how to determinate destination MAC address

Question

My application is running on CentOS 5.5 I need to send raw packets using libpcap API:

pcap_inject() or pcap_sendpacket()

To the specific IP add

Answer 1

In general, MAC addresses don't matter for remote targets. They are not routable; a router here at my office doesn't know the MAC addresses of network cards across the Internet. That's what IP addresses are for. Do you mean local only?

Answer 2

It looks like what you want is ioctl and SIOCGARP. That should let you query your arp cache. I'm assuming that the host in question is on your local network or all you're going to get is your router.

You can also read from /proc/net/arp, which seems easier. You'll need to get an arp request returned first but you'll be doing that whether your tool does it or some third-party makes the request.