Add best exit selection (#486)

* docs: add best exit selection design

* feat: add best exit selection

go-gost/x/registry/chain.go

@@ -12,10 +12,25 @@ type chainRegistry struct {
 	registry[chain.Chainer]
 }
 
+func ReplaceChain(name string, v chain.Chainer) error {
+	if name == "" {
+		return nil
+	}
+	if r, ok := chainReg.(*chainRegistry); ok {
+		r.replace(name, v)
+		return nil
+	}
+	return chainReg.Register(name, v)
+}
+
 func (r *chainRegistry) Register(name string, v chain.Chainer) error {
 	return r.registry.Register(name, v)
 }
 
+func (r *chainRegistry) replace(name string, v chain.Chainer) {
+	r.m.Store(name, v)
+}
+
 func (r *chainRegistry) Get(name string) chain.Chainer {
 	if name != "" {
 		return &chainWrapper{name: name, r: r}

go-gost/x/registry/chain_test.go

@@ -0,0 +1,51 @@
+package registry
+
+import (
+	"context"
+	"net"
+	"testing"
+
+	"github.com/go-gost/core/chain"
+)
+
+type testChainer struct {
+	route chain.Route
+}
+
+func (c testChainer) Route(context.Context, string, string, ...chain.RouteOption) chain.Route {
+	return c.route
+}
+
+type testRoute struct {
+	nodes []*chain.Node
+}
+
+func (r testRoute) Dial(context.Context, string, string, ...chain.DialOption) (net.Conn, error) {
+	return nil, nil
+}
+
+func (r testRoute) Bind(context.Context, string, string, ...chain.BindOption) (net.Listener, error) {
+	return nil, nil
+}
+
+func (r testRoute) Nodes() []*chain.Node {
+	return r.nodes
+}
+
+func TestReplaceChainOverwritesExistingRegistration(t *testing.T) {
+	name := "replace_chain_tdd"
+	ChainRegistry().Unregister(name)
+	defer ChainRegistry().Unregister(name)
+
+	if err := ChainRegistry().Register(name, testChainer{route: testRoute{nodes: []*chain.Node{{Name: "old"}}}}); err != nil {
+		t.Fatalf("register old chain: %v", err)
+	}
+	if err := ReplaceChain(name, testChainer{route: testRoute{nodes: []*chain.Node{{Name: "new"}}}}); err != nil {
+		t.Fatalf("replace chain: %v", err)
+	}
+
+	route := ChainRegistry().Get(name).Route(context.Background(), "tcp", "example.com:443")
+	if route == nil || len(route.Nodes()) != 1 || route.Nodes()[0].Name != "new" {
+		t.Fatalf("expected replacement chain route, got %#v", route)
+	}
+}

go-gost/x/socket/chain.go

@@ -38,21 +38,21 @@ func createChain(req createChainRequest) error {
 }
 
 func updateChain(req updateChainRequest) error {
-
 	name := strings.TrimSpace(req.Chain)
-
-	if registry.ChainRegistry().IsRegistered(name) {
-		registry.ChainRegistry().Unregister(name)
+	if name == "" {
+		name = strings.TrimSpace(req.Data.Name)
+	}
+	if name == "" {
+		return errors.New("chain name is required")
 	}
 
 	req.Data.Name = name
-
 	v, err := parser.ParseChain(&req.Data, logger.Default())
 	if err != nil {
 		return errors.New("create chain " + name + " failed: " + err.Error())
 	}
 
-	if err := registry.ChainRegistry().Register(name, v); err != nil {
+	if err := registry.ReplaceChain(name, v); err != nil {
 		return errors.New("chain " + name + " already exists")
 	}
 

go-gost/x/socket/chain_test.go

@@ -0,0 +1,69 @@
+package socket
+
+import (
+	"testing"
+
+	corelogger "github.com/go-gost/core/logger"
+	"github.com/go-gost/x/config"
+	_ "github.com/go-gost/x/connector/relay"
+	_ "github.com/go-gost/x/dialer/tcp"
+	xlogger "github.com/go-gost/x/logger"
+	"github.com/go-gost/x/registry"
+)
+
+func TestUpdateChainParseFailureKeepsExistingChainRegistered(t *testing.T) {
+	corelogger.SetDefault(xlogger.Nop())
+
+	name := "chain_update_parse_failure_tdd"
+	originalConfig := config.Global()
+	defer config.Set(originalConfig)
+	registry.ChainRegistry().Unregister(name)
+	defer registry.ChainRegistry().Unregister(name)
+	config.Set(&config.Config{})
+
+	valid := config.ChainConfig{
+		Name: name,
+		Hops: []*config.HopConfig{{
+			Name: "hop-valid",
+			Nodes: []*config.NodeConfig{{
+				Name:      "node-valid",
+				Addr:      "127.0.0.1:443",
+				Connector: &config.ConnectorConfig{Type: "relay"},
+				Dialer:    &config.DialerConfig{Type: "tcp"},
+			}},
+		}},
+	}
+	if err := createChain(createChainRequest{Data: valid}); err != nil {
+		t.Fatalf("create valid chain: %v", err)
+	}
+	before := registry.ChainRegistry().Get(name)
+	if before == nil || !registry.ChainRegistry().IsRegistered(name) {
+		t.Fatalf("expected chain registered before update")
+	}
+
+	invalid := config.ChainConfig{
+		Hops: []*config.HopConfig{{
+			Name: "hop-invalid",
+			Nodes: []*config.NodeConfig{{
+				Name:      "node-invalid",
+				Addr:      "127.0.0.1:443",
+				Connector: &config.ConnectorConfig{Type: "connector-does-not-exist"},
+				Dialer:    &config.DialerConfig{Type: "tcp"},
+			}},
+		}},
+	}
+	err := updateChain(updateChainRequest{Chain: name, Data: invalid})
+	if err == nil {
+		t.Fatalf("expected invalid chain update to fail")
+	}
+	if !registry.ChainRegistry().IsRegistered(name) {
+		t.Fatalf("expected old chain to remain registered after failed update")
+	}
+	cfg := config.Global()
+	if len(cfg.Chains) != 1 || cfg.Chains[0] == nil || cfg.Chains[0].Name != name {
+		t.Fatalf("expected original chain config to remain, got %#v", cfg.Chains)
+	}
+	if got := cfg.Chains[0].Hops[0].Name; got != "hop-valid" {
+		t.Fatalf("expected original chain config to remain, got hop %q", got)
+	}
+}