From: Donald Sharp <sharpd@nvidia.com>
Date: Mon, 12 Apr 2021 18:16:30 +0000 (-0400)
Subject: bgpd: Address LL peer not NHT when receiving connection attempt
X-Git-Tag: base_8.0~122^2
X-Git-Url: https://git.puffer.fish/?a=commitdiff_plain;h=refs%2Fpull%2F8456%2Fhead;p=mirror%2Ffrr.git

bgpd: Address LL peer not NHT when receiving connection attempt

The new LL code in:
8761cd6ddb5437767625f58c8e9cc3ccda7887ab

Introduced the idea of the bgp unnumbered peers using interface up/down
events to track the bgp peers nexthop.  This code was not properly
working when a connection was received from a peer in some circumstances.

Effectively the connection from a peer was immediately skipping state transitions
and FRR was never properly tracking the peers nexthop.  When we receive the
connection attempt, let's track the nexthop now.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>
---

diff --git a/bgpd/bgp_fsm.c b/bgpd/bgp_fsm.c
index 45a856a459..88c44fc984 100644
--- a/bgpd/bgp_fsm.c
+++ b/bgpd/bgp_fsm.c
@@ -101,7 +101,7 @@ static int bgp_delayopen_timer(struct thread *);
 static int bgp_start(struct peer *);
 
 /* Register peer with NHT */
-static int bgp_peer_reg_with_nht(struct peer *peer)
+int bgp_peer_reg_with_nht(struct peer *peer)
 {
 	int connected = 0;
 
@@ -340,6 +340,8 @@ static struct peer *peer_xfer_conn(struct peer *from_peer)
 	 * needed, even on a passive connection.
 	 */
 	bgp_peer_reg_with_nht(peer);
+	if (from_peer)
+		bgp_replace_nexthop_by_peer(from_peer, peer);
 
 	bgp_reads_on(peer);
 	bgp_writes_on(peer);
diff --git a/bgpd/bgp_fsm.h b/bgpd/bgp_fsm.h
index bcf697e153..12cbad3eb8 100644
--- a/bgpd/bgp_fsm.h
+++ b/bgpd/bgp_fsm.h
@@ -179,4 +179,5 @@ const char *print_peer_gr_mode(enum peer_mode pr_mode);
 const char *print_peer_gr_cmd(enum peer_gr_command pr_gr_cmd);
 const char *print_global_gr_mode(enum global_mode gl_mode);
 const char *print_global_gr_cmd(enum global_gr_command gl_gr_cmd);
+int bgp_peer_reg_with_nht(struct peer *peer);
 #endif /* _QUAGGA_BGP_FSM_H */
diff --git a/bgpd/bgp_network.c b/bgpd/bgp_network.c
index 4821ce8ddb..8d9024e07c 100644
--- a/bgpd/bgp_network.c
+++ b/bgpd/bgp_network.c
@@ -569,6 +569,7 @@ static int bgp_accept(struct thread *thread)
 	peer1->doppelganger = peer;
 	peer->fd = bgp_sock;
 	vrf_bind(peer->bgp->vrf_id, bgp_sock, bgp_get_bound_name(peer));
+	bgp_peer_reg_with_nht(peer);
 	bgp_fsm_change_status(peer, Active);
 	BGP_TIMER_OFF(peer->t_start); /* created in peer_create() */
 
diff --git a/bgpd/bgp_nht.c b/bgpd/bgp_nht.c
index 9c8d7878c5..7ccfae4ba4 100644
--- a/bgpd/bgp_nht.c
+++ b/bgpd/bgp_nht.c
@@ -98,6 +98,31 @@ void bgp_unlink_nexthop(struct bgp_path_info *path)
 	bgp_unlink_nexthop_check(bnc);
 }
 
+void bgp_replace_nexthop_by_peer(struct peer *from, struct peer *to)
+{
+	struct prefix pp;
+	struct prefix pt;
+	struct bgp_nexthop_cache *bncp, *bnct;
+	afi_t afi;
+
+	if (!sockunion2hostprefix(&from->su, &pp))
+		return;
+
+	afi = family2afi(pp.family);
+	bncp = bnc_find(&from->bgp->nexthop_cache_table[afi], &pp, 0);
+
+	if (!sockunion2hostprefix(&to->su, &pt))
+		return;
+
+	bnct = bnc_find(&to->bgp->nexthop_cache_table[afi], &pt, 0);
+
+	if (bnct != bncp)
+		return;
+
+	if (bnct)
+		bnct->nht_info = to;
+}
+
 void bgp_unlink_nexthop_by_peer(struct peer *peer)
 {
 	struct prefix p;
@@ -273,8 +298,16 @@ int bgp_find_or_add_nexthop(struct bgp *bgp_route, struct bgp *bgp_nexthop,
 			(bgp_path_info_extra_get(pi))->igpmetric = bnc->metric;
 		else if (pi->extra)
 			pi->extra->igpmetric = 0;
-	} else if (peer)
-		bnc->nht_info = (void *)peer; /* NHT peer reference */
+	} else if (peer) {
+		/*
+		 * Let's not accidently save the peer data for a peer
+		 * we are going to throw away in a second or so.
+		 * When we come back around we'll fix up this
+		 * data properly in replace_nexthop_by_peer
+		 */
+		if (CHECK_FLAG(peer->flags, PEER_FLAG_CONFIG_NODE))
+			bnc->nht_info = (void *)peer; /* NHT peer reference */
+	}
 
 	/*
 	 * We are cheating here.  Views have no associated underlying
diff --git a/bgpd/bgp_nht.h b/bgpd/bgp_nht.h
index a1683e1511..9268b225ca 100644
--- a/bgpd/bgp_nht.h
+++ b/bgpd/bgp_nht.h
@@ -51,7 +51,7 @@ extern int bgp_find_or_add_nexthop(struct bgp *bgp_route,
  */
 extern void bgp_unlink_nexthop(struct bgp_path_info *p);
 void bgp_unlink_nexthop_by_peer(struct peer *peer);
-
+void bgp_replace_nexthop_by_peer(struct peer *from, struct peer *to);
 /**
  * bgp_delete_connected_nexthop() - Reset the 'peer' pointer for a connected
  * nexthop entry. If no paths reference the nexthop, it will be unregistered