hotfix(portforwarding): disallow setting ports when running port forwarding code

internal/portforward/service/command.go

@@ -15,7 +15,11 @@ func runCommand(ctx context.Context, cmder Cmder, logger Logger,
 	}
 	portsString := strings.Join(portStrings, ",")
 	commandString := strings.ReplaceAll(commandTemplate, "{{PORTS}}", portsString)
-	commandString = strings.ReplaceAll(commandString, "{{PORT}}", portStrings[0])
+	var firstPort string
+	if len(portStrings) > 0 {
+		firstPort = portStrings[0]
+	}
+	commandString = strings.ReplaceAll(commandString, "{{PORT}}", firstPort)
 	commandString = strings.ReplaceAll(commandString, "{{VPN_INTERFACE}}", vpnInterface)
 	return cmder.RunAndLog(ctx, commandString, logger)
 }

internal/portforward/service/service.go

@@ -2,6 +2,7 @@ package service
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net/http"
 	"slices"
@@ -59,6 +60,10 @@ func (s *Service) SetPortsForwarded(ctx context.Context, ports []uint16) (err er
 	s.portMutex.Lock()
 	defer s.portMutex.Unlock()
 
+	if s.settings.PortForwarder != nil {
+		return errors.New("setting port forwarded at runtime is not supported with internally running port forwarding code")
+	}
+
 	slices.Sort(ports)
 	if slices.Equal(s.ports, ports) {
 		return nil
@@ -78,7 +83,5 @@ func (s *Service) SetPortsForwarded(ctx context.Context, ports []uint16) (err er
 		return fmt.Errorf("handling new ports: %w", err)
 	}
 
-	s.logger.Info("updated: " + portsToString(s.ports))
-
 	return nil
 }