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[2a02:3100:5dd2:bcfc:4dfb:2ac9:70ba:48bd]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4887a355c65sm5863049f8f.19.2026.09.25.02.52.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 25 Sep 2026 02:52:53 -0700 (PDT) Message-ID: <21bfa8a9-c488-49aa-b2a1-4d282fd51c42@gmail.com> Date: Fri, 25 Sep 2026 11:52:52 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/4] net: hsr: unfold GSO super-packets at the forward entry To: Sebastian Andrzej Siewior Cc: netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, andrew+netdev@lunn.ch, shuah@kernel.org, kees@kernel.org, petr.wozniak@gmail.com, qingfang.deng@linux.dev, fmaurer@redhat.com, luka.gejak@linux.dev, xiaoliang.yang_1@nxp.com, skhawaja@google.com, liuhangbin@gmail.com, stable@vger.kernel.org, sdf.kernel@gmail.com References: <20260809121455.1745-1-xiexinet@gmail.com> <20260809121455.1745-4-xiexinet@gmail.com> <20260923104346.ur63K3h2@linutronix.de> <2cf54664-c07d-471f-af6d-4b70e09626b4@gmail.com> <20260925082954.MYDugnDU@linutronix.de> Content-Language: en-GB From: Xin Xie Autocrypt: addr=xiexinet@gmail.com; keydata= xsDNBGpiHugBDADJ5KuJaOYfUx7TGbRw0UE1km4dLnJomCSNtgq2T9BqgZ6TRPEy37soAmW3 XxCPvhfL6CPLldzy6O6EkUD7/8zlbQP1DM6gUIQUyKxxkb8uR+oCogDKjsxt0QPycP/dR9fk SL4qKReprnkOOcGeLahLHzofVdn46mc5igCBsAA/PPSpo1GqsfGk+zYV97rSVa8zhnSXsqZ/ 9DbUfQynZKVqYN4tm1B30JE5SEWDCko95Qw9fAORX2W356MOQJGr05z9qMSy7CkF7bAUkziG d6ZSPsGEsel5jYByP8ZvwQ2A8kdKpRy8+zQCaC+vEotTH7Fs7SIzE/Z5mEVIi1xQqEzN1rqG BW7KgzRDWjw8lKsoBbxv20nfhUzuZLan2HzUJ+LxZ18Os4zkWg9sxHgMi+AGqn/+0ppbDcOH 9Jm072/xA7O1MCXLgr4FOP+4PJH1vcqU+0EZVz7KCjrwkdz+l5Ojso2FLXq2MGoqWGShIsDV bF1JYpgm4spdPbnISkidUC0AEQEAAc0cWGluIFhpZSA8eGlleGluZXRAZ21haWwuY29tPsLB DQQTAQgANxYhBAHOahKZFnMu2n/CxrTrSufyPi3LBQJqYh7oBQkFo5qAAhsDBAsJCAcFFQgJ CgsFFgIDAQAACgkQtOtK5/I+LctmngwAlmrGPWnWxDW6PSJeR9SM0faqwuY33TWAE35nshm/ EEkBgpVVhG4z4Cdy7L+6TG6NHVDnvl+IHLyyOZlL3LQPQIpiKVgo6jHmm9TF6mK+Vo3nsXAA uSJYu9iY9Aywmy2JVQ15ttQ0NfcoZ0sV14bT7pSr9zXB6D8p3XA4AQI6IBeLvj993Z1+tPyC 6BJ+2aWWLBx7xGpFo3X8dhjS/Lm8QoietKbI+ACefKKCDNiM2KG53P76wdXJp52u4dqP6eFc +Qv35QefnALoPkOGQEdd1qvUycyZhuaCj8h0AxDu7bL3G/IM8G2K8qsbSJuui8zCSZ9b/QZf H7u1nevPOgxyWC1Pep/TbRZ62ktn8lrmWA8PZjuaJJQGjahuK1GgTQZNG+7DB7NwjLr6aXIm JirtT4FeR+IUovvL/ll+VHzpGpFbgXz4GTsWsikQkT1huFSB8MRLlWMXdAKblL96L754j8Z5 p/YV26YTppXI56uJ3XyOwZSrfrK1pfqNIp2Yr9vUzsDNBGpiHukBDACePM1YZ1FvAiFay/2v KVDNpuazmpVb1CBFy+rqM9HcuHe+5CuxLd4RI4hb0qmjlm5Vi5M8+AuNB/wi/f8oDuhJwlMn v9L0lfgpRRdShnB26hnt2wWwWFgOU3BwymSruxhEYq+eIjjxCAo6yW7Qm+ArZ+riETMI67sy ZyLx6o4yRiWxOrh1nhwV/f6PIOl+Iv4yLAG3eFXpU7/EZpim610bKMwcXEpiRkf3NjiflIha adoKHV0LCiVNrU7r8TICjjnugpl1tXAR2RlaRcSxmvOzrXY2O/xBLpwPr5erbdk8RCaxUzS0 kK0hw+/On3Sr4Z4gtLl2xtDkjRh3KQ9ZqMPrFD/5XOs842ueNivwIyAf2kQJjKfJGWc771EM 0ZWo1r1AthbuM+IeN5QM74rMJxaf5WyDX3ZeqBA55fCJGJ3zrp7Tqeoq8DYufiNkppE9S71z Cvxva2f8mUWTlTUf8s33sRD7C87XpT0whKpn1I9/nJB9Kb0dKyRCdcsT4o1ynxUAEQEAAcLA /AQYAQgAJhYhBAHOahKZFnMu2n/CxrTrSufyPi3LBQJqYh7pBQkFo5qAAhsMAAoJELTrSufy Pi3L/iwL/3aoCeq19Pog3fqisRyEZeX8pXw2GYlrJWYoM0mQ1USaTpdsMwCXaoFMoSBqid0F VPrqlH4bSIEEAzVmFPX0NjGhREDMrQ9eR5S9yqSpBvX+hz+xgpt4NOPhbVQmV+9f4lX9TJT7 GOO3EX2eeokg6ZAISycCAx7srXuc8oyRTJtnUQziH9GXrEeon88LHf1QHg0Z0sL/c7DfDqvW 9924M4ngQAZ8RgCBGZocoWuXCemSPkfQVLt5DzycSgSQODhbNSEmr+jb1V9Svf9D9k0CQfEY cB3uwOHWb6Z/yaEARbGZPSPn89YjXBncQTpgSvUM578b5x3pKi6PjZB/hwtUsRgrWGWoIwRi +ZmcHnCzsuo6uuNYX8VvmWqYsVajykjnpjdCGmU89QUsVmrtnDPBrfr8VVJcZPnCJhE595Pk LO29Oj0au9kr7kMW5Q+fBeHj5zz6VggAaRRU74/sgtwLODBWESPZ9LqUUdB5L/XbrSq2VDlD sNySbH3veZ/55EtlXA== In-Reply-To: <20260925082954.MYDugnDU@linutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 25/09/2026 10:29, Sebastian Andrzej Siewior wrote: > So you disable GRO on the interlink port and still receive GRO packets? > Or is this performance related where you want to keep GRO enabled on the > interlink port? I am not trying to keep GRO enabled for performance. The difference is between a physical interlink and a veth interlink. With a physical interlink, TCP data is split into packets before it goes onto the wire via TSO/GSO. If GRO is off at the receiver, this interlink RX path needs no extra segmentation. Patch 3 is indeed unnecessary in this case. With a veth interlink, there is no physical wire: TCP -> prp0-peer -> prp0-int (interlink) -> PRP A veth pair is simply an in-kernel memory pipe. When a large TCP skb arrives at prp0-peer, veth does not trigger TSO or software segmentation, it simply hands over the intact skb pointer directly to prp0-int. Turning GRO off on prp0-int does not force prp0-peer to split it. I confirmed this with ordinary TCP traffic in a VM, with GRO off on both veth ends. Patch 3 splits that skb before PRP assigns sequence numbers and adds RCTs. Each resulting frame needs its own sequence number and RCT. Ordinary non-GSO skbs skip the segmentation path. In addition, if GRO disablement fails (e.g., buggy drivers or hardware-fixed GRO_HW that cannot be turned off via ethtool), Patch 3 also acts as a fallback defense for these edge cases. -- Xin