fix(config): stop mutating shared config structs during parsing

Prevent data loss and nil panics across 5 parse functions:
- chain: nil-guard hop entries to avoid deref on empty YAML lists
- hop: build merged metadata map instead of writing inherited values
  into the original NodeConfig; swap+restore around ParseNode call
- node: use local connCfg/dialCfg instead of overwriting cfg.Connector
  and cfg.Dialer fields; only fill in Type when empty
- parser: preserve existing config file fields when env vars override
  Level/Addr (was replacing the entire struct)
- router: only update ipNet from dst CIDR if parse succeeds, keeping
  the route.Net fallback instead of overwriting with nil

config/parsing/chain/parse.go

@@ -33,6 +33,10 @@ func ParseChain(cfg *config.ChainConfig, log logger.Logger) (chain.Chainer, erro
 	)
 
 	for _, ch := range cfg.Hops {
+		if ch == nil {
+			continue
+		}
+
 		var hop hop.Hop
 		var err error
 

config/parsing/hop/parse.go

@@ -78,12 +78,13 @@ func ParseHop(cfg *config.HopConfig, log logger.Logger) (hop.Hop, error) {
 			continue
 		}
 
-		m := v.Metadata
-		if m == nil {
-			m = map[string]any{}
-			v.Metadata = m
+		// Build a merged metadata map for inheritance without mutating
+		// the original node config.
+		merged := make(map[string]any)
+		for k, val := range v.Metadata {
+			merged[k] = val
 		}
-		md := metadata.NewMetadata(m)
+		md := metadata.NewMetadata(merged)
 
 		if v.Resolver == "" {
 			v.Resolver = cfg.Resolver
@@ -93,37 +94,30 @@ func ParseHop(cfg *config.HopConfig, log logger.Logger) (hop.Hop, error) {
 		}
 
 		if !md.IsExists(parsing.MDKeyInterface) {
-			// inherit from hop
 			if ifce != "" {
-				m[parsing.MDKeyInterface] = ifce
+				merged[parsing.MDKeyInterface] = ifce
 			}
-			// node level
 			if v.Interface != "" {
-				m[parsing.MDKeyInterface] = v.Interface
+				merged[parsing.MDKeyInterface] = v.Interface
 			}
 		}
 		if !md.IsExists(parsing.MDKeySoMark) {
-			// inherit from hop
 			if soMark != 0 {
-				m[parsing.MDKeySoMark] = soMark
+				merged[parsing.MDKeySoMark] = soMark
 			}
-			// node level
 			if v.SockOpts != nil && v.SockOpts.Mark != 0 {
-				m[parsing.MDKeySoMark] = v.SockOpts.Mark
+				merged[parsing.MDKeySoMark] = v.SockOpts.Mark
 			}
 		}
 		if !md.IsExists(parsing.MDKeyProxyProtocol) && ppv > 0 {
-			// inherit from hop
-			m[parsing.MDKeyProxyProtocol] = ppv
+			merged[parsing.MDKeyProxyProtocol] = ppv
 		}
 		if !md.IsExists(parsing.MDKeyNetns) {
-			// inherit from hop
 			if netns != "" {
-				m[parsing.MDKeyNetns] = netns
+				merged[parsing.MDKeyNetns] = netns
 			}
-			// node level
 			if v.Netns != "" {
-				m[parsing.MDKeyNetns] = v.Netns
+				merged[parsing.MDKeyNetns] = v.Netns
 			}
 		}
 
@@ -141,7 +135,11 @@ func ParseHop(cfg *config.HopConfig, log logger.Logger) (hop.Hop, error) {
 			v.Dialer.Type = "tcp"
 		}
 
+		// Temporarily swap merged metadata so ParseNode sees inherited values.
+		origMeta := v.Metadata
+		v.Metadata = merged
 		node, err := node_parser.ParseNode(cfg.Name, v, log)
+		v.Metadata = origMeta
 		if err != nil {
 			return nil, err
 		}

config/parsing/node/parse.go

@@ -29,29 +29,33 @@ func ParseNode(hop string, cfg *config.NodeConfig, log logger.Logger) (*chain.No
 		return nil, nil
 	}
 
-	if cfg.Connector == nil {
-		cfg.Connector = &config.ConnectorConfig{
-			Type: "http",
-		}
+	connCfg := cfg.Connector
+	if connCfg == nil {
+		connCfg = &config.ConnectorConfig{}
+	}
+	if connCfg.Type == "" {
+		connCfg.Type = "http"
 	}
 
-	if cfg.Dialer == nil {
-		cfg.Dialer = &config.DialerConfig{
-			Type: "tcp",
-		}
+	dialCfg := cfg.Dialer
+	if dialCfg == nil {
+		dialCfg = &config.DialerConfig{}
+	}
+	if dialCfg.Type == "" {
+		dialCfg.Type = "tcp"
 	}
 
 	nodeLogger := log.WithFields(map[string]any{
 		"hop":       hop,
 		"kind":      "node",
 		"node":      cfg.Name,
-		"connector": cfg.Connector.Type,
-		"dialer":    cfg.Dialer.Type,
+		"connector": connCfg.Type,
+		"dialer":    dialCfg.Type,
 	})
 
 	serverName, _, _ := net.SplitHostPort(cfg.Addr)
 
-	tlsCfg := cfg.Connector.TLS
+	tlsCfg := connCfg.TLS
 	if tlsCfg == nil {
 		tlsCfg = &config.TLSConfig{}
 	}
@@ -68,25 +72,22 @@ func ParseNode(hop string, cfg *config.NodeConfig, log logger.Logger) (*chain.No
 		"kind": "connector",
 	})
 	var cr connector.Connector
-	if rf := registry.ConnectorRegistry().Get(cfg.Connector.Type); rf != nil {
+	if rf := registry.ConnectorRegistry().Get(connCfg.Type); rf != nil {
 		cr = rf(
-			connector.AuthOption(auth_parser.Info(cfg.Connector.Auth)),
+			connector.AuthOption(auth_parser.Info(connCfg.Auth)),
 			connector.TLSConfigOption(tlsConfig),
 			connector.LoggerOption(connectorLogger),
 		)
 	} else {
-		return nil, fmt.Errorf("unregistered connector: %s", cfg.Connector.Type)
+		return nil, fmt.Errorf("unregistered connector: %s", connCfg.Type)
 	}
 
-	if cfg.Connector.Metadata == nil {
-		cfg.Connector.Metadata = make(map[string]any)
-	}
-	if err := cr.Init(mdx.NewMetadata(cfg.Connector.Metadata)); err != nil {
+	if err := cr.Init(mdx.NewMetadata(connCfg.Metadata)); err != nil {
 		connectorLogger.Error("init: ", err)
 		return nil, err
 	}
 
-	tlsCfg = cfg.Dialer.TLS
+	tlsCfg = dialCfg.TLS
 	if tlsCfg == nil {
 		tlsCfg = &config.TLSConfig{}
 	}
@@ -106,21 +107,18 @@ func ParseNode(hop string, cfg *config.NodeConfig, log logger.Logger) (*chain.No
 	})
 
 	var d dialer.Dialer
-	if rf := registry.DialerRegistry().Get(cfg.Dialer.Type); rf != nil {
+	if rf := registry.DialerRegistry().Get(dialCfg.Type); rf != nil {
 		d = rf(
-			dialer.AuthOption(auth_parser.Info(cfg.Dialer.Auth)),
+			dialer.AuthOption(auth_parser.Info(dialCfg.Auth)),
 			dialer.TLSConfigOption(tlsConfig),
 			dialer.LoggerOption(dialerLogger),
 			dialer.ProxyProtocolOption(mdutil.GetInt(md, parsing.MDKeyProxyProtocol)),
 		)
 	} else {
-		return nil, fmt.Errorf("unregistered dialer: %s", cfg.Dialer.Type)
+		return nil, fmt.Errorf("unregistered dialer: %s", dialCfg.Type)
 	}
 
-	if cfg.Dialer.Metadata == nil {
-		cfg.Dialer.Metadata = make(map[string]any)
-	}
-	if err := d.Init(mdx.NewMetadata(cfg.Dialer.Metadata)); err != nil {
+	if err := d.Init(mdx.NewMetadata(dialCfg.Metadata)); err != nil {
 		dialerLogger.Error("init: ", err)
 		return nil, err
 	}

config/parsing/parser/parser.go

@@ -84,24 +84,28 @@ func (p *parser) Parse() (*config.Config, error) {
 	}
 
 	if v := os.Getenv("GOST_LOGGER_LEVEL"); v != "" {
-		cfg.Log = &config.LogConfig{
-			Level: v,
+		if cfg.Log == nil {
+			cfg.Log = &config.LogConfig{}
 		}
+		cfg.Log.Level = v
 	}
 	if v := os.Getenv("GOST_API"); v != "" {
-		cfg.API = &config.APIConfig{
-			Addr: v,
+		if cfg.API == nil {
+			cfg.API = &config.APIConfig{}
 		}
+		cfg.API.Addr = v
 	}
 	if v := os.Getenv("GOST_METRICS"); v != "" {
-		cfg.Metrics = &config.MetricsConfig{
-			Addr: v,
+		if cfg.Metrics == nil {
+			cfg.Metrics = &config.MetricsConfig{}
 		}
+		cfg.Metrics.Addr = v
 	}
 	if v := os.Getenv("GOST_PROFILING"); v != "" {
-		cfg.Profiling = &config.ProfilingConfig{
-			Addr: v,
+		if cfg.Profiling == nil {
+			cfg.Profiling = &config.ProfilingConfig{}
 		}
+		cfg.Profiling.Addr = v
 	}
 
 	if p.args.Debug || p.args.Trace {

config/parsing/router/parse.go

@@ -51,7 +51,9 @@ func ParseRouter(cfg *config.RouterConfig) router.Router {
 		_, ipNet, _ := net.ParseCIDR(route.Net)
 		dst := route.Dst
 		if dst != "" {
-			_, ipNet, _ = net.ParseCIDR(dst)
+			if _, parsed, _ := net.ParseCIDR(dst); parsed != nil {
+				ipNet = parsed
+			}
 		} else {
 			if ipNet != nil {
 				dst = ipNet.String()