Re: Can we make NM automatically handle the need for proxy arp?

["Darren Albers" <dalbers gmail com>]

Ted, I am not sure if you are subscribed to the list or not so I am
ccing you.  If you are subscribed let me know.

On 8/27/06, Ted Lemon <mellon fugue com> wrote:
> Hm.  I would argue that it actually is appropriate for NM to do it,
> because NM is at the UI level, and you really want this to be a
> controllable behavior.   For example, one good UI for this would be to
> pop up a widget that says "yo, the DHCP server is giving bad
> information" and give the user the option of "Try ignoring this
> server" or "Try to make it work anyway."   Or you could make the
> behavior invisible to the user by having the DHCP client try to find a
> different DHCP server, and if it failed, only then try the
> workaround.   You would probably want to have a configuration
> parameter to control it - the current ISC client gives you the option
> of putting a bad DHCP server on a reject list.

I agree that the user should be informed that something is wrong, but
the messages can't confuse the user.

> You really want route add <bogus route> to print an error, and it
> wouldn't do that if you installed the workaround in the kernel.   Then
> you're going to get cases where a user manually mistypes the router IP
> address and doesn't get any feedback, and wastes twenty minutes
> debugging the problem.   Also, if you do the workaround in the kernel,
> you still need a UI to control that behavior, and NM is a fairly
> logical place to put it.   :')

I suspect that when the Network Manager UI for static addresses is
developed that it won't let someone enter an invalid subnet mask or
default gateway.

So back to the original topic, after a couple of google searches I
think that the Linux networking stack will utilize ARP to discover
routes if the default gateway does not exist and since dhclient will
reject bad default gateways then it should "just work" via arp
assuming that arp is enabled and arp_ignore is not set to 1.

So is the real issue here that dhclient is aborting completely when it
gets an invalid default route or is it accepting all the information
just rejecting the bad gateway?