[INET]: Justification for local port range robustness.

  There is a justifying patch for Stephen's patches. Stephen's patches
disallows using a port range of one single port and brakes the meaning
of the 'remaining' variable, in some places it has different meaning.
My patch gives back the sense of 'remaining' variable. It should mean
how many ports are remaining and nothing else. Also my patch allows
using a single port.

  I sure we must be able to use mentioned port range, this does not
restricted by documentation and does not brake current behavior.

usefull links:
Patches posted by Stephen Hemminger
  http://marc.info/?l=linux-netdev&m=119206106218187&w=2
  http://marc.info/?l=linux-netdev&m=119206109918235&w=2

Andrew Morton's comment
  http://marc.info/?l=linux-kernel&m=119248225007737&w=2

1. Allows using a port range of one single port.
2. Gives back sense of 'remaining' variable.

Signed-off-by: Anton Arapov <aarapov@redhat.com>
Acked-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 3cef128..8fb6ca2 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -93,7 +93,7 @@
 		int remaining, rover, low, high;
 
 		inet_get_local_port_range(&low, &high);
-		remaining = high - low;
+		remaining = (high - low) + 1;
 		rover = net_random() % remaining + low;
 
 		do {
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index fac6398..16eecc7 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -286,7 +286,7 @@
 		struct inet_timewait_sock *tw = NULL;
 
 		inet_get_local_port_range(&low, &high);
-		remaining = high - low;
+		remaining = (high - low) + 1;
 
 		local_bh_disable();
 		for (i = 1; i <= remaining; i++) {
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index c78acc1..ffddd2b 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -122,7 +122,7 @@
 	ret = proc_dointvec_minmax(&tmp, write, filp, buffer, lenp, ppos);
 
 	if (write && ret == 0) {
-		if (range[1] <= range[0])
+		if (range[1] < range[0])
 			ret = -EINVAL;
 		else
 			set_local_port_range(range);
@@ -150,7 +150,7 @@
 
 	ret = sysctl_intvec(&tmp, name, nlen, oldval, oldlenp, newval, newlen);
 	if (ret == 0 && newval && newlen) {
-		if (range[1] <= range[0])
+		if (range[1] < range[0])
 			ret = -EINVAL;
 		else
 			set_local_port_range(range);
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index cb9fc58..35d2b0e 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -147,13 +147,14 @@
 	write_lock_bh(&udp_hash_lock);
 
 	if (!snum) {
-		int i, low, high;
+		int i, low, high, remaining;
 		unsigned rover, best, best_size_so_far;
 
 		inet_get_local_port_range(&low, &high);
+		remaining = (high - low) + 1;
 
 		best_size_so_far = UINT_MAX;
-		best = rover = net_random() % (high - low) + low;
+		best = rover = net_random() % remaining + low;
 
 		/* 1st pass: look for empty (or shortest) hash chain */
 		for (i = 0; i < UDP_HTABLE_SIZE; i++) {