From a783cc05f0870f686785edf0c4ca12fb6036716f Mon Sep 17 00:00:00 2001
From: Xiao Liang <shaw.leon@gmail.com>
Date: Wed, 14 Sep 2022 11:13:41 +0800
Subject: [PATCH] bgpd: Handle route-refresh request received before EoR

See the BGP message sequence:

    R1                  R2
    |      updates      |
    |------------------>|
    |                   |
    |  refresh request  |
    x<------------------|
    |                   |
    |   updates cont.   |
    |------------------>|
    |                   |
    |    end-of-rib     |
    |------------------>|
    |                   |

When R1 and R2 establish BGP session, R1 begins to send initial updates.
If R2 sends a route-refresh request before EoR, it's silently ignored
by R1, and routes received earlier have no chance to be processed again.

RFC7313 says, "for a BGP speaker that supports the BGP Graceful Restart,
it MUST NOT send a BoRR for an <AFI, SAFI> to a neighbor before it sends
the EoR for the <AFI, SAFI> to the neighbor." But it doesn't forbid
route-refresh request to be sent before receiving EoR.

To handle this scenario, postpone response to refresh request until EoR
is sent.

Signed-off-by: Xiao Liang <shaw.leon@gmail.com>
---
 bgpd/bgp_packet.c | 31 +++++++++++++++++++++++++++++++
 bgpd/bgpd.h       |  1 +
 2 files changed, 32 insertions(+)

diff --git a/bgpd/bgp_packet.c b/bgpd/bgp_packet.c
index 90695219a7..cc18808373 100644
--- a/bgpd/bgp_packet.c
+++ b/bgpd/bgp_packet.c
@@ -360,6 +360,31 @@ int bgp_nlri_parse(struct peer *peer, struct attr *attr,
 	return BGP_NLRI_PARSE_ERROR;
 }
 
+
+/*
+ * Check if route-refresh request from peer is pending (received before EoR),
+ * and process it now.
+ */
+static void bgp_process_pending_refresh(struct peer *peer, afi_t afi,
+					safi_t safi)
+{
+	if (CHECK_FLAG(peer->af_sflags[afi][safi],
+		       PEER_STATUS_REFRESH_PENDING)) {
+		UNSET_FLAG(peer->af_sflags[afi][safi],
+			   PEER_STATUS_REFRESH_PENDING);
+		bgp_route_refresh_send(peer, afi, safi, 0, 0, 0,
+				       BGP_ROUTE_REFRESH_BORR);
+		if (bgp_debug_neighbor_events(peer))
+			zlog_debug(
+				"%pBP sending route-refresh (BoRR) for %s/%s (for pending REQUEST)",
+				peer, afi2str(afi), safi2str(safi));
+
+		SET_FLAG(peer->af_sflags[afi][safi], PEER_STATUS_BORR_SEND);
+		UNSET_FLAG(peer->af_sflags[afi][safi], PEER_STATUS_EORR_SEND);
+		bgp_announce_route(peer, afi, safi, true);
+	}
+}
+
 /*
  * Checks a variety of conditions to determine whether the peer needs to be
  * rescheduled for packet generation again, and does so if necessary.
@@ -558,6 +583,9 @@ void bgp_generate_updgrp_packets(struct thread *thread)
 							BGP_UPDATE_EOR_PKT(
 								peer, afi, safi,
 								s);
+							bgp_process_pending_refresh(
+								peer, afi,
+								safi);
 						}
 					}
 				}
@@ -2564,6 +2592,9 @@ static int bgp_route_refresh_receive(struct peer *peer, bgp_size_t size)
 						"%pBP rcvd route-refresh (REQUEST) for %s/%s before EoR",
 						peer, afi2str(afi),
 						safi2str(safi));
+				/* Can't send BoRR now, postpone after EoR */
+				SET_FLAG(peer->af_sflags[afi][safi],
+					 PEER_STATUS_REFRESH_PENDING);
 				return BGP_PACKET_NOOP;
 			}
 
diff --git a/bgpd/bgpd.h b/bgpd/bgpd.h
index 28883c9e7c..f6162f33e4 100644
--- a/bgpd/bgpd.h
+++ b/bgpd/bgpd.h
@@ -1456,6 +1456,7 @@ struct peer {
 #define PEER_STATUS_EORR_RECEIVED (1U << 10) /* EoRR received from peer */
 /* LLGR aware peer */
 #define PEER_STATUS_LLGR_WAIT (1U << 11)
+#define PEER_STATUS_REFRESH_PENDING (1U << 12) /* refresh request from peer */
 
 	/* Configured timer values. */
 	_Atomic uint32_t holdtime;