Date: Tue, 9 Apr 2019 12:29:12 -0700 From: John Baldwin <jhb@FreeBSD.org> To: 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: <47360aeb-c2d0-7fc9-1924-399c34766547@FreeBSD.org> In-Reply-To: <969703ae8558b4b6f2930208e9c36927b546bb77.camel@freebsd.org> References: <201904091354.x39Ds9e6070857@repo.freebsd.org> <ea3cb1dd-585b-e60f-294a-743645492d69@FreeBSD.org> <bd56e7a51ccc99aca6300ddafa449e6de95a1e20.camel@freebsd.org> <33d96fdb-0218-6555-6f03-3105649a1904@FreeBSD.org> <969703ae8558b4b6f2930208e9c36927b546bb77.camel@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. -- John Baldwin
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