From owner-svn-src-all@FreeBSD.ORG Thu Oct 31 22:14:59 2013 Return-Path: Delivered-To: svn-src-all@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id 91182ACB; Thu, 31 Oct 2013 22:14:59 +0000 (UTC) (envelope-from jmg@h2.funkthat.com) Received: from h2.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 5CF2227BE; Thu, 31 Oct 2013 22:14:59 +0000 (UTC) Received: from h2.funkthat.com (localhost [127.0.0.1]) by h2.funkthat.com (8.14.3/8.14.3) with ESMTP id r9VMEwJm058737 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 31 Oct 2013 15:14:58 -0700 (PDT) (envelope-from jmg@h2.funkthat.com) Received: (from jmg@localhost) by h2.funkthat.com (8.14.3/8.14.3/Submit) id r9VMEvYL058735; Thu, 31 Oct 2013 15:14:57 -0700 (PDT) (envelope-from jmg) Date: Thu, 31 Oct 2013 15:14:57 -0700 From: John-Mark Gurney To: Luigi Rizzo Subject: Re: svn commit: r257455 - head/sys/net Message-ID: <20131031221457.GG58155@funkthat.com> References: <201310311546.r9VFkAIb049844@svn.freebsd.org> <20131031180336.GA62132@onelab2.iet.unipi.it> <5272AAC4.4030700@freebsd.org> <1383247645.31172.29.camel@revolution.hippie.lan> <20131031200502.GB83212@onelab2.iet.unipi.it> <20131031204916.GF58155@funkthat.com> <20131031211337.GA83561@onelab2.iet.unipi.it> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131031211337.GA83561@onelab2.iet.unipi.it> User-Agent: Mutt/1.4.2.3i X-Operating-System: FreeBSD 7.2-RELEASE i386 X-PGP-Fingerprint: 54BA 873B 6515 3F10 9E88 9322 9CB1 8F74 6D3F A396 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.2 (h2.funkthat.com [127.0.0.1]); Thu, 31 Oct 2013 15:14:58 -0700 (PDT) Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org, Andre Oppermann , Ian Lepore X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 31 Oct 2013 22:14:59 -0000 Luigi Rizzo wrote this message on Thu, Oct 31, 2013 at 22:13 +0100: > On Thu, Oct 31, 2013 at 01:49:16PM -0700, John-Mark Gurney wrote: > > Luigi Rizzo wrote this message on Thu, Oct 31, 2013 at 21:05 +0100: > > > On Thu, Oct 31, 2013 at 01:27:25PM -0600, Ian Lepore wrote: > > > ... > > > > Is there any chance all this reworking might get us to a position where > > > > the protocol header in an mbuf doesn't have to be 32-bit aligned > > > > anymore? We pay a pretty heavy price for that requirement in the > > > > drivers of the least capable hardware we support, the systems that have > > > > the least horsepower to spare to make an extra copy of each packet to > > > > realign it. > > > > > > So are you suggesting to use some 'copy_unaligned_32()' function/macro to > > > access 32-bit protocol fields in the network stack ? > > > (16-bit entries should not be an issue) > > > > my idea has been to make a change to the various ip/tcp/udp layers > > that is dependant upon __NO_STRICT_ALIGNMENT and if we do require > > strict alignment to copy the header to a stack buffer to align the > > data... > > I'd rather use accessors functions/macros to read/write > the unaligned headers so we can hide the #ifdefs in only > one place. I am/was trying to prevent massive code curn... > The copy to a stack buffer is probably useful even for readability Oh, I also realized I left out another part of it... void ip_input(struct mbuf *m) { #ifndef __NO_STRICT_ALIGNMENT struct ip tmpip; #endif struct ip *ip = NULL; #ifndef __NO_STRICT_ALIGNMENT bcopy(mtod(m, struct ip *), &tmpip, sizeof tmpip); ip = &tmpip; #else ip = mtod(m, struct ip *); #endif } > regardless of alignment (i do this in ipfw so i parse the > packet only once, and those values are used often), > but we should be careful to keep the copy in > sync with the original in places where those headers are modified > (NAT, ipfw fwd, maybe somewhere else ?) If you modify the packet, you need to be careful to write back the data when needed, i.e. passing the mbuf to another layer or returning.. But that isn't anything too different than other functions... Looks like I'll have to revive my TS-7200 port for testing as npe on AVILA apparently can handle the slightly odd alignment... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."