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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3147e1ca3efsm12881928eec.30.2026.07.22.08.47.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Jul 2026 08:47:00 -0700 (PDT) Date: Wed, 22 Jul 2026 08:46:55 -0700 From: Stephen Hemminger To: anthony.l.nguyen@intel.com, przemyslaw.kitszel@intel.com Cc: intel-wired-lan@lists.osuosl.org Message-ID: <20260722084655.2d190adf@phoenix.local> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Mailman-Original-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20251104.gappssmtp.com; s=20251104; t=1784735221; x=1785340021; darn=lists.osuosl.org; h=content-transfer-encoding:content-type:mime-version:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=rOQtYMvADZ9GLCsvMLq3axtJoWiekLX/s0A7KPeUo5A=; b=tELW+jzhQDU473CVjmQuUd2jgBzq08oC9kJYasN0J1fIN4p2lCkJ5M6IKW//udCw+K wz7KfTNr+RNh+NaMFEug1AQz4V8AvT/PuiA/HnZGWcYY9AzTQCSJojZ/UScJDfH9eomd sT78RexDIHPgsveKnXgDs299kp7hjTVVQXJeGUO47ulJ20l8iVd84iTsaU5Hs4HS2+Db P7qyiHu1NidOB54H6GKGE57XPwMl07LL+iXfsmrep0EkpjZWfZN3mxlGOOxgzf0vSLyn hHlL6kQJ5KKG+4bqQkJTXZCUleH8tVGovOFKhCnrKFW1nCMDbTWYr9mDOCnBATf17vvN R8sw== X-Mailman-Original-Authentication-Results: smtp3.osuosl.org; dmarc=pass (p=quarantine dis=none) header.from=networkplumber.org X-Mailman-Original-Authentication-Results: smtp3.osuosl.org; dkim=pass (2048-bit key, unprotected) header.d=networkplumber-org.20251104.gappssmtp.com header.i=@networkplumber-org.20251104.gappssmtp.com header.a=rsa-sha256 header.s=20251104 header.b=tELW+jzh Subject: [Intel-wired-lan] Fw: [Bug 221750] New: igc: Intel I225 silently drops UDP broadcast to port 68 (DHCP) when interface is a bridge member X-BeenThere: intel-wired-lan@osuosl.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Intel Wired Ethernet Linux Kernel Driver Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-wired-lan-bounces@osuosl.org Sender: "Intel-wired-lan" Linux networking does not really use bugzilla, instead use email. $ ./scripts/get_maintainer.pl drivers/net/ethernet/intel/igc Tony Nguyen (maintainer:INTEL ETHERNET DRIVERS) Przemek Kitszel (maintainer:INTEL ETHERNET DRIVERS) Andrew Lunn (maintainer:NETWORKING DRIVERS) "David S. Miller" (maintainer:NETWORKING DRIVERS) Eric Dumazet (maintainer:NETWORKING DRIVERS) Jakub Kicinski (maintainer:NETWORKING DRIVERS) Paolo Abeni (maintainer:NETWORKING DRIVERS) intel-wired-lan@lists.osuosl.org (moderated list:INTEL ETHERNET DRIVERS) netdev@vger.kernel.org (open list:NETWORKING DRIVERS) Begin forwarded message: Date: Mon, 13 Jul 2026 16:20:22 +0000 From: bugzilla-daemon@kernel.org To: stephen@networkplumber.org Subject: [Bug 221750] New: igc: Intel I225 silently drops UDP broadcast to port 68 (DHCP) when interface is a bridge member https://bugzilla.kernel.org/show_bug.cgi?id=221750 Bug ID: 221750 Summary: igc: Intel I225 silently drops UDP broadcast to port 68 (DHCP) when interface is a bridge member Product: Networking Version: 2.5 Hardware: Intel OS: Linux Status: NEW Severity: normal Priority: P3 Component: Other Assignee: stephen@networkplumber.org Reporter: eslopez92@gmail.com Regression: No ## Description When an Intel I225-LM NIC using the igc driver is added as a member of a Linux bridge, UDP broadcast packets with destination port 68 (DHCP client port) are silently dropped at the TX path. The kernel queues the packet for transmission (visible via AF_PACKET capture on the interface showing PACKET_OUTGOING), but the frame never appears on the physical wire. All other UDP broadcast ports (e.g., port 9998) transmit correctly through the same bridge, same interface, same code path. Only destination port 67/68 (DHCP) is affected. This breaks any DHCP server (e.g., dnsmasq) running on the bridge host, as DHCP offers never reach clients. ### Keywords igc, I225, bridge, DHCP, broadcast, TX drop, dnsmasq ### Kernel version Linux version 6.8.0-134-generic (Ubuntu 24.04) Also tested: 6.17.0-35-generic (Ubuntu 24.04 HWE) - same behavior ### How to reproduce 1. System: Supermicro X13SAZ-F with Intel I225-LM (PCI 8086:15f2), igc driver 2. Create a Linux bridge and enslave the igc interface: ip link add br-fvn type bridge ip link set eno1 master br-fvn ip addr add 172.31.0.3/16 dev br-fvn ip link set br-fvn up 3. Run dnsmasq as DHCP server on br-fvn: dnsmasq --interface=br-fvn --dhcp-range=172.31.100.1,172.31.254.255,255.255.0.0,12h --dhcp-authoritative 4. Connect a DHCP client to eno1 (directly or via switch) 5. Observe: dnsmasq logs show DHCPDISCOVER received and DHCPOFFER sent, but the client never receives the offer ### Verification that the bug is interface-specific - Replacing eno1 (igc, I225-LM) with a USB ethernet adapter (r8152, RTL8153) in the same bridge: DHCP works immediately - Using an Intel I210 NIC (igb driver) in the same bridge on identical kernel: DHCP works - Sending UDP broadcast to port 9998 from the same bridge via the same igc interface: packets arrive at client - Sending UDP broadcast to port 68 from the same bridge via the same igc interface: packets never arrive - AF_PACKET raw capture on eno1 (host side) shows the DHCP offer as PACKET_OUTGOING (type=4), confirming the kernel hands it to the driver, but the frame never hits the wire - Wireshark/tcpdump on the client confirms zero DHCP offers received ### Environment Processor: Intel Core i9-14900K Board: Supermicro X13SAZ-F NIC: Intel I225-LM (8086:15f2, subsystem 15d9:15f2) Driver: igc Firmware: 1073:8754 Bus: 0000:01:00.0 (PCIe x1, 5.0 GT/s) OS: Ubuntu Core 24 (snap-based) ### Other notes - ethtool -K br-fvn tx-checksum-ip-generic off was tested - no change - bridge-nf-call-iptables=0 was tested - no change - br_netfilter module unloaded - no change - net.ipv4.ip_forward=1 was tested - no change - No iptables, nftables, or ebtables rules present - No eBPF/XDP programs attached - The igb driver (Intel I210) does NOT exhibit this behavior on the same kernel -- You may reply to this email to add a comment. 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