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From: Marty C. <md...@et...> - 2005-09-14 14:14:47
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On Sep 14, 2005, at 8:36 AM, Harald Welte wrote: > Hi! > I spent the last three hours debugging a problem where suddenly a > number > of my diskless embedded systems refused to boot. Those systems are > based on etherboot (http://www.etherboot.org/). > After adding tons of debug statements to the etherboot code, I > found out > that Herald, Many thanks for your debugging. We were recently made aware of the problem: http://sourceforge.net/mailarchive/forum.php? thread_id=8122799&forum_id=6401 It certainly is something we need to address. > 1) Etherboot DHCP client code ignores a DHCPOFFER with "siaddr" > 0.0.0.0 > 2) dhcp-3.0.2 suddenly changed the default from the dhcp server > address > to 0.0.0.0. This is mentioned in the changelog, but is > contradicted > by the dhcpd.conf.5 manpage (which still states that the DHCP > server > address is used as default). > I don't really understand the reasoning of the change in > dhcp-3.0.2. I > think it will cause many similar setups to break, and if admins look > into the dhcpd.conf.5, they verify that their setup is correct > according > to the documentation - but it ceases to work after a isc dhcp upgrade. > Please find the patch below for dhcpd.conf.5 Perhaps someone on the dhc...@is... list will have something to say about the reasoning behind this. If I was to venture a guess, I would guess that it has something to do with interoperability with other DHCP server implementations. > If you still want to continue the semantic change of the default > value, > I strongly suggest to print a warning or even make server startup > fail, > if > A) any netbooting related directive (root-path, filename, ...) is used > _AND_ > B) no "next-server" directive is present in the configuration. > This way the admin at least knows that something is wrong and has > to be > changed. Documentation is often the hardest thing to keep up to date. It's good you mentioned this. > For the etherboot folks: I've attached a suggested patch that prints a > message if a zero siaddr dhcpoffer is ignored. The current silent > failiure makes debugging hard. The Etherboot patch looks fine at first glance. I think the wording should be a little more general, something like: + printf("Ignoring DHCP offer without valid 'siaddr' field,\n " + "DHCP config may require explicit 'next-server' declaration.\n"); instead of: + printf("ignoring DHCP offer without valid 'siaddr' field, on " + "ISC dhcpd >= 3.0.2 use 'next-server' configuration\n"); This would make the condition more general, in case other servers do this as well. > Thanks for your consideration, > -- > - Harald Welte <la...@gn...> http:// > gnumonks.org/ > <dhcpd-3.0.3-manpage-siaddr.patch> > <etherboot-5.4.1-dhcp-zero-siaddr-warning.patch> Thank you for your debugging and patch. Let's see what other folks think. Marty -- Try: http://rom-o-matic.net/ to make Etherboot images instantly. Name: Marty Connor US Mail: Entity Cyber, Inc.; P.O. Box 391827; Cambridge, MA 02139; USA Voice: (617) 491-6935; Fax: (617) 491-7046 Email: md...@et... Web: http://www.etherboot.org/ |
