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, 2 insertions, 2 deletions

diff --git a/conf.c b/conf.c
index 4e86508..993f840 100644
--- a/conf.c
+++ b/conf.c
@@ -209,7 +209,7 @@ static int conf_ports(const struct ctx *c, char optname, const char *optarg,
 		if (sep == p)
 			break;
 
-		if (port > USHRT_MAX || errno)
+		if (port >= NUM_PORTS || errno)
 			goto bad;
 
 		switch (*sep) {
@@ -276,7 +276,7 @@ static int conf_ports(const struct ctx *c, char optname, const char *optarg,
 		if (sep == p)
 			break;
 
-		if (port > USHRT_MAX || errno)
+		if (port >= NUM_PORTS || errno)
 			goto bad;
 
 		/* -p 22