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_windows.go

@@ -25,7 +25,8 @@ type famPort struct {
 }
 
 type windowsImpl struct {
-	known map[famPort]*portMeta // inode string => metadata
+	known            map[famPort]*portMeta // inode string => metadata
+	includeLocalhost bool
 }
 
 type portMeta struct {
@@ -33,9 +34,10 @@ type portMeta struct {
 	keep bool
 }
 
-func newWindowsImpl() osImpl {
+func newWindowsImpl(includeLocalhost bool) osImpl {
 	return &windowsImpl{
-		known: map[famPort]*portMeta{},
+		known:            map[famPort]*portMeta{},
+		includeLocalhost: includeLocalhost,
 	}
 }
 
@@ -58,7 +60,7 @@ func (im *windowsImpl) AppendListeningPorts(base []Port) ([]Port, error) {
 		if e.State != "LISTEN" {
 			continue
 		}
-		if !e.Local.Addr().IsUnspecified() {
+		if !im.includeLocalhost && !e.Local.Addr().IsUnspecified() {
 			continue
 		}
 		fp := famPort{
@@ -83,6 +85,7 @@ func (im *windowsImpl) AppendListeningPorts(base []Port) ([]Port, error) {
 				Proto:   "tcp",
 				Port:    e.Local.Port(),
 				Process: process,
+				Pid:     e.Pid,
 			},
 		}
 		im.known[fp] = pm