em device hangs on ifconfig alias ...

[Robert Watson]

On Fri, 7 Jul 2006, User Freebsd wrote:

>> I think that I have patched, built and loaded the em(4) kernel module 
>> correctly. After applying the patch there were no rejects, before building 
>> the module I intentionally appended " (patched)" to its version string in 
>> if_em.c, and could see that in dmesg every time I loaded the module: em1: 
>> <Intel(R) PRO/1000 Network Connection Version - 3.2.18 (patched)>
>
> Is it possible that we're going at this issue backwards?  It isn't the lack 
> of ARP packet going out that is causing the problems with moving IPs, but 
> that delay that we're seeing when aliasing a new IP on the stack?  The ARP 
> packet *is* being attempted, but is timing out before the re-init is 
> completing?

Yes -- basically, there are two problems:

(1) A little problem, in which an arp announcement is sent before the link has
     settled after reset.

(2) A big problem, in which the interface is gratuitously recent requiring
     long settling times.

I'd really like to see a fix to the second of these problems (not resetting 
when an IP is added or removed, resulting in link renegotiation); the first 
one I'm less concerned about, although it would make some amount of sense to 
do an arp announcement when the link goes up.

Robert N M Watson
Computer Laboratory
University of Cambridge