ipeth_main() helps initialize an ip port whose underlying link layer device is an ethernet device. ipeth_main() calls eth_ioctl(), which configures the ethernet file descriptor that corresponds to the ip port and then calls arp_set_cb() to initialize the arp port that is associated with this ip port. After the initialization, ipeth_main() calls do_eth_read() to process any ethernet packets that have arrived at the ethernet file descriptor that was just opened.