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[2a02:3100:59ae:19fc:400:b6b0:efdd:810c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49fcd0f8563sm32070215e9.6.2026.09.18.16.46.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 18 Sep 2026 16:46:35 -0700 (PDT) Message-ID: <7c09a44a-19d9-43f5-a852-12f5b6579641@gmail.com> Date: Sat, 19 Sep 2026 01:46:34 +0200 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] net: hsr: fix packet drops caused by GRO superpackets To: Jakub Kicinski Cc: netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net, edumazet@google.com, 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, bigeasy@linutronix.de, 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> <20260809121455.1745-2-xiexinet@gmail.com> <20260813182111.088aee3d@kernel.org> 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: <20260813182111.088aee3d@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 14/08/2026 03:21, Jakub Kicinski wrote: > 1) could you explain in more detail why GRO is breaking things? > GRO shouldn't merge packets with different L2/L2.5 and packets > with trailers? The reproducer is plain SAN traffic entering a PRP RedBox's interlink: matching Ethernet headers, no RCT yet, so GRO can merge it. PRP then appends one RCT to the aggregate, using its length for LSDU_size and assigning one sequence number. If the aggregate LSDU exceeds 4095, the 12-bit field truncates it. Later TCP segmentation cannot generate per-segment RCTs. An aggregate left unsegmented may instead be dropped for exceeding the lower device's frame-size limit. Our wire captures showed segments without RCTs and duplicate delivery through the two LANs.Disabling interlink GRO raised single-stream TCP throughput from 27-37 Mbit/s to about 94 Mbit/s on the 100 Mbit/s rig. > 2) the code seems inspired by LRO but LRO also has > NETIF_F_UPPER_DISABLES. This change looks rather incomplete. > Calling it "best effort" seems like an excuse. NETIF_F_UPPER_DISABLES prevents a lower's ethtool request from overriding an upper's LRO-off policy. GRO is outside that mask and remains changeable; extending the global mask would affect other stacked devices too. Patch 1 sets the GRO-off default, while patch 3 segments plain, trailer-free aggregates before tagging, including when GRO is re-enabled or GSO arrives directly. GRO_HW can also be fixed on, so feature disabling alone cannot exclude all aggregates; device-specific hardware-coalesced formats remain outside v6's segmentation guarantee. I should have explained this distinction from LRO explicitly. > 3) Clashiko has a number of other comments: > https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260809121455.1745-1-xiexinet@gmail.com I have retrieved both v6 AI reviews and will address each comment with a fix or technical explanation before posting another revision. -- Xin