and net.bpf.peers sysctls respectively.
A new structure was added to describe the external (user viewable)
representation of a BPF file; a new entry was added to the bpf_d
structure to store the PID of the calling process; a simple_lock was added
to protect the insert/removal from the net.bpf.peers sysctl handler.
This idea came from FreeBSD (Christian S.J. Peron) but while it is
implemented with sysctl's it differs a bit.
Reviewed by: christos@ and atatat@ (who gave me the tip for the net.bpf.peers
sysctl helper function).