From patchwork Fri Nov 17 09:31:42 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hangbin Liu X-Patchwork-Id: 13458615 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="YMjWBOb6" 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 7C8141727 for ; Fri, 17 Nov 2023 01:32:25 -0800 (PST) Received: by mail-pf1-x430.google.com with SMTP id d2e1a72fcca58-6b709048d8eso1636543b3a.2 for ; Fri, 17 Nov 2023 01:32:25 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1700213544; x=1700818344; 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=9Vo75FcuvNVlq4TjmwAxJVAawHxP5B8FdSellSWuvng=; b=YMjWBOb6H1P5+EMm05vbjvgguxceFkcRLNZ3v1ynhUdkQ4T+v0X4BoSV+QVnO6DVvg 0gDo8hOQtCJotnQ7rItZP+/zDVbmrtdNBpsrFhbRoWhCqhiENW4LxJkp7ZTqT8smmFQR d5ONeF9xBusbM38M42roukEyotAmDziqtJGqJH4ldX6hQ/jTnMhDVrsTk82inJbzhhWS VkJLeu4IpZY0FMo9DVRrfwkwehDjexctRnly2ZCdhQbyhKQLHmhMiniDD0F3rBK2YKUd K4kkyjLV6N+Rm2mc+uvTcYSEq8/GdYTVsktf+7hCUk0sAFsZcDWX8CWMeJPSjGnVaNJf h5Ug== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1700213544; x=1700818344; 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=9Vo75FcuvNVlq4TjmwAxJVAawHxP5B8FdSellSWuvng=; b=BYaP61Nrs0UEJ/dE6k57O9VWxlkmidfCGwH1nq8liYlU5y0aRescyZRSW8IZKd2+/G ybfzQ/ffZYB8YkdhdRQ39QnHDLOfqAJU+PqJiYR3BugaAKfqT9xEQKKZT3PUOKPqPJoj aM15tYkv/rxjqVpVK5fmonnL4iOWMYRS6K6N5PBJ5viQHnyW6333V/+o6CYbprz75db2 BQpTgNhhDZrW5nOaR504xjY2NWSmOpCQRdUpy+CiSqfXgtHLk+fiSuyIOXZFIyA9sKKA X5PMBowRyJy8B/ZuRyjtm84auFLF3bpr7yORx1jgLnvIVjNSrMRHAoZnB/EnVLPhQl19 vW9Q== X-Gm-Message-State: AOJu0YyuuOiT7Ge5lzDoPqbq6fuiUOebsd+ObzIqg+wDhOiLMGQoV1WQ BZ0ULv9xl0U6mE3uKawj9idWX66ZH2Cse+Ix X-Google-Smtp-Source: AGHT+IHXeLA6fVZUE/3M/3VuEy7Auh3kgakaShFZy1NY18t8ZpYap6dg4Tt7SkgtwYxQa8SuRigRyQ== X-Received: by 2002:a05:6a20:e111:b0:188:c44:5e5 with SMTP id kr17-20020a056a20e11100b001880c4405e5mr1867004pzb.30.1700213544260; Fri, 17 Nov 2023 01:32:24 -0800 (PST) Received: from Laptop-X1.redhat.com ([43.228.180.230]) by smtp.gmail.com with ESMTPSA id p9-20020a17090adf8900b0027ceac90684sm964060pjv.18.2023.11.17.01.32.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Nov 2023 01:32:23 -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: [PATCH net-next 07/10] docs: bridge: add multicast doc Date: Fri, 17 Nov 2023 17:31:42 +0800 Message-ID: <20231117093145.1563511-8-liuhangbin@gmail.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20231117093145.1563511-1-liuhangbin@gmail.com> References: <20231117093145.1563511-1-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. Signed-off-by: Hangbin Liu --- Documentation/networking/bridge.rst | 55 +++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) diff --git a/Documentation/networking/bridge.rst b/Documentation/networking/bridge.rst index f70f42ab7396..62cb6695cd22 100644 --- a/Documentation/networking/bridge.rst +++ b/Documentation/networking/bridge.rst @@ -165,6 +165,61 @@ 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 ===