1 files changed, 85 insertions, 0 deletions
diff --git a/net/netfilter/nf_nat_proto_tcp.c b/net/netfilter/nf_nat_proto_tcp.c
new file mode 100644
index 000000000000..83ec8a6e4c36
--- /dev/null
+++ b/net/netfilter/nf_nat_proto_tcp.c
@@ -0,0 +1,85 @@
+/* (C) 1999-2001 Paul `Rusty' Russell
+ * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
+ *
+ * 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/init.h>
+#include <linux/export.h>
+#include <linux/tcp.h>
+
+#include <linux/netfilter.h>
+#include <linux/netfilter/nfnetlink_conntrack.h>
+#include <net/netfilter/nf_nat.h>
+#include <net/netfilter/nf_nat_l3proto.h>
+#include <net/netfilter/nf_nat_l4proto.h>
+#include <net/netfilter/nf_nat_core.h>
+
+static u16 tcp_port_rover;
+
+static void
+tcp_unique_tuple(const struct nf_nat_l3proto *l3proto,
+		 struct nf_conntrack_tuple *tuple,
+		 const struct nf_nat_range *range,
+		 enum nf_nat_manip_type maniptype,
+		 const struct nf_conn *ct)
+{
+	nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,
+				    &tcp_port_rover);
+}
+
+static bool
+tcp_manip_pkt(struct sk_buff *skb,
+	      const struct nf_nat_l3proto *l3proto,
+	      unsigned int iphdroff, unsigned int hdroff,
+	      const struct nf_conntrack_tuple *tuple,
+	      enum nf_nat_manip_type maniptype)
+{
+	struct tcphdr *hdr;
+	__be16 *portptr, newport, oldport;
+	int hdrsize = 8; /* TCP connection tracking guarantees this much */
+
+	/* this could be a inner header returned in icmp packet; in such
+	   cases we cannot update the checksum field since it is outside of
+	   the 8 bytes of transport layer headers we are guaranteed */
+	if (skb->len >= hdroff + sizeof(struct tcphdr))
+		hdrsize = sizeof(struct tcphdr);
+
+	if (!skb_make_writable(skb, hdroff + hdrsize))
+		return false;
+
+	hdr = (struct tcphdr *)(skb->data + hdroff);
+
+	if (maniptype == NF_NAT_MANIP_SRC) {
+		/* Get rid of src port */
+		newport = tuple->src.u.tcp.port;
+		portptr = &hdr->source;
+	} else {
+		/* Get rid of dst port */
+		newport = tuple->dst.u.tcp.port;
+		portptr = &hdr->dest;
+	}
+
+	oldport = *portptr;
+	*portptr = newport;
+
+	if (hdrsize < sizeof(*hdr))
+		return true;
+
+	l3proto->csum_update(skb, iphdroff, &hdr->check, tuple, maniptype);
+	inet_proto_csum_replace2(&hdr->check, skb, oldport, newport, 0);
+	return true;
+}
+
+const struct nf_nat_l4proto nf_nat_l4proto_tcp = {
+	.l4proto		= IPPROTO_TCP,
+	.manip_pkt		= tcp_manip_pkt,
+	.in_range		= nf_nat_l4proto_in_range,
+	.unique_tuple		= tcp_unique_tuple,
+#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
+	.nlattr_to_range	= nf_nat_l4proto_nlattr_to_range,
+#endif
+};