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From: Luigi Rizzo <luigi@labinfo.iet.unipi.it>
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Subject: Re: your mail
To: cher@test.phys.msu.su (Alicher O Alikhodjaev)
Date: Mon, 15 Jan 1996 16:57:34 +0100 (MET)
Cc: hackers@FreeBSD.ORG
In-Reply-To: <199601151322.QAA06200@test.phys.msu.su> from "Alicher O Alikhodjaev" at Jan 15, 96 04:22:11 pm
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> SUMMARY:
> 	This patch adds multicast support for 3c5x9 (ep) driver
> INSTALLATION:
>     cd /sys                     # your local kernel source tree
>     patch -p < this_file
>     # then rebuild your kernel

Does the 3c5x9 have an internal hash table for (partial) filtering of
incoming multicasts ?

If it does, I do not see any code here (or in the
2.1R if_ep.c) to set the hash table according to the content of the
multicast address list.

If it doesn't, it means that any multicast address effectively puts
the board in promiscuous mode -> the kernel must process and discard
any non-matching packet -> lots of work on a busy segment, and not
certainly the thing you want to build a router.

I am asking because I was looking at some 3c5xx driver for Linux
a couple of days ago, and it implemented multicast by switching to
promiscuos mode. I suspect many ethernet drivers may have this
problem.

	Luigi
====================================================================
Luigi Rizzo                     Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it       Universita' di Pisa
tel: +39-50-568533              via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522              http://www.iet.unipi.it/~luigi/
====================================================================