From owner-svn-src-head@freebsd.org Thu Mar 23 21:56:38 2017 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 572D7CA1BEC; Thu, 23 Mar 2017 21:56:38 +0000 (UTC) (envelope-from lidl@FreeBSD.org) Received: from hydra.pix.net (hydra.pix.net [IPv6:2001:470:e254::4]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "mail.pix.net", Issuer "Pix.Com Technologies LLC CA" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 0B22113E2; Thu, 23 Mar 2017 21:56:37 +0000 (UTC) (envelope-from lidl@FreeBSD.org) Received: from torb.pix.net (torb.pix.net [IPv6:2001:470:e254:10:1042:6a31:1deb:9f8a]) (authenticated bits=0) by hydra.pix.net (8.16.0.19/8.15.2) with ESMTPA id v2NLuPxB038678; Thu, 23 Mar 2017 17:56:25 -0400 (EDT) (envelope-from lidl@FreeBSD.org) Subject: Re: svn commit: r315653 - in head: lib/libstand sys/boot/common sys/boot/i386/libi386 To: Toomas Soome , Ian Lepore References: <201703202220.v2KMKHVP050735@repo.freebsd.org> <20170321123547.GC86500@zxy.spb.ru> <1490109312.13094.41.camel@freebsd.org> Cc: Slawa Olhovchenkov , Toomas Soome , src-committers , svn-src-all@freebsd.org, svn-src-head@freebsd.org From: Kurt Lidl Reply-To: lidl@FreeBSD.org Message-ID: <978b5e59-97f5-459e-5a8e-00848fe2dab1@FreeBSD.org> Date: Thu, 23 Mar 2017 17:56:25 -0400 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.23 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: Thu, 23 Mar 2017 21:56:38 -0000 On 3/21/17 11:53 AM, Toomas Soome wrote: > >> On 21. märts 2017, at 17:15, Ian Lepore wrote: >> >> On Tue, 2017-03-21 at 15:35 +0300, Slawa Olhovchenkov wrote: >>> On Mon, Mar 20, 2017 at 10:20:17PM +0000, Toomas Soome wrote: >>> >>>> >>>> Author: tsoome >>>> Date: Mon Mar 20 22:20:17 2017 >>>> New Revision: 315653 >>>> URL: https://svnweb.freebsd.org/changeset/base/315653 >>>> >>>> Log: >>>> loader: verify the value from dhcp.interface-mtu and use snprintf >>>> to set mtu >>>> >>>> Since the uset can set dhcp.interface-mtu, we need to try to >>>> validate the >>>> value. So we verify if the conversion to int is successful and we >>>> will not >>>> allow to set value greater than max IPv4 packet size. >>>> >>>> + tmp > USHRT_MAX) { >>>> + printf("%s: bad value: >>>> \"%s\", " >>>> + "ignoring\n", >>>> + "dhcp.interface-mtu", >>>> val); >>> === >>> USHRT_MAX Maximum value for an object of type unsigned short >>> int >>> 65535 (216-1) or greater* >>> >>> * the actual value depends on the particular system and library >>> implementation, but shall reflect the limits of these types in the >>> target platform. >>> === >>> >>> I mean IF_MAXMTU more correct. >>> >> >> The context here is libstand; because it is standalone by design, the >> code doesn't have access to IF_MAXMTU or other kernel/userland >> constants. There is also no question that a short is 16 bits or that >> USHRT_MAX will be anything other than 65535 in that environment. If >> some platform did appear that had a different-sized short by default, >> we would add whatever flags are necessary to force it back to 16 bits >> in src/share/mk/bsd.stand.mk. >> > > > Also note the “upper” value is entirely fictional - we felt we need > to pick some “sane” default, with current (common 1Gb/s) ethernet hardware > you will be in trouble long before reaching that value;) All the world is not an VAX, nor is every network Ethernet. HIPPI, not that you see much of it nowadays, had a MTU for switched networks of 65280 (64K - 216 bytes of overhead). Using USHRT_MAX is exactly the right thing here. -Kurt