From 84cac51a51fc29349077e8cecadf1aed11f9b824 Mon Sep 17 00:00:00 2001
From: "Ondrej Zajicek (work)" <santiago@crfreenet.org>
Date: Tue, 30 Aug 2016 17:17:27 +0200
Subject: [PATCH] Nest: Keep multipath next hops sorted

---
 nest/route.h          |  2 ++
 nest/rt-attr.c        | 28 ++++++++++++++++++++++++++++
 nest/rt-table.c       |  7 +++++++
 proto/rip/rip.c       |  5 +----
 proto/static/static.c |  5 +----
 5 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/nest/route.h b/nest/route.h
index 3969db6b..bb4674b9 100644
--- a/nest/route.h
+++ b/nest/route.h
@@ -506,6 +506,8 @@ int mpnh__same(struct mpnh *x, struct mpnh *y); /* Compare multipath nexthops */
 static inline int mpnh_same(struct mpnh *x, struct mpnh *y)
 { return (x == y) || mpnh__same(x, y); }
 struct mpnh *mpnh_merge(struct mpnh *x, struct mpnh *y, int rx, int ry, int max, linpool *lp);
+void mpnh_insert(struct mpnh **n, struct mpnh *y);
+int mpnh_is_sorted(struct mpnh *x);
 
 void rta_init(void);
 rta *rta_lookup(rta *);			/* Get rta equivalent to this one, uc++ */
diff --git a/nest/rt-attr.c b/nest/rt-attr.c
index 42b74f34..ab0069b5 100644
--- a/nest/rt-attr.c
+++ b/nest/rt-attr.c
@@ -302,6 +302,34 @@ mpnh_merge(struct mpnh *x, struct mpnh *y, int rx, int ry, int max, linpool *lp)
   return root;
 }
 
+void
+mpnh_insert(struct mpnh **n, struct mpnh *x)
+{
+  for (; *n; n = &((*n)->next))
+  {
+    int cmp = mpnh_compare_node(*n, x);
+
+    if (cmp < 0)
+      continue;
+    else if (cmp > 0)
+      break;
+    else
+      return;
+  }
+
+  x->next = *n;
+  *n = x;
+}
+
+int
+mpnh_is_sorted(struct mpnh *x)
+{
+  for (; x && x->next; x = x->next)
+    if (mpnh_compare_node(x, x->next) >= 0)
+      return 0;
+
+  return 1;
+}
 
 static struct mpnh *
 mpnh_copy(struct mpnh *o)
diff --git a/nest/rt-table.c b/nest/rt-table.c
index 9baf2849..f4df22aa 100644
--- a/nest/rt-table.c
+++ b/nest/rt-table.c
@@ -804,6 +804,13 @@ rte_validate(rte *e)
       return 0;
     }
 
+  if ((e->attrs->dest == RTD_MULTIPATH) && !mpnh_is_sorted(e->attrs->nexthops))
+    {
+      log(L_WARN "Ignoring unsorted multipath route %I/%d received via %s",
+	  n->n.prefix, n->n.pxlen, e->sender->proto->name);
+      return 0;
+    }
+
   return 1;
 }
 
diff --git a/proto/rip/rip.c b/proto/rip/rip.c
index c85fd69b..36527253 100644
--- a/proto/rip/rip.c
+++ b/proto/rip/rip.c
@@ -173,7 +173,6 @@ rip_announce_rte(struct rip_proto *p, struct rip_entry *en)
     {
       /* ECMP route */
       struct mpnh *nhs = NULL;
-      struct mpnh **nhp = &nhs;
       int num = 0;
 
       for (rt = en->routes; rt && (num < p->ecmp); rt = rt->next)
@@ -185,9 +184,7 @@ rip_announce_rte(struct rip_proto *p, struct rip_entry *en)
 	nh->gw = rt->next_hop;
 	nh->iface = rt->from->nbr->iface;
 	nh->weight = rt->from->ifa->cf->ecmp_weight;
-	nh->next = NULL;
-	*nhp = nh;
-	nhp = &(nh->next);
+	mpnh_insert(&nhs, nh);
 	num++;
 
 	if (rt->tag != rt_tag)
diff --git a/proto/static/static.c b/proto/static/static.c
index be808593..d54302a8 100644
--- a/proto/static/static.c
+++ b/proto/static/static.c
@@ -81,7 +81,6 @@ static_install(struct proto *p, struct static_route *r, struct iface *ifa)
     {
       struct static_route *r2;
       struct mpnh *nhs = NULL;
-      struct mpnh **nhp = &nhs;
 
       for (r2 = r->mp_next; r2; r2 = r2->mp_next)
 	if (r2->installed)
@@ -90,9 +89,7 @@ static_install(struct proto *p, struct static_route *r, struct iface *ifa)
 	    nh->gw = r2->via;
 	    nh->iface = r2->neigh->iface;
 	    nh->weight = r2->masklen; /* really */
-	    nh->next = NULL;
-	    *nhp = nh;
-	    nhp = &(nh->next);
+	    mpnh_insert(&nhs, nh);
 	  }
 
       /* There is at least one nexthop */