Explicit address mapping.

This is the implementation of the draft http://tools.ietf.org/html/draft-anderson-v6ops-siit-eam-00, attending the issue #116.
The new files aren't incorporated to the jool application yet. We could say that this is an approach, we need to see how Jool will behave as a Stateles NAT64, and then connect this files.
I did a unit test to see if this new feature behave as expected.

TODO: I need to program how to delete an EAM entry from the database when requested. This will be ready when this feature are connected to Jool.

include/nat64/comm/types.h

@@ -106,6 +106,17 @@ struct ipv6_transport_addr {
 	__u16 l4;
 };
 
+/**
+ * TODO:(dhernandez) check if this description is correct.
+ * A member of the IPv4 pool; the network component of a IPv4 address.
+ */
+struct ipv4_prefix {
+	/** IPv4 prefix. */
+	struct in_addr address;
+	/** Number of bits from "address" which represent the network. */
+	__u8 len;
+};
+
 /**
  * A member of the IPv6 pool; the network component of a IPv6 address.
  */

include/nat64/mod/address_mapping.h

@@ -0,0 +1,56 @@
+#ifndef _JOOL_MOD_ADDRESS_MAPPING_H
+#define _JOOL_MOD_ADDRESS_MAPPING_H
+
+/*
+ * address_mapping.h
+ *
+ *  Created on: Nov 25, 2014
+ *  @author: Daniel Hdz Felix
+ */
+
+#include "nat64/comm/types.h"
+
+/**
+ * Explicit Address Mapping definition.
+ * Intended to be a row in the Explicit Address Mapping Table, bind an IPv4 Prefix to an IPv6 Prefix
+ * and vice versa.
+ */
+struct eam_entry {
+	/** The prefix address for the IPv4 network. */
+	struct ipv4_prefix pref4;
+	/** The prefix address for the IPv6 network. */
+	struct ipv6_prefix pref6;
+	/** Appends this entry to the database's IPv6 index. */
+	struct rb_node tree6_hook;
+	/** Appends this entry to the database's IPv4 index. */
+	struct rb_node tree4_hook;
+};
+
+/**
+ *	Insert IPv6 Prefix "ip6_pref" and IPv4 Prefix "ip4_pref" to the database, return zero if the
+ *	insert was successful.
+ *
+ *	If the "ipX_pref" contains or is part of a prefix indexed in the databases, then returns error.
+ */
+int address_mapping_insert_entry(struct ipv6_prefix *ip6_pref, struct ipv4_prefix *ip4_pref);
+
+/**
+ * Look in the IPv4 address mapping table, if the IPv4 address "addr" is part of a prefix indexed
+ * in the table, if "addr" exists, append the mapped IPv6 prefix to "result" and also append the
+ * suffix from "addr" to "result".
+ *
+ * otherwise return error.
+ */
+int address_mapping_get_ipv6_by_ipv4(struct in_addr *addr, struct in6_addr *result);
+
+/**
+ * Look in the IPv6 address mapping table, if the IPv6 address "addr6" is part of a prefix indexed
+ * in the table, if "addr6" exists, append the mapped IPv4 prefix to "result" and also append the
+ * suffix from "addr6" to "result".
+ *
+ * otherwise return error.
+ */
+int address_mapping_get_ipv4_by_ipv6(struct in6_addr *addr6, struct in_addr *result);
+
+
+#endif /* _JOOL_MOD_ADDRESS_MAPPING_H */