[patch] bpf race condition fix

[Christian S.J. Peron]

All,

As many of you may know, there is a nasty race which exists in bpf(4). 
This race is responsible for some of tcpdump ctrl+c panics, as well as 
panics associated with dhclient. Some others include nessus. It was also 
one of the show stopper items on the 6.1-RELEASE TODO list.

This work was done in collaboration with myself and Sam Leffler, and it 
would be appreciated if people could review and test it:

http://people.freebsd.org/~csjp/bpf.1149157192.diff

-- 
Christian S.J. Peron
csjp at FreeBSD.ORG
FreeBSD Committer
FreeBSD Security Team