From patchwork Tue Nov 28 08:49:40 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hangbin Liu X-Patchwork-Id: 13470695 X-Patchwork-Delegate: kuba@kernel.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="J4efwJ4A" Received: from mail-pf1-x430.google.com (mail-pf1-x430.google.com [IPv6:2607:f8b0:4864:20::430]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 19337E7 for ; Tue, 28 Nov 2023 00:50:40 -0800 (PST) Received: by mail-pf1-x430.google.com with SMTP id d2e1a72fcca58-6b7f0170d7bso4879921b3a.2 for ; Tue, 28 Nov 2023 00:50:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1701161439; x=1701766239; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=ND75AnxP9o6edoo6d0k++1k4h8vC8KMUihiX/v8OTos=; b=J4efwJ4AGZopp/4qD+seEQzYv7NfWnmaxEg/tWT5U6T7OrRDbeo/92JtgzYzOLwt6n 49WDUxzDVkZshqQYD9Q8q864qPPCTH5TsI0NDzOE9Vdn6dbHOkB9xFWHMh+N+9fdaEtx tIldED9lkrYVnjw50srHSnPt7CTi8eEut/q9sN/GeauO4yaymSU1AOZP1jCl8MgTUx2L tYTu49hGnx294/Mf5k1pkBhaLfPV47r3Ss4t+RyzP52lfidZxj7QPXWl3ZnIV0MH6k0+ 4REx6j8yJsI6ykgIVxTQp5VW7VVosYpD8Aj6/Zx8I/8E1nQ3d0wEaartkhxLVyR0VwL1 eSJA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1701161439; x=1701766239; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=ND75AnxP9o6edoo6d0k++1k4h8vC8KMUihiX/v8OTos=; b=on3H4DFK/hGXTFjnezTIyXwxcaOzNiGQpiOhjAGuq9QI8Uwmzejy3ZWDbzk0oelT7N CqYIPWnGjYZb9fvGxJvtvv/p00hB05NE7xJSnl3oHtKBTLQ/Ji9eYYakJRr84HeYueu1 XuQ7MUcfMgfdQUHylvZIEW3lG3bKYzYcHazxkdSFvz7JHTulwaAiBnMu0ZEEr7WcO1VO aoA4iBDjKTAyEDsndpIpn9g//GTMVuxJh3YxFIoewKUouA9m1ltip9t3xzNzhInG1ND/ JuhImQCHEhutkkMmNWUEYbiwITbjYH2mLo4/DFqXoUo01wA3otDYqdu7j3lz28XQiNus Jy/Q== X-Gm-Message-State: AOJu0YwXBf4fWSoH6hFUnm3uy+zldhMIbfks6AZTWMI+Sedipau3Sqqp vRLJuqBeGDPRcslrEyrQgpdGxf3bWoj00KOR X-Google-Smtp-Source: AGHT+IEDwdl4H1SNovDrvpQEXVl5l+VHekDEpF015DN0iW9aHqkhuD+NMbHIMclVsligRuJJnY3NJA== X-Received: by 2002:a05:6a00:8f0c:b0:6cc:298:eb30 with SMTP id ji12-20020a056a008f0c00b006cc0298eb30mr15668799pfb.29.1701161438859; Tue, 28 Nov 2023 00:50:38 -0800 (PST) Received: from Laptop-X1.redhat.com ([43.228.180.230]) by smtp.gmail.com with ESMTPSA id d25-20020aa78159000000b006cbae51f335sm8766513pfn.144.2023.11.28.00.50.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Nov 2023 00:50:38 -0800 (PST) From: Hangbin Liu To: netdev@vger.kernel.org Cc: "David S . Miller" , David Ahern , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Ido Schimmel , Nikolay Aleksandrov , Roopa Prabhu , Stephen Hemminger , Florian Westphal , Andrew Lunn , Florian Fainelli , Vladimir Oltean , Jiri Pirko , Marc Muehlfeld , Hangbin Liu Subject: [PATCHv3 net-next 07/10] docs: bridge: add multicast doc Date: Tue, 28 Nov 2023 16:49:40 +0800 Message-ID: <20231128084943.637091-8-liuhangbin@gmail.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20231128084943.637091-1-liuhangbin@gmail.com> References: <20231128084943.637091-1-liuhangbin@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org Add multicast part for bridge document. Acked-by: Nikolay Aleksandrov Signed-off-by: Hangbin Liu Reviewed-by: Florian Fainelli --- Documentation/networking/bridge.rst | 55 +++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) diff --git a/Documentation/networking/bridge.rst b/Documentation/networking/bridge.rst index 764d44c93c65..956583d2a184 100644 --- a/Documentation/networking/bridge.rst +++ b/Documentation/networking/bridge.rst @@ -161,6 +161,61 @@ on a bridge is disabled by default. After enabling VLAN filtering on a bridge, it will start forwarding frames to appropriate destinations based on their destination MAC address and VLAN tag (both must match). +Multicast +========= + +The Linux bridge driver has multicast support allowing it to process Internet +Group Management Protocol (IGMP) or Multicast Listener Discovery (MLD) +messages, and to efficiently forward multicast data packets. The bridge +driver support IGMPv2/IGMPv3 and MLDv1/MLDv2. + +Multicast snooping +------------------ + +Multicast snooping is a networking technology that allows network switches +to intelligently manage multicast traffic within a local area network (LAN). + +The switch maintains a multicast group table, which records the association +between multicast group addresses and the ports where hosts have joined these +groups. The group table is dynamically updated based on the IGMP/MLD messages +received. With the multicast group information gathered through snooping, the +switch optimizes the forwarding of multicast traffic. Instead of blindly +broadcasting the multicast traffic to all ports, it sends the multicast +traffic based on the destination MAC address only to ports which have joined +the respective destination multicast group. + +When created, the Linux bridge devices have multicast snooping enabled by +default. It maintains a Multicast forwarding database (MDB) which keeps track +of port and group relationships. + +IGMPv3/MLDv2 EHT support +------------------------ + +The Linux bridge supports IGMPv3/MLDv2 EHT (Explicit Host Tracking), which +was added by `474ddb37fa3a ("net: bridge: multicast: add EHT allow/block handling") +`_ + +The explicit host tracking enables the device to keep track of each +individual host that is joined to a particular group or channel. The main +benefit of the explicit host tracking in IGMP is to allow minimal leave +latencies when a host leaves a multicast group or channel. + +The length of time between a host wanting to leave and a device stopping +traffic forwarding is called the IGMP leave latency. A device configured +with IGMPv3 or MLDv2 and explicit tracking can immediately stop forwarding +traffic if the last host to request to receive traffic from the device +indicates that it no longer wants to receive traffic. The leave latency +is thus bound only by the packet transmission latencies in the multiaccess +network and the processing time in the device. + +Other multicast features +------------------------ +The Linux bridge also supports `per-VLAN multicast snooping +`_, +which is disabled by default but can be enabled. And `Multicast Router Discovery +`_, +which help identify the location of multicast routers. + FAQ ===