Setting a NIC to Promiscuous Mode

[kardon33]

Hello all,

I am trying to write a C program on Unix (OpenBSD 4.3) that will be sniffing a certain packet which is being sent by a diff rent machine to another different machine.

The only way I believe this is possible is to set my NIC into promiscuous mode.

I would like to set the NIC to Promiscuous mode in my C program but I would also be content if anyone knows a way to just set it in that mode permanently, but thats more of a question for an BSD forum.

As for the code method, I have searched google for awhile now but have still not found a technique that works, everything I try usually doesn't work because the header file #include <netinet/tcp.h> has errors in it.


Here is the method that I found in a bunch of places online, I get syntax errors in the #include <netinet/ip.h> #include <netinet/tcp.h> header files.

/usr/include/netinet/ip.h:156: error: syntax error before "n_time"

#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <linux/if.h>
#include <sys/ioctl.h>

int promisc(){

	int fd;
	struct ifreq eth;
	
	fd = socket(AF_INET, SOCK_PACKET, htons(0x800));
	
	strcpy(eth.ifr_name, "eth0");
	
	ioctl(fd, SIOCGIFFLAGS, &eth);
	
	eth.ifr_flags |= IFF_PROMISC;
	
	ioctl(fd, SIOCSIFFLAGS, &eth);


}

[gpraghuram]

I grepped for n_time in the folder /usr/include/netinet and got these
$ grep n_time /usr/include/netinet/*.h
/usr/include/netinet/in_systm.h:type def u_int32_t n_time; /* ms since 00:00 GMT, byte rev */

Try including this header file or check whether you have to have some specific #define for this

Raghu