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[67.216.200.102]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1903ca044d4sm14095227c88.17.2026.10.22.02.16.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Oct 2026 02:16:24 -0700 (PDT) From: Cheng Yongkang To: Nikolay Aleksandrov , Ido Schimmel Cc: "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , bridge@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [BUG] net: bridge: VLAN operations emit wrong link event types Date: Thu, 22 Oct 2026 02:16:18 -0700 Message-Id: <20261022091618.3651826-1-teel4res@gmail.com> X-Mailer: git-send-email 2.34.1 X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi all, br_vlan_rtm_process_one() reuses the VLAN operation command map for the RTNLGRP_LINK notification type. A successful RTM_NEWVLAN therefore multicasts RTM_SETLINK, while RTM_DELVLAN multicasts RTM_DELLINK even though the target netdevice still exists. br_fill_ifinfo() also omits IFLA_PROTINFO unless the event is RTM_NEWLINK. Observed on Linux v7.3, commit 08ab31164c55f20c7a2653de3186ae333470e2c1: RTM_NEWVLAN -> ACK 0 link notification nlmsg_type=19 (RTM_SETLINK) IFLA_PROTINFO absent RTM_DELVLAN -> ACK 0 link notification nlmsg_type=17 (RTM_DELLINK) IFLA_PROTINFO absent target port still exists after the DELVLAN The kernel's dynamic-debug output independently confirmed br_fill_ifinfo event 19 and event 17 for the port. The request handlers need RTM_SETLINK/RTM_DELLINK operation semantics, but successful VLAN changes should emit RTM_NEWLINK, matching the older br_setlink()/br_dellink() notification paths. The 2015 notification compatibility fix established that ABI, and the later RTM VLAN path regressed it. I found no matching upstream fix or CVE. The self-contained PoC and full serial log are available on request. This was found with a multi-agent workflow; both event types were reproduced in QEMU. Thanks, Cheng Yongkang