em(4) on FreeBSD is sometimes annoying

[Jeremy Chadwick]

On Mon, Aug 04, 2008 at 11:00:16AM +0100, Chris Rees wrote:
> Martin <nakal at web.de> wrote:
> 
> > On Sat, 02 Aug 2008 12:55:53 +0200
> > Torfinn Ingolfsen <torfinn.ingolfsen at broadpark.no> wrote:
> >
> >> Just to be sure: also if the first command you try on the interface is
> >> 'ifconfig up'?
> >
> > Hello Torfinn,
> >
> > good point, no. The problem appears when the first thing called on this
> > interface is dhclient (caused by ifconfig_em0="DHCP"). I could also
> > provoke this behavior after the interface was once up had an IP and was
> > working (ping). All I need to do is to disconnect the NIC from the
> > switch when I type "/etc/rc.d/netif restart".
> >
> > I have noticed further strange effects here. The behavior seems to
> > be even more complex.
> >
> > After I typed "/etc/rc.d/netif restart", I waited until I get "giving
> > up" message. Then I plugged the cable in. After about 30 seconds the
> > link LED was on. I noticed that at this point I couldn't get an address
> > using DHCP.
> >
> > So I disconnected physically the NIC (no cable) and link LED was
> > still on! ifconfig showed me "state: active" with no cable plugged in.
> > After further 30 seconds the LED went off.
> >
> > I attached the NIC again to the switch again and after 30 seconds
> > again I got some other effect. The link LED went on (status: active)
> > and the data LED was permanently blinking (about 2,5 times a second). I
> > pulled the cable again and now the link LED is still on and the data
> > LED still blinking (since about 10 minutes already).
> >
> > By the way...
> > Now I'm typing this E-Mail without an ethernet cable plugged in and the
> > link status LED is still on and the other data LED is blinking.
> >
> > --
> > Martin
> >
> I may have misunderstood the purpose of this, but do you have the bpf
> compiled into your kernel? If you're having DHCP troubles, this could
> be a problem.

I have never seen "device bpf" cause any sort of DHCP-related problems
on FreeBSD.

Can you expand on this, and provide reference material confirming such?

-- 
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |