- Don't dereference a NULL hostent pointer (if T_PTR lookup fails).
- Today I asked myself: "Self, you wrote this nifty async resolver
that does a great job handling delayed replies to clients using
the UDP transport, and the yplib code in libc always uses UDP
(except for yp_all()). But what if some dork makes a DNS lookup using
TCP?" Being the only dork on hand at the time, I tried it and was
enlightened. As I suspected, my transaction ID frobbing hacks cause
fireworks if called on a TCP transport handle (duh: the structures
are different). Fix: check the type of socket in xprt->xp_sock using
getsockopt() and don't use svcudp_get_xid() and svcudp_set_xid() for
anything except SOCK_DGRAM sockets. (Since accept() gives you a
new socket for each connection, the transaction ID munging isn't
needed for TCP anyway.)