feat(portforwarding): allow running script upon port forwarding success (#2399)

internal/portforward/service/command.go

@@ -0,0 +1,59 @@
+package service
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+	"strings"
+
+	"github.com/qdm12/gluetun/internal/command"
+)
+
+func runUpCommand(ctx context.Context, cmder Cmder, logger Logger,
+	commandTemplate string, ports []uint16,
+) (err error) {
+	portStrings := make([]string, len(ports))
+	for i, port := range ports {
+		portStrings[i] = fmt.Sprint(int(port))
+	}
+	portsString := strings.Join(portStrings, ",")
+	commandString := strings.ReplaceAll(commandTemplate, "{{PORTS}}", portsString)
+	args, err := command.Split(commandString)
+	if err != nil {
+		return fmt.Errorf("parsing command: %w", err)
+	}
+
+	cmd := exec.CommandContext(ctx, args[0], args[1:]...) // #nosec G204
+	stdout, stderr, waitError, err := cmder.Start(cmd)
+	if err != nil {
+		return err
+	}
+
+	streamCtx, streamCancel := context.WithCancel(context.Background())
+	streamDone := make(chan struct{})
+	go streamLines(streamCtx, streamDone, logger, stdout, stderr)
+
+	err = <-waitError
+	streamCancel()
+	<-streamDone
+	return err
+}
+
+func streamLines(ctx context.Context, done chan<- struct{},
+	logger Logger, stdout, stderr <-chan string,
+) {
+	defer close(done)
+
+	var line string
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case line = <-stdout:
+			logger.Info(line)
+		case line = <-stderr:
+			logger.Error(line)
+		}
+	}
+}