correct icmp masks, handle icmp type without code
correct icmp masks, handle icmp type without code

jncornett/libdnet,kbandla/libdnet,wtfbbqhax/libdnet,kbandla/libdnet,wtfbbqhax/libdnet,jncornett/libdnet,kbandla/libdnet,wtfbbqhax/libdnet,jncornett/libdnet