[$] Bpfilter (and user-mode blobs) for 4.18

In February, the bpfilter mechanism wasfirst posted to the mailing lists. Bpfilter is meant to be a replacementfor the current in-kernel firewall/packet-filtering code. It provideslittle functionality itself; instead, it creates a set of hooks that canrun BPF programs to make the packet-filtering decisions. A version of that patch set has been mergedinto the net-next tree for 4.18. It will not be replacing any existingpacket filters in its current form, but it does feature a significantchange to one of its more controversial features: the new user-mode helpermechanism.