Title: eth_ioctl()


The actions of eth_ioctl(fd, req) depend on req, eth_ioctl()'s second parameter:

NWIOSETHOPT (NetWork IO Set ETHernet OPTions):

If req is NWIOSETHOPT, eth_ioctl() configures the ethernet file descriptor fd (eth_ioctl()'s first parameter), which can then be used by a higher layer (e.g., ip, arp).

NWIOGETHSTAT (NetWork IO Get ETHernet STATs):

Only the arp code calls eth_ioctl() with the second parameter set to NWIOGETHSTAT. In this case, the ap_ethaddr field of the arp port is set to the ethernet address of the ethernet file descriptor's underlying ethernet port.