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b=khkM1dEgKKPZ0XlRmbz2Bv2xRGQDoBSlH/AX1CqOSxJJgAH4lU2qcUTAZkdpuwBWIj U3iArANRtiO35xoMT9UNJnExP4jIRrwrdhfDyjqICgTnBa4++sn/52sZzW0nSffOKkIM iIov9Ma9uYdNlzZbLMWqYZtm2rSKuEntpH37c/gEMJbUhY/fNxgra1ZVSUWIV4H6CgHq oRsWhICqmM8wsyDXxH+OHv8QvRKPJxycD0pYwt54RFgtG04TpAMqCGsogwzt673hMifX Vmt3ami/LQZpGUHj2jUn9c2r/SLpKAzbTLoZwXYup/wPZPsgFIOQBZEF+16M9ob8N+H9 fbCQ== X-Forwarded-Encrypted: i=1; AKwUvBy6oB1R5OFp7OWwjv0DRrgHLdf4kMrZd74ifJpEgAtZUXi944ZkVCLeEdqadnGLtmtwb/8JvUQ=@vger.kernel.org X-Gm-Message-State: APuU4Z/m1cwFO04LjSjsxrJdANNbh9qB/SGT2VCI711jPKd4FDXd0yVh JT7QIGRCByirl7an63tu+LQK4NqGRZjIC5fj+esYjWwnoe44PatGaj5jMFJAiR1WhVDew89XSbY s/sUtqA== X-Received: from plbbb6.prod.google.com ([2002:a17:902:bc86:b0:2e8:18c6:a093]) (user=kuniyu job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:f712:b0:2e9:5829:9b40 with SMTP id d9443c01a7336-2eb3649be7emr111118405ad.9.1793683772335; Mon, 02 Nov 2026 21:29:32 -0800 (PST) Date: Tue, 3 Nov 2026 05:29:31 +0000 In-Reply-To: <20261101061331.286404-5-jiayuan.chen@linux.dev> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 References: <20261101061331.286404-1-jiayuan.chen@linux.dev> <20261101061331.286404-5-jiayuan.chen@linux.dev> Message-ID: Subject: Re: [PATCH net v3 4/5] ipv4: restrict igmp_qrv to 255 From: Kuniyuki Iwashima To: Jiayuan Chen Cc: netdev@vger.kernel.org, stable@vger.kernel.org, Fernando Fernandez Mancera , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Jonathan Corbet , Shuah Khan , Randy Dunlap , David Ahern , Ido Schimmel , Joel Granados , Thomas Gleixner , Petr Pavlu , Maoyi Xie , Jiri Wiesner , Oleg Nesterov , Gerd Rausch , Neal Cardwell , Chia-Yu Chang , Yung Chih Su , Wyatt Feng , Hannes Frederic Sowa , Flavio Leitner , "Paul E. McKenney" , Petr Mladek , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="us-ascii" On Sun, 01 Nov 2026 14:12:02 +0800, Jiayuan Chen wrote: > net.ipv4.igmp_qrv only has a lower bound, but ip_mc_reset() stores it > into the u8 in_device::mr_qrv, and the IGMPv3 retransmit counters filled > from it (crcount, sf_crcount) are u8 as well. Anything above 255 > silently wraps. With 256, mr_qrv becomes 0, every > "in_dev->mr_qrv ?: sysctl_igmp_qrv" falls back to 256, which truncates > to 0 again in crcount, and igmpv3_send_cr() never puts the state change > records for the group into a report. The older version querier present > timeout (mr_qrv * mr_qi + mr_qri) also collapses to just mr_qri. > > Make the sysctl a u8 like mr_qrv and switch to proc_dou8vec_minmax(), > which rejects anything above 255, and document it. > > Fixes: a9fe8e29945d ("ipv4: implement igmp_qrv sysctl to tune igmp robustness variable") > Cc: stable@vger.kernel.org > Reviewed-by: Fernando Fernandez Mancera > Signed-off-by: Jiayuan Chen Reviewed-by: Kuniyuki Iwashima