packetType values — how the packet relates to the capturing host,
mirroring the PACKET_* values Linux reports via sockaddr_ll.
HOST: number
Packet addressed to the capturing host.
BROADCAST: number
Physical-layer broadcast packet.
MULTICAST: number
Packet sent to a physical-layer multicast address.
OTHER_HOST: number
Packet addressed to another host, seen because the interface is promiscuous.
OUTGOING: number
Packet sent by the capturing host.