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Miller" , "Eric Dumazet" , "Jakub Kicinski" , "Paolo Abeni" , "Simon Horman" , "Shuah Khan" , , , Subject: Re: [PATCH net-next v2 0/3] ipv4/ipv6: Cache pmtu on all paths of a multipath route From: "Vladimir Vdovin" To: , "Vladimir Vdovin" X-Mailer: aerc 0.22.0 References: <20261110095903.84813-1-deliran@verdict.gg> <179430520494.488859.8396860489135491042@kernel.org> In-Reply-To: <179430520494.488859.8396860489135491042@kernel.org> X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMTExMDAzNyBTYWx0ZWRfX9XAf6MsiQ2dB oQiR6mWlSiHpvOPZsX/S/TDT1oCsipu/wWhOdidgIcgq1f94wFO+5ymo3+AaoSB6AS4Eg351Cih kPvGXn0lXZmnEB3KYC0Z2p0q7+N1woZMjjt13QHNqbBwqt0xzKaW+YrEC4KVt2FHyM34Bwk5Q5s H2gkjkShiuUX/fTmpO7sOijD7I+MPE23FgquDCBFDjybnLINyIlzcNIrevcihNPCzHgIwpR3Jue bQtyrkO7C6wftrDptlVXNgL9uCXMUShxX/lQXDUxli3xYH/64ExwyJbJsqMdFJvGvxWkXUwXqOf i+w8qemp/KuUJs0GSl85AOvnfYLSXOB5FOnK5DD+Z86v42WR0gZ2kODLPS+1o8= X-Proofpoint-Spam-Info: AW1haW4tMjYxMTExMDAzNyBTYWx0ZWRfX4prJEIYIvlJI 90w/x+gyjFtlqXAQGHWPONIVeEvB27GLuQKgcC7a1JRccu7eGNKedGKjS1ZO71bHDt1yni6h+95 EBmRLWic11xjY91P9X3obLY5aJXkQyg= X-Proofpoint-GUID: 1gpICloqEuvM2jL9llB7HfrG0NqYtiPg X-Proofpoint-ORIG-GUID: 1gpICloqEuvM2jL9llB7HfrG0NqYtiPg X-Authority-Info-Out: v=2.4 cv=W7qtxhWk c=1 sm=1 tr=0 ts=6af43369 cx=c_apl:c_pps:t_out a=kRaGL2Q7qLiahLf3O6OaIA==:117 a=kRaGL2Q7qLiahLf3O6OaIA==:17 a=IkcTkHD0fZMA:10 a=zJRp6_cAMcgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=Lz8lNifEoAKVmCoaIBl5:22 a=nt9yOg7Ld-NCdoK0S7LV:22 a=VwQbUJbxAAAA:8 a=slS2ziH7K9J5olFhi2UA:9 a=QEXdDO2ut3YA:10 X-JNJ: AAAAAAAB1zj+NsaxmxfPI77N0QmgMnZta+6UzS2tAB+wCuqrmJjmSn+VokQoxYC5Zycux8 hLUVNtLDUoif5Wo0JN7UJX3ATlXdTImnJtaFU5gFDaetqrmcamqVtT7bFVQYUn8WFcbZFP 3KMf5sviVUFn2T1ABRPn7LsQ/FHXb6wtH81FSr9UsfFMRrU1jqE9KlupXfQOSUr2VWGmox x3caz6SPF/N12ORrx5l+V5akPmfyNUSfjjbpYxWqNDO4XusDsmS40FZGVsaoRXoo2WMFwO A5CxaBoVSXwoTZGfCUXTc4cjG9al90iDyq3FVrtFYl/gIZ6n2Z0tRgZH2Ygo4CSJHf4twc GmOZtNNDFEvFRgqtmk9V/CLeVJypVlAd2oiQQpwsUW2MOn8nKslEZVyn6uKVDk6pP7ktAc g8Wt6zMuVOrLFNcsSh71HA0gEBmBacmnjcRUx6G8arxjQl1gsYKT0MILul0YbOfVrJVPo/ uV9KFhfSty5RLErGwoonCzbDoHgHTyW1P2Z0wRz52Qi+LG0j7SZr7hQgVTYwoLwW6LTHnA RFqf1Z58D2GAf8rOW3u3JdUcV67T/qMTemfdnzsdCcCgwCEihYVxNhGfaD4zHothGYY/1h n4OKjNl2DURITXoz7b7hcHieWXT55xpSsxVICX6tciT7rfqh/7z7H4SM0UGCkKwn23yav5 1J7Kgqfy9A1PuFnxDXSt3io0iZiiw78KmXk+6rvAxDNZeOPopJpLwJXkTViS2QRjSJb5xP InJ7wx0GIJM0TbEAbqv+9i5PU84Hbj8n4ApQNeaHjFiL37dCmrqC3cL4uSRfTDARt+LEiR 7mCXPAW+5s5Nx4J5cFbLURBvA60N/Z//tjYcwuR8GvRv9x3b1Nu3aolc2n8UlZeYpWltDM zQe6ZHPcJtWPid2VDQnJMvwEP8zxKPJb6VqOzRAOxoyOTSiPcNtD8tRcFF7Iup5oNcDKwt PAL3uCCcdqt4aCMH/B5b1jQtkpN1VOkfHWhsYtJ+VkE3fc+iFTV6Ej8iJHJZ8jahG17NRE cM8ulYcKAVpgvSOl99nGTz6s9gC0oX7jXJQm6G3TMkhWEGUCmsXWFLem+SKxC1WS5QKCiN tvwRGWZDpQTUPn9m4jrqIJGIFGCiJDCFwj3NNxwxkL1/boQEMGAiClsl4V6yJjdUE8/hjz advbX8lbo/d6pneh5HwRThQ2yJZz0G+tFNiGZvvlFWjRCpNcfnAC5k2dbB9JI9sF85r8e/ wIFOY3ADFpvPUnpPPKryq1vmUOEMkiAlrbcZ3eMNfQYa+PblIVSvVGAce/1wVT7igm2GUN Uopeod2UpiDFgf71I43j1nx04mdgxIsLb5R/z5ljrrV/tPhZCVhfklv+nwHdK1x0Hw+7hw 5ZBqbqGayLnVxg7g1QnRBSvQ On Tue, Nov 10, 2026 at 10:06:44AM +0000, netdev-bot+sinfo wrote: > - How the issue was discovered, e.g. hit in production, hit during > development, syzbot report, manual code inspection, LLM or static > analysis tool scan. Patch 2 (ipv6) is the counterpart of the IPv4 issue fixed in commit 7d3f3b4367f3 ("net: ipv4: Cache pmtu for all packet paths if multipath enabled") [1]: a host with two ECMP uplinks and a smaller MTU further down the path had flows blackholing after a Packet Too Big. The IPv6 side was deferred back then at David's request [2]. The new pmtu.sh tests in patch 3 reproduce it and fail without patch 2. Patch 1 (ipv4) was found by code inspection while reworking v1 after the Sashiko (LLM) review of it [3]: the same "replace the exception" step that review flagged in the IPv6 code is in the IPv4 fan-out from 7d3f3b4367f3 as well. [1] https://lore.kernel.org/netdev/20241108093427.317942-1-deliran@verdict.= gg/ [2] https://lore.kernel.org/netdev/ad29493c-9e48-4a94-b327-e47af3a9d137@ker= nel.org/ [3] https://lore.kernel.org/netdev/179236119085.3135.2701233313088371263@ke= rnel.org/