lib: Add hash function for nexthop groups

Add a hash function to turn a nexthop group into a 32 bit unsigned hash key with jhash. We do not care to hash any recursively resolved nexthops, just the group. Signed-off-by: Stephen Worley <sworley@cumulusnetworks.com>
FRRouting · Apr 5, 2019 · bd495cc · bd495cc
1 parent 5eec461
commit bd495cc
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Showing 4 changed files with 63 additions and 7 deletions.
diff --git a/lib/nexthop.c b/lib/nexthop.c
@@ -314,14 +314,52 @@ unsigned int nexthop_level(struct nexthop *nexthop)
 	return rv;
 }
 
-uint32_t nexthop_hash(struct nexthop *nexthop)
+uint32_t nexthop_hash(const struct nexthop *nexthop)
 {
-	uint32_t key;
+	uint32_t key = 0x45afe398;
 
-	key = jhash_1word(nexthop->vrf_id, 0x45afe398);
-	key = jhash_1word(nexthop->ifindex, key);
-	key = jhash_1word(nexthop->type, key);
-	key = jhash(&nexthop->gate, sizeof(union g_addr), key);
+	key = jhash_3words(nexthop->type, nexthop->vrf_id,
+			   nexthop->nh_label_type, key);
+	/* gate and blackhole are together in a union */
+	key = jhash(&nexthop->gate, sizeof(nexthop->gate), key);
+	key = jhash(&nexthop->src, sizeof(nexthop->src), key);
+	key = jhash(&nexthop->rmap_src, sizeof(nexthop->rmap_src), key);
 
+	if (nexthop->nh_label) {
+		int labels = nexthop->nh_label->num_labels;
+		int i = 0;
+
+		while (labels >= 3) {
+			key = jhash_3words(nexthop->nh_label->label[i],
+					   nexthop->nh_label->label[i + 1],
+					   nexthop->nh_label->label[i + 2],
+					   key);
+			labels -= 3;
+			i += 3;
+		}
+
+		if (labels >= 2) {
+			key = jhash_2words(nexthop->nh_label->label[i],
+					   nexthop->nh_label->label[i + 1],
+					   key);
+			labels -= 2;
+			i += 2;
+		}
+
+		if (labels >= 1)
+			key = jhash_1word(nexthop->nh_label->label[i], key);
+	}
+
+	switch (nexthop->type) {
+	case NEXTHOP_TYPE_IPV4_IFINDEX:
+	case NEXTHOP_TYPE_IPV6_IFINDEX:
+	case NEXTHOP_TYPE_IFINDEX:
+		key = jhash_1word(nexthop->ifindex, key);
+		break;
+	case NEXTHOP_TYPE_BLACKHOLE:
+	case NEXTHOP_TYPE_IPV4:
+	case NEXTHOP_TYPE_IPV6:
+		break;
+	}
 	return key;
 }
diff --git a/lib/nexthop.h b/lib/nexthop.h
@@ -136,7 +136,7 @@ void nexthop_del_labels(struct nexthop *);
  * Returns:
  *    32-bit hash of nexthop
  */
-uint32_t nexthop_hash(struct nexthop *nexthop);
+uint32_t nexthop_hash(const struct nexthop *nexthop);
 
 extern bool nexthop_same(const struct nexthop *nh1, const struct nexthop *nh2);
 

diff --git a/lib/nexthop_group.c b/lib/nexthop_group.c
@@ -25,6 +25,7 @@
 #include <nexthop_group.h>
 #include <vty.h>
 #include <command.h>
+#include <jhash.h>
 
 #ifndef VTYSH_EXTRACT_PL
 #include "lib/nexthop_group_clippy.c"
@@ -147,6 +148,21 @@ void copy_nexthops(struct nexthop **tnh, const struct nexthop *nh,
 	}
 }
 
+uint32_t nexthop_group_hash(const struct nexthop_group *nhg)
+{
+	struct nexthop *nh;
+	uint32_t key = 0;
+
+	/*
+	 * We are not interested in hashing over any recursively
+	 * resolved nexthops
+	 */
+	for (nh = nhg->nexthop; nh; nh = nh->next) {
+		key = jhash_1word(nexthop_hash(nh), key);
+	}
+	return key;
+}
+
 static void nhgc_delete_nexthops(struct nexthop_group_cmd *nhgc)
 {
 	struct nexthop *nexthop;

diff --git a/lib/nexthop_group.h b/lib/nexthop_group.h
@@ -47,6 +47,8 @@ void nexthop_del(struct nexthop_group *nhg, struct nexthop *nexthop);
 void copy_nexthops(struct nexthop **tnh, const struct nexthop *nh,
 		   struct nexthop *rparent);
 
+uint32_t nexthop_group_hash(const struct nexthop_group *nhg);
+
 /* The following for loop allows to iterate over the nexthop
  * structure of routes.
  *