From owner-svn-src-head@freebsd.org Sat Aug 20 16:57:36 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 B14DDBC0071; Sat, 20 Aug 2016 16:57:36 +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 7D3E51DC9; Sat, 20 Aug 2016 16:57:36 +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 5EDB220413; Sat, 20 Aug 2016 12:57:35 -0400 (EDT) Received: from frontend1 ([10.202.2.160]) by compute2.internal (MEProxy); Sat, 20 Aug 2016 12:57:35 -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=R46HCLwo9z5g0uEpAZRtscNLB18=; b=W5qdJB mjU6W1YBNBTyabt+INad7/g/oP4F1yhiQvQz0MuEjd2iXBdOm7l5Gr7cD8HThuby tv9kyW4YYGlC0FDPtXgt7LXFSCVNxPrvF6lv7zJKQeBj10tTZvCOTy4GV6Tv+7Z3 jYvIzeGNCbd53UCULSiRA9ZWknATq5jyWIVz4= 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=R46HCLwo9z5g0uE pAZRtscNLB18=; b=ja21MswIV2b5L8lWV340DRWm7PqEgn9BswQGQW8vbS81S+l HCpL1UySkjMt+zix2wuPXAtLcPN/zKz0IwJ2jXsTukrRpDbeoDEntVvocyMvq/V4 yzZak+lMj+ECVTmgKuoFBb7rukNFGSfbsY1siHNIPrJcwX7Xx2LigC5HQCx8= X-Sasl-enc: TI4htLTa4peMX11iDWGh9oqCjxxD8hXV/nysyvOmuR3V 1471712255 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 7A1FFF296E; Sat, 20 Aug 2016 12:57:34 -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> <990e003f-6180-b016-3b5f-6bdf579d073f@fastmail.net> Cc: Ryan Stone , "src-committers@freebsd.org" , "svn-src-all@freebsd.org" , "svn-src-head@freebsd.org" , Adrian Chadd From: Bruce Simpson Message-ID: <7779ae65-5366-0f42-4369-7f0647abca3c@fastmail.net> Date: Sat, 20 Aug 2016 17:57:26 +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: <990e003f-6180-b016-3b5f-6bdf579d073f@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 16:57:36 -0000 On 20/08/16 17:49, Bruce Simpson wrote: >> - Providing a mechanism for ip_input() to signal to udp_input() that the >> packet was addressed to an L3 broadcast address would require >> rototilling the pr_input interface, and I'd have to carefully ensure >> that if anything might interpose itself between the two layers (IPSec?) >> that the flag would have to be passed through correctly. > (We had to do something similar for ILNPv6, because of how IPv6 input > works, so it allocates an unused bit from the IPv6 flow label.) In case anyone's interested, IPSEC is one big reason we had to do this. Performance was another; without marking ILNPv6 traffic, demultiplexing an ILNPv6 packet -- even 'just enough' to forward it -- would have required processing all IPv6 extension headers, and additional state lookups. Using a bit from the flow label means ILNPv6 routers don't need to do any of that, and it got translated into an M_ILNP mbuf flag internally. I shudder to think what gymnastics the FreeBSD stack may have to endure to accommodate modern Ethernet switching capabilities, though.