nf_nat: use secure_ipv4_port_ephemeral() for NAT port randomization

Use incoming network tuple as seed for NAT port randomization.
This avoids concerns of leaking net_random() bits, and also gives better
port distribution. Don't have NAT server, compile tested only.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>

[ added missing EXPORT_SYMBOL_GPL ]

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 2 deletions

diff --git a/net/ipv4/netfilter/nf_nat_proto_common.c b/net/ipv4/netfilter/nf_nat_proto_common.c
index 91537f11273f..6c4f11f51446 100644
--- a/net/ipv4/netfilter/nf_nat_proto_common.c
+++ b/net/ipv4/netfilter/nf_nat_proto_common.c
@@ -73,9 +73,13 @@ bool nf_nat_proto_unique_tuple(struct nf_conntrack_tuple *tuple,
                 range_size = ntohs(range->max.all) - min + 1;
         }
 
-        off = *rover;
         if (range->flags & IP_NAT_RANGE_PROTO_RANDOM)
-                off = net_random();
+                off = secure_ipv4_port_ephemeral(tuple->src.u3.ip, tuple->dst.u3.ip,
+                                                 maniptype == IP_NAT_MANIP_SRC
+                                                 ? tuple->dst.u.all
+                                                 : tuple->src.u.all);
+        else
+                off = *rover;
 
         for (i = 0; i < range_size; i++, off++) {
                 *portptr = htons(min + off % range_size);