Adds some options and documentation related to recursive next hops.

proto/bgp/bgp.h

@@ -23,6 +23,7 @@ struct bgp_config {
   ip_addr source_addr;			/* Source address to use */
   int next_hop_self;			/* Always set next hop to local IP address */
   int missing_lladdr;			/* What we will do when we don' know link-local addr, see MLL_* */
+  int gw_mode;				/* How we compute route gateway from next_hop attr, see GW_* */
   int compare_path_lengths;		/* Use path lengths when selecting best route */
   int prefer_older;			/* Prefer older routes according to RFC 5004 */
   u32 default_local_pref;		/* Default value for LOCAL_PREF attribute */
@@ -53,6 +54,9 @@ struct bgp_config {
 #define MLL_DROP 2
 #define MLL_IGNORE 3
 
+#define GW_DIRECT 1
+#define GW_RECURSIVE 2
+
 struct bgp_conn {
   struct bgp_proto *bgp;
   struct birdsock *sk;