I needed to find a way to get the physical (MAC) address using C. From what I could gather from searching opensolaris.org, there are two methods for retrieving it: libdlpi and arp. libdlpi is the more elegant solution as it requires a simple call to dlpi_get_physaddr(). This is how ifconfig prints your network interface's MAC address. Unfortunately, libdlpi calls are only permitted as root.
The reason it was like this was historical: getting the MAC address in ifconfig meant opening up the DLPI node and talking to the driver. As the drivers didn't have discrete privileges for each operation, and you had to be almighty root to touch them, 'ifconfig' didn't show the MAC address when not privileged.*whatever*
The second solution is to use arp. In Solaris you can determine the physical address by looking at the arp tables directly (`arp -a | grep <INTERFACE>` or `netstat -p | grep <INTERFACE>`). With C, this can be done by using the if sockets and arp libraries.
I wrote up a solution called "getmac" using both methods. You can gather it here.
$ wget http://www.pauliesworld.org/project/getmac.c $ gcc getmac.c -o getmac -lsocket -ldlpi $ ./getmac <interface_name> arp: ffffffffffff dlpi: dlpi failure, are you root? $ pfexec ./getmac <interface_name> arp: ffffffffffff dlpi: ffffffffffff