Date: Mon, 7 Dec 2009 11:48:31 -0600 From: Brooks Davis <brooks@freebsd.org> To: Angelo Hongens <angelo@hongens.nl> Cc: Brooks Davis <brooks@freebsd.org>, "freebsd-current@freebsd.org" <freebsd-current@freebsd.org> Subject: Re: FreeBSD 8.0 problems with interface renaming and dhcp? Message-ID: <20091207174831.GA75154@lor.one-eyed-alien.net> In-Reply-To: <4B1A0B39.5060201@hongens.nl> References: <4B195845.4000201@hongens.nl> <20091204221530.GA42198@lor.one-eyed-alien.net> <4B1A0B39.5060201@hongens.nl>
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[-- Attachment #1 --] On Sat, Dec 05, 2009 at 08:26:49AM +0100, Angelo Hongens wrote: > On 04-12-2009 23:15, Brooks Davis wrote: > > On Fri, Dec 04, 2009 at 07:43:17PM +0100, Angelo Hongens wrote: > >> On most of my BSD machines I rename the interfaces to nic0. This way, I > >> can swap cards and drivers, and keep the rest of my config the same. > >> > >> I upgraded one of these machines from 7.2 to 8.0 (both standard kernel), > >> and suddenly the machine would not get a dhcp lease. > >> > >> In my /etc/rc.conf: > >> > >> ifconfig_em0_name="nic0" > >> ifconfig_nic0="DHCP" > >> > >> The machine woud boot, but not get an ip. (and no dhclient output while > >> booting). And ifconfig would show the nic nic0 up, but without an ip. If > >> I do 'dhclient nic0' it immediately gets an ip, and all is well. > >> > >> If I do NOT rename the interface but just config: ifconfig_em0="DHCP" > >> everything works as well.. > >> > >> So is this a new bug or feature introduced in FreeBSD8? Is it something > >> that can be fixed? (So dhclient is executed for renamed interfaces.) > > > > I think the problem here is that with the new DHCP configuration where > > we only start DHCP based on link events we're loosing a race between the > > link coming up and the rename occurring. The absolutely correct answer is > > that the nic should no be trying to do anything until it is configured > > up and I don't think that happens before the rename (it shouldn't). > > It's likely the case though that a number of nics incorrectly start doing > > things before they are configured and thus racing the rename. The > > easiest workaround in the rc.d code would probably be to add some code > > to the rename section to take the interface down and then bring it back > > up after the rename. That should cause it to renegotiate and generate > > an event. > > > > The no code change workaround is to change DHCP to SYNCDHCP which will > > restore the old behavior on this interface. > > > > -- Brooks > > Great, configuring SYNCDHCP does exactly what it should do. I'm happy. > > If I understand you correctly, the long term solution would be to fix > the 'em' driver so that it never does anything with an interface until > it's configured (in my case: renamed). I never even touched C code, so I > hope someone else will look into that ;) My view is that interfaces should be "down" and ideally in maximum power save mode until they are configured "up" due to having an ifconfig_<ifn> or related entry in /etc/rc.conf. As a result, they shouldn't do anything that would result in events being generated until after a rename. -- Brooks [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iD8DBQFLHT/vXY6L6fI4GtQRAkKeAJwN0WpDoOEc31e4Zf5rcP0gf0FZMACZAYAD Tq7YkGTae+fGIYfY1JbeO4w= =77uc -----END PGP SIGNATURE-----help
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