Title: udp_ip_arrived()

udp_ip_arrived() is called either (indirectly) from the ip code or from udp_put_data() and is one of the last functions called for a read request from a user process. udp_ip_arrived() does some checks (e.g., a checksum check) and figures out the destination udp file descriptor before calling udp_packet2user() to deliver the packet to the process that requested the read.