Problems with OpenBSD dhclient
Chuck Swiger
cswiger at mac.com
Fri Jul 15 05:22:23 GMT 2005
Andrea Campi wrote:
> picking one random message to answer to...
Agreed. :-)
> let's not forget Zeroconf (169.254.x.x) address assignment. I have
> (admittedly outdated now) patches to howl to make it work that are
> waiting on someone to help me finalize them AND most integrate with
> appropriate scripts so that things work as expected. This means
> removing the autoconfigured address when obtaining a proper address
> via DHCP, and vice versa.
>
> A full solution should IMHO take this into account, too.
For the wired case, it's entirely reasonable to respond to a link down/link up
combination by doing an ARPOP_REQUEST to the IP address of a router (which
quite probably provides the default route) on that interface's associated
network, and/or the IP address of the DHCP server which assigned your machine
it's IP.
If your router/DHCP server still thinks that your MAC address belongs to that
IP address, well, the system ought to rely on TCP retransmissions or the design
of higher levels to handle a timeperiod of no traffic without needlessly
dropping connections by dropping routes, closing open TCP sockets before their
time, etc.
In other words, an interface link down event should *not* blindly remove or
change the assigned IP address on an interface, only a link up event might, and
only then after checking via ARP (or a DHCP query, or similar variants).
In the meantime, and in the absense of having "multiple default routes" (routes
have metrics, can't one use them to prioritize and choose an alternate path if
the packets get routed through a link which is down?), it might be nice to pick
an alternate default route upon a link-down event.
I don't understand the layer-2 aspects of 802.11 wireless stuff modulo the
various flavors of WEP and WPA encryption to know whether there is an exact
equivalent to ARP, but I'd imagine something could be used to check whether the
AP you were just connected to still thinks your machine is what it saw a minute
or two ago, before your signal dropped off for a bit...
--
-Chuck
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