The socket module make a great effort to be thread-
safe, but misses one 
big point - it uses single per-instance buffer to hold 
resolved 
sockaddr_xxx structures. Therefore, on SMP system it 
is possible that 
several threads calling functions that perform address 
resolution in 
parallel will stomp on each other resulting in 
incorrect or invalid address 
to be used in each case.

For example, two threads calling sendto() in parallel 
can result in packets 
to be sent to incorrect addresses - packets from 
thread one from time to 
time will be sent to address requested by thread two 
and vice versa.

Another, smaller issue is that the call to getnameinfo
() is not protected 
with netdb mutex on systems that don't have thread-
safe resolver.

P.S. This is very serious problem for us. For some 
reason my previous patch submission has been 
downgraded to bug report and forgotten completely, so 
that I am re-submitting.