health: delete ReceiveFunc health checks

They were not doing their job.
They need yet another conceptual re-think.
Start by clearing the decks.

Signed-off-by: Josh Bleecher Snyder <josharian@gmail.com>

health/health.go

@@ -36,10 +36,6 @@ var (
 	ipnState                string
 	ipnWantRunning          bool
 	anyInterfaceUp          = true // until told otherwise
-
-	ReceiveIPv4 = ReceiveFuncState{name: "IPv4"}
-	ReceiveIPv6 = ReceiveFuncState{name: "IPv6"}
-	ReceiveDERP = ReceiveFuncState{name: "DERP"}
 )
 
 // Subsystem is the name of a subsystem whose health can be monitored.
@@ -217,68 +213,6 @@ func SetAnyInterfaceUp(up bool) {
 	selfCheckLocked()
 }
 
-// ReceiveFuncState tracks the state of a wireguard-go conn.ReceiveFunc.
-type ReceiveFuncState struct {
-	// name is a mnemonic for the receive func, used in error messages.
-	name string
-	// started indicates whether magicsock.connBind.Open
-	// has requested that wireguard-go start its receive func
-	// goroutine (without a corresponding connBind.Close).
-	started bool
-	// running models whether wireguard-go's receive func
-	// goroutine is actually running. We cannot easily introspect that,
-	// so it is based on our knowledge of wireguard-go's internals.
-	running bool
-}
-
-// err returns the error state (if any) that s represents.
-func (s ReceiveFuncState) err() error {
-	// Possible states:
-	//   | started | running | notes
-	//   | ------- | ------- | -----
-	//   | true    | true    | normal operation
-	//   | true    | false   | we prematurely returned a permanent error from this receive func
-	//   | false   | true    | we have told package health that we're closing the bind, but the receive funcs haven't closed yet (transient)
-	//   | false   | false   | not running
-
-	// The problematic case is started && !running.
-	// If that happens, wireguard-go will no longer request packets,
-	// and we'll lose an entire communication channel.
-	if s.started && !s.running {
-		return fmt.Errorf("receive%s started but not running", s.name)
-	}
-	return nil
-}
-
-// Open tells r that connBind.Open has requested wireguard-go open a conn.Bind that includes r.
-func (r *ReceiveFuncState) Open() {
-	mu.Lock()
-	defer mu.Unlock()
-	r.started = true
-	r.running = true
-	selfCheckLocked()
-}
-
-// Stop tells r that we have returned a permanent error to wireguard-go.
-// wireguard-go's receive func goroutine for r will soon stop.
-func (r *ReceiveFuncState) Stop() {
-	mu.Lock()
-	defer mu.Unlock()
-	r.running = false
-	selfCheckLocked()
-}
-
-// Close tells r that connBind.Close has requested wireguard-go close the bind for r.
-// This will stop the corresponding receive func goroutine.
-// Close must be called before actually closing the underlying connection,
-// to avoid a small window of false positives.
-func (r *ReceiveFuncState) Close() {
-	mu.Lock()
-	defer mu.Unlock()
-	r.started = false
-	selfCheckLocked()
-}
-
 func timerSelfCheck() {
 	mu.Lock()
 	defer mu.Unlock()
@@ -329,11 +263,6 @@ func overallErrorLocked() error {
 	_ = lastMapRequestHeard
 
 	var errs []error
-	for _, recv := range []ReceiveFuncState{ReceiveIPv4, ReceiveIPv6, ReceiveDERP} {
-		if err := recv.err(); err != nil {
-			errs = append(errs, err)
-		}
-	}
 	for sys, err := range sysErr {
 		if err == nil || sys == SysOverall {
 			continue

wgengine/magicsock/magicsock.go

@@ -1584,9 +1584,6 @@ func (c *Conn) receiveIPv6(b []byte) (int, conn.Endpoint, error) {
 	for {
 		n, ipp, err := c.pconn6.ReadFromNetaddr(b)
 		if err != nil {
-			if isPermanentNetError(err) {
-				health.ReceiveIPv6.Stop()
-			}
 			return 0, nil, err
 		}
 		if ep, ok := c.receiveIP(b[:n], ipp, &c.ippEndpoint6); ok {
@@ -1600,9 +1597,6 @@ func (c *Conn) receiveIPv4(b []byte) (n int, ep conn.Endpoint, err error) {
 	for {
 		n, ipp, err := c.pconn4.ReadFromNetaddr(b)
 		if err != nil {
-			if isPermanentNetError(err) {
-				health.ReceiveIPv4.Stop()
-			}
 			return 0, nil, err
 		}
 		if ep, ok := c.receiveIP(b[:n], ipp, &c.ippEndpoint4); ok {
@@ -1663,7 +1657,6 @@ func (c *connBind) receiveDERP(b []byte) (n int, ep conn.Endpoint, err error) {
 		}
 		return n, ep, nil
 	}
-	health.ReceiveDERP.Stop()
 	return 0, nil, net.ErrClosed
 }
 
@@ -1734,18 +1727,6 @@ func (c *Conn) processDERPReadResult(dm derpReadResult, b []byte) (n int, ep con
 	return n, ep
 }
 
-// isPermanentNetError reports whether err is permanent.
-// It matches an equivalent check in wireguard-go's RoutineReceiveIncoming.
-func isPermanentNetError(err error) bool {
-	// Once this module requires Go 1.17, the comparison to net.ErrClosed can be removed.
-	// See https://github.com/golang/go/issues/45357.
-	if errors.Is(err, net.ErrClosed) {
-		return true
-	}
-	neterr, ok := err.(net.Error)
-	return ok && !neterr.Temporary()
-}
-
 // discoLogLevel controls the verbosity of discovery log messages.
 type discoLogLevel int
 
@@ -2430,11 +2411,8 @@ func (c *connBind) Open(ignoredPort uint16) ([]conn.ReceiveFunc, uint16, error)
 	}
 	c.closed = false
 	fns := []conn.ReceiveFunc{c.receiveIPv4, c.receiveDERP}
-	health.ReceiveIPv4.Open()
-	health.ReceiveDERP.Open()
 	if c.pconn6 != nil {
 		fns = append(fns, c.receiveIPv6)
-		health.ReceiveIPv6.Open()
 	}
 	// TODO: Combine receiveIPv4 and receiveIPv6 and receiveIP into a single
 	// closure that closes over a *RebindingUDPConn?
@@ -2456,15 +2434,12 @@ func (c *connBind) Close() error {
 	}
 	c.closed = true
 	// Unblock all outstanding receives.
-	health.ReceiveIPv4.Close()
 	c.pconn4.Close()
 	if c.pconn6 != nil {
-		health.ReceiveIPv6.Close()
 		c.pconn6.Close()
 	}
 	// Send an empty read result to unblock receiveDERP,
 	// which will then check connBind.Closed.
-	health.ReceiveDERP.Close()
 	c.derpRecvCh <- derpReadResult{}
 	return nil
 }