raw.h

#define ETH_LEN	1518
#define ETHER_TYPE	0x0800
#define DEFAULT_IF	"eth0"

struct eth_hdr {
	uint8_t dst_addr[6];
	uint8_t src_addr[6];
	uint16_t eth_type;
};

struct ip_hdr {
	uint8_t ver;			/* version, header length */
	uint8_t tos;			/* type of service */
	int16_t len;			/* total length */
	uint16_t id;			/* identification */
	int16_t off;			/* fragment offset field */
	uint8_t ttl;			/* time to live */
	uint8_t proto;			/* protocol */
	uint16_t sum;			/* checksum */
	uint8_t src[4];			/* source address */
	uint8_t dst[4];			/* destination address */
};

struct icmp_hdr {
	uint8_t type;
	uint8_t code;
	uint16_t checksum;
	union {
		struct {
			uint16_t id;
			uint16_t sequence;
		} echo;
		uint32_t gateway;
		struct {
			uint16_t __unused;
			uint16_t mtu;
		} frag;
		uint8_t reserved[4];
	} un;
};

struct bepis_hdr {
	uint32_t target_ip;
};

struct bepis_packet {
	struct ip_hdr iphdr;
	struct icmp_hdr icmphdr;
	struct bepis_hdr bepishdr;
	uint8_t raw_data[ETH_LEN - sizeof(struct eth_hdr) - sizeof(struct ip_hdr) - sizeof(struct icmp_hdr) - sizeof(struct bepis_hdr)];
};

struct icmp_packet {
	struct ip_hdr iphdr;
	struct icmp_hdr icmphdr;
};

struct tcp_hdr {
	uint16_t	source;
	uint16_t	dest;
	uint32_t	seq;
	uint32_t	ack_seq;
#if defined(__LITTLE_ENDIAN_BITFIELD)
	uint16_t	res1:4,
			doff:4,
			fin:1,
			syn:1,
			rst:1,
			psh:1,
			ack:1,
			urg:1,
			ece:1,
			cwr:1;
#elif defined(__BIG_ENDIAN_BITFIELD)
	uint16_t	doff:4,
			res1:4,
			cwr:1,
			ece:1,
			urg:1,
			ack:1,
			psh:1,
			rst:1,
			syn:1,
			fin:1;
#else
#error	"Adjust your <asm/byteorder.h> defines"
#endif	
	uint16_t	window;
	uint16_t	check;
	uint16_t	urg_ptr;
};

struct tcp_packet {
	struct ip_hdr iphdr;
	struct tcp_hdr tcphdr;
};

struct udp_hdr {
	uint16_t src_port;
	uint16_t dst_port;
	uint16_t udp_len;
	uint16_t udp_chksum;
};

struct udp_packet {
	struct ip_hdr iphdr;
	struct udp_hdr udphdr;
};

union packet_u {
	struct ip_hdr ip;
	struct icmp_packet icmp;
	struct udp_packet udp;
	struct tcp_packet tcp;
	struct bepis_packet bepis;
};

#pragma pack(push, 1)
struct eth_frame_s {
	struct eth_hdr ethernet;
	union packet_u payload;
};
#pragma pack(pop)

union eth_buffer {
	struct eth_frame_s cooked_data;
	uint8_t raw_data[ETH_LEN];
};