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@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.
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