[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>

1 files changed, 3 insertions, 2 deletions

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index cb9fc58efb2f..35d2b0e9e10b 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -147,13 +147,14 @@ int __udp_lib_get_port(struct sock *sk, unsigned short snum,
         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++) {