Send TCP protocol using socket RAW socket

Socket use Af_inet protocol family, and create sock_raw original socket, fill in the IP header and TCP header, it is familiar with the lower head structure.

* ===================================================================================== * * FILENAME:RAW.C * *
 Description: Uses the original socket to send the TCP protocol and take out its own data.         * * version:1.0 * created:2012 September 11 10:39 00 seconds * Revision: * COMPILER:GCC * * AUTHOR:YADON.Z * * ===================================================================================== * * #in Clude <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/socket.h> #include < netinet/in.h> #include <netinet/ip.h> #include <netinet/tcp.h> #include <arpa/inet.h> #define DATA "Hello" #define packet_size sizeof (struct IPHDR) + sizeof (struct TCPHDR) + sizeof (data)/*-------------------------- -------------------------------Function name:check_sum () Descrypthon: Checksum calculation, excerpt from UNP source------------------------------
   ------------------------------*/unsigned short check_sum (unsigned short *addr, int len) {int nleft = Len; int sum = 0;
    unsigned short *w = addr;
    Short answer = 0;
        while (Nleft > 1) {sum + = *w++;
    Nleft-=2;
        } if (nleft = = 1) {* (unsigned char *) (&answer) = * (unsigned char *) W;
    sum + = answer;
    } sum = (sum >> +) + (sum & 0xFFFF);
    sum + = (sum >> 16);
    Answer = ~sum;
return answer; }/*---------------------------------------------------------Function Name:init_socket () Descrypthon: Initialize socket, using Raw socket------------------------------------------------------------*/int init_socket (int sockfd, struct sockaddr_in *
    target,\ const char *DST_ADDR, const char *dst_port) {CONST int flag = 1;
    target->sin_family = af_inet;
    Target->sin_port = htons (atoi (Dst_port));
        if (Inet_aton (dst_addr, &target->sin_addr) = = 0) {perror ("Inet_aton fail\n");
    Exit (-1); } if ((SOCKFD = socket (af_inet, Sock_raw, ipproto_tcp)) < 0) {perror ("ErroR ");
    Exit (-1); } if (setsockopt (Sockfd,ipproto_ip, Ip_hdrincl, &flag, sizeof (flag)) < 0) {perror ("setsockopt fail \ n")
        );
    Exit (-1);
} return SOCKFD; }/*---------------------------------------------------------------Function NAME:BUILE_IPHDR () Descrypthon: Build IP Header Data, the source address uses a pseudo-random address-----------------------------------------------------------------*/void Buile_iphdr (struct sockaddr
    _in *target, char *buffer) {struct IPHDR *ip = (struct IPHDR *) (buffer);
    Ip->version = 4;
    IP-&GT;IHL = 5;
    Ip->tos = 0;
    Ip->tot_len = htons (packet_size);
    Ip->id = 0;
    Ip->frag_off = 0;
    Ip->ttl = 255;
    Ip->protocol = ipproto_tcp;
    Ip->check = 0;
    IP-&GT;SADDR = random ();
    
    IP-&GT;DADDR = target->sin_addr.s_addr;
Ip->check = Check_sum ((unsigned short *) IP, sizeof (struct IPHDR) + sizeof (DATA)); }/*---------------------------------------------------------------Function name:buile_tCPHDR () Descrypthon: Constructs TCP header information, adds some of its own data, and then verifies the calculation. -----------------------------------------------------------------*/void Buile_tcphdr (struct sockaddr_in *target,
    const Char *src_port, char *buffer) {struct TCPHDR *tcp = (struct TCPHDR *) (buffer);
    Tcp->source = htons (atoi (Src_port));
    Tcp->dest = target->sin_port;
    Tcp->seq = random ();
    Tcp->doff = 5;
    Tcp->syn = 1;
    Buffer + = sizeof (struct TCPHDR);
    memcpy (buffer, data, sizeof (data)); 
Tcp->check = Check_sum ((unsigned short *) TCP, sizeof (struct TCPHDR) + sizeof (DATA));
    } int main (int argc, const char *argv[]) {char *buffer;
    char *buffer_head = NULL;
    int sockfd = 0;
    struct sockaddr_in *target;
        if (argc! = 4) {printf ("usage:destination addresss, Destination port, source port \ n");
    Exit (-1);
    } const char *dst_addr = argv[1];
    const char *dst_port = argv[2];
    const char *src_port = argv[3]; target = Calloc (sizeof (struct sockaddr_in), 1);
    Buffer = Calloc (packet_size, 1);
    Buffer_head = buffer;
    SOCKFD = Init_socket (SOCKFD, Target, dst_addr, dst_port);
    BUILE_IPHDR (target, buffer);
    Buffer + = sizeof (struct IPHDR);
    BUILE_TCPHDR (target, src_port, buffer); SendTo (SOCKFD, Buffer_head, packet_size, 0,\ (struct sockaddr *) target, sizeof (struct SOCKAD
    dr_in));
    Free (buffer_head);

    Free (target);
return 0;
 }