kern/44675: Changing link level address on "tlp" card, while up, hangs machine (PCI/i386)

[magetoo%fastmail.fm@localhost]

>Number:         44675
>Category:       kern
>Synopsis:       Changing link level address on "tlp" card, while up, hangs 
>machine (PCI/i386)
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Mar 03 22:35:00 +0000 2011
>Originator:     Magnus Eriksson
>Release:        5.0_STABLE
>Organization:
>Environment:
NetBSD myhost 5.0_STABLE NetBSD 5.0_STABLE (MYHOST) #4: Sat Feb 20 15:39:17 CET 
2010  magetoo@myhost:/obj/sys/arch/i386/compile/MYHOST i386
>Description:
Changing the link level address of the network card, while the interface is 
configured up, repeatably locks up my machine.

Problem occurs with at least one card which is supported by the "tlp" driver.  
No other cards tested; and trying to provoke the same hang with a "tap" 
pseudo-device does not cause the same behaviour.

It is possible to enter ddb, but trying to get a backtrace did not work. 
(appears to trigger a fault in ddb, and no serial console was attached - any 
useful output had scrolled off screen)

However: bringing the interface down, then changing the address, and taking it 
back up, works as expected.
>How-To-Repeat:
ifconfig tlp0 up
ifconfig tlp0 link 02:01:01:01:01:01 active
>Fix:
Suggestion for fix: Require interfaces to not be configured "up" before 
changing the active link level address.

(This may be considered hiding a bug rather than fixing it, but should at least 
prevent lockups.)