I've been running NetBSD for.. well pretty much forever it seems, and 
recently (within the last year I guess) I've bumped into some troubles 
when running most NIC (Intel etherexpress to 3com 3c905) under the 
netbsd releases in that time period. Maybe it's just me but for some 
reason putting the card into promiscuous mode sometimes freezes all 
network operations for about a second or two. Similar UNIX-like systems 
don't show any tcpdump output for a moment, but they all continue to 
pass in/out network traffic from the rest of the system while the 
interface is being put into promisc.

Probably not related to pr/22120 because it happens in a 3com as well.

Happens on:
NetBSD 2.99.10 (DRACO) #9: Thu Nov 25 15:36:18 PST 2004
[...]
fxp0 at pci1 dev 2 function 0: i82559 Ethernet, rev 8
fxp0: interrupting at irq 11
fxp0: Ethernet address 00:d0:b7:75:c6:40
inphy0 at fxp0 phy 1: i82555 10/100 media interface, rev. 4
inphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
fxp1 at pci1 dev 3 function 0: i82559 Ethernet, rev 8
fxp1: interrupting at irq 5
fxp1: Ethernet address 00:d0:b7:ba:91:13
inphy1 at fxp1 phy 1: i82555 10/100 media interface, rev. 4
inphy1: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
[...]

Also on:
NetBSD loki 1.6.2 NetBSD 1.6.2 (GENERIC) #0: Tue Feb 10 21:53:10 UTC 
2004 
autobuild@tgm.netbsd.org:/autobuild/netbsd-1-6-PATCH002/i386/OBJ/autobuild/netbsd-1-6-PATCH002/src/sys/arch/i386/compile/GENERIC 
i386
[...]
ex0 at pci0 dev 10 function 0: 3Com 3c905B-TX 10/100 Ethernet (rev. 
0x30)
ex0: interrupting at irq 10
ex0: MAC address 00:01:02:c8:50:b2
exphy0 at ex0 phy 24: 3Com internal media interface
exphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
ex1 at pci0 dev 12 function 0: 3Com 3c905B-TX 10/100 Ethernet (rev. 
0x30)
ex1: interrupting at irq 11
ex1: MAC address 00:01:02:c9:45:c2
exphy1 at ex1 phy 24: 3Com internal media interface
exphy1: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
[...]

It does not seem to happen on:

NetBSD kimmie 2.99.10 NetBSD 2.99.10 (kimmie) #10: Thu Nov 25 15:04:27 
PST 2004  root@kimmie:/usr/src-current/sys/arch/i386/compile/kimmie 
i386
[...]
ne0 at pci0 dev 13 function 0: Realtek 8029 Ethernet
ne0: Ethernet address 00:60:67:2d:3b:39
ne0: 10base2, 10baseT, 10baseT-FDX, auto, default [0x00 0x30] auto
ne0: interrupting at irq 10

... which seems strange to me because RealTek seem to be traditionally 
associated with ultra-cheap, low-end crappy NICs. They also seem to get 
starved out in a busy network, while the others don't.

Comments appreciated. Note that my email address cannot receive email, 
even without the NO@SPAM part, so please only follow-up to the list as 
per Reply-To: Thanks!