BPF support for linux

[anthraxx]

It looks like BPF is not supported for Linux variant, while the configure summary clearly says "BSD BPF" it is still auto-detected and needs explicit fiddling to get tcpreplay compiled.

Either way, support for linux eBPF would be cool, right now it fails with:

sendpacket.c: In function ‘sendpacket_open_bpf’:
sendpacket.c:1052:24: error: storage size of ‘bv’ isn’t known
     struct bpf_version bv;
                        ^~
compilation terminated due to -Wfatal-errors.
make[4]: *** [Makefile:455: sendpacket.o] Error 1
make[4]: *** Waiting for unfinished jobs....

[fklassen]

Will investigate.

[fklassen]

eBPF is not the same as BPF. Will defer eBPF support until BSD license updates make it into mainline kernel, and libraries stabilize.