diff --git a/ospf6d/ospf6_gr_helper.c b/ospf6d/ospf6_gr_helper.c
index e02a841d00..639d56e273 100644
--- a/ospf6d/ospf6_gr_helper.c
+++ b/ospf6d/ospf6_gr_helper.c
@@ -145,7 +145,7 @@ static int ospf6_extract_grace_lsa_fields(struct ospf6_lsa *lsa,
 
 	length = ntohs(lsah->length) - OSPF6_LSA_HEADER_SIZE;
 
-	for (tlvh = TLV_HDR_TOP(lsah); sum < length && tlvh;
+	for (tlvh = lsdesc_start(lsah); sum < length && tlvh;
 	     tlvh = TLV_HDR_NEXT(tlvh)) {
 
 		/* Check TLV len against overall LSA */
@@ -1241,7 +1241,7 @@ static int ospf6_grace_lsa_show_info(struct vty *vty, struct ospf6_lsa *lsa,
 		zlog_debug("  TLV info:");
 	}
 
-	for (tlvh = TLV_HDR_TOP(lsah); sum < length && tlvh;
+	for (tlvh = lsdesc_start(lsah); sum < length && tlvh;
 	     tlvh = TLV_HDR_NEXT(tlvh)) {
 
 		/* Check TLV len */
diff --git a/ospf6d/ospf6_intra.c b/ospf6d/ospf6_intra.c
index f12f125b7b..470fc66084 100644
--- a/ospf6d/ospf6_intra.c
+++ b/ospf6d/ospf6_intra.c
@@ -246,9 +246,7 @@ void ospf6_router_lsa_originate(struct event *thread)
 	ospf6_router_lsa_options_set(oa, router_lsa);
 
 	/* describe links for each interfaces */
-	lsdesc = (struct ospf6_router_lsdesc
-			  *)((caddr_t)router_lsa
-			     + sizeof(struct ospf6_router_lsa));
+	lsdesc = lsdesc_start_lsa_type(lsa_header, OSPF6_LSTYPE_ROUTER);
 
 	for (ALL_LIST_ELEMENTS(oa->if_list, node, nnode, oi)) {
 		/* Interfaces in state Down or Loopback are not described */
@@ -271,9 +269,9 @@ void ospf6_router_lsa_originate(struct event *thread)
 		    && ((size_t)((char *)lsdesc - buffer)
 				+ sizeof(struct ospf6_router_lsdesc)
 			> oa->router_lsa_size_limit)) {
-			if ((caddr_t)lsdesc
-			    == (caddr_t)router_lsa
-				       + sizeof(struct ospf6_router_lsa)) {
+			if (lsdesc ==
+			    lsdesc_start_lsa_type(lsa_header,
+						  OSPF6_LSTYPE_ROUTER)) {
 				zlog_warn(
 					"Size limit setting for Router-LSA too short");
 				return;
@@ -307,9 +305,8 @@ void ospf6_router_lsa_originate(struct event *thread)
 			ospf6_router_lsa_options_set(oa, router_lsa);
 
 			/* describe links for each interfaces */
-			lsdesc = (struct ospf6_router_lsdesc
-					  *)((caddr_t)router_lsa
-					     + sizeof(struct ospf6_router_lsa));
+			lsdesc = lsdesc_start_lsa_type(lsa_header,
+						       OSPF6_LSTYPE_ROUTER);
 
 			link_state_id++;
 		}
@@ -571,9 +568,7 @@ void ospf6_network_lsa_originate(struct event *thread)
 		network_lsa->options[2] |= link_lsa->options[2];
 	}
 
-	lsdesc = (struct ospf6_network_lsdesc
-			  *)((caddr_t)network_lsa
-			     + sizeof(struct ospf6_network_lsa));
+	lsdesc = lsdesc_start_lsa_type(lsa_header, OSPF6_LSTYPE_NETWORK);
 
 	/* set Link Description to the router itself */
 	lsdesc->router_id = oi->area->ospf6->router_id;
@@ -797,8 +792,7 @@ void ospf6_link_lsa_originate(struct event *thread)
 	       sizeof(struct in6_addr));
 	link_lsa->prefix_num = htonl(oi->route_connected->count);
 
-	op = (struct ospf6_prefix *)((caddr_t)link_lsa
-				     + sizeof(struct ospf6_link_lsa));
+	op = lsdesc_start_lsa_type(lsa_header, OSPF6_LSTYPE_LINK);
 
 	/* connected prefix to advertise */
 	for (route = ospf6_route_head(oi->route_connected); route;
@@ -1109,12 +1103,10 @@ void ospf6_intra_prefix_lsa_originate_stub(struct event *thread)
 
 	/* put prefixes to advertise */
 	prefix_num = 0;
-	op = (struct ospf6_prefix *)((caddr_t)intra_prefix_lsa
-				     + sizeof(struct ospf6_intra_prefix_lsa));
+	op = lsdesc_start_lsa_type(lsa_header, OSPF6_LSTYPE_INTRA_PREFIX);
 	for (route = ospf6_route_head(route_advertise); route;
 	     route = ospf6_route_best_next(route)) {
 		if (((caddr_t)op - (caddr_t)lsa_header) > MAX_LSA_PAYLOAD) {
-
 			intra_prefix_lsa->prefix_num = htons(prefix_num);
 
 			/* Fill LSA Header */
@@ -1149,10 +1141,8 @@ void ospf6_intra_prefix_lsa_originate_stub(struct event *thread)
 
 			/* Put next set of prefixes to advertise */
 			prefix_num = 0;
-			op = (struct ospf6_prefix
-				      *)((caddr_t)intra_prefix_lsa
-					 + sizeof(struct
-						  ospf6_intra_prefix_lsa));
+			op = lsdesc_start_lsa_type(lsa_header,
+						   OSPF6_LSTYPE_INTRA_PREFIX);
 		}
 
 		op->prefix_length = route->prefix.prefixlen;
@@ -1339,8 +1329,7 @@ void ospf6_intra_prefix_lsa_originate_transit(struct event *thread)
 			zlog_debug("Trailing garbage in %s", lsa->name);
 	}
 
-	op = (struct ospf6_prefix *)((caddr_t)intra_prefix_lsa
-				     + sizeof(struct ospf6_intra_prefix_lsa));
+	op = lsdesc_start_lsa_type(lsa_header, OSPF6_LSTYPE_INTRA_PREFIX);
 
 	prefix_num = 0;
 	for (route = ospf6_route_head(route_advertise); route;
diff --git a/ospf6d/ospf6_lsa.c b/ospf6d/ospf6_lsa.c
index d8d13d4b4b..de04391b6b 100644
--- a/ospf6d/ospf6_lsa.c
+++ b/ospf6d/ospf6_lsa.c
@@ -37,6 +37,37 @@ DEFINE_MTYPE_STATIC(OSPF6D, OSPF6_LSA,         "OSPF6 LSA");
 DEFINE_MTYPE_STATIC(OSPF6D, OSPF6_LSA_HEADER,  "OSPF6 LSA header");
 DEFINE_MTYPE_STATIC(OSPF6D, OSPF6_LSA_SUMMARY, "OSPF6 LSA summary");
 
+const uint8_t ospf6_lsa_min_size[OSPF6_LSTYPE_SIZE] = {
+	[OSPF6_LSTYPE_UNKNOWN] = 0,
+	[0x00ff & OSPF6_LSTYPE_ROUTER] = OSPF6_ROUTER_LSA_MIN_SIZE,
+	[0x00ff & OSPF6_LSTYPE_NETWORK] = OSPF6_NETWORK_LSA_MIN_SIZE,
+	[0x00ff & OSPF6_LSTYPE_INTER_PREFIX] = OSPF6_INTER_PREFIX_LSA_MIN_SIZE,
+	[0x00ff & OSPF6_LSTYPE_INTER_ROUTER] = OSPF6_INTER_ROUTER_LSA_FIX_SIZE,
+	[0x00ff & OSPF6_LSTYPE_AS_EXTERNAL] = OSPF6_AS_EXTERNAL_LSA_MIN_SIZE,
+	[0x00ff & OSPF6_LSTYPE_GROUP_MEMBERSHIP] = 0, /* Unused */
+	[0x00ff & OSPF6_LSTYPE_TYPE_7] = OSPF6_AS_EXTERNAL_LSA_MIN_SIZE,
+	[0x00ff & OSPF6_LSTYPE_LINK] = OSPF6_LINK_LSA_MIN_SIZE,
+	[0x00ff & OSPF6_LSTYPE_INTRA_PREFIX] = OSPF6_INTRA_PREFIX_LSA_MIN_SIZE,
+	[0x00ff & OSPF6_LSTYPE_GRACE_LSA] = 0
+};
+
+void *lsdesc_start_lsa_type(struct ospf6_lsa_header *header, int lsa_type)
+{
+	uint8_t t = (0x00ff & lsa_type);
+
+	if (t == OSPF6_LSTYPE_UNKNOWN || t >= OSPF6_LSTYPE_SIZE) {
+		zlog_debug("Cannot get descriptor offset for unknown lsa type 0x%x",
+			   t);
+		return ospf6_lsa_end(header);
+	}
+	return (char *)lsa_after_header(header) + ospf6_lsa_min_size[t];
+}
+
+void *lsdesc_start(struct ospf6_lsa_header *header)
+{
+	return lsdesc_start_lsa_type(header, ntohs(header->type));
+}
+
 static struct ospf6_lsa_handler *lsa_handlers[OSPF6_LSTYPE_SIZE];
 
 struct ospf6 *ospf6_get_by_lsdb(struct ospf6_lsa *lsa)
diff --git a/ospf6d/ospf6_lsa.h b/ospf6d/ospf6_lsa.h
index 9a8b9b0dcd..2f443603c2 100644
--- a/ospf6d/ospf6_lsa.h
+++ b/ospf6d/ospf6_lsa.h
@@ -87,6 +87,8 @@ struct ospf6_lsa_header {
 	uint16_t length;     /* LSA length */
 };
 
+
+
 static inline char *ospf6_lsa_header_end(struct ospf6_lsa_header *header)
 {
 	return (char *)header + sizeof(struct ospf6_lsa_header);
@@ -121,7 +123,6 @@ static inline uint16_t ospf6_lsa_size(struct ospf6_lsa_header *header)
 #define OSPF6_LSA_IS_CHANGED(L1, L2) ospf6_lsa_is_changed (L1, L2)
 #define OSPF6_LSA_IS_SEQWRAP(L) ((L)->header->seqnum == htonl(OSPF_MAX_SEQUENCE_NUMBER + 1))
 
-
 /* Router-LSA */
 #define OSPF6_ROUTER_LSA_MIN_SIZE              4U
 struct ospf6_router_lsa {
@@ -369,4 +370,8 @@ extern void ospf6_flush_self_originated_lsas_now(struct ospf6 *ospf6);
 extern struct ospf6 *ospf6_get_by_lsdb(struct ospf6_lsa *lsa);
 struct ospf6_lsa *ospf6_find_external_lsa(struct ospf6 *ospf6,
 					  struct prefix *p);
+
+void *lsdesc_start_lsa_type(struct ospf6_lsa_header *header, int lsa_type);
+void *lsdesc_start(struct ospf6_lsa_header *header);
+
 #endif /* OSPF6_LSA_H */
diff --git a/ospf6d/ospf6_tlv.h b/ospf6d/ospf6_tlv.h
index f94d7f2621..a687a05939 100644
--- a/ospf6d/ospf6_tlv.h
+++ b/ospf6d/ospf6_tlv.h
@@ -27,9 +27,6 @@ struct tlv_header {
 
 #define TLV_SIZE(tlvh) ((uint32_t)(TLV_HDR_SIZE + TLV_BODY_SIZE(tlvh)))
 
-#define TLV_HDR_TOP(lsah)                                                      \
-	((struct tlv_header *)((char *)(lsah) + OSPF6_LSA_HEADER_SIZE))
-
 #define TLV_HDR_NEXT(tlvh)                                                     \
 	((struct tlv_header *)((char *)(tlvh) + TLV_SIZE(tlvh)))