BGP multipath support

Kernel option 'merge paths' allows to merge routes exported to kernel
protocol (currently BGP and static routes) to multipath routes.

3 files changed, 18 insertions, 6 deletions

diff --git a/sysdep/unix/krt.Y b/sysdep/unix/krt.Y
index 630cda38..e036081d 100644
--- a/sysdep/unix/krt.Y
+++ b/sysdep/unix/krt.Y
@@ -17,7 +17,7 @@ CF_DEFINES
 
 CF_DECLS
 
-CF_KEYWORDS(KERNEL, PERSIST, SCAN, TIME, LEARN, DEVICE, ROUTES, GRACEFUL, RESTART, KRT_SOURCE, KRT_METRIC)
+CF_KEYWORDS(KERNEL, PERSIST, SCAN, TIME, LEARN, DEVICE, ROUTES, GRACEFUL, RESTART, KRT_SOURCE, KRT_METRIC, MERGE, PATHS)
 
 CF_GRAMMAR
 
@@ -47,6 +47,8 @@ kern_item:
    }
  | DEVICE ROUTES bool { THIS_KRT->devroutes = $3; }
  | GRACEFUL RESTART bool { THIS_KRT->graceful_restart = $3; }
+ | MERGE PATHS bool { THIS_KRT->merge_paths = $3 ? KRT_DEFAULT_ECMP_LIMIT : 0; }
+ | MERGE PATHS bool LIMIT expr { THIS_KRT->merge_paths = $3 ? $5 : 0; if (($5 <= 0) || ($5 > 255)) cf_error("Merge paths limit must be in range 1-255"); }
  ;
 
 /* Kernel interface protocol */
diff --git a/sysdep/unix/krt.c b/sysdep/unix/krt.c
index d8d28c7c..2eab5cb2 100644
--- a/sysdep/unix/krt.c
+++ b/sysdep/unix/krt.c
@@ -595,9 +595,13 @@ krt_flush_routes(struct krt_proto *p)
 static struct rte *
 krt_export_net(struct krt_proto *p, net *net, rte **rt_free, ea_list **tmpa)
 {
-  struct filter *filter = p->p.main_ahook->out_filter;
+  struct announce_hook *ah = p->p.main_ahook;
+  struct filter *filter = ah->out_filter;
   rte *rt;
 
+  if (p->p.accept_ra_types == RA_MERGED)
+    return rt_export_merged(ah, net, rt_free, tmpa, 1);
+
   rt = net->routes;
   *rt_free = NULL;
 
@@ -1091,11 +1095,13 @@ krt_rte_same(rte *a, rte *b)
 struct krt_config *krt_cf;
 
 static struct proto *
-krt_init(struct proto_config *c)
+krt_init(struct proto_config *C)
 {
-  struct krt_proto *p = proto_new(c, sizeof(struct krt_proto));
+  struct krt_proto *p = proto_new(C, sizeof(struct krt_proto));
+  struct krt_config *c = (struct krt_config *) C;
 
-  p->p.accept_ra_types = RA_OPTIMAL;
+  p->p.accept_ra_types = c->merge_paths ? RA_MERGED : RA_OPTIMAL;
+  p->p.merge_limit = c->merge_paths;
   p->p.import_control = krt_import_control;
   p->p.rt_notify = krt_rt_notify;
   p->p.if_notify = krt_if_notify;
@@ -1161,7 +1167,8 @@ krt_reconfigure(struct proto *p, struct proto_config *new)
     return 0;
 
   /* persist, graceful restart need not be the same */
-  return o->scan_time == n->scan_time && o->learn == n->learn && o->devroutes == n->devroutes;
+  return o->scan_time == n->scan_time && o->learn == n->learn &&
+    o->devroutes == n->devroutes && o->merge_paths == n->merge_paths;
 }
 
 static void
diff --git a/sysdep/unix/krt.h b/sysdep/unix/krt.h
index 1940cbcd..9d5d4e8c 100644
--- a/sysdep/unix/krt.h
+++ b/sysdep/unix/krt.h
@@ -26,6 +26,8 @@ struct kif_proto;
 #define KRF_DELETE 3			/* Should be deleted */
 #define KRF_IGNORE 4			/* To be ignored */
 
+#define KRT_DEFAULT_ECMP_LIMIT	16
+
 #define EA_KRT_SOURCE	EA_CODE(EAP_KRT, 0)
 #define EA_KRT_METRIC	EA_CODE(EAP_KRT, 1)
 
@@ -47,6 +49,7 @@ struct krt_config {
   int learn;			/* Learn routes from other sources */
   int devroutes;		/* Allow export of device routes */
   int graceful_restart;		/* Regard graceful restart recovery */
+  int merge_paths;		/* Exported routes are merged for ECMP */
 };
 
 struct krt_proto {