Maint: port forwarding refactoring (#543)

- portforward package
- portforward run loop
- Less functional arguments and cycles

internal/portforward/run.go

@@ -0,0 +1,97 @@
+package portforward
+
+import (
+	"context"
+	"strconv"
+
+	"github.com/qdm12/gluetun/internal/constants"
+)
+
+type Runner interface {
+	Run(ctx context.Context, done chan<- struct{})
+}
+
+func (l *Loop) Run(ctx context.Context, done chan<- struct{}) {
+	defer close(done)
+
+	select {
+	case <-l.start: // l.state.SetStartData called beforehand
+	case <-ctx.Done():
+		return
+	}
+
+	for ctx.Err() == nil {
+		pfCtx, pfCancel := context.WithCancel(ctx)
+
+		portCh := make(chan uint16)
+		errorCh := make(chan error)
+
+		startData := l.state.GetStartData()
+
+		go func(ctx context.Context, startData StartData) {
+			port, err := startData.PortForwarder.PortForward(ctx, l.client, l.logger,
+				startData.Gateway, startData.ServerName)
+			if err != nil {
+				errorCh <- err
+				return
+			}
+			portCh <- port
+
+			// Infinite loop
+			err = startData.PortForwarder.KeepPortForward(ctx, l.client, l.logger,
+				port, startData.Gateway, startData.ServerName)
+			errorCh <- err
+		}(pfCtx, startData)
+
+		if l.userTrigger {
+			l.userTrigger = false
+			l.running <- constants.Running
+		} else { // crash
+			l.backoffTime = defaultBackoffTime
+			l.statusManager.SetStatus(constants.Running)
+		}
+
+		stayHere := true
+		for stayHere {
+			select {
+			case <-ctx.Done():
+				pfCancel()
+				<-errorCh
+				close(errorCh)
+				close(portCh)
+				l.removePortForwardedFile()
+				l.firewallBlockPort(ctx)
+				l.state.SetPortForwarded(0)
+				return
+			case <-l.start:
+				l.userTrigger = true
+				l.logger.Info("starting")
+				pfCancel()
+				stayHere = false
+			case <-l.stop:
+				l.userTrigger = true
+				l.logger.Info("stopping")
+				pfCancel()
+				<-errorCh
+				l.removePortForwardedFile()
+				l.firewallBlockPort(ctx)
+				l.state.SetPortForwarded(0)
+				l.stopped <- struct{}{}
+			case port := <-portCh:
+				l.logger.Info("port forwarded is " + strconv.Itoa(int(port)))
+				l.firewallBlockPort(ctx)
+				l.state.SetPortForwarded(port)
+				l.firewallAllowPort(ctx)
+				l.writePortForwardedFile(port)
+			case err := <-errorCh:
+				pfCancel()
+				close(errorCh)
+				close(portCh)
+				l.statusManager.SetStatus(constants.Crashed)
+				l.logAndWait(ctx, err)
+				stayHere = false
+			}
+		}
+		pfCancel() // for linting
+	}
+}