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Packet sockets
Packet sockets allow a program to more directly interface with the networking stack than standard Layer 4 Berkeley sockets (e.g. AF_INET + SOCK_STREAM, AF_INET6 + SOCK_DGRAM).
PF_PACKET
As described in packet(7), this is a packet interface at the device level (Layer 2). The protocol field is either an IEEE 802.3 protocol number (found in linux/if_ether.h or ETH_P_ALL in network byte order. The CAP_NET_RAW capability or UID 0 are requisite to open a packet socket. bind(2) can be used to select a single interface to use with the packet socket.
SOCK_RAW
Raw packets including the link-level header.
SOCK_DGRAM
Cooked packets (common, protocol-independent link-layer header in a sockaddr_ll).
AF_INET/AF_INET6
The protocol field restricts the Layer 3 protocols which will be passed to the socket; IPPROTO_RAW can set arbitrary IP protocol values, and thus implies the IP_HDRINCL socket option.
SOCK_RAW
SOCK_PACKET
Obsolete since Linux 2.0.
