Subject: Re: IPv4 multicast transmission when there's no interface address
To: None <firstname.lastname@example.org>
From: David Laight <David.Laight@btinternet.com>
Date: 01/08/2002 14:58:56
> > when there's no IPv4 address assigned to the multicast outgoing
> > interface (specified by setsockopt), kernel made panic. i've
> > committed
> > the following change to avoid the kernel panic. historic behavior
> > was to use 0.0.0.0 as source.
> > my question is, which behavior look better? do any of you know
> > apps that assumes "0.0.0.0 as source" behavior?
> > reasoning for using 0.0.0.0 as source:
> > "0.0.0.0 as source" is legal only while the interface is
> > being initialized (RFC1122 p30), therefore, if there's some
> > user program that uses multicast for interface
> > initialization,
> > they want the behavior.
> > reasoning for forbidding packet transmission:
> > IP source address must be one of the interface addresses that
> > belong to outgoing interface (RFC1112 p6). if there's none,
> > we shouldn't send packet.
> If NetBSD supported unnumbered interfaces, then the proper thing would be to
> use the parent interface's primary address. If the the parent's primary
> wasn't set, then you'd default back to the router-id of the system. If no
> router-id was set, you'd return EADDRNOTAVAIL. You would never use 0.0.0.0 as
> the source address.
It's about the best address for the dhcpc request...
We don't want to have to use bpf to send it now, do we....