[ECOS] IP limited broadcasts problems

[Robin Farine <acnrf at dial dot eunet dot ch>]

Hi,

It seems to me that the OpenBSD IP stack does not handle correctly IP limited
broadcasts. Take a host with N Ethernet interfaces, each with an IP address on a
separate IP subnet and with the flag IFF_BROADCAST set. The host sends an IP
limited broadcast. I would expect that an Ethernet broadcast goes out of each
interface (provided that a route to the interface's specific IP subnet exists
for each interface). But ip_output() handles limited broadcast the same way as
any other packet: it looks for a matching route and passes the packet to the
interface associated with the route. The net result: the packet does not appear
on any interface but the matched one.

Moreover, if one adds a default route with a gateway, the stack then sends a
limited IP broadcast packet as an Ethernet *unicast* to the gateway!

Did someone already observed & reported this problem or should I rather go to
sleep, and then read TCP/IP Illustrated again?

Robin