feat: simplify configuration and diagnostics, harden native recovery

README.md

@@ -163,8 +163,10 @@ fork 的 ChromeParrot 行为，但仍属于 web H3，不会切换成 `autocar/2`
 `doctor` 不以“本地端口已监听”代替中继健康。它会通过经过证书和令牌认证的
 隧道实际打开一次目标 TCP 连接，再报告真正选中的 `quic`、`tls`、`h3` 或 `h2`
 以及耗时；native QUIC 还报告 pacing 与协商速率，web 路径则报告
-`not-applicable`。加 `--json` 可得到稳定的机器可读结果；失败 JSON 只包含稳定错误码
-和脱敏说明，原始网络错误、远端消息及本地路径仅在人类输出的诊断日志中出现。退出码
+`not-applicable`。加 `--json` 可得到稳定的机器可读结果；失败保留稳定错误码
+和脱敏说明，另附 `diagnosis` 分类与 `hint` 排查建议。人读模式也给出安全提示，
+不回显原始远端消息、参数值或本地路径。无法可靠分类的错误会提示检查两端配置，
+不会把所有失败都断言成认证问题。退出码
 `0` 表示探测成功，`1` 表示网络/认证/目标探测失败，`2` 表示参数或本地配置错误。
 成功只证明该 TCP 路径此刻可用，不代表目标应用协议正确、不可识别或链路更快。
 
@@ -181,6 +183,40 @@ fork 的 ChromeParrot 行为，但仍属于 web H3，不会切换成 `autocar/2`
 
 `socks5h` 会把域名交给远端。AutoCAR 不伪造目标证书，也不解密目标 HTTPS。
 
+### 保存配置，启动和诊断共用
+
+以下配置文件功能为 v1.0.1 之后新增，需使用包含本改动的构建。
+不必每次重复填写连接参数：将 [客户端模板](examples/client.json) 保存为
+自己的 `client.json`，修改中继地址，并把证书与令牌放在配置文件旁：
+
+```json
+{
+  "server": "relay.example.com:8443",
+  "ca": "server.crt",
+  "token-file": "relay-token",
+  "transport": "auto"
+}
+```
+
+```bash
+./autocar client --config /path/to/client.json
+./autocar doctor --config /path/to/client.json --target example.com:443 --json
+# 临时强制 TCP/TLS 诊断，不修改配置文件
+./autocar doctor --config /path/to/client.json --transport tls --target example.com:443
+```
+
+字段名对应命令行长选项，但不加 `--`；命令行同名选项优先。配置中的相对文件路径
+以配置文件所在目录为基准，命令行路径仍以当前目录为基准。布尔值用 JSON
+`true/false`，时长用 `"15s"` 等字符串。未知字段、重复字段与无效值会直接报错；
+不支持注释、环境变量展开或配置嵌套。令牌和私钥仍单独存文件并检查权限，
+不要把原文写进 JSON。
+
+要让 `client` 和 `doctor` 共用同一个文件，只保存二者共有的隧道参数；
+`socks/http/https` 等客户端专属参数放在启动命令中。中继使用单独的
+[服务端模板](examples/server.json)：`./autocar server --config /path/to/server.json`。
+配置仅在进程启动时读取，修改后需重启；自动回退和恢复只影响新连接，
+已中断的业务连接仍需要应用重新发起，不会自动重放请求。
+
 ## Pacing 模式
 
 ```bash

cmd/autocar/client.go

@@ -38,7 +38,7 @@ func runClient(parent context.Context, args []string) error {
 	maxConnections := fs.Int("max-connections", 1024, "maximum clients per local proxy listener")
 	idleTimeout := fs.Duration("idle-timeout", 5*time.Minute, "local proxy idle timeout")
 	shutdownTimeout := fs.Duration("shutdown-timeout", 10*time.Second, "graceful shutdown timeout")
-	if err := fs.Parse(args); err != nil {
+	if err := parseFlagsWithConfig(fs, args); err != nil {
 		return err
 	}
 	if *socksAddress == "" && *httpAddress == "" && *httpsAddress == "" {

cmd/autocar/config_file.go

@@ -0,0 +1,189 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"time"
+)
+
+const maxCommandConfigSize = 64 << 10
+
+// parseFlagsWithConfig preserves flag's CLI syntax and precedence. A config is
+// a single, bounded JSON object whose keys are this command's long flag names.
+// It contains file references, never inline credentials. Each command still
+// performs its normal semantic and credential validation after parsing.
+func parseFlagsWithConfig(fs *flag.FlagSet, args []string) error {
+	configPath := fs.String("config", "", "JSON options file; CLI overrides it, file paths are relative to its directory")
+	if err := fs.Parse(args); err != nil {
+		return err
+	}
+	if fs.NArg() != 0 {
+		return errors.New("positional arguments are not supported; use named options")
+	}
+	if *configPath == "" {
+		return nil
+	}
+	// Save explicit flags before Set marks config options as visited too.
+	explicit := make(map[string]string)
+	fs.Visit(func(f *flag.Flag) { explicit[f.Name] = f.Value.String() })
+	values, err := readCommandConfig(*configPath)
+	if err != nil {
+		return err
+	}
+	base, err := filepath.Abs(filepath.Dir(*configPath))
+	if err != nil {
+		return fmt.Errorf("resolve config directory: %w", err)
+	}
+	keys := make([]string, 0, len(values))
+	for name := range values {
+		keys = append(keys, name)
+	}
+	sort.Strings(keys)
+	for _, name := range keys {
+		f := fs.Lookup(name)
+		if f == nil || name == "config" {
+			return fmt.Errorf("unknown or unsupported config option %q for %s", name, fs.Name())
+		}
+		value, err := commandConfigValue(f, values[name])
+		if err != nil {
+			return fmt.Errorf("config option %q: %w", name, err)
+		}
+		if commandConfigFileOption(name) && value != "" && !filepath.IsAbs(value) {
+			value = filepath.Join(base, value)
+		}
+		// Validate even overridden entries so stale/invalid config never goes
+		// unnoticed. Do not include a possibly sensitive value in diagnostics.
+		if err := fs.Set(name, value); err != nil {
+			return fmt.Errorf("invalid config option %q; see command help for its type and format", name)
+		}
+		if cliValue, ok := explicit[name]; ok {
+			if err := fs.Set(name, cliValue); err != nil {
+				return fmt.Errorf("restore command-line option %q: %w", name, err)
+			}
+		}
+	}
+	return nil
+}
+
+func readCommandConfig(path string) (map[string]any, error) {
+	// Check before opening so accidental directories/devices/FIFOs are not
+	// treated as configuration streams. Check the opened file again below.
+	info, err := os.Stat(path)
+	if err != nil {
+		return nil, fmt.Errorf("stat config file: %w", err)
+	}
+	if !info.Mode().IsRegular() || info.Size() > maxCommandConfigSize {
+		return nil, errors.New("config must be a regular JSON file no larger than 64 KiB")
+	}
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, fmt.Errorf("open config file: %w", err)
+	}
+	defer f.Close()
+	info, err = f.Stat()
+	if err != nil {
+		return nil, fmt.Errorf("stat opened config file: %w", err)
+	}
+	if !info.Mode().IsRegular() || info.Size() > maxCommandConfigSize {
+		return nil, errors.New("config must be a regular JSON file no larger than 64 KiB")
+	}
+	data, err := io.ReadAll(io.LimitReader(f, maxCommandConfigSize+1))
+	if err != nil {
+		return nil, fmt.Errorf("read config file: %w", err)
+	}
+	if len(data) > maxCommandConfigSize {
+		return nil, errors.New("config exceeds 64 KiB")
+	}
+	return decodeCommandConfig(data)
+}
+
+func decodeCommandConfig(data []byte) (map[string]any, error) {
+	// Token-by-token decoding detects duplicate keys that a normal map decode
+	// would silently accept (including escaped spellings of the same key).
+	d := json.NewDecoder(bytes.NewReader(data))
+	d.UseNumber()
+	token, err := d.Token()
+	if err != nil || token != json.Delim('{') {
+		return nil, errors.New("config must contain one JSON object")
+	}
+	values := make(map[string]any)
+	for d.More() {
+		token, err := d.Token()
+		if err != nil {
+			return nil, errors.New("invalid config JSON")
+		}
+		name, ok := token.(string)
+		if !ok || name == "" {
+			return nil, errors.New("config option names must be nonempty strings")
+		}
+		if _, exists := values[name]; exists {
+			return nil, fmt.Errorf("duplicate config option %q", name)
+		}
+		var value any
+		if err := d.Decode(&value); err != nil {
+			return nil, errors.New("invalid config JSON")
+		}
+		switch value.(type) {
+		case string, bool, json.Number:
+		default:
+			return nil, fmt.Errorf("config option %q must be a string, boolean, or integer", name)
+		}
+		values[name] = value
+	}
+	if token, err := d.Token(); err != nil || token != json.Delim('}') {
+		return nil, errors.New("invalid config JSON")
+	}
+	if _, err := d.Token(); err != io.EOF {
+		return nil, errors.New("config must contain exactly one JSON object")
+	}
+	return values, nil
+}
+
+func commandConfigValue(f *flag.Flag, value any) (string, error) {
+	getter, ok := f.Value.(flag.Getter)
+	if !ok {
+		return "", errors.New("unsupported option type")
+	}
+	switch getter.Get().(type) {
+	case string:
+		if text, ok := value.(string); ok {
+			return text, nil
+		}
+		return "", errors.New("must be a JSON string")
+	case bool:
+		if enabled, ok := value.(bool); ok {
+			return strconv.FormatBool(enabled), nil
+		}
+		return "", errors.New("must be a JSON boolean")
+	case time.Duration:
+		if text, ok := value.(string); ok {
+			return text, nil
+		}
+		return "", errors.New("must be a duration string such as 15s")
+	default:
+		// Numeric flags require JSON numbers, not CLI-specific string syntax.
+		// flag's integer parser still enforces integral values and range limits.
+		if v, ok := value.(json.Number); ok {
+			return v.String(), nil
+		}
+		return "", errors.New("must be a JSON integer")
+	}
+}
+
+func commandConfigFileOption(name string) bool {
+	switch name {
+	case "ca", "client-cert", "client-key", "token-file", "proxy-cert", "proxy-key",
+		"proxy-password-file", "cert", "key", "client-ca", "cover-root":
+		return true
+	default:
+		return false
+	}
+}