Subject: port-macppc/12088: mc0: underflow brings interface down
To: None <>
From: Ben Harris <>
List: netbsd-bugs
Date: 01/31/2001 08:08:19
>Number:         12088
>Category:       port-macppc
>Synopsis:       mc0: underflow brings interface down
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    port-macppc-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Jan 31 08:11:00 PST 2001
>Originator:     Ben Harris
>Release:        1.5
NetBSD viking 1.5 NetBSD 1.5 (VIKING) #4: Fri Jan 26 23:16:18 GMT 2001 bjh21@viking:/usr/src/sys/arch/macppc/compile/VIKING macppc

Recently, the mc0 built-in Ethernet on my G3-upgraded Power Macintosh 8500
spontaneously lost its IFF_UP flag (according to ifconfig(8)), and
accordingly stopped talking to the network.  At about the same time, it
generated this log message:

Jan 31 00:05:40 viking /netbsd: mc0: underflow

Looking at the code in sys/arch/macppc/dev/am79c950.c, it looks like the
message is produced just before a call to mcreset(), which calls
mcstop() and mcinit().  mcstop() clears IFF_UP, but mcinit() never sets
it, so a call to mcreset() will leave the interface down, which is
probably not what is required here.

Not known.  The problem appeared to be spontaneous.