MAC address / per-proto ARP caching in 8.1-RELEASE

[Steve Polyack]

On 03/15/11 14:26, Jeremy Chadwick wrote:
> On Tue, Mar 15, 2011 at 09:30:39AM -0400, Steve Polyack wrote:
>> Is anyone aware of some sort of facility in either FreeBSD
>> 8.1-RELEASE or the em(4) driver which would cause it to cache MAC
>> addresses / ARP entries for hosts on a per-protocol basis?
>>
>> [snipping remaining details; readers can read it here instead:]
>> [http://lists.freebsd.org/pipermail/freebsd-stable/2011-March/061908.html]
> The only thing I can think of would be flowtable, but I'm not sure
> if it's enabled by default on 8.1-RELEASE-p2.  You can try the following
> sysctl to disable it (I would recommend setting this in sysctl.conf and
> rebooting; I don't know what happens in the case you set it on a live
> system that's already experiencing the MAC issue you describe).
>
> net.inet.flowtable.enable=0
>
> Details:
>
> http://conferences.sigcomm.org/sigcomm/2009/workshops/presto/papers/p37.pdf
>
It looks like it is enabled by default on 8.1-RELEASE.  Here's the 
net.inet.flowtable tree from the box in question:
[spolyack at web00 ~]$ sysctl net.inet.flowtable
net.inet.flowtable.stats:
table name: ipv4
     collisions: 1
     allocated: 0
     misses: 20013
     max_depth: 0
     free_checks: 377953
     frees: 19993
     hits: 69519580
     lookups: 69539593

net.inet.flowtable.nmbflows: 50176
net.inet.flowtable.tcp_expire: 86400
net.inet.flowtable.fin_wait_expire: 600
net.inet.flowtable.udp_expire: 300
net.inet.flowtable.syn_expire: 300
net.inet.flowtable.enable: 1
net.inet.flowtable.debug: 0

I'm planning on setting net.inet.flowtable.debug=1 next time we see this 
behavior, but from looking at the code, it looks like we might have to 
rebuild with -DFLOWTABLE_DEBUG to get really useful information.  It's 
too bad that there is not yet a method to dump the contents of the 
flowtable.

Thanks for the suggestion.