Extract route table from Stack lock

PiperOrigin-RevId: 354746864

pkg/tcpip/stack/stack.go

@@ -385,6 +385,15 @@ type Stack struct {
 
 	stats tcpip.Stats
 
+	// LOCK ORDERING: mu > route.mu.
+	route struct {
+		mu struct {
+			sync.RWMutex
+
+			table []tcpip.Route
+		}
+	}
+
 	mu   sync.RWMutex
 	nics map[tcpip.NICID]*NIC
 
@@ -392,11 +401,6 @@ type Stack struct {
 	cleanupEndpointsMu sync.Mutex
 	cleanupEndpoints   map[TransportEndpoint]struct{}
 
-	// route is the route table passed in by the user via SetRouteTable(),
-	// it is used by FindRoute() to build a route for a specific
-	// destination.
-	routeTable []tcpip.Route
-
 	*ports.PortManager
 
 	// If not nil, then any new endpoints will have this probe function
@@ -813,38 +817,37 @@ func (s *Stack) Forwarding(protocolNum tcpip.NetworkProtocolNumber) bool {
 //
 // This method takes ownership of the table.
 func (s *Stack) SetRouteTable(table []tcpip.Route) {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-
-	s.routeTable = table
+	s.route.mu.Lock()
+	defer s.route.mu.Unlock()
+	s.route.mu.table = table
 }
 
 // GetRouteTable returns the route table which is currently in use.
 func (s *Stack) GetRouteTable() []tcpip.Route {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	return append([]tcpip.Route(nil), s.routeTable...)
+	s.route.mu.RLock()
+	defer s.route.mu.RUnlock()
+	return append([]tcpip.Route(nil), s.route.mu.table...)
 }
 
 // AddRoute appends a route to the route table.
 func (s *Stack) AddRoute(route tcpip.Route) {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	s.routeTable = append(s.routeTable, route)
+	s.route.mu.Lock()
+	defer s.route.mu.Unlock()
+	s.route.mu.table = append(s.route.mu.table, route)
 }
 
 // RemoveRoutes removes matching routes from the route table.
 func (s *Stack) RemoveRoutes(match func(tcpip.Route) bool) {
-	s.mu.Lock()
-	defer s.mu.Unlock()
+	s.route.mu.Lock()
+	defer s.route.mu.Unlock()
 
 	var filteredRoutes []tcpip.Route
-	for _, route := range s.routeTable {
+	for _, route := range s.route.mu.table {
 		if !match(route) {
 			filteredRoutes = append(filteredRoutes, route)
 		}
 	}
-	s.routeTable = filteredRoutes
+	s.route.mu.table = filteredRoutes
 }
 
 // NewEndpoint creates a new transport layer endpoint of the given protocol.
@@ -1017,17 +1020,18 @@ func (s *Stack) removeNICLocked(id tcpip.NICID) tcpip.Error {
 	delete(s.nics, id)
 
 	// Remove routes in-place. n tracks the number of routes written.
+	s.route.mu.Lock()
 	n := 0
-	for i, r := range s.routeTable {
-		s.routeTable[i] = tcpip.Route{}
+	for i, r := range s.route.mu.table {
+		s.route.mu.table[i] = tcpip.Route{}
 		if r.NIC != id {
 			// Keep this route.
-			s.routeTable[n] = r
+			s.route.mu.table[n] = r
 			n++
 		}
 	}
-
-	s.routeTable = s.routeTable[:n]
+	s.route.mu.table = s.route.mu.table[:n]
+	s.route.mu.Unlock()
 
 	return nic.remove()
 }
@@ -1352,39 +1356,49 @@ func (s *Stack) FindRoute(id tcpip.NICID, localAddr, remoteAddr tcpip.Address, n
 
 	// Find a route to the remote with the route table.
 	var chosenRoute tcpip.Route
-	for _, route := range s.routeTable {
-		if len(remoteAddr) != 0 && !route.Destination.Contains(remoteAddr) {
-			continue
-		}
+	if r := func() *Route {
+		s.route.mu.RLock()
+		defer s.route.mu.RUnlock()
 
-		nic, ok := s.nics[route.NIC]
-		if !ok || !nic.Enabled() {
-			continue
-		}
+		for _, route := range s.route.mu.table {
+			if len(remoteAddr) != 0 && !route.Destination.Contains(remoteAddr) {
+				continue
+			}
 
-		if id == 0 || id == route.NIC {
-			if addressEndpoint := s.getAddressEP(nic, localAddr, remoteAddr, netProto); addressEndpoint != nil {
-				var gateway tcpip.Address
-				if needRoute {
-					gateway = route.Gateway
+			nic, ok := s.nics[route.NIC]
+			if !ok || !nic.Enabled() {
+				continue
+			}
+
+			if id == 0 || id == route.NIC {
+				if addressEndpoint := s.getAddressEP(nic, localAddr, remoteAddr, netProto); addressEndpoint != nil {
+					var gateway tcpip.Address
+					if needRoute {
+						gateway = route.Gateway
+					}
+					r := constructAndValidateRoute(netProto, addressEndpoint, nic /* outgoingNIC */, nic /* outgoingNIC */, gateway, localAddr, remoteAddr, s.handleLocal, multicastLoop)
+					if r == nil {
+						panic(fmt.Sprintf("non-forwarding route validation failed with route table entry = %#v, id = %d, localAddr = %s, remoteAddr = %s", route, id, localAddr, remoteAddr))
+					}
+					return r
 				}
-				r := constructAndValidateRoute(netProto, addressEndpoint, nic /* outgoingNIC */, nic /* outgoingNIC */, gateway, localAddr, remoteAddr, s.handleLocal, multicastLoop)
-				if r == nil {
-					panic(fmt.Sprintf("non-forwarding route validation failed with route table entry = %#v, id = %d, localAddr = %s, remoteAddr = %s", route, id, localAddr, remoteAddr))
-				}
-				return r, nil
+			}
+
+			// If the stack has forwarding enabled and we haven't found a valid route
+			// to the remote address yet, keep track of the first valid route. We
+			// keep iterating because we prefer routes that let us use a local
+			// address that is assigned to the outgoing interface. There is no
+			// requirement to do this from any RFC but simply a choice made to better
+			// follow a strong host model which the netstack follows at the time of
+			// writing.
+			if canForward && chosenRoute == (tcpip.Route{}) {
+				chosenRoute = route
 			}
 		}
 
-		// If the stack has forwarding enabled and we haven't found a valid route to
-		// the remote address yet, keep track of the first valid route. We keep
-		// iterating because we prefer routes that let us use a local address that
-		// is assigned to the outgoing interface. There is no requirement to do this
-		// from any RFC but simply a choice made to better follow a strong host
-		// model which the netstack follows at the time of writing.
-		if canForward && chosenRoute == (tcpip.Route{}) {
-			chosenRoute = route
-		}
+		return nil
+	}(); r != nil {
+		return r, nil
 	}
 
 	if chosenRoute != (tcpip.Route{}) {