the
> coalesced packet payload can be > MSS, but < MSS + 20.
> bpf_skb_proto_6_to_4 will upgrade the MSS and it can be > the payload
> length. After then tcp_gso_segment checks for the payload length if it
> is <= MSS. The condition is causing the packet to be dropped.
> 
> tcp_gso_segment():
>         [...]
>         mss = skb_shinfo(skb)->gso_size;
>         if (unlikely(skb->len <= mss))
>                 goto out;
>         [...]
> 
> [...]

Here is the summary with links:
  - [bpf-next,v3] bpf: check for BPF_F_ADJ_ROOM_FIXED_GSO when bpf_skb_change_proto
    https://git.kernel.org/bpf/bpf-next/c/fa7b83bf3b15

You are awesome, thank you!
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