Right now the bpf(4) driver uses the cloning API to generate /dev/bpf%u.
When an application such as tcpdump needs a BPF, it opens /dev/bpf0,
/dev/bpf1, etc. until it opens the first available device node. We used
this approach, because our devfs implementation didn't allow
per-descriptor data.
Now that we can, make it use devfs_get_cdevpriv() to obtain the private
data. To remain compatible with the existing implementation, add a
symlink from /dev/bpf0 to /dev/bpf. I've already changed libpcap to
compile with HAVE_CLONING_BPF, which makes it use /dev/bpf. There may be
other applications in the base system (dhclient) that use the loop to
obtain a valid bpf.
Discussed on: src-committers
Approved by: csjp
