[SOLVED] Raw Socket Programming question (my head is going to explode)

aztroboy · 11-11-2010, 04:03 PM

Greetings,

This is my main question:

Quote:

In raw socket sniffing: how do I copy data from a structure into a char[] or pointer?

My problem:

I started doing some raw socket programming in OpenWRT (I'm a newbie) for research. It's been a long time since the last time I programmed in C, so here's my newbie question/problem.

I'm receiving packets and using an .h file with the structures to get the information of each 802.11 packet in monitor mode (attached to this post).

My (simple) goal is to get the Tx MAC Address. No luck.

This is my "read the prism header" function:

Code:

ParsePrismHeader(unsigned char *packet,int len)
{
	wlan_header *wlan;ieee_802_11_header *i802;u_int16_t eth_type;
	unsigned char *mac;unsigned char *mac2;

	wlan = (wlan_header *)packet;
	i802 = (ieee_802_11_header *)(packet + wlan->msglen);

	//copy the DESTINATION mac address to a pointer
	getMACaddr((i802)->mac1,mac);
	
	//is this packet for me? -- Is the DES MAC my mac?
	if(strcmp(localMAC,mac)==0)
	{
		//let's print my own mac address (DEST mac)
                printf(" %s ",mac);
		//now copy the Transmitting mac
        	getMACaddr((i802)->mac2,mac2);
	}
}

this is the getMACaddr function:

Code:

getMACaddr(unsigned char *p,unsigned char *macx){
	int s=0;
	char tmp[50]="";

	for( s = 0; s < 6; s++ )
	{
		sprintf(tmp,"%.2X", *p);
		strcat(macx,tmp);
		p++;
	}
		size_t begin=1;
		size_t end=12;

		sprintf(macx,"%s",substring(macx,begin,end));

}

mac, which is the Destination MAC (my mac), does the job and prints it without problem

BUT when I use getMACaddress the second time, it prompts the 'C' character, like this:

Code:

 687F7427B81C  4FD370694
 687F7427B81C 4FD3706940
 687F7427B81C  4FD37069404
 687F7427B81C  4FD370694040
 687F7427B81C  FD3706940404
 687F7427B81C  D37069404040
 687F7427B81C  370694040404
 687F7427B81C  706940404040
 687F7427B81C  069404040404
 687F7427B81C  694040404040
 687F7427B81C  940404040400

the first one is my MAC (it's ok), the second it's NOT :/

now again, HOW do I copy data from a structure TO a char[] or a pointer? why is it copying one and not the other one?

thank you for your indulgence.

Sergei Steshenko · 11-11-2010, 04:20 PM

Quote:

Originally Posted by aztroboy

... HOW do I copy data from a structure TO a char[] or a pointer?
...

man 3 strcpy
.

aztroboy · 11-11-2010, 07:38 PM

Quote:

Originally Posted by Sergei Steshenko

man 3 strcpy
.

I actually did this

Code:

...
	unsigned char *mac2;
...
	getMACaddr((i802)->mac1,mac); // I made this function. It won't work with "mac2" after I use it with "mac"
...
        strcpy(mac2, (unsigned char *)((i802)->mac2) );
        printf(" %s ",mac);
        printf(" %s \n",mac2);

this is what I got:

Code:

 687F7427B81C  Ä,æãÖ=VX\ÐÀªª
 687F7427B81C  Ä,æãÖ=VX\Áªª
 687F7427B81C  Ä,æãÖ=VX\0Áªª
 687F7427B81C  Ä,æãÖ=VX\PÁªª
 687F7427B81C  Ä,æãÖ=VX\`Áªª
 687F7427B81C  Ä,æãÖ=VX\Áªª
 687F7427B81C  Ä,æãÖ=VX\°Áªª
 687F7427B81C  Ä,æãÖ=VX\ÐÁªª
 687F7427B81C  Ä,æãÖ=VX\
 687F7427B81C  Ä,æãÖ=VX\0Âªª

Am I printing it wrong? The second one is a mess. The first on is copied without trouble.

aztroboy · 11-11-2010, 08:57 PM

I actually got it, thanks, it worked

What was I doing wrong? printing the string that I strcpy'ed.