add secondary-route feature for router server

if an export policy rejects a selected route, try the next route in
order until one that is accepted is found or all routes for the peer
are rejected.

the default is disabled. You can enable this feature in the following
way:

[neighbors.route-server.config]
  route-server-client = true
  secondary-route = true

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>

3 files changed, 114 insertions, 16 deletions

diff --git a/pkg/server/grpc_server.go b/pkg/server/grpc_server.go
index d4b3a09e..6923e43d 100644
--- a/pkg/server/grpc_server.go
+++ b/pkg/server/grpc_server.go
@@ -638,6 +638,7 @@ func newNeighborFromAPIStruct(a *api.Peer) (*config.Neighbor, error) {
 	}
 	if a.RouteServer != nil {
 		pconf.RouteServer.Config.RouteServerClient = a.RouteServer.RouteServerClient
+		pconf.RouteServer.Config.SecondaryRoute = a.RouteServer.SecondaryRoute
 	}
 	if a.GracefulRestart != nil {
 		pconf.GracefulRestart.Config.Enabled = a.GracefulRestart.Enabled
@@ -740,6 +741,7 @@ func newPeerGroupFromAPIStruct(a *api.PeerGroup) (*config.PeerGroup, error) {
 	}
 	if a.RouteServer != nil {
 		pconf.RouteServer.Config.RouteServerClient = a.RouteServer.RouteServerClient
+		pconf.RouteServer.Config.SecondaryRoute = a.RouteServer.SecondaryRoute
 	}
 	if a.GracefulRestart != nil {
 		pconf.GracefulRestart.Config.Enabled = a.GracefulRestart.Enabled
diff --git a/pkg/server/peer.go b/pkg/server/peer.go
index d7fb46c3..910c7472 100644
--- a/pkg/server/peer.go
+++ b/pkg/server/peer.go
@@ -147,6 +147,12 @@ func (peer *peer) isRouteServerClient() bool {
 	return peer.fsm.pConf.RouteServer.Config.RouteServerClient
 }
 
+func (peer *peer) isSecondaryRouteEnabled() bool {
+	peer.fsm.lock.RLock()
+	defer peer.fsm.lock.RUnlock()
+	return peer.fsm.pConf.RouteServer.Config.RouteServerClient && peer.fsm.pConf.RouteServer.Config.SecondaryRoute
+}
+
 func (peer *peer) isRouteReflectorClient() bool {
 	peer.fsm.lock.RLock()
 	defer peer.fsm.lock.RUnlock()
diff --git a/pkg/server/server.go b/pkg/server/server.go
index 229f1a8f..c2158aa7 100644
--- a/pkg/server/server.go
+++ b/pkg/server/server.go
@@ -557,7 +557,7 @@ func filterpath(peer *peer, path, old *table.Path) *table.Path {
 	return path
 }
 
-func (s *BgpServer) filterpath(peer *peer, path, old *table.Path) *table.Path {
+func (s *BgpServer) prePolicyFilterpath(peer *peer, path, old *table.Path) (*table.Path, *table.PolicyOptions, bool) {
 	// Special handling for RTM NLRI.
 	if path != nil && path.GetRouteFamily() == bgp.RF_RTC_UC && !path.IsWithdraw {
 		// If the given "path" is locally generated and the same with "old", we
@@ -571,7 +571,7 @@ func (s *BgpServer) filterpath(peer *peer, path, old *table.Path) *table.Path {
 				"Path":  path,
 			}).Debug("given rtm nlri is already sent, skipping to advertise")
 			peer.fsm.lock.RUnlock()
-			return nil
+			return nil, nil, true
 		}
 
 		if old != nil && old.IsLocal() {
@@ -611,13 +611,13 @@ func (s *BgpServer) filterpath(peer *peer, path, old *table.Path) *table.Path {
 	peer.fsm.lock.RUnlock()
 	if path != nil && peerVrf != "" {
 		if f := path.GetRouteFamily(); f != bgp.RF_IPv4_VPN && f != bgp.RF_IPv6_VPN {
-			return nil
+			return nil, nil, true
 		}
 		vrf := peer.localRib.Vrfs[peerVrf]
 		if table.CanImportToVrf(vrf, path) {
 			path = path.ToLocal()
 		} else {
-			return nil
+			return nil, nil, true
 		}
 	}
 
@@ -629,7 +629,7 @@ func (s *BgpServer) filterpath(peer *peer, path, old *table.Path) *table.Path {
 	peer.fsm.lock.RUnlock()
 
 	if path = filterpath(peer, path, old); path == nil {
-		return nil
+		return nil, nil, true
 	}
 
 	peer.fsm.lock.RLock()
@@ -644,16 +644,10 @@ func (s *BgpServer) filterpath(peer *peer, path, old *table.Path) *table.Path {
 	}
 	peer.fsm.lock.RUnlock()
 
-	path = peer.policy.ApplyPolicy(peer.TableID(), table.POLICY_DIRECTION_EXPORT, path, options)
-	// When 'path' is filtered (path == nil), check 'old' has been sent to this peer.
-	// If it has, send withdrawal to the peer.
-	if path == nil && old != nil {
-		o := peer.policy.ApplyPolicy(peer.TableID(), table.POLICY_DIRECTION_EXPORT, old, options)
-		if o != nil {
-			path = old.Clone(true)
-		}
-	}
+	return path, options, false
+}
 
+func (s *BgpServer) postFilterpath(peer *peer, path *table.Path) *table.Path {
 	// draft-uttaro-idr-bgp-persistence-02
 	// 4.3.  Processing LLGR_STALE Routes
 	//
@@ -677,6 +671,24 @@ func (s *BgpServer) filterpath(peer *peer, path, old *table.Path) *table.Path {
 	return path
 }
 
+func (s *BgpServer) filterpath(peer *peer, path, old *table.Path) *table.Path {
+	path, options, stop := s.prePolicyFilterpath(peer, path, old)
+	if stop {
+		return path
+	}
+	path = peer.policy.ApplyPolicy(peer.TableID(), table.POLICY_DIRECTION_EXPORT, path, options)
+	// When 'path' is filtered (path == nil), check 'old' has been sent to this peer.
+	// If it has, send withdrawal to the peer.
+	if path == nil && old != nil {
+		o := peer.policy.ApplyPolicy(peer.TableID(), table.POLICY_DIRECTION_EXPORT, old, options)
+		if o != nil {
+			path = old.Clone(true)
+		}
+	}
+
+	return s.postFilterpath(peer, path)
+}
+
 func clonePathList(pathList []*table.Path) []*table.Path {
 	l := make([]*table.Path, 0, len(pathList))
 	for _, p := range pathList {
@@ -896,6 +908,25 @@ func (s *BgpServer) notifyRecvMessageWatcher(peer *peer, timestamp time.Time, ms
 func (s *BgpServer) getBestFromLocal(peer *peer, rfList []bgp.RouteFamily) ([]*table.Path, []*table.Path) {
 	pathList := []*table.Path{}
 	filtered := []*table.Path{}
+
+	if peer.isSecondaryRouteEnabled() {
+		for _, family := range peer.toGlobalFamilies(rfList) {
+			dsts := s.rsRib.Tables[family].GetDestinations()
+			dl := make([]*table.Update, 0, len(dsts))
+			for _, d := range dsts {
+				l := d.GetAllKnownPathList()
+				pl := make([]*table.Path, len(l))
+				copy(pl, l)
+				u := &table.Update{
+					KnownPathList: pl,
+				}
+				dl = append(dl, u)
+			}
+			pathList = append(pathList, s.sendSecondaryRoutes(peer, nil, dl)...)
+		}
+		return pathList, filtered
+	}
+
 	for _, family := range peer.toGlobalFamilies(rfList) {
 		pl := func() []*table.Path {
 			if peer.isAddPathSendEnabled(family) {
@@ -919,13 +950,13 @@ func (s *BgpServer) getBestFromLocal(peer *peer, rfList []bgp.RouteFamily) ([]*t
 	return pathList, filtered
 }
 
-func (s *BgpServer) processOutgoingPaths(peer *peer, paths, olds []*table.Path) []*table.Path {
+func needToAdvertise(peer *peer) bool {
 	peer.fsm.lock.RLock()
 	notEstablished := peer.fsm.state != bgp.BGP_FSM_ESTABLISHED
 	localRestarting := peer.fsm.pConf.GracefulRestart.State.LocalRestarting
 	peer.fsm.lock.RUnlock()
 	if notEstablished {
-		return nil
+		return false
 	}
 	if localRestarting {
 		peer.fsm.lock.RLock()
@@ -934,6 +965,59 @@ func (s *BgpServer) processOutgoingPaths(peer *peer, paths, olds []*table.Path)
 			"Key":   peer.fsm.pConf.State.NeighborAddress,
 		}).Debug("now syncing, suppress sending updates")
 		peer.fsm.lock.RUnlock()
+		return false
+	}
+	return true
+}
+
+func (s *BgpServer) sendSecondaryRoutes(peer *peer, newPath *table.Path, dsts []*table.Update) []*table.Path {
+	if !needToAdvertise(peer) {
+		return nil
+	}
+	pl := make([]*table.Path, 0, len(dsts))
+
+	f := func(path, old *table.Path) *table.Path {
+		path, options, stop := s.prePolicyFilterpath(peer, path, old)
+		if stop {
+			return nil
+		}
+		path = peer.policy.ApplyPolicy(peer.TableID(), table.POLICY_DIRECTION_EXPORT, path, options)
+		if path != nil {
+			return s.postFilterpath(peer, path)
+		}
+		return nil
+	}
+
+	for _, dst := range dsts {
+		old := func() *table.Path {
+			for _, old := range dst.OldKnownPathList {
+				o := f(old, nil)
+				if o != nil {
+					return o
+				}
+			}
+			return nil
+		}()
+		path := func() *table.Path {
+			for _, known := range dst.KnownPathList {
+				path := f(known, old)
+				if path != nil {
+					return path
+				}
+			}
+			return nil
+		}()
+		if path != nil {
+			pl = append(pl, path)
+		} else if old != nil {
+			pl = append(pl, old.Clone(true))
+		}
+	}
+	return pl
+}
+
+func (s *BgpServer) processOutgoingPaths(peer *peer, paths, olds []*table.Path) []*table.Path {
+	if !needToAdvertise(peer) {
 		return nil
 	}
 
@@ -1185,6 +1269,12 @@ func (s *BgpServer) propagateUpdateToNeighbors(source *peer, newPath *table.Path
 			}
 			oldList = nil
 		} else if targetPeer.isRouteServerClient() {
+			if targetPeer.isSecondaryRouteEnabled() {
+				if paths := s.sendSecondaryRoutes(targetPeer, newPath, dsts); len(paths) > 0 {
+					sendfsmOutgoingMsg(targetPeer, paths, nil, false)
+				}
+				continue
+			}
 			bestList, oldList, _ = dstsToPaths(targetPeer.TableID(), targetPeer.AS(), dsts)
 		} else {
 			bestList = gBestList