Sending a broadcast packet to another network

Sylvain Langlois RCG-ARS sylvain at lvbull.UUCP
Fri Apr 19 12:41:18 AEST 1985



In article <674 at oddjob.UUCP>, matt at oddjob.UUCP (Matt Crawford) says:
	>...My intent was to get the gateway to perform a broadcast 
	>on an adjacent net.
I don't really understand that, if the segment is forwarded to the gateway,
how does this one know he will have to broadcast it? But, that is not the 
reason of my answer...

	>So the gateway's refusal to forward my packet seems to be 
	>a by-product of the restriction that only the super-user 
	>can broadcast and the need not to repeat broadcasts endlessly.  
I think, allowing only suto broadcast packets is a good idea. You don't
really want to see everybody broadcasting junk all over the world, especially
if you have a strongly interconnected set of networks (LANs and WANs). The
broadcasting facility is to be used only by networks administrators (who may 
not be real su's, but it helps!!) or some special deamons, such as ARP for 
example.

	>ipintr() would also have to be changed to forward broadcast 
	>packets whose source address is not on the destination network.  
	>This would mean that certain packets are both forwarded and 
	>passed on to the next protocol level.  
This suppose copying the packet for local use and forwarding to packet to
the next host. But it also means you are entering an infinite loop. Each
host receiving this packet will broadcast it back to where it comes from, and
so on. When do you stop it ( it seems only possible with token rings, where
packets are destroyed when seen too often!).

-- 
Sylvain "Panic Trap" Langlois		
UUCP Address:	(...!mcvax!vmucnam!lvbull!sylvain)
Postal Address:	BULL, PC 33/05, 68 route de Versailles,
		F-78430 Louveciennes, France.



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