net/netmon, wgengine/magicsock: be quieter with portmapper logs

This adds a new helper to the netmon package that allows us to
rate-limit log messages, so that they only print once per (major)
LinkChange event. We then use this when constructing the portmapper, so
that we don't keep spamming logs forever on the same network.

Updates #13145

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I6e7162509148abea674f96efd76be9dffb373ae4

wgengine/magicsock/magicsock.go

@@ -177,6 +177,10 @@ type Conn struct {
 	// port mappings from NAT devices.
 	portMapper *portmapper.Client
 
+	// portMapperLogfUnregister is the function to call to unregister
+	// the portmapper log limiter.
+	portMapperLogfUnregister func()
+
 	// derpRecvCh is used by receiveDERP to read DERP messages.
 	// It must have buffer size > 0; see issue 3736.
 	derpRecvCh chan derpReadResult
@@ -532,10 +536,15 @@ func NewConn(opts Options) (*Conn, error) {
 	c.idleFunc = opts.IdleFunc
 	c.testOnlyPacketListener = opts.TestOnlyPacketListener
 	c.noteRecvActivity = opts.NoteRecvActivity
+
+	// Don't log the same log messages possibly every few seconds in our
+	// portmapper.
+	portmapperLogf := logger.WithPrefix(c.logf, "portmapper: ")
+	portmapperLogf, c.portMapperLogfUnregister = netmon.LinkChangeLogLimiter(portmapperLogf, opts.NetMon)
 	portMapOpts := &portmapper.DebugKnobs{
 		DisableAll: func() bool { return opts.DisablePortMapper || c.onlyTCP443.Load() },
 	}
-	c.portMapper = portmapper.NewClient(logger.WithPrefix(c.logf, "portmapper: "), opts.NetMon, portMapOpts, opts.ControlKnobs, c.onPortMapChanged)
+	c.portMapper = portmapper.NewClient(portmapperLogf, opts.NetMon, portMapOpts, opts.ControlKnobs, c.onPortMapChanged)
 	c.portMapper.SetGatewayLookupFunc(opts.NetMon.GatewayAndSelfIP)
 	c.netMon = opts.NetMon
 	c.health = opts.HealthTracker
@@ -2481,6 +2490,7 @@ func (c *Conn) Close() error {
 	}
 	c.stopPeriodicReSTUNTimerLocked()
 	c.portMapper.Close()
+	c.portMapperLogfUnregister()
 
 	c.peerMap.forEachEndpoint(func(ep *endpoint) {
 		ep.stopAndReset()