Date: Thu, 23 Mar 2017 17:56:25 -0400 From: Kurt Lidl <lidl@FreeBSD.org> To: Toomas Soome <tsoome@me.com>, Ian Lepore <ian@freebsd.org> Cc: Slawa Olhovchenkov <slw@zxy.spb.ru>, Toomas Soome <tsoome@FreeBSD.org>, src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r315653 - in head: lib/libstand sys/boot/common sys/boot/i386/libi386 Message-ID: <978b5e59-97f5-459e-5a8e-00848fe2dab1@FreeBSD.org> In-Reply-To: <EBAA7588-B735-438A-A851-77A8B7DC63CC@me.com> References: <201703202220.v2KMKHVP050735@repo.freebsd.org> <20170321123547.GC86500@zxy.spb.ru> <1490109312.13094.41.camel@freebsd.org> <EBAA7588-B735-438A-A851-77A8B7DC63CC@me.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On 3/21/17 11:53 AM, Toomas Soome wrote: > >> On 21. märts 2017, at 17:15, Ian Lepore <ian@freebsd.org> 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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?978b5e59-97f5-459e-5a8e-00848fe2dab1>