[NETFILTER]: nf_nat: add helpers for common NAT protocol operations

Add generic ->in_range and ->unique_tuple ops to avoid duplicating them
again and again for future NAT modules and save a few bytes of text:

net/ipv4/netfilter/nf_nat_proto_tcp.c:
  tcp_in_range     |  -62 (removed)
  tcp_unique_tuple | -259 # 271 -> 12, # inlines: 1 -> 0, size inlines: 7 -> 0
 2 functions changed, 321 bytes removed

net/ipv4/netfilter/nf_nat_proto_udp.c:
  udp_in_range     |  -62 (removed)
  udp_unique_tuple | -259 # 271 -> 12, # inlines: 1 -> 0, size inlines: 7 -> 0
 2 functions changed, 321 bytes removed

net/ipv4/netfilter/nf_nat_proto_gre.c:
  gre_in_range |  -62 (removed)
 1 function changed, 62 bytes removed

vmlinux:
 5 functions changed, 704 bytes removed

Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 85 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/nf_nat_proto_common.c b/net/ipv4/netfilter/nf_nat_proto_common.c
new file mode 100644
index 00000000000..a124213fb9d
--- /dev/null
+++ b/net/ipv4/netfilter/nf_nat_proto_common.c
@@ -0,0 +1,85 @@
+/* (C) 1999-2001 Paul `Rusty' Russell
+ * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
+ * (C) 2008 Patrick McHardy <kaber@trash.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/types.h>
+#include <linux/random.h>
+#include <linux/ip.h>
+
+#include <linux/netfilter.h>
+#include <net/netfilter/nf_nat.h>
+#include <net/netfilter/nf_nat_core.h>
+#include <net/netfilter/nf_nat_rule.h>
+#include <net/netfilter/nf_nat_protocol.h>
+
+int nf_nat_proto_in_range(const struct nf_conntrack_tuple *tuple,
+			  enum nf_nat_manip_type maniptype,
+			  const union nf_conntrack_man_proto *min,
+			  const union nf_conntrack_man_proto *max)
+{
+	__be16 port;
+
+	if (maniptype == IP_NAT_MANIP_SRC)
+		port = tuple->src.u.all;
+	else
+		port = tuple->dst.u.all;
+
+	return ntohs(port) >= ntohs(min->all) &&
+	       ntohs(port) <= ntohs(max->all);
+}
+EXPORT_SYMBOL_GPL(nf_nat_proto_in_range);
+
+int nf_nat_proto_unique_tuple(struct nf_conntrack_tuple *tuple,
+			      const struct nf_nat_range *range,
+			      enum nf_nat_manip_type maniptype,
+			      const struct nf_conn *ct,
+			      u_int16_t *rover)
+{
+	unsigned int range_size, min, i;
+	__be16 *portptr;
+
+	if (maniptype == IP_NAT_MANIP_SRC)
+		portptr = &tuple->src.u.all;
+	else
+		portptr = &tuple->dst.u.all;
+
+	/* If no range specified... */
+	if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)) {
+		/* If it's dst rewrite, can't change port */
+		if (maniptype == IP_NAT_MANIP_DST)
+			return 0;
+
+		if (ntohs(*portptr) < 1024) {
+			/* Loose convention: >> 512 is credential passing */
+			if (ntohs(*portptr) < 512) {
+				min = 1;
+				range_size = 511 - min + 1;
+			} else {
+				min = 600;
+				range_size = 1023 - min + 1;
+			}
+		} else {
+			min = 1024;
+			range_size = 65535 - 1024 + 1;
+		}
+	} else {
+		min = ntohs(range->min.all);
+		range_size = ntohs(range->max.all) - min + 1;
+	}
+
+	if (range->flags & IP_NAT_RANGE_PROTO_RANDOM)
+		*rover = net_random();
+
+	for (i = 0; i < range_size; i++, (*rover)++) {
+		*portptr = htons(min + *rover % range_size);
+		if (!nf_nat_used_tuple(tuple, ct))
+			return 1;
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nf_nat_proto_unique_tuple);