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b=ILDSjCINZlEORlPVOz0s01LlXfaW7nTAM1gTKOrhFg3c1YvcoeKj+B9uKgYkwen7PvWhuz isIQLplQgL68QHAw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 928E0133F3; Fri, 23 Oct 2026 14:15:35 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id etWoGAds22oiewAAD6G6ig (envelope-from ); Fri, 23 Oct 2026 14:15:35 +0000 Message-ID: <68ac72a8-7642-4d10-ae61-8fc547b9c40a@suse.de> Date: Fri, 23 Oct 2026 16:14:33 +0200 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net 4/5] ipv4: restrict igmp_qrv to 255 To: Jiayuan Chen , netdev@vger.kernel.org Cc: stable@vger.kernel.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , David Ahern , Ido Schimmel , Kuniyuki Iwashima , Joel Granados , Chia-Yu Chang , Wyatt Feng , Yung Chih Su , Hannes Frederic Sowa , Flavio Leitner , Petr Mladek , "Paul E. McKenney" , linux-kernel@vger.kernel.org References: <20261023091419.167088-1-jiayuan.chen@linux.dev> <20261023091419.167088-5-jiayuan.chen@linux.dev> Content-Language: en-US From: Fernando Fernandez Mancera In-Reply-To: <20261023091419.167088-5-jiayuan.chen@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C435522199 X-Spam-Level: X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Flag: NO X-Spamd-Result: default: False [-13.50 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; BAYES_HAM(-3.00)[99.99%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; XM_UA_NO_VERSION(0.01)[]; MX_GOOD(-0.01)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCPT_COUNT_TWELVE(0.00)[20]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com,icloud.com]; RCVD_TLS_ALL(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[vger.kernel.org,davemloft.net,kernel.org,redhat.com,nvidia.com,google.com,nokia-bell-labs.com,icloud.com,gmail.com,stressinduktion.org,suse.com]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:106:10:150:64:167:received,2a07:de40:b281:104:10:150:64:97:from]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; MID_RHS_MATCH_FROM(0.00)[]; DKIM_TRACE(0.00)[suse.de:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,suse.de:dkim,suse.de:email] X-Spam-Score: -13.50 On 10/23/26 11:13 AM, 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. > > Unlike MLD there is no WARN_ON() here, the reports just go missing. > > Cap the sysctl at U8_MAX, the largest value mr_qrv can actually hold. > > Fixes: a9fe8e29945d ("ipv4: implement igmp_qrv sysctl to tune igmp robustness variable") > Cc: stable@vger.kernel.org > Signed-off-by: Jiayuan Chen Reviewed-by: Fernando Fernandez Mancera Thanks!