From f7e61bbe1e42c9ea36091b86bd8a7b0a194fb12b Mon Sep 17 00:00:00 2001
From: Emanuele Di Pascale <emanuele@voltanet.io>
Date: Fri, 8 Jan 2021 15:55:37 +0100
Subject: [PATCH] isisd: ignore routes w/ incompatible metric style

Currently the transition metric style is redundant because isis will
always read both reachability TLVs regardless of the configured
metric style. Correct this by only considering TLVs matching our
configuration.

Signed-off-by: Emanuele Di Pascale <emanuele@voltanet.io>
---
 isisd/isis_spf.c | 77 +++++++++++++++++++++++++++---------------------
 1 file changed, 44 insertions(+), 33 deletions(-)

diff --git a/isisd/isis_spf.c b/isisd/isis_spf.c
index 57b1d66c22..7e046167f6 100644
--- a/isisd/isis_spf.c
+++ b/isisd/isis_spf.c
@@ -820,7 +820,8 @@ lspfragloop:
 #endif /* EXTREME_DEBUG */
 
 	if (no_overload) {
-		if (pseudo_lsp || spftree->mtid == ISIS_MT_IPV4_UNICAST) {
+		if ((pseudo_lsp || spftree->mtid == ISIS_MT_IPV4_UNICAST)
+		    && spftree->area->oldmetric) {
 			struct isis_oldstyle_reach *r;
 			for (r = (struct isis_oldstyle_reach *)
 					 lsp->tlvs->oldstyle_reach.head;
@@ -848,42 +849,47 @@ lspfragloop:
 			}
 		}
 
-		struct isis_item_list *te_neighs = NULL;
-		if (pseudo_lsp || spftree->mtid == ISIS_MT_IPV4_UNICAST)
-			te_neighs = &lsp->tlvs->extended_reach;
-		else
-			te_neighs = isis_lookup_mt_items(&lsp->tlvs->mt_reach,
-							 spftree->mtid);
-
-		struct isis_extended_reach *er;
-		for (er = te_neighs
-				  ? (struct isis_extended_reach *)
-					    te_neighs->head
-				  : NULL;
-		     er; er = er->next) {
-			/* C.2.6 a) */
-			/* Two way connectivity */
-			if (!LSP_PSEUDO_ID(er->id)
-			    && !memcmp(er->id, root_sysid, ISIS_SYS_ID_LEN))
-				continue;
-			if (!pseudo_lsp
-			    && !memcmp(er->id, null_sysid, ISIS_SYS_ID_LEN))
-				continue;
-			dist = cost
-			       + (CHECK_FLAG(spftree->flags,
-					     F_SPFTREE_HOPCOUNT_METRIC)
-					  ? 1
-					  : er->metric);
-			process_N(spftree,
-				  LSP_PSEUDO_ID(er->id) ? VTYPE_PSEUDO_TE_IS
-							: VTYPE_NONPSEUDO_TE_IS,
-				  (void *)er->id, dist, depth + 1, NULL,
-				  parent);
+		if (spftree->area->newmetric) {
+			struct isis_item_list *te_neighs = NULL;
+			if (pseudo_lsp || spftree->mtid == ISIS_MT_IPV4_UNICAST)
+				te_neighs = &lsp->tlvs->extended_reach;
+			else
+				te_neighs = isis_lookup_mt_items(
+					&lsp->tlvs->mt_reach, spftree->mtid);
+
+			struct isis_extended_reach *er;
+			for (er = te_neighs ? (struct isis_extended_reach *)
+						      te_neighs->head
+					    : NULL;
+			     er; er = er->next) {
+				/* C.2.6 a) */
+				/* Two way connectivity */
+				if (!LSP_PSEUDO_ID(er->id)
+				    && !memcmp(er->id, root_sysid,
+					       ISIS_SYS_ID_LEN))
+					continue;
+				if (!pseudo_lsp
+				    && !memcmp(er->id, null_sysid,
+					       ISIS_SYS_ID_LEN))
+					continue;
+				dist = cost
+				       + (CHECK_FLAG(spftree->flags,
+						     F_SPFTREE_HOPCOUNT_METRIC)
+						  ? 1
+						  : er->metric);
+				process_N(spftree,
+					  LSP_PSEUDO_ID(er->id)
+						  ? VTYPE_PSEUDO_TE_IS
+						  : VTYPE_NONPSEUDO_TE_IS,
+					  (void *)er->id, dist, depth + 1, NULL,
+					  parent);
+			}
 		}
 	}
 
 	if (!fabricd && !pseudo_lsp && spftree->family == AF_INET
-	    && spftree->mtid == ISIS_MT_IPV4_UNICAST) {
+	    && spftree->mtid == ISIS_MT_IPV4_UNICAST
+	    && spftree->area->oldmetric) {
 		struct isis_item_list *reachs[] = {
 			&lsp->tlvs->oldstyle_ip_reach,
 			&lsp->tlvs->oldstyle_ip_reach_ext};
@@ -908,6 +914,10 @@ lspfragloop:
 		}
 	}
 
+	/* we can skip all the rest if we're using metric style narrow */
+	if (!spftree->area->newmetric)
+		goto end;
+
 	if (!pseudo_lsp && spftree->family == AF_INET) {
 		struct isis_item_list *ipv4_reachs;
 		if (spftree->mtid == ISIS_MT_IPV4_UNICAST)
@@ -1027,6 +1037,7 @@ lspfragloop:
 		}
 	}
 
+end:
 	if (fragnode == NULL)
 		fragnode = listhead(lsp->lspu.frags);
 	else
-- 
2.39.5