AF_INET socket when only IPv6 addresses are available on system?

Question

Can you open AF_INET socket when only IPv6 addresses are available on system?

I'm trying to get the HWADDR for one system that may have only IPv6 addresses active (not dual stack).

Will I be able to open a socket using AF_INET? I'm only interested in finding the MAC address

Answer 1

I fail to see the problem. You can call SIOCGIFHWADDR on both IPv4 and IPv6 sockets.

No matter if I use AF_INET or AF_INET6 to create the socket, the ioctl() call succeeds and gives me the HW addr of the device I ask for.

Answer 2

You surely could create an IPv4 socket using the system call socket(). However binding it to an IPv6 interface using bind() would fail.

Answer 3

You can create an IPv4 socket. If you could not, the system would also not be able to accept an IPv4 address when you connect to a v4-able network next month, see?

But I'm not sure SIOCGIFHWADDR will work without routes through a non-loopback interface. You could try tat on your target systems, or just try both AF_INET and AF_INET6, catch the error(s) and use whatever returns a result.