Creating ip network packets [closed]

问题:

I have to create my own network packets manually Using any Protocol.i should send it to the client and parse or analyse the packet.Can any1 help me out with where and hpw to start ??? I have idea about socket programming..

回答1:

You can use <linux/ip.h> it contains structure to point to ip packet. also you can use socket.

here after an example. This example send an ICMP ECHO packet and wait for response

/* send icmp packet example */
#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>
#include <linux/ip.h>
#include <linux/icmp.h>

int main(int argc, char* argv[])
{
    struct iphdr *ip, *ip_reply;
    struct icmphdr* icmp;
    struct sockaddr_in connection;
    char *dst_addr="192.168.1.33";
    char *src_addr="192.168.1.34";
    char *packet, *buffer;
    int sockfd, optval, addrlen;

    packet = malloc(sizeof(struct iphdr) + sizeof(struct icmphdr));
    buffer = malloc(sizeof(struct iphdr) + sizeof(struct icmphdr));
    ip = (struct iphdr*) packet;
    icmp = (struct icmphdr*) (packet + sizeof(struct iphdr));

    ip->ihl         = 5;
    ip->version     = 4;
    ip->tot_len     = sizeof(struct iphdr) + sizeof(struct icmphdr);
    ip->protocol    = IPPROTO_ICMP;
    ip->saddr       = inet_addr(src_addr);
    ip->daddr       = inet_addr(dst_addr);
    ip->check = in_cksum((unsigned short *)ip, sizeof(struct iphdr)); 

    icmp->type      = ICMP_ECHO;
    icmp->checksum = in_cksum((unsigned short *)icmp, sizeof(struct icmphdr));

    /* open ICMP socket */
    if ((sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP)) == -1) {
        perror("socket");
        exit(EXIT_FAILURE);
    }
     /* IP_HDRINCL must be set on the socket so that the kernel does not attempt 
     *  to automatically add a default ip header to the packet*/
    setsockopt(sockfd, IPPROTO_IP, IP_HDRINCL, &optval, sizeof(int));

    connection.sin_family       = AF_INET;
    connection.sin_addr.s_addr  = ip->daddr;
    sendto(sockfd, packet, ip->tot_len, 0, (struct sockaddr *)&connection, sizeof(struct sockaddr));
    printf("Sent %d byte packet to %s\n", ip->tot_len, dst_addr);

    addrlen = sizeof(connection);
    if (recvfrom(sockfd, buffer, sizeof(struct iphdr) + sizeof(struct icmphdr), 0, (struct sockaddr *)&connection, &addrlen) == -1)
        {
        perror("recv");
        }
    else
        {
        char *cp;
        ip_reply = (struct iphdr*) buffer;
        cp = (char *)&ip_reply->saddr;
        printf("Received %d byte reply from %u.%u.%u.%u:\n", ntohs(ip_reply->tot_len), cp[0]&0xff,cp[1]&0xff,cp[2]&0xff,cp[3]&0xff);
        printf("ID: %d\n", ntohs(ip_reply->id));
        printf("TTL: %d\n", ip_reply->ttl);
        }

}

unsigned short in_cksum(unsigned short *addr, int len)
{
    register int sum = 0;
    u_short answer = 0;
    register u_short *w = addr;
    register int nleft = len;
    /*
     * Our algorithm is simple, using a 32 bit accumulator (sum), we add
     * sequential 16 bit words to it, and at the end, fold back all the
     * carry bits from the top 16 bits into the lower 16 bits.
     */
    while (nleft > 1)
    {
      sum += *w++;
      nleft -= 2;
    }
    /* mop up an odd byte, if necessary */
    if (nleft == 1)
    {
      *(u_char *) (&answer) = *(u_char *) w;
      sum += answer;
    }
    /* add back carry outs from top 16 bits to low 16 bits */
    sum = (sum >> 16) + (sum & 0xffff);     /* add hi 16 to low 16 */
    sum += (sum >> 16);             /* add carry */
    answer = ~sum;              /* truncate to 16 bits */
    return (answer);
}

回答2:

use raw sockets.

u can refer to http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html for socket programming & for raw sockets too.

and i think this http://csis.bits-pilani.ac.in/faculty/dk_tyagi/Study_stuffs/raw.html