RAW SOCKET sendto fails

peter_holmes2003@yahoo.co · *nix forums beginner Joined: 02 Feb 2005 Posts: 2

I am trying to send a packet over a RAW socket with the IP header
provided. The sendto() function returns "invalid argument". If I don't
suppy the IP header the program works fine. I am attaching my test
program below

Can someone suggest anything I am missing or doing wrong.

#include <stdio.h>
#include <errno.h>
#include <time.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/socket.h>

#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netinet/if_ether.h> /* includes net/ethernet.h */

#define BUFFER_SIZE 1024

u_short
in_cksum(const u_short *addr, register int len, u_short csum)
{
register int nleft = len;
const u_short *w = addr;
register u_short answer;
register int sum = csum;

/*
* 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)
sum += htons(*(unsigned char *)w << Cool

;

/*
* 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);
}

int
main(int argc, char * argv[])
{
int sock;
struct sockaddr_in sin;
unsigned short local_port;
unsigned char protocol;
char * buffer, * buffer2, * dnsdata;
struct ip * ip_header;
struct icmp * icmp_header;
char * remote_ip_str="10.10.10.10";
unsigned short buffer_size, buffer_size2;
int tmp, len;
short randomseq;

protocol = IPPROTO_ICMP;

local_port = atoi(argv[1]);

if ((sock = socket(AF_INET, SOCK_RAW, protocol)) < 0) {
perror("socket");
exit(1);
}
memset(& sin, 0, sizeof(sin));

tmp = 1;
setsockopt(sock, 0, IP_HDRINCL, & tmp, sizeof(tmp));

buffer_size = sizeof(struct ip) + sizeof(struct icmp);
buffer_size2 = BUFFER_SIZE;
buffer = (char *) malloc(buffer_size);
buffer2 = (char *) malloc(buffer_size2);

memset(buffer, 0, sizeof(buffer));

memset(& sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = inet_addr(remote_ip_str);

ip_header = (struct ip *) buffer;
ip_header->ip_hl = 5;
ip_header->ip_v = 4;
ip_header->ip_tos = 0;
ip_header->ip_len = htons(buffer_size);
ip_header->ip_id = rand();
ip_header->ip_ttl = 64;
ip_header->ip_off = 0x40;
ip_header->ip_p = protocol;
ip_header->ip_sum = 0; /* This will be done in the kernel */
ip_header->ip_dst.s_addr = inet_addr(remote_ip_str);
/* Leave src IP address blank, kernel will fill it out. */
//ip_header->ip_src = 0;

icmp_header = (struct icmp *) (ip_header + 1);
icmp_header->icmp_type = htons(ICMP_ECHO);
icmp_header->icmp_code = 0;
icmp_header->icmp_id = htons(local_port);
icmp_header->icmp_seq = 0;
icmp_header->icmp_cksum = in_cksum((const u_short *) icmp_header,
sizeof(struct icmp), 0);

dump((short *)ip_header, ntohs(ip_header->ip_len));

if (sendto(sock, buffer, buffer_size, 0, (struct sockaddr *) &sin,
sizeof(struct sockaddr_in)) < 0)
{
perror("sendto");
}

printf("sent query\n");

len = sizeof(sin);
if (recvfrom(sock, buffer2, buffer_size2, 0, (struct sockaddr *)
&sin, &len) < 0) {
perror("recvfrom");
return 1;
}
printf("received response\n");

close(sock);
return 0;
}

Giorgos Keramidas · *nix forums Guru Joined: 10 May 2002 Posts: 330

On 2005-02-13 14:53, peter_holmes2003@yahoo.com wrote:

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