linux-kernel - Re: [PATCH v4] net: fix segmentation of forwarding fraglist GRO

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Message-ID: <willemdebruijn.kernel.11a4b80935127@gmail.com>
Date: Mon, 26 Jan 2026 11:49:26 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jibin Zhang <jibin.zhang@...iatek.com>, 
 Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, 
 Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, 
 Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, 
 John Fastabend <john.fastabend@...il.com>, 
 KP Singh <kpsingh@...nel.org>, 
 Stanislav Fomichev <sdf@...ichev.me>, 
 Hao Luo <haoluo@...gle.com>, 
 Jiri Olsa <jolsa@...nel.org>, 
 "David S . Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, 
 Simon Horman <horms@...nel.org>, 
 Neal Cardwell <ncardwell@...gle.com>, 
 Kuniyuki Iwashima <kuniyu@...gle.com>, 
 David Ahern <dsahern@...nel.org>, 
 Matthias Brugger <matthias.bgg@...il.com>, 
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
 bpf@...r.kernel.org, 
 netdev@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, 
 linux-mediatek@...ts.infradead.org, 
 steffen.klassert@...unet.com
Cc: wsd_upstream@...iatek.com, 
 Jibin Zhang <jibin.zhang@...iatek.com>
Subject: Re: [PATCH v4] net: fix segmentation of forwarding fraglist GRO

[PATCH net v4]

Jibin Zhang wrote:
> This patch enhances GSO segment handling by properly checking
> the SKB_GSO_DODGY flag for frag_list GSO packets, addressing
> low throughput issues observed when a station accesses IPv4
> servers via hotspots with an IPv6-only upstream interface.
> 
> Specifically, it fixes a bug in GSO segmentation when forwarding
> GRO packets containing a frag_list. The function skb_segment_list
> cannot correctly process GRO skbs that have been converted by XLAT,
> since XLAT only translates the header of the head skb. Consequently,
> skbs in the frag_list may remain untranslated, resulting in protocol
> inconsistencies and reduced throughput.
> 
> To address this, the patch explicitly sets the SKB_GSO_DODGY flag
> for GSO packets in XLAT's IPv4/IPv6 protocol translation helpers
> (bpf_skb_proto_4_to_6 and bpf_skb_proto_6_to_4). This marks GSO
> packets as potentially modified after protocol translation. As a
> result, GSO segmentation will avoid using skb_segment_list and
> instead falls back to skb_segment for packets with the SKB_GSO_DODGY
> flag. This ensures that only safe and fully translated frag_list
> packets are processed by skb_segment_list, resolving protocol
> inconsistencies and improving throughput when forwarding GRO packets
> converted by XLAT.

Fixes: 9fd1ff5d2ac7 ("udp: Support UDP fraglist GRO/GSO.")
Cc: stable@...r.kernel.org