struct iphdr {
 // ihl ==> Internet Header Length
#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; //Type of service
 __be16 tot_len; //Total length of the ip packet
 __be16 id; //Packet sequence number
 __be16 frag_off; // Fragment Offset
 __u8 ttl; // Time to live
 __u8 protocol; // Transport layer protocol
 __sum16 check; // Header checksum
 __be32 saddr; // Source address
 __be32 daddr; // Destination Address
 /*The options start here. */
};