zebra: extern/extract some functions from rt_netlink.c

* zebra/{rib.h,zebra_rib.c}

    Add nexthop_type_to_str(), which returns a human-readable string
    corresponding to a nexthop type.

  * zebra/rt_netlink.[hc]

    - Add new header file that exposes some existing and new
      netlink-related functions from rt_netlink.c to the rest of
      zebra.

        addattr32
        addattr_l
        rta_addattr_l
        nl_msg_type_to_str (new)
        nl_rtproto_to_str (new)

    - Use nexthop_type_to_str() instead of the static array
      'nexthop_types_desc'.

Signed-off-by: Avneesh Sachdev <avneesh@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/zebra/rt_netlink.h b/zebra/rt_netlink.h
new file mode 100644
index 0000000..529fa51
--- /dev/null
+++ b/zebra/rt_netlink.h
@@ -0,0 +1,46 @@
+/* Header file exported by rt_netlink.c to zebra.
+ * Copyright (C) 1997, 98, 99 Kunihiro Ishiguro
+ *
+ * This file is part of GNU Zebra.
+ *
+ * GNU Zebra is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * GNU Zebra is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Zebra; see the file COPYING.  If not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#ifndef _ZEBRA_RT_NETLINK_H
+#define _ZEBRA_RT_NETLINK_H
+
+#ifdef HAVE_NETLINK
+
+#define NL_PKT_BUF_SIZE 4096
+
+extern int
+addattr32 (struct nlmsghdr *n, int maxlen, int type, int data);
+extern int
+addattr_l (struct nlmsghdr *n, int maxlen, int type, void *data, int alen);
+
+extern int
+rta_addattr_l (struct rtattr *rta, int maxlen, int type, void *data, int alen);
+
+extern const char *
+nl_msg_type_to_str (uint16_t msg_type);
+
+extern const char *
+nl_rtproto_to_str (u_char rtproto);
+
+
+#endif /* HAVE_NETLINK */
+
+#endif /* _ZEBRA_RT_NETLINK_H */