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From: Amos K. <ak...@re...> - 2011-09-18 01:05:31
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----- Original Message ----- > Whole Archive: http://marc.info/?l=kvm&m=131609166918121&w=2 > > ----- Original Message ----- > > On Thu, 2011-09-15 at 10:43 -0400, Amos Kong wrote: > > > ----- Original Message ----- > > > > ----- Original Message ----- > > > > > On Thu, 15 Sep 2011 21:00:38 +0800, Amos Kong > > > > > <ak...@re...> > > > > > wrote: > > > > > > > > > > > + netdev->xid = random(); > > > > > > > > > > This will not work for reboots. The decision that the > > > > > hardware > > > > > address > > > > > is > > > > > choosen was not accidental. Not sure if some DHCP server will > > > > > count > > > > > on > > > > > the > > > > > ID. (RFC 2131 "Retain DHCP client configuration across server > > > > > reboots, > > > > > and, > > > > > whenever possible, a DHCP client should be assigned the same > > > > > configuration > > > > > parameters despite restarts of the DHCP mechanism"). If not > > > > > so I > > > > > am > > > > > fine > > > > > with the patch. > > > > > > Hi Hagen, > > > > > > rfc2131 clearly describes that we need a random xid, > > > I don't think xid is a port of "DHCP client configuration", > > > it only be used to associate messages and responses between > > > client > > > and server. > > > > > > I would post a patch to ipxe maillist later if it's ok. > > > > rfc2131 only required that "A DHCP client MUST choose 'xid's in > > such a > > way as to minimize the chance of using an 'xid' identical to one > > used > > by another client.". > > > > The 'random xid' suggestion is listed merely as an example. > > > > The way I see it using a xid based on MAC instead of a random > > number > > is > > safer since the odds for same MAC on the same network are pretty > > slim > > since it would cause problems on other layers in the network. > > Users may boot up a QEMU guest without default mac address, it's easy > to repeat. > > Yaniv, what real problem do you touched? only not in accordance to > the RFC? Answer from Yaniv: Indeed. I saw some people complaining on inability to get a DHCP address, and from the network capture saw that. We have no idea why the failed most of the times to get an IP address with PXE boot. |
