ICMP messages - Scan or exploit attempt?

["Compra, Fred" <fredco () HUSHMAIL COM>]

I checked the logs on my masquerading Linux box a while ago to find that
ippl had logged some "ippl: ICMP message type destination unreachable -
bad host from xxx.xxx.xxx.xxx" messages with plenty of "last message repeated
xx times" following them.  (The x'd out IP address is the external interface
on the box.)

I saw no other connection attempts during this time, but I wasn't logging
UDP, only TCP and ICMP. Could these messages be the result of a UDP scan
of some sort, or even an attempt to exploit the Linux UDP masquerading vulnerability?
(Does anyone know if this has been fixed?)

Thanks to all,
Fred