From: Mark Stapp <mstapp@nvidia.com>
Date: Tue, 5 Oct 2021 15:49:20 +0000 (-0400)
Subject: bgpd: BGP-LU use implicit-null in some cases
X-Git-Tag: base_8.2~312^2~2
X-Git-Url: https://git.puffer.fish/?a=commitdiff_plain;h=bb2ca6927f98b53e9d860697ed82477eddbebe5c;p=matthieu%2Ffrr.git

bgpd: BGP-LU use implicit-null in some cases

In some cases where bgp is at the mpls edge, where it has a BGP-LU
peer downstream but an IP peer upstream, it can advertise the
IMPLICIT_NULL label instead of a per-prefix label.

Signed-off-by: Mark Stapp <mstapp@nvidia.com>
---

diff --git a/bgpd/bgp_label.c b/bgpd/bgp_label.c
index 3c8f2f3668..fa2a445165 100644
--- a/bgpd/bgp_label.c
+++ b/bgpd/bgp_label.c
@@ -244,6 +244,10 @@ void bgp_reg_dereg_for_label(struct bgp_dest *dest, struct bgp_path_info *pi,
 
 	p = bgp_dest_get_prefix(dest);
 
+	if (BGP_DEBUG(labelpool, LABELPOOL))
+		zlog_debug("%s: %pFX: %s ", __func__, p,
+			   (reg ? "reg" : "dereg"));
+
 	if (reg) {
 		assert(pi);
 		/*
diff --git a/bgpd/bgp_route.c b/bgpd/bgp_route.c
index fc97178450..f278cef77c 100644
--- a/bgpd/bgp_route.c
+++ b/bgpd/bgp_route.c
@@ -2711,6 +2711,28 @@ static void bgp_process_evpn_route_injection(struct bgp *bgp, afi_t afi,
 		bgp_evpn_withdraw_type5_route(bgp, p, afi, safi);
 }
 
+/*
+ * Utility to determine whether a particular path_info should use
+ * the IMPLICIT_NULL label. This is pretty specialized: it's only called
+ * in a path where we basically _know_ this is a BGP-LU route.
+ */
+static bool bgp_lu_need_imp_null(const struct bgp_path_info *new_select)
+{
+	/* Certain types get imp null; so do paths where the nexthop is
+	 * not labeled.
+	 */
+	if (new_select->sub_type == BGP_ROUTE_STATIC
+	    || new_select->sub_type == BGP_ROUTE_AGGREGATE
+	    || new_select->sub_type == BGP_ROUTE_REDISTRIBUTE)
+		return true;
+	else if (new_select->extra == NULL ||
+		 !bgp_is_valid_label(&new_select->extra->label[0]))
+		/* TODO -- should be configurable? */
+		return true;
+	else
+		return false;
+}
+
 /*
  * old_select = The old best path
  * new_select = the new best path
@@ -2802,11 +2824,7 @@ static void bgp_process_main_one(struct bgp *bgp, struct bgp_dest *dest,
 				 * implicit-null for local routes, aggregate
 				 * and redistributed routes
 				 */
-				if (new_select->sub_type == BGP_ROUTE_STATIC
-				    || new_select->sub_type
-						== BGP_ROUTE_AGGREGATE
-				    || new_select->sub_type
-						== BGP_ROUTE_REDISTRIBUTE) {
+				if (bgp_lu_need_imp_null(new_select)) {
 					if (CHECK_FLAG(
 						    dest->flags,
 						    BGP_NODE_REGISTERED_FOR_LABEL)