// IP header
typedef struct _tagX_iphdr
{
unsigned char h_len:4; // length of the header
unsigned char version:4; // Version of IP
unsigned char tos; // Type of service
unsigned short total_len; // total length of the packet
unsigned short ident; // unique identifier
unsigned short frag_and_flags; // flags
unsigned char ttl; // ttl
unsigned char proto; // protocol (TCP, UDP etc)
unsigned short checksum; // IP checksum
unsigned int sourceIP;
unsigned int destIP;
}XIpHeader;
// ICMP header
typedef struct _tagX_icmphdr
{
unsigned char i_type;
unsigned char i_code;
unsigned short i_cksum;
unsigned short i_id;
unsigned short i_seq;
unsigned long i_timestamp;
}XIcmpHeader;
//puclic code
//网际校验和生产算法
//网际校验和是被校验数据16位值的反码和(ones-complement sum)
unsigned short in_cksum(unsigned short* addr, int len)
{
int nleft = len;
int sum = 0;
unsigned short* w = addr;
unsigned short answer = 0;