30.8 TCP Preforked Server, Thread Locking Around accept

Exercises

29.1	What is the purpose of the canjump flag in Figure 29.11?
29.2	In our udpcksum program, common error replies are an ICMP "port unreachable" (the destination is not running a name server) or an ICMP "host unreachable." In either case, we need not wait for a timeout of our udp_read in Figure 29.10 because the ICMP error is essentially a reply to our DNS query. Modify the program to catch these ICMP errors.