Date: Mon, 26 Apr 2004 23:40:06 -0700 (PDT) From: Gleb Smirnoff <glebius@cell.sick.ru> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/63317: make ng_ether(4) support "lower" and "orphans"simultaneously Message-ID: <200404270640.i3R6e6Xt055791@freefall.freebsd.org>
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The following reply was made to PR kern/63317; it has been noted by GNATS.
From: Gleb Smirnoff <glebius@cell.sick.ru>
To: Archie Cobbs <archie@dellroad.org>
Cc: Maxim Konovalov <maxim@macomnet.ru>,
bzeeb-lists@lists.zabbadoz.net, FreeBSD-gnats-submit@FreeBSD.ORG
Subject: Re: kern/63317: make ng_ether(4) support "lower" and "orphans"simultaneously
Date: Tue, 27 Apr 2004 10:33:34 +0400
On Mon, Apr 26, 2004 at 04:49:48PM -0500, Archie Cobbs wrote:
A> Gleb Smirnoff wrote:
A> > A> Let me be more specific. Suppose both lower and orphans are connected.
A> > A> A packet is received from the Ethernet hardware with ethertype
A> > A> 0x1234 (i.e., unrecognized). Which hook(s) (lower and/or orphans)
A> > A> does that packet get written to?
A> >
A> > It'll be written to orphans surely.
A>
A> OK, then this is a change in semantics: whereas before, connecting
A> to lower meant always getting all packets, now connecting to lower
A> means always getting all packets UNLESS somebody else is connected
A> to orphans... could be a completely different and unknown process.
It is said in current manpage, that ng_ether sends all packets to lower,
however code reveals the truth. Here is a sniplet from ng_ether_input_orphan(),
which is a hook called by ethernet stack:
/* If "orphan" hook not connected, let packet continue */
if (priv->lower == NULL || !priv->lowerOrphan) {
m_freem(m);
return;
}
To make sure, I've made an experiment. I have a notebook in a network where many IPX
broadcasts live. So I typed:
+ mkpeer fxp0: etf lower downstream
+ name fxp0:lower etf
+ connect etf: dummy ipx
+ msg etf: setfilter { matchhook="ipx" ethertype=0x8137 }
I've waited for half a minute, and no packets arrived. Then, I've typed:
+ shutdown etf:
+ shutdown fxp0:
+ mkpeer fxp0: etf orphans downstream
+ name fxp0:orphans etf
+ connect etf: dummy ipx
+ msg etf: setfilter { matchhook="ipx" ethertype=0x8137 }
And I began receiving packets on dummy.
A> To preserve the existing behavior, the node would need to duplicate
A> the orphanable packets and send them to BOTH connected hooks.
So behavior didn't change. Even we have found some inexactitude in
manpage.
A> Also, will this change cause packets to go up into the protocol
A> stack that previously would not have? E.g., before, if lower were
A> connected, then no packets ever reach the protocol stack... is that
A> still going to be true?
Yes, since "orphaned" packets won't reach it anyway.
--
Totus tuus, Glebius.
GLEBIUS-RIPN GLEB-RIPE
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