Remove unnecessary locking

The thing the lock protects will never be accessed concurrently.

PiperOrigin-RevId: 356423331

pkg/tcpip/network/ipv6/ndp.go

@@ -466,20 +466,6 @@ type ndpState struct {
 	temporaryAddressDesyncFactor time.Duration
 }
 
-type remainingCounter struct {
-	mu struct {
-		sync.Mutex
-
-		remaining uint8
-	}
-}
-
-func (r *remainingCounter) init(max uint8) {
-	r.mu.Lock()
-	defer r.mu.Unlock()
-	r.mu.remaining = max
-}
-
 // defaultRouterState holds data associated with a default router discovered by
 // a Router Advertisement (RA).
 type defaultRouterState struct {
@@ -1687,7 +1673,8 @@ func (ndp *ndpState) startSolicitingRouters() {
 		return
 	}
 
-	if ndp.configs.MaxRtrSolicitations == 0 {
+	remaining := ndp.configs.MaxRtrSolicitations
+	if remaining == 0 {
 		return
 	}
 
@@ -1698,9 +1685,6 @@ func (ndp *ndpState) startSolicitingRouters() {
 		delay = time.Duration(rand.Int63n(int64(ndp.configs.MaxRtrSolicitationDelay)))
 	}
 
-	var remaining remainingCounter
-	remaining.init(ndp.configs.MaxRtrSolicitations)
-
 	// Protected by ndp.ep.mu.
 	done := false
 
@@ -1754,19 +1738,13 @@ func (ndp *ndpState) startSolicitingRouters() {
 				panic(fmt.Sprintf("failed to add IP header: %s", err))
 			}
 
-			// Okay to hold this lock while writing packets since we use a different
-			// lock per router solicitaiton timer so there will not be any lock
-			// contention.
-			remaining.mu.Lock()
-			defer remaining.mu.Unlock()
-
 			if err := ndp.ep.nic.WritePacketToRemote(header.EthernetAddressFromMulticastIPv6Address(header.IPv6AllRoutersMulticastAddress), nil /* gso */, ProtocolNumber, pkt); err != nil {
 				sent.dropped.Increment()
 				// Don't send any more messages if we had an error.
-				remaining.mu.remaining = 0
+				remaining = 0
 			} else {
 				sent.routerSolicit.Increment()
-				remaining.mu.remaining--
+				remaining--
 			}
 
 			ndp.ep.mu.Lock()
@@ -1777,7 +1755,7 @@ func (ndp *ndpState) startSolicitingRouters() {
 				return
 			}
 
-			if remaining.mu.remaining == 0 {
+			if remaining == 0 {
 				// We are done soliciting routers.
 				ndp.stopSolicitingRouters()
 				return

pkg/tcpip/stack/neighbor_entry.go

@@ -146,20 +146,6 @@ func newStaticNeighborEntry(cache *neighborCache, addr tcpip.Address, linkAddr t
 	return n
 }
 
-type remainingCounter struct {
-	mu struct {
-		sync.Mutex
-
-		remaining uint32
-	}
-}
-
-func (r *remainingCounter) init(max uint32) {
-	r.mu.Lock()
-	defer r.mu.Unlock()
-	r.mu.remaining = max
-}
-
 // notifyCompletionLocked notifies those waiting for address resolution, with
 // the link address if resolution completed successfully.
 //
@@ -298,8 +284,7 @@ func (e *neighborEntry) setStateLocked(next NeighborState) {
 		// Protected by e.mu.
 		done := false
 
-		var remaining remainingCounter
-		remaining.init(config.MaxUnicastProbes)
+		remaining := config.MaxUnicastProbes
 		addr := e.mu.neigh.Addr
 		linkAddr := e.mu.neigh.LinkAddr
 
@@ -310,13 +295,8 @@ func (e *neighborEntry) setStateLocked(next NeighborState) {
 		e.mu.timer = timer{
 			done: &done,
 			timer: e.cache.nic.stack.Clock().AfterFunc(0, func() {
-				// Okay to hold this lock while writing packets since we use a different
-				// lock per probe timer so there will not be any lock contention.
-				remaining.mu.Lock()
-				defer remaining.mu.Unlock()
-
 				var err tcpip.Error
-				timedoutResolution := remaining.mu.remaining == 0
+				timedoutResolution := remaining == 0
 				if !timedoutResolution {
 					err = e.cache.linkRes.LinkAddressRequest(addr, "" /* localAddr */, linkAddr)
 				}
@@ -335,7 +315,7 @@ func (e *neighborEntry) setStateLocked(next NeighborState) {
 					return
 				}
 
-				remaining.mu.remaining--
+				remaining--
 				e.mu.timer.timer.Reset(config.RetransmitTimer)
 			}),
 		}
@@ -373,8 +353,7 @@ func (e *neighborEntry) handlePacketQueuedLocked(localAddr tcpip.Address) {
 		// Protected by e.mu.
 		done := false
 
-		var remaining remainingCounter
-		remaining.init(config.MaxMulticastProbes)
+		remaining := config.MaxMulticastProbes
 		addr := e.mu.neigh.Addr
 
 		// Send a probe in another gorountine to free this thread of execution
@@ -384,13 +363,8 @@ func (e *neighborEntry) handlePacketQueuedLocked(localAddr tcpip.Address) {
 		e.mu.timer = timer{
 			done: &done,
 			timer: e.cache.nic.stack.Clock().AfterFunc(0, func() {
-				// Okay to hold this lock while writing packets since we use a different
-				// lock per probe timer so there will not be any lock contention.
-				remaining.mu.Lock()
-				defer remaining.mu.Unlock()
-
 				var err tcpip.Error
-				timedoutResolution := remaining.mu.remaining == 0
+				timedoutResolution := remaining == 0
 				if !timedoutResolution {
 					// As per RFC 4861 section 7.2.2:
 					//
@@ -416,7 +390,7 @@ func (e *neighborEntry) handlePacketQueuedLocked(localAddr tcpip.Address) {
 					return
 				}
 
-				remaining.mu.remaining--
+				remaining--
 				e.mu.timer.timer.Reset(config.RetransmitTimer)
 			}),
 		}