Thread: Passing an ip address to iph/tcphdr [SOCK_RAW]

This code compiles and run fines, however, I have not been able to change the ip address to a real adddress. Any help would be greatly appreciated.

Thanks


The function in question:

Code:

#include <stdio.h>#include <string.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <errno.h>
#include <netinet/tcp.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include "ourCheckSum.h"
#include "RSTInjector.h"










int RSTInjector(const char  connectionSource[32], int connectionPort, const char  connectionDest[32])
{


//Var
int socketMaster;
char datagram[4096]; //Contains entire packet iphdr + tcphdr
struct ip *iph = (struct ip *) datagram;
struct tcphdr *tcph = (struct tcphdr *) datagram +sizeof(struct ip);
struct sockaddr_in sin;
struct sockaddr_in din;


//Var mem
    connectionSource = malloc(4);
    connectionDest = malloc(4);
    


//Creat Socket
socketMaster = socket(PF_INET, SOCK_RAW, IPPROTO_TCP);
    if (socketMaster == -1){
        perror("Could Not Open Socket");
        return -1;
    }
    
//
sin.sin_family = AF_INET;
din.sin_family = AF_INET;
sin.sin_port = htons(connectionPort);
din.sin_port = htons(connectionPort);
sin.sin_addr.s_addr = inet_addr(connectionDest); // DEST or SRC
din.sin_addr.s_addr = inet_addr(connectionSource);


//Clean datagram
memset(datagram, 0, 4096);


//Construct Headers
//IP Headers
iph->ip_hl = 5;
iph->ip_v = 4;
iph->ip_tos = 0;
iph->ip_len = sizeof(struct ip) + sizeof(struct tcphdr);
iph->ip_id = htonl(2539);
iph->ip_off = 0;
iph->ip_ttl = 255;
iph->ip_p = 6;
iph->ip_sum = 0; //csum will be calculated later
iph->ip_src.s_addr = inet_addr(connectionSource); //Connection Source
iph->ip_dst.s_addr = inet_addr(connectionDest); //Uses previuse host or connection dest


//TCP Headers
tcph->th_sport = htons(connectionPort); //TCP Port
tcph->th_dport = htons(connectionPort); //TCP Port
tcph->th_seq = rand(); // We really dont care as this is to close a connection
tcph->th_ack = 0; //Is 0 in first packet -- Lets hope it dosent have to be the real value
tcph->th_x2 = 0;
tcph->th_off = 0;
tcph->th_flags = TH_RST; //RST the connection, killing it
tcph->th_win = htonl(65535); //Not sure about this number
tcph->th_sum = 0; // Kernal *should* fill this value in correctly
tcph->th_urp = 0; //What does this do?


//Checksum call
//IP Header
iph->ip_sum = ourCheckSum((unsigned short *) datagram, iph->ip_len >> 1);
    
    
//Inform Kernal of header inclusion
    {
    int one = 1;
    const int *val = &one;
    if (setsockopt(socketMaster, IPPROTO_IP, IP_HDRINCL, val, sizeof(one)) < 0){
        perror("Could Not Set HDRINCL");
    }
    }


//Inject RST Packet
    if (sendto(socketMaster, datagram, iph->ip_len, 0, (struct sockaddr *) &sin, sizeof(sin)) < 0) {
        perror("Could not inject RST packet");
        return  -1;
        close(socketMaster);
    }
    else 
    return 0;
    close(socketMaster);




              
}

Originally Posted by November

Code:

//Var mem
    connectionSource = malloc(4);
    connectionDest = malloc(4);

Why are you throwing away the connectionSource and connectionDest pointers (I assume they're strings) that were passed into your function? And what does the magic value 4 represent?