zebra: deduplicate nexthops

There exists situations where it is possible to have duplicate
nexthops passed from a higher level protocol into zebra.

This code notices this duplication of nexthops and marks
the duplicates as DUPLICATE so we don't attempt to install
it into the kernel.

This is important on *BSD as I understand it because passing
duplicate nexthops will cause the route to be rejected.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>

2 files changed, 43 insertions, 0 deletions

diff --git a/lib/nexthop.c b/lib/nexthop.c
index 2dba412f45..ea6a310a4a 100644
--- a/lib/nexthop.c
+++ b/lib/nexthop.c
@@ -71,6 +71,39 @@ int nexthop_same_no_recurse(const struct nexthop *next1,
 	return 1;
 }
 
+int
+nexthop_same_firsthop (struct nexthop *next1, struct nexthop *next2)
+{
+	int type1 = NEXTHOP_FIRSTHOPTYPE(next1->type);
+	int type2 = NEXTHOP_FIRSTHOPTYPE(next2->type);
+
+	if (type1 != type2)
+		return 0;
+	switch (type1)
+	{
+	case NEXTHOP_TYPE_IPV4_IFINDEX:
+		if (! IPV4_ADDR_SAME (&next1->gate.ipv4, &next2->gate.ipv4))
+			return 0;
+		if (next1->ifindex != next2->ifindex)
+			return 0;
+		break;
+	case NEXTHOP_TYPE_IFINDEX:
+		if (next1->ifindex != next2->ifindex)
+			return 0;
+		break;
+	case NEXTHOP_TYPE_IPV6_IFINDEX:
+		if (! IPV6_ADDR_SAME (&next1->gate.ipv6, &next2->gate.ipv6))
+			return 0;
+		if (next1->ifindex != next2->ifindex)
+			return 0;
+		break;
+	default:
+		/* do nothing */
+		break;
+	}
+	return 1;
+}
+
 /*
  * nexthop_type_to_str
  */
diff --git a/lib/nexthop.h b/lib/nexthop.h
index 781eb93413..20b0cd5227 100644
--- a/lib/nexthop.h
+++ b/lib/nexthop.h
@@ -50,6 +50,11 @@ enum blackhole_type {
 	BLACKHOLE_ADMINPROHIB,
 };
 
+/* IPV[46] -> IPV[46]_IFINDEX */
+#define NEXTHOP_FIRSTHOPTYPE(type) \
+	((type) == NEXTHOP_TYPE_IFINDEX || (type) == NEXTHOP_TYPE_BLACKHOLE) \
+		? (type) : ((type) | 1)
+
 /* Nexthop label structure. */
 struct nexthop_label {
 	u_int8_t num_labels;
@@ -74,6 +79,10 @@ struct nexthop {
 #define NEXTHOP_FLAG_ONLINK     (1 << 3) /* Nexthop should be installed onlink. */
 #define NEXTHOP_FLAG_MATCHED    (1 << 4) /* Already matched vs a nexthop */
 #define NEXTHOP_FLAG_FILTERED   (1 << 5) /* rmap filtered, used by static only */
+#define NEXTHOP_FLAG_DUPLICATE  (1 << 6) /* nexthop duplicates another active one */
+#define NEXTHOP_IS_ACTIVE(flags) \
+	(CHECK_FLAG(flags, NEXTHOP_FLAG_ACTIVE) \
+		&& !CHECK_FLAG(flags, NEXTHOP_FLAG_DUPLICATE))
 
 	/* Nexthop address */
 	union {
@@ -141,6 +150,7 @@ extern const char *nexthop_type_to_str(enum nexthop_types_t nh_type);
 extern int nexthop_same_no_recurse(const struct nexthop *next1,
 				   const struct nexthop *next2);
 extern int nexthop_labels_match(struct nexthop *nh1, struct nexthop *nh2);
+extern int nexthop_same_firsthop (struct nexthop *next1, struct nexthop *next2);
 
 extern const char *nexthop2str(struct nexthop *nexthop, char *str, int size);
 extern struct nexthop *nexthop_next(struct nexthop *nexthop);