Title: read_ip_packets() / udp
read_ip_packets() is called only a single time, during the initialization of the udp code.
read_ip_packets() reads all packets (by repeatedly calling ip_read()) in the udp port's associated ip file descriptor's read queue until all of the packets have either been delivered to the processes that issued the read requests (provided that the packets have not expired) or placed in the udp file descriptor's read queue.
read_ip_packets() is also called by udp_get_data(). However, this line of code is never executed (see comment for line 61391).