Subject: Re: IPv4 multicast transmission when there's no interface
To: David Laight <firstname.lastname@example.org>
From: Matt Thomas <email@example.com>
Date: 01/08/2002 07:24:05
At 02:58 PM 1/8/2002 +0000, David Laight wrote:
> > > 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
> > > 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
> > address
> > 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...
Reread. We aren't talking about DHCP here.
Matt Thomas Internet: firstname.lastname@example.org
3am Software Foundry WWW URL: http://www.3am-software.com/bio/matt/
Cupertino, CA Disclaimer: I avow all knowledge of this message