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[34.85.207.234]) by smtp.gmail.com with ESMTPSA id 00721157ae682-85e65f146edsm76395397b3.32.2026.09.01.07.11.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Sep 2026 07:11:00 -0700 (PDT) Date: Tue, 01 Sep 2026 10:11:00 -0400 From: Willem de Bruijn To: zhaoping.shu@mediatek.com, edumazet@google.com, ncardwell@google.com, kuniyu@google.com, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, matthias.bgg@gmail.com, angelogioacchino.delregno@collabora.com, dsahern@kernel.org, willemb@google.com, netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org Cc: haijun.liu@mediatek.com, xiayu.zhang@mediatek.com, lambert.wang@mediatek.com, Iven.Yang@mediatek.com, nbd@nbd.name, HW He , Zhaoping Shu Message-ID: In-Reply-To: <20260901082312.14596-1-zhaoping.shu@mediatek.com> References: <20260901082312.14596-1-zhaoping.shu@mediatek.com> Subject: Re: [PATCH net v5] net: gro: Fix nesting of TCP GSO SKBs in skb_gro_receive_list() Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit zhaoping.shu@ wrote: > From: HW He > > Fraglist GRO and hardware GRO can create an fraglist of > HW-GRO packets. This cannot be segmented back into > the original form on TCP tethering scenario. > > Avoid constructing such a GSO packet, by flushing an already > built fraglist GRO packet if a hardware GRO packet arrives. > > Scenario (Tethering/Forwarding): > 1.Driver submits a single TCP packet, P1. P1 is kept in the > gro_list as the first packet. > > 2. The driver submits a TCP GSO skb, P2. P2 has already aggregated > multiple TCP packets by HW_GRO, and its non-linear data is stored in > frags[]. > > 3. P1 and P2 match the GRO rules, and since there is no local socket, > they are aggregated by skb_gro_receive_list(). The resulting skb, > P3, has a frag_list entry that still contains frags[]: > P3: [ Linear Data ] -> frag_list -> [ Linear Data ] > [ frag[1] ] > [ frag[2] ] > ... > 4. Later, tcp4_gso_segment() or tcp6_gso_segment() calls > skb_segment_list() to segment P3. However, skb_segment_list() only > segments the entries in frag_list. It does not segment the frags[] > inside P2, so P3 is not restored to the original packets, which leads > to IP fragmentation or packet drop in the following path. > > Check skb_is_gso(skb) and current GRO method, make sure fraglist GRO > applies to consecutive non-GSO skb, others adopt regular GRO path. > > Fixes: 8d95dc474f85 ("net: add code for TCP fraglist GRO") > Signed-off-by: Zhaoping Shu > Signed-off-by: HW He Reviewed-by: Willem de Bruijn