Date: Mon, 27 Aug 2001 19:01:24 +0400 (MSK) From: Grigory Kljuchnikov <grn@ispras.ru> To: <stable@FreeBSD.ORG> Subject: Ethernet behaviour if dst ether addr = local ether addr Message-ID: <Pine.GSO.4.33.0108271826190.22284-100000@gate.ispras.ru>
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Hello,
I know my question may be out of this list scope, but
perhaps anybody knows answer...
I'm interested in how ethernet process a packet with ethernet
dst address = local ethernet address. Does this packet appear
on the wire? If not, who does loopback IP or Ethernet?
And does that behaviour define in IEEE 802.3 standard?
If not, which standard define the ethernet (or IP) behaviour in this case?
I've looked the source code of ether_output() function (from
/usr/src/sys/net/if_ethersubr.c) and found an interesting
comment (lines 320-328):
/*
* If a simplex interface, and the packet is being sent to our
* Ethernet address or a broadcast address, loopback a copy.
* XXX To make a simplex device behave exactly like a duplex
* device, we should copy in the case of sending to our own
* ethernet address (thus letting the original actually appear
* on the wire). However, we don't do that here for security
* reasons and compatibility with the original behavior.
*/
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In this case what is 'the original behavior'?
And what about duplex device behaviour?
Sorry, if I take your time!
Thanks.
Grigory Klyuchnikov, System Engineer,
Institute for System Programming
Russian Academy of Sciences
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