man 4 icmp man 4 ip man 2 socket man 5 protocols
https://stackoverflow.com/questions/13543554/how-to-receive-icmp-request-in-c-with-raw-sockets
RFC 791: Internet Protocol (IP) RFC 792: Internet Control Message Protocol (ICMP)
reading RFC's on mac
brew install bfontaine/utils/rfc
rfc 791`
rfc 792`less /etc/protocols