Implementation of Master Arbitration.

gnmi_server/server.go

@@ -39,6 +39,10 @@ type Server struct {
 	config  *Config
 	cMu     sync.Mutex
 	clients map[string]*Client
+	// ReqFromMaster point to a function that is called to verify if the request
+	// comes from a master controller.
+	ReqFromMaster func(req *gnmipb.SetRequest, masterEID *uint128) error
+	masterEID     uint128
 }
 type AuthTypes map[string]bool
 
@@ -56,6 +60,7 @@ type Config struct {
 }
 
 var AuthLock sync.Mutex
+var maMu sync.Mutex
 
 func (i AuthTypes) String() string {
 	if i["none"] {
@@ -136,6 +141,10 @@ func NewServer(config *Config, opts []grpc.ServerOption) (*Server, error) {
 		s:       s,
 		config:  config,
 		clients: map[string]*Client{},
+		// ReqFromMaster point to a function that is called to verify if
+		// the request comes from a master controller.
+		ReqFromMaster: ReqFromMasterDisabledMA,
+		masterEID:     uint128{High: 0, Low: 0},
 	}
 	var err error
 	if srv.config.Port < 0 {
@@ -377,6 +386,28 @@ func (s *Server) Get(ctx context.Context, req *gnmipb.GetRequest) (*gnmipb.GetRe
 }
 
 func (s *Server) Set(ctx context.Context, req *gnmipb.SetRequest) (*gnmipb.SetResponse, error) {
+	e := s.ReqFromMaster(req, &s.masterEID)
+	if e != nil {
+		ret, ok := status.FromError(e)
+		if !ok {
+			return nil, fmt.Errorf("MA: Error in parsing Master Aribitration availability")
+		}
+
+		err_code := ret.Code()
+		switch err_code {
+			case codes.Unavailable:
+				log.V(0).Infof("MA: Master Arbitration is not in setRequest extension.")
+			case codes.InvalidArgument:
+				return nil, status.Errorf(codes.InvalidArgument, "MA: ElectionId missing")
+			case codes.Unimplemented:
+				return nil, status.Errorf(codes.Unimplemented, "MA: Role is not implemented")
+			case codes.PermissionDenied:
+				return nil, status.Errorf(codes.PermissionDenied, "MA: Set request is rejected")
+			default:
+				return nil, fmt.Errorf("MA: Unexpected error. Got %v", err_code)
+		}
+	}
+
 	common_utils.IncCounter(common_utils.GNMI_SET)
 	if s.config.EnableTranslibWrite == false && s.config.EnableNativeWrite == false {
 		common_utils.IncCounter(common_utils.GNMI_SET_FAIL)
@@ -515,3 +546,79 @@ func (s *Server) Capabilities(ctx context.Context, req *gnmipb.CapabilityRequest
 		GNMIVersion:        "0.7.0",
 		Extension:          exts}, nil
 }
+
+type uint128 struct {
+	High uint64
+	Low  uint64
+}
+
+func (lh *uint128) Compare(rh *uint128) int {
+	if rh == nil {
+		// For MA disabled case, EID supposed to be 0.
+		rh = &uint128{High: 0, Low: 0}
+	}
+	if lh.High > rh.High {
+		return 1
+	}
+	if lh.High < rh.High {
+		return -1
+	}
+	if lh.Low > rh.Low {
+		return 1
+	}
+	if lh.Low < rh.Low {
+		return -1
+	}
+	return 0
+}
+
+// ReqFromMasterEnabledMA returns true if the request is sent by the master
+// controller.
+func ReqFromMasterEnabledMA(req *gnmipb.SetRequest, masterEID *uint128) error {
+	// Read the election_id.
+	reqEID := uint128{High: 0, Low: 0}
+	hasMaExt := false
+	// It can be one of many extensions, so iterate through them to find it.
+	for _, e := range req.GetExtension() {
+		ma := e.GetMasterArbitration()
+		if ma == nil {
+			continue
+		}
+
+		hasMaExt = true
+		// The Master Arbitration descriptor has been found.
+		if ma.ElectionId == nil {
+			return status.Errorf(codes.InvalidArgument, "MA: ElectionId missing")
+		}
+
+		if ma.Role != nil {
+			// Role will be implemented later.
+			return status.Errorf(codes.Unimplemented, "MA: Role is not implemented")
+		}
+
+		reqEID = uint128{High: ma.ElectionId.High, Low: ma.ElectionId.Low}
+		// Use the election ID that is in the last extension, so, no 'break' here.
+	}
+
+	if !hasMaExt {
+		log.V(0).Infof("MA: No Master Arbitration in setRequest extension, masterEID %v is not updated", masterEID)
+		return nil
+	}
+
+	maMu.Lock()
+	defer maMu.Unlock()
+	switch masterEID.Compare(&reqEID) {
+	case 1: // This Election ID is smaller than the known Master Election ID.
+		return status.Errorf(codes.PermissionDenied, "Election ID is smaller than the current master. Rejected. Master EID: %v. Current EID: %v.", masterEID, reqEID)
+	case -1: // New Master Election ID received!
+		log.V(0).Infof("New master has been elected with %v\n", reqEID)
+		*masterEID = reqEID
+	}
+	return nil
+}
+
+// ReqFromMasterDisabledMA always returns true. It is used when Master Arbitration
+// is disabled.
+func ReqFromMasterDisabledMA(req *gnmipb.SetRequest, masterEID *uint128) error {
+	return status.Errorf(codes.Unavailable, "MA: Master Arbitration is disabled.")
+}