From owner-svn-src-head@freebsd.org Sat Aug 20 16:27:24 2016 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 08A1EBC07AE; Sat, 20 Aug 2016 16:27:24 +0000 (UTC) (envelope-from bms@fastmail.net) Received: from out2-smtp.messagingengine.com (out2-smtp.messagingengine.com [66.111.4.26]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id CF3251575; Sat, 20 Aug 2016 16:27:23 +0000 (UTC) (envelope-from bms@fastmail.net) Received: from compute2.internal (compute2.nyi.internal [10.202.2.42]) by mailout.nyi.internal (Postfix) with ESMTP id A0BFC201CC; Sat, 20 Aug 2016 12:27:22 -0400 (EDT) Received: from frontend1 ([10.202.2.160]) by compute2.internal (MEProxy); Sat, 20 Aug 2016 12:27:22 -0400 DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d=fastmail.net; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-sasl-enc :x-sasl-enc; s=mesmtp; bh=xeOSLIFBYuICVQfKvILC/IX2ZFc=; b=GsZEPA zrZLqLn+kyIQ765wk8GyNAVwIJ9YoXTK3PC8z/7ko2lyAqa8J+ivS9oghN5Ze6E3 dBhGAKsU6ixfI5s7CoIvd8SjKBVvldoigIfVfL1qPsd/ERIaPkRxQ2ahxNkBNbfv EKF7USPU7siiA9lSVX0Ry6lm2t6Avx+q+7zdA= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :subject:to:x-sasl-enc:x-sasl-enc; s=smtpout; bh=xeOSLIFBYuICVQf KvILC/IX2ZFc=; b=IWDvx4/recMznSVftLj0jn4lS1SacKEMeOksDRyY8Yg7DRK vaA9UG9REBOiSGFosf/RXoNOznvcP4W+/QwDzwik5CHzprEOOrNclTLxLFD7+0tn gMksPF27d6jEpEwjKSJub76tJq7GLr5xEeOuxsLIG7Cz7llSeZeEWUE02UKU= X-Sasl-enc: 8tOkE+GdM5NfsFvgM7oX/e7b7B5yi9jGaRo4kcdOwaWV 1471710442 Received: from pion.local (cpc96954-walt26-2-0-cust843.13-2.cable.virginm.net [82.31.91.76]) by mail.messagingengine.com (Postfix) with ESMTPA id BDA1DF2986; Sat, 20 Aug 2016 12:27:21 -0400 (EDT) Subject: Re: svn commit: r304436 - in head: . sys/netinet To: Ryan Stone References: <201608182259.u7IMx5oW002018@repo.freebsd.org> <4fbc2e1d-3a62-5963-83d5-f9c931503e51@fastmail.net> <3806700d-ed27-7915-4818-c2d64f7b806d@fastmail.net> <6f4449f2-d145-8b49-c3f0-433e8ff4d2a2@fastmail.net> Cc: Ryan Stone , "src-committers@freebsd.org" , "svn-src-all@freebsd.org" , "svn-src-head@freebsd.org" From: Bruce Simpson Message-ID: <091555f6-05a8-3f91-0486-beb6531abd34@fastmail.net> Date: Sat, 20 Aug 2016 17:27:13 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <6f4449f2-d145-8b49-c3f0-433e8ff4d2a2@fastmail.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 20 Aug 2016 16:27:24 -0000 On 20/08/16 16:42, Bruce Simpson wrote: > On 20/08/16 16:27, Ryan Stone wrote: >> Can you send a broadcast packet through an L3 tunnel? I thought that a >> L2 tunnel was required. > > Yes. This is perfectly legal and necessary for forwarding of IPv4 > broadcasts to work. (it is Internet Protocol after all, not > Infernal-ethernet-extension Protocol. ;-)) For completeness: This does not hold true for L2 in L2, the most obvious example being Metro Ethernet VMAN style service. There, Ethernet is the transport (link layer), as well as the payload. That's a concrete example of the kind of L2 'tunnel' you may be referring to. Sometimes, specific Ethernet [broad|multi]cast destinations -- notably L2 control protocols, e.g. RSTP within the customer VLAN, may need to be tunnelled (Provider-Backbone-Bridges (PBB) style). Alternatively, the L2 destination MAC may be rewritten for that specific address, to avoid the destination being interpreted by routers in the Metro Ethernet core. It can be considered a crude form of Ethernet NAT, but it's common practice. But, for IP, forwarding IPv4 directed broadcast packets over a non-broadcast link is completely legal (and required for normal operation).