Description of problem:
   There is a bug about icmp netunreach.
   If the kernel does not find a route for a packet, 
   it must send a icmp netunreach packet to the source host, 
   and  discard  the packet. But the  kernel  does not send 
   a icmp netunreach packet because of the  fib_lookup
   return value  of -ESRCH when a route  is not found. 

Version-Release number of selected component (if applicable):
Fedora8 (2.6.23.1-42.fc8)

How reproducible:

TN ---------------------NUT

Steps to Reproduce:
1.  TN send a echo request to a unknown dest address to NUT
2.  
3.
  
Actual results:
TN can not receive netunreach packet packet

Expected results:
TN can receive netunreach packet packet

Additional info: