Neither do I I think, that's why I'm posting this :)
I'm working on the isdn4linux pppd. That (old) code sets the netmask on
the interface from a) a command line option or b) derives it from the
interface address (class A,B,C).
I would expect that in that case the "magic" route added by the kernel also
uses this netmask but no, the netmask of the interface gets resetted
to 0xffffffff.
Why is this useful? Well, suppose I dial into my companies network. They
have a class C, 192.168.2.0/24. Now if I set the netmask to 255.255.255.0,
a route would be added automatically to the remote system - that's useful,
and that is what you would expect.
However you still want to keep the IFF_POINTOPOINT flag on the interface,
so that "everybody" (routing protocols etc) know that it's just a pointopoint
route and not a non-broadcast network. Or not? [confused here]
This makes sense when you're used to Ciscos and the way routing is
handled; there are 3 types of routes - Connected, Static and routing
protocol (ofcourse there can be multiple routing protocols, but oh well).
I don't think this is a nessecety or something; you can always add routes
manually etc. I just think it looks cleaner and makes more sense. But
it might be that I'm totally wrong; that's why I'm asking... :)
Mike.
-- | Miquel van Smoorenburg | "I need more space" "Well, why not move to Texas" | | miquels@cistron.nl | "No, on my account, stupid." "Stupid? Uh-oh.." | | PGP fingerprint: FE 66 52 4F CD 59 A5 36 7F 39 8B 20 F1 D6 74 02 |