baseline: api+gui traffic mode + candidates picker

Snapshot before app-launcher (cgroup/mark) work; ignore binaries/backups.

selective-vpn-api/app/shell.go

@@ -0,0 +1,72 @@
+package app
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os/exec"
+	"strings"
+	"time"
+)
+
+// ---------------------------------------------------------------------
+// низкоуровневые helpers
+// ---------------------------------------------------------------------
+
+// EN: Low-level command execution adapters with timeout handling and small
+// EN: policy-route verification helper used by higher-level handlers.
+// RU: Низкоуровневые адаптеры запуска команд с таймаутами и вспомогательной
+// RU: проверкой policy-route, используемой верхнеуровневыми обработчиками.
+
+func runCommand(name string, args ...string) (string, string, int, error) {
+	return runCommandTimeout(60*time.Second, name, args...)
+}
+
+// ---------------------------------------------------------------------
+// policy route check
+// ---------------------------------------------------------------------
+
+func checkPolicyRoute(iface, table string) (bool, error) {
+	stdout, _, exitCode, err := runCommand("ip", "route", "show", "table", table)
+	if exitCode != 0 {
+		if err == nil {
+			err = fmt.Errorf("ip route show exited with %d", exitCode)
+		}
+		return false, err
+	}
+	want := fmt.Sprintf("default dev %s", iface)
+	for _, line := range strings.Split(stdout, "\n") {
+		line = strings.TrimSpace(line)
+		if strings.HasPrefix(line, want) {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+// ---------------------------------------------------------------------
+// command timeout helper
+// ---------------------------------------------------------------------
+
+func runCommandTimeout(timeout time.Duration, name string, args ...string) (string, string, int, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
+
+	cmd := exec.CommandContext(ctx, name, args...)
+	out, err := cmd.CombinedOutput()
+	stdout := string(out)
+	stderr := stdout
+
+	exitCode := 0
+	if err != nil {
+		if ee, ok := err.(*exec.ExitError); ok {
+			exitCode = ee.ExitCode()
+		} else if errors.Is(err, context.DeadlineExceeded) {
+			exitCode = -1
+			err = fmt.Errorf("command timeout: %w", err)
+		} else {
+			exitCode = -1
+		}
+	}
+	return stdout, stderr, exitCode, err
+}