Date: Tue, 9 Apr 2019 12:48:11 -0700 (PDT) From: "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net> To: John Baldwin <jhb@freebsd.org> Cc: Ian Lepore <ian@freebsd.org>, Ganbold Tsagaankhuu <ganbold@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r346052 - head/sys/dev/usb/net Message-ID: <201904091948.x39JmBZk061857@gndrsh.dnsmgr.net> In-Reply-To: <47360aeb-c2d0-7fc9-1924-399c34766547@FreeBSD.org>
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> On 4/9/19 9:59 AM, Ian Lepore wrote: > > On Tue, 2019-04-09 at 09:33 -0700, John Baldwin wrote: > >> On 4/9/19 9:17 AM, Ian Lepore wrote: > >>> On Tue, 2019-04-09 at 09:11 -0700, John Baldwin wrote: > >>>> On 4/9/19 6:54 AM, Ganbold Tsagaankhuu wrote: > >>>>> Author: ganbold > >>>>> Date: Tue Apr 9 13:54:08 2019 > >>>>> New Revision: 346052 > >>>>> URL: https://svnweb.freebsd.org/changeset/base/346052 > >>>>> > >>>>> Log: > >>>>> In some cases like NanoPI R1, its second USB ethernet > >>>>> RTL8152 (chip version URE_CHIP_VER_4C10) doesn't > >>>>> have hardwired MAC address, in other words, it is all zeros. > >>>>> This commit fixes it by setting random MAC address > >>>>> when MAC address is all zeros. > >>>>> > >>>>> Reviewed by: kevlo > >>>>> Differential Revision: > >>>>> https://reviews.freebsd.org/D19856 > >>>> > >>>> It would be best to not use a purely random mac address and to > >>>> use > >>>> the > >>>> function kevans@ added recently. That function generates a MAC > >>>> address > >>>> from the FreeBSD OUI using a cryptographic hash so you get a > >>>> stable address across boots on a given host. > >>>> > >>> > >>> How could that possibly work? If it's not random, you can't have > >>> two > >>> such devices on the same network. If it is random, it's not stable > >>> from one boot to the next. > >> > >> It uses the UUID and interface name as input into the hash. > > > >> The UUID is per-host. > > > > Oh, so it only works on x86 (or I guess any system that has something > > like a bios that can provide you with a uuid that doesn't change from > > one boot to the next). > > The function is in one centralized place where you are free to add other > data as input into the hash. We do always generate a uuid that we save > on boot if we aren't seeded with one by firmware, though that is probably > too late for this driver (so +1 may in fact be a better route). It should > be fine for psuedo interfaces created post-boot though even on non-x86 due > to /etc/rc.d/hostid. Pure random MAC's are not really great either. Cant the loader load /etc/rc.d/hostid and put it in something that the kernel could get at, or a module written that handles this? > -- > John Baldwin -- Rod Grimes rgrimes@freebsd.org
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