well, documentation is better than nothing. i didn't have time to fully debug this situation today, but i noticed that on some hosts, icmp unreachable messages do not terminate the connection, though snoopy did see the icmp packet.
for example, on host a telnet 40.10.10.10 hangs, but on host b, it returned connection unreachable or some such. the gateway returning the unreachable message was the same in both cases. this smells like a race, as tcp accesses the connection outside the lock. - erik
