Please please help me ...injecting packets

[bhupeshchawda]

Hi all,
Friends I have a built an IP packet and I need to inject this packet to a machine on my LAN. Hence I need a different ethernet header. I have used sockets and managed to inject a raw packet on to the wire but what exactly I want is that the kernel should build the ethernet header for me. The IP_HDRINCL option in setsockopt() does exactly this...but I get an error on setsockopt() with errno = 92 ...
Here is my code ...

inject(u_char *pkt, int nr) 
{ /*open socket*/
 fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); if (fd == -1) 
{
 printf("\nSocket failed!!"); 
} 

ret_val=setsockopt (fd, IPPROTO_IP, IP_HDRINCL,(const void *) val, sizeof (one));
if(ret_val<0)
	printf("iphdrincl error ...error no=%d",errno);

/*Select interface*/ 
memset(&ifr, 0, sizeof(ifr)); 
strncpy (ifr.ifr_name, iftext, sizeof(ifr.ifr_name) - 1); 
ifr.ifr_name[sizeof(ifr.ifr_name)-1] = '\0'; 
if (ioctl(fd, SIOCGIFINDEX, &ifr) == -1) 
{ 
 printf("No such interface: %s\n", iftext); 
 return -1; 
}
 ioctl(fd, SIOCGIFFLAGS, &ifr); 
if ( (ifr.ifr_flags & IFF_UP) == 0)
 { printf("Interface %s is down\n", iftext);
 return -1;
 } 
ioctl(fd, SIOCGIFINDEX, &ifr);
 memset(&sa, 0, sizeof (sa));
 sa.sll_family = AF_PACKET;
 sa.sll_ifindex = ifr.ifr_ifindex;
 sa.sll_protocol = htons(ETH_P_ALL); 
/*Send*/ 
c = sendto(fd, pkt, nr, 0, (struct sockaddr *)&sa, sizeof (sa));
 }

Please help me...any help will be appreciated.

[bhaslinux]

placing the ethernet header is done at the DataLink Layer (DLL) which is
into the firmware of the device.
You cannot order device to send some other frame into the LAN whereas
the device you bought does say 802.3

[bhupeshchawda]

Yes...I understand that the ethernet 802.3 header is attached at the device itself ...
Is there no way it can be done...I hope u got my problem...
Also what do u have to say about the code...will that work??

[bhupeshchawda]

I hope u got my problem...

I'll again explain my problem for better understanding...I have a packet :

DATA->IP_HEADER->TCP_HEADER->ETHERNET_HEADER.

This ETHERNET_HEADER has destination MAC address of my machine. I need to send this packet to another computer on my LAN...For this I would have to strip out the previous ETHERNET_HEADER and attach a new one based on the MAC address of the destination machine...

So I pass :
DATA->IP_HEADER->TCP_HEADER
to the inject function and expect it to attach a new ethernet header...

my code works for RAW packets but it does not attach the new Ethernet header...

Also note : The IP_HDRINCL option in setsockopt() gives an error on setsockopt() with errno = 92 ...

Please please do help me...any help will be appreciated.

[hiren_gajjar]

I'll again explain my problem for better understanding...I have a packet :

DATA->IP_HEADER->TCP_HEADER->ETHERNET_HEADER.

This ETHERNET_HEADER has destination MAC address of my machine. I need to send this packet to another computer on my LAN...For this I would have to strip out the previous ETHERNET_HEADER and attach a new one based on the MAC address of the destination machine...

So I pass :
DATA->IP_HEADER->TCP_HEADER
to the inject function and expect it to attach a new ethernet header...

my code works for RAW packets but it does not attach the new Ethernet header...

Also note : The IP_HDRINCL option in setsockopt() gives an error on setsockopt() with errno = 92 ...

Please please do help me...any help will be appreciated.

IP_HDRINCL is just an intimation to Kernel that you will be providing the IP stack. When you say so, why can't u build up etherner header itself?

[bhaslinux]

The way in which the card works is there is always a
bios on the card which takes care of putting the 802.3 header.
If you want to bypass the header, the only way is to re-write the
BIOS on the card.
Your program works at the level above layer 2 and you want something
to work on layer 2. I donnot know if tweaking the kernel even can do you
any help !