Communication using RAW sockets

ThirtySixBelow · 12-22-2009, 02:07 PM

I'm trying to create a simple program that sends and receives ethernet frames. I'm using ubuntu 9.04 and tried to follow the raw manpage on the ubuntu website but it doesn't seem to be working properly. There are so many resources that give different ideas and I feel like I'm just messing around trying to find the correct combination of code. All I want to do is send [dst_mac_addr|src_mac_addr|type|data] ... it can't be that difficult. The code below is what I'm working with and it currently fails on send. You can notice some different ideas I've tried from the commented out code. Any help would be amazing.

Code:

#include <sys/socket.h>
#include <netinet/in.h>
//#include <netdb.h>
//#include <arpa/inet.h>
//#include <sys/param.h>
#include <netpacket/packet.h>
#include <net/ethernet.h>
//#include <linux/if_packet.h>
//#include <linux/if_ether.h>
//#include <linux/if_arp.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <sys/time.h>

int main (int argc, char*argv[]) {
	int i,j;
	struct timeval start,stop;
	unsigned char* buffer = (unsigned char*)malloc(ETH_FRAME_LEN);
	unsigned char* etherhead = buffer;
	unsigned char* data = buffer + 14;
	struct ethhdr *eh = (struct ethhdr *)etherhead;
	struct sockaddr_in servaddr;
	
	servaddr.sin_family = AF_INET;
	servaddr.sin_port = htons(80);
	servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");
	
	int s = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
	if(s == -1) {
		printf("socket failed\n");
		exit(0);
	}	
	if(setsockopt(s,SOL_SOCKET,SO_BINDTODEVICE,"eth0",4) == -1) {
		printf("sockopt failed\n");
		exit(0);
	}

	int send_result = 0;
	int length = 0;

	unsigned char src_mac[6] = {0x00,0x21,0x97,0x45,0x6b,0x3b};
	unsigned char dest_mac[6] = {0x00,0x0a,0x35,0x00,0x01,0x02};
//
//	struct sockaddr_ll socket_address;
//	socket_address.sll_family = AF_PACKET;
//	socket_address.sll_protocol = 0;
//	socket_address.sll_ifindex = if_nametoindex("eth0");
//	socket_address.sll_hatype = 0;
//	socket_address.sll_pkttype = 0;
//	socket_address.sll_halen = ETH_ALEN;
//
//	/*MAC - begin*/
//	socket_address.sll_addr[0]  = 0x00;		
//	socket_address.sll_addr[1]  = 0x21;		
//	socket_address.sll_addr[2]  = 0x97;
//	socket_address.sll_addr[3]  = 0x45;
//	socket_address.sll_addr[4]  = 0x6b;
//	socket_address.sll_addr[5]  = 0x3b;
//	/*MAC - end*/
//	socket_address.sll_addr[6]  = 0x00;/*not used*/
//	socket_address.sll_addr[7]  = 0x00;/*not used*/
//

	/*set the frame header*/
	memcpy((void*)buffer, (void*)dest_mac, ETH_ALEN);
	memcpy((void*)(buffer+ETH_ALEN), (void*)src_mac, ETH_ALEN);
	eh->h_proto = 0x00;
	/*fill the frame with some data*/
	for (j = 0; j < 1500; j++) {
		data[j] = (unsigned char)((int) (255.0*rand()/(RAND_MAX+1.0)));
	}

	//if(bind(s,(struct sockaddr *)&socket_address, sizeof(socket_address))<0){
	//	printf("binding error\n");
	//	exit(0);
	//}

	//start = clock();
	gettimeofday(&start,0);
	for(i=0;i<100;i++){
		/*send the packet*/
		send_result = sendto(s, buffer, ETH_FRAME_LEN, 0, 
	      		(struct sockaddr*)&servaddr, sizeof(servaddr));
		if (send_result == -1) { printf("send error\n");return 1;}

		length = recvfrom(s, buffer, ETH_FRAME_LEN, 0, NULL, NULL);
		if (length == -1) { printf("rcv error\n");return 1; }
	}
	//stop = clock();
	gettimeofday(&stop,0);
	printf("%ld\n",stop.tv_usec-start.tv_usec);
	return 0;
}

kanver · 12-23-2009, 02:52 PM

How does it fail? Does the program crash? If so, what's the error message? "xy doesn't work, what to do?" never induced any useful answer.

kbp · 12-23-2009, 04:00 PM

When running under strace I found this message:

Code:

sendto(3, "\0\n5\0\1\2\0!\227Ek;\0\0\326d\307\313\3502U\303F\215y\240]\202\362\351\242\266"..., 1514, 0, {sa_family=AF_INET, sin_port=htons(80), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EMSGSIZE (Message too long)

...maybe it's relevant

cheers