From 338ec3b86723f19bc43df9899e345811ad5f80d0 Mon Sep 17 00:00:00 2001
From: Mark Stapp <mjs@voltanet.io>
Date: Mon, 29 Mar 2021 16:09:40 -0400
Subject: [PATCH] lib: add basic nexthop comparison api

Add a simpler, more limited nexthop comparison function. This
compares a few key attributes, such as vrf, gateway, labels.

Signed-off-by: Mark Stapp <mjs@voltanet.io>
---
 lib/nexthop.c | 99 +++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/nexthop.h |  5 +++
 2 files changed, 104 insertions(+)

diff --git a/lib/nexthop.c b/lib/nexthop.c
index 6b15442a87..0ac6c0ae1b 100644
--- a/lib/nexthop.c
+++ b/lib/nexthop.c
@@ -203,6 +203,105 @@ int nexthop_cmp(const struct nexthop *next1, const struct nexthop *next2)
 	return ret;
 }
 
+/*
+ * More-limited comparison function used to detect duplicate
+ * nexthops. This is used in places where we don't need the full
+ * comparison of 'nexthop_cmp()'.
+ */
+int nexthop_cmp_basic(const struct nexthop *nh1,
+		      const struct nexthop *nh2)
+{
+	int ret = 0;
+	const struct mpls_label_stack *nhl1 = NULL;
+	const struct mpls_label_stack *nhl2 = NULL;
+
+	if (nh1 == NULL && nh2 == NULL)
+		return 0;
+
+	if (nh1 && !nh2)
+		return 1;
+
+	if (!nh1 && nh2)
+		return -1;
+
+	if (nh1->vrf_id < nh2->vrf_id)
+		return -1;
+
+	if (nh1->vrf_id > nh2->vrf_id)
+		return 1;
+
+	if (nh1->type < nh2->type)
+		return -1;
+
+	if (nh1->type > nh2->type)
+		return 1;
+
+	if (nh1->weight < nh2->weight)
+		return -1;
+
+	if (nh1->weight > nh2->weight)
+		return 1;
+
+	switch (nh1->type) {
+	case NEXTHOP_TYPE_IPV4:
+	case NEXTHOP_TYPE_IPV6:
+		ret = nexthop_g_addr_cmp(nh1->type, &nh1->gate, &nh2->gate);
+		if (ret != 0)
+			return ret;
+		break;
+	case NEXTHOP_TYPE_IPV4_IFINDEX:
+	case NEXTHOP_TYPE_IPV6_IFINDEX:
+		ret = nexthop_g_addr_cmp(nh1->type, &nh1->gate, &nh2->gate);
+		if (ret != 0)
+			return ret;
+		/* Intentional Fall-Through */
+	case NEXTHOP_TYPE_IFINDEX:
+		if (nh1->ifindex < nh2->ifindex)
+			return -1;
+
+		if (nh1->ifindex > nh2->ifindex)
+			return 1;
+		break;
+	case NEXTHOP_TYPE_BLACKHOLE:
+		if (nh1->bh_type < nh2->bh_type)
+			return -1;
+
+		if (nh1->bh_type > nh2->bh_type)
+			return 1;
+		break;
+	}
+
+	/* Compare source addr */
+	ret = nexthop_g_addr_cmp(nh1->type, &nh1->src, &nh2->src);
+	if (ret != 0)
+		goto done;
+
+	nhl1 = nh1->nh_label;
+	nhl2 = nh2->nh_label;
+
+	/* No labels is a match */
+	if (!nhl1 && !nhl2)
+		return 0;
+
+	if (nhl1 && !nhl2)
+		return 1;
+
+	if (nhl2 && !nhl1)
+		return -1;
+
+	if (nhl1->num_labels > nhl2->num_labels)
+		return 1;
+
+	if (nhl1->num_labels < nhl2->num_labels)
+		return -1;
+
+	ret = memcmp(nhl1->label, nhl2->label,
+		     (nhl1->num_labels * sizeof(mpls_label_t)));
+
+done:
+	return ret;
+}
+
 /*
  * nexthop_type_to_str
  */
diff --git a/lib/nexthop.h b/lib/nexthop.h
index f1ad195cf4..d6ea83cf06 100644
--- a/lib/nexthop.h
+++ b/lib/nexthop.h
@@ -207,6 +207,11 @@ extern int nexthop_g_addr_cmp(enum nexthop_types_t type,
 			      const union g_addr *addr1,
 			      const union g_addr *addr2);
 
+/* More-limited comparison function used to detect duplicate nexthops.
+ * Returns -1, 0, 1
+ */
+int nexthop_cmp_basic(const struct nexthop *nh1, const struct nexthop *nh2);
+
 extern const char *nexthop_type_to_str(enum nexthop_types_t nh_type);
 extern bool nexthop_labels_match(const struct nexthop *nh1,
 				 const struct nexthop *nh2);
-- 
2.39.5