struct iphdr {
#if defined(__LITTLE_ENDIAN_BITFIELD)
	__u8	ihl:4,
		version:4;
#elif defined (__BIG_ENDIAN_BITFIELD)
	__u8	version:4,
  		ihl:4;
#else
#error	"Please fix <asm/byteorder.h>"
#endif
	__u8	tos;
	__be16	tot_len;
	__be16	id;
	__be16	frag_off;
	__u8	ttl;
	__u8	protocol;
	__sum16	check;
	__be32	saddr;
	__be32	daddr;
	/*The options start here. */
};