Help Broadcasting a UDP packet on the LAN:URGENT

[Wes Peters]

On Tuesday 21 October 2003 03:23 pm, Barney Wolff wrote:
> Bruce M Simpson wrote pointing
> out AODV (RFC 3561) as an example of a routing protocol needing to
> send to 255.255.255.255 on multiple interfaces at once.  I withdraw
> my scorn of kernel mods to facilitate this.

To me it's not a matter of "boot code" vs. general usefulness so much as 
it's just obviously the right way to do it.  We use all-ones packets well 
after boot to have our appliances identify each other on the network and 
share configuration information, and it's not always evident which 
network interface(s) they should be using to do this.

The current code binds to each of the interfaces and blats out a packet, 
but it just seems obvious that the all-ones address implies all attached 
interfaces because you have a per-network broadcast address if you want 
to do per-interface broadcasts.

I've been working with Bruce on this and there are parts that still worry 
me.  If you want to poke holes in the thinking we've been doing, I'm 
always happy to have another set of eyeballs on the design and I'm sure 
Bruce will too.  Interactions with VLANs, for instance.  If you send an 
all-ones broadcast on an interface that has one or more VLANs configured, 
do you repeat them "on" each VLAN as well?  Ugh.  What about 
point-to-point links?  Are those always considered gateways to a foreign 
network, or just another form of locally attached network?

I'm pretty certain the code won't be all that difficult if we just fully 
understand the problem before we jump in, but I'm also pretty certain we 
don't fully understand the problem, let alone the solution.  ;^)

-- 

        Where am I, and what am I doing in this handbasket?

Wes Peters                                               wes at softweyr.com