#include <arpa/inet.h>
#include <string.h>
#include <sys/types.h>

#define PKTBUFSRX 4
#define PKTSIZE_ALIGN 1536
#define PKTALIGN 16

#define ETH_HDR_SIZE 14
#define IP_HDR_SIZE 20

#define IP_FLAGS_DFRAG 0x4000

static uint8_t net_pkt_buf[(PKTBUFSRX+1) * PKTSIZE_ALIGN + PKTALIGN];

static unsigned net_ip_id;

/*
 *	Internet Protocol (IP) + UDP header.
 */
struct ip_udp_hdr {
	uint8_t		ip_hl_v;	/* header length and version	*/
	uint8_t		ip_tos;		/* type of service		*/
	uint16_t	ip_len;		/* total length			*/
	uint16_t	ip_id;		/* identification		*/
	uint16_t	ip_off;		/* fragment offset field	*/
	uint8_t		ip_ttl;		/* time to live			*/
	uint8_t		ip_p;		/* protocol			*/
	uint16_t	ip_sum;		/* checksum			*/
	struct in_addr	ip_src;		/* Source IP address		*/
	struct in_addr	ip_dst;		/* Destination IP address	*/
};

void net_set_ip_header(uint8_t *pkt, struct in_addr dest, struct in_addr source)
{
	struct ip_udp_hdr *ip = (struct ip_udp_hdr *)pkt;

	/*
	 *	Construct an IP header.
	 */
	ip->ip_hl_v  = 0x45;
    //asm("nop");
	ip->ip_tos   = 0;
	ip->ip_len   = htons(IP_HDR_SIZE);
	ip->ip_id    = htons(net_ip_id++);
	ip->ip_off   = htons(IP_FLAGS_DFRAG);	/* Don't fragment */
	ip->ip_ttl   = 255;
	ip->ip_sum   = 0;
	/* already in network byte order */
	memcpy((void *)&ip->ip_src, &source, sizeof(struct in_addr));
	/* already in network byte order */
	memcpy((void *)&ip->ip_dst, &dest, sizeof(struct in_addr));
}

int main(int argc, char** argv) {
	uint8_t *pkt;
	struct in_addr bcast_ip, src_ip;

	bcast_ip.s_addr = 0xFFFFFFFFL;
	src_ip.s_addr = 0x0L;

	pkt = net_pkt_buf;
	memset((void *)pkt, 0, sizeof(net_pkt_buf));
	pkt += ETH_HDR_SIZE;

	net_set_ip_header(pkt, bcast_ip, src_ip);

	return 1;
}