server: fix handling the best path change from ebgp to ibgp

We have the best path from ebgp and advertise it to an ibgp peer. Then
we got the new best from ibgp and then we have to explicitly withdraw
the old best (and don't send the new best from ibgp to the ibgp peer).

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

1 files changed, 11 insertions, 0 deletions

diff --git a/server/server.go b/server/server.go
index 6fa8fe4b..ae036a83 100644
--- a/server/server.go
+++ b/server/server.go
@@ -339,6 +339,17 @@ func filterpath(peer *Peer, path *table.Path, withdrawals []*table.Path) *table.
 		}
 
 		if ignore {
+
+			for _, adv := range peer.adjRibOut.PathList([]bgp.RouteFamily{path.GetRouteFamily()}, false) {
+				// we advertise a route from ebgp,
+				// which is the old best. We got the
+				// new best from ibgp. We don't
+				// advertise the new best and need to
+				// withdraw the old.
+				if path.GetNlri().String() == adv.GetNlri().String() {
+					return adv.Clone(true)
+				}
+			}
 			log.WithFields(log.Fields{
 				"Topic": "Peer",
 				"Key":   peer.ID(),