Title: ip_checkopt()

ip_checkopt() checks the validity of an ip file descriptor's options. For example, ip_checkopt() verifies that one flag (disable or enable) is set in each set of flags (e.g., the NWIO_ACC_MASK set of flags). ip_checkopt() also verifies that the ip header options are valid.

If the flags are acceptable, the ip file descriptor is placed in its corresponding ip port's appropriate linked list.