*: support long lived graceful restart

Signed-off-by: Wataru Ishida <ishida.wataru@lab.ntt.co.jp>

2 files changed, 26 insertions, 0 deletions

diff --git a/table/destination.go b/table/destination.go
index 58991a35..50b946e9 100644
--- a/table/destination.go
+++ b/table/destination.go
@@ -47,6 +47,7 @@ const (
 	BPR_IGP_COST           BestPathReason = "IGP Cost"
 	BPR_ROUTER_ID          BestPathReason = "Router ID"
 	BPR_OLDER              BestPathReason = "Older"
+	BPR_NON_LLGR_STALE     BestPathReason = "no LLGR Stale"
 )
 
 func IpToRadixkey(b []byte, max uint8) string {
@@ -479,6 +480,11 @@ func (p paths) Less(i, j int) bool {
 	var better *Path
 	reason := BPR_UNKNOWN
 
+	// draft-uttaro-idr-bgp-persistence-02
+	if better == nil {
+		better = compareByLLGRStaleCommunity(path1, path2)
+		reason = BPR_NON_LLGR_STALE
+	}
 	// Follow best path calculation algorithm steps.
 	// compare by reachability
 	if better == nil {
@@ -545,6 +551,17 @@ func (p paths) Less(i, j int) bool {
 	return false
 }
 
+func compareByLLGRStaleCommunity(path1, path2 *Path) *Path {
+	p1 := path1.IsLLGRStale()
+	p2 := path2.IsLLGRStale()
+	if p1 == p2 {
+		return nil
+	} else if p1 {
+		return path2
+	}
+	return path1
+}
+
 func compareByReachableNexthop(path1, path2 *Path) *Path {
 	//	Compares given paths and selects best path based on reachable next-hop.
 	//
diff --git a/table/path.go b/table/path.go
index b0f21e04..f8058730 100644
--- a/table/path.go
+++ b/table/path.go
@@ -348,6 +348,15 @@ func (path *Path) IsStale() bool {
 	return path.OriginInfo().stale
 }
 
+func (path *Path) IsLLGRStale() bool {
+	for _, c := range path.GetCommunities() {
+		if c == bgp.COMMUNITY_LLGR_STALE {
+			return true
+		}
+	}
+	return false
+}
+
 func (path *Path) GetSourceAs() uint32 {
 	attr := path.getPathAttr(bgp.BGP_ATTR_TYPE_AS_PATH)
 	if attr != nil {