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Date:      Tue, 23 May 2000 22:21:59 -0400
From:      Andrew Heybey <ath@niksun.com>
To:        freebsd-hackers@freebsd.org
Subject:   Receive-only FDDI
Message-ID:  <200005240221.WAA39762@stiegl.niksun.com>

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I am trying to monitor (eg use bpf & tcpdump to see packets) a FDDI
ring with a Digital DEFPA FDDI NIC (and the fpa driver) via a fiber
tap.  Therefore the interface only gets to receive, not transmit.

This doesn't work, I assume because the firmware on the DEFPA
wants/needs to participate in the exchange of SMT frames on the ring
(I am not familiar with FDDI detail so I do not know exactly what is
going on).

Under certain conditions, the DEFPA will receive frames for a short
period of time before declaring that the link is unavailable.
Specifically, if I break the ring (with the monitoring interface still
plugged into the tap) then reconnect it, then I get the following
sequence of log messages:

May 17 14:16:39 demo4 /kernel: fpa1: Link Available
May 17 14:16:39 demo4 /kernel: fpa1: Unsolicited Event: Link: Ring Beacon Initi
ated
May 17 14:16:41 demo4 /kernel: fpa1: Link Unavailable
May 17 14:16:53 demo4 /kernel: fpa1: Unsolicited Event: Link: Trace Initiated
May 17 14:17:08 demo4 /kernel: fpa1: Halted: halt code = 5 (PC Trace Path Test)
May 17 14:17:09 demo4 /kernel: fpa1: Link Unavailable

tcpdump gets packets from the "Link Available" through about 10
seconds before "Halted".

I am hoping that the DEFPA can be told to "don't worry be happy" and
ignore the lack of participation in the ring.

Has anyone done anything like this?

Does anyone know where to get a programming manual for the DEFPA?

thanks,
andrew



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