This code largely inspired by tap.c. Allows for testing iPXE on real
NICs from within Linux. For example:
make bin-x86_64-linux/af_packet.linux
valgrind ./bin-x86_64-linux/af_packet.linux --net af_packet,if=eth3
Tested as x86_64 and i386 binary.
Signed-off-by: Michael Brown <mcb30@ipxe.org>