Date: Mon, 11 Feb 2002 23:36:27 +0100 From: Dan Lukes <dan@obluda.cz> To: freebsd-hackers@freebsd.org Subject: Limited broadcast procesing. Message-ID: <3C68476B.6DDBFEFB@obluda.cz>
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I'm sending the same message on Feb 10, but I think it hasn't be
delivered to list. I'm sorry if my assumption is bad and you received it
twice.
-------------
Hi.
I don't understand some aspects of processing of packets with
destination address 255.255.255.255
a) if first interface is broadcast capable then the destination address
is unconditionally rewritten with no warning to primary address network
broadcast on that interface and send; else the destination address is
left intact and continue to b)
b) if SO_DONTROUTE not set then routing table apply (most important rule
is "default"); else packet discarded (no route to ...)
My first question:
Why the silent rewritting of one destination address to other is used ?
There must be a good reason to change explicit user request and rewrite
it to another one, but I have no idea about it. I track history of it
code in in_pcb.c - I found it in 4.3BSD (dated 6/29/88) - so it's an
ancient relict ?
Second question(s):
How to send a packet to limited broadcast address over specific
interface (using standard socket interface, not bpf)? If there no way to
do it, should be ?
If there is no way to do it and should be, I have a idea how to do it.
If source address is set to a interface address and SO_DONTROUTE is in
effect, then packet adressed to limited broadcast is sent over the
interface specified by the source address (current processing discard it
with "no route to ..." unless silent rewritting of destination address
do it's dirty work). The silent rewriting of destination address must
not occur for those packets. It is acceptable ? I see no
contraindication.
I read the sys/netinet/ from first line to last line several times, but
it's possible i'm missed something, of course.
Dan
Please note the english isn't my native language, but I hope it's
readable.
--
Dan Lukes tel: +420 2 21914205, fax: +420 2 21914206
root of FIONet, KolejNET, webmaster of www.freebsd.cz
AKA: dan@obluda.cz, dan@freebsd.cz, dan@kolej.mff.cuni.cz
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