Fix widespread off-by-one error dealing with port numbers

Port numbers (for both TCP and UDP) are 16-bit, and so fit exactly into a
'short'.  USHRT_MAX is therefore the maximum port number and this is widely
used in the code.  Unfortunately, a lot of those places don't actually
want the maximum port number (USHRT_MAX == 65535), they want the total
number of ports (65536).  This leads to a number of potentially nasty
consequences:

 * We have buffer overruns on the port_fwd::delta array if we try to use
   port 65535
 * We have similar potential overruns for the tcp_sock_* arrays
 * Interestingly udp_act had the correct size, but we can calculate it in
   a more direct manner
 * We have a logical overrun of the ports bitmap as well, although it will
   just use an unused bit in the last byte so isnt harmful
 * Many loops don't consider port 65535 (which does mitigate some but not
   all of the buffer overruns above)
 * In udp_invert_portmap() we incorrectly compute the reverse port
   translation for return packets

Correct all these by using a new NUM_PORTS defined explicitly for this
purpose.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

1 files changed, 1 insertions, 1 deletions

diff --git a/udp.h b/udp.h
index bc7b259..d14df0a 100644
--- a/udp.h
+++ b/udp.h
@@ -50,7 +50,7 @@ union udp_epoll_ref {
  */
 struct udp_port_fwd {
 	struct port_fwd f;
-	in_port_t rdelta[USHRT_MAX];
+	in_port_t rdelta[NUM_PORTS];
 };
 
 /**