portlist: add Poller.IncludeLocalhost option

This PR parameterizes receiving loopback updates from the portlist package.
Callers can now include services bound to localhost if they want.
Note that this option is off by default still.

Fixes #8171

Signed-off-by: Marwan Sulaiman <marwan@tailscale.com>

portlist/portlist_macos.go

@@ -29,8 +29,9 @@ type macOSImpl struct {
 	known       map[protoPort]*portMeta // inode string => metadata
 	netstatPath string                  // lazily populated
 
-	br       *bufio.Reader // reused
-	portsBuf []Port
+	br               *bufio.Reader // reused
+	portsBuf         []Port
+	includeLocalhost bool
 }
 
 type protoPort struct {
@@ -43,10 +44,11 @@ type portMeta struct {
 	keep bool
 }
 
-func newMacOSImpl() osImpl {
+func newMacOSImpl(includeLocalhost bool) osImpl {
 	return &macOSImpl{
-		known: map[protoPort]*portMeta{},
-		br:    bufio.NewReader(bytes.NewReader(nil)),
+		known:            map[protoPort]*portMeta{},
+		br:               bufio.NewReader(bytes.NewReader(nil)),
+		includeLocalhost: includeLocalhost,
 	}
 }
 
@@ -119,7 +121,7 @@ func (im *macOSImpl) appendListeningPortsNetstat(base []Port) ([]Port, error) {
 	defer cmd.Process.Wait()
 	defer cmd.Process.Kill()
 
-	return appendParsePortsNetstat(base, im.br)
+	return appendParsePortsNetstat(base, im.br, im.includeLocalhost)
 }
 
 var lsofFailed atomic.Bool
@@ -170,6 +172,7 @@ func (im *macOSImpl) addProcesses() error {
 	im.br.Reset(outPipe)
 
 	var cmd, proto string
+	var pid int
 	for {
 		line, err := im.br.ReadBytes('\n')
 		if err != nil {
@@ -184,6 +187,10 @@ func (im *macOSImpl) addProcesses() error {
 			// starting a new process
 			cmd = ""
 			proto = ""
+			pid = 0
+			if p, err := mem.ParseInt(mem.B(val), 10, 0); err == nil {
+				pid = int(p)
+			}
 		case 'c':
 			cmd = string(val) // TODO(bradfitz): avoid garbage; cache process names between runs?
 		case 'P':
@@ -202,6 +209,7 @@ func (im *macOSImpl) addProcesses() error {
 			switch {
 			case m != nil:
 				m.port.Process = cmd
+				m.port.Pid = pid
 			default:
 				// ignore: processes and ports come and go
 			}