feat: add CLI connector for unix domain socket (#186)

* feat: Add cli connector for unix domain socket

* Update cmd/uncloud/main.go

---------

Co-authored-by: Pasha Sviderski <me@psviderski.name>

cmd/uncloud/main.go

@@ -58,11 +58,12 @@ func main() {
 					conn = &config.MachineConnection{
 						SSHCLI: config.SSHDestination(dest),
 					}
-				} else {
-					dest := opts.connect
-					if strings.HasPrefix(dest, "ssh://") {
-						dest = dest[len("ssh://"):]
+				} else if strings.HasPrefix(opts.connect, "unix://") {
+					conn = &config.MachineConnection{
+						Unix: opts.connect[len("unix://"):],
 					}
+				} else {
+					dest := strings.TrimPrefix(opts.connect, "ssh://")
 					conn = &config.MachineConnection{
 						SSH: config.SSHDestination(dest),
 					}
@@ -81,7 +82,7 @@ func main() {
 
 	cmd.PersistentFlags().StringVar(&opts.connect, "connect", "",
 		"Connect to a remote cluster machine without using the Uncloud configuration file. [$UNCLOUD_CONNECT]\n"+
-			"Format: [ssh://]user@host[:port], ssh+cli://user@host[:port], or tcp://host:port")
+			"Format: [ssh://]user@host[:port], ssh+cli://user@host[:port], tcp://host:port, or unix:///path/to/uncloud.sock")
 	cmd.PersistentFlags().StringVar(&opts.configPath, "uncloud-config", "~/.config/uncloud/config.yaml",
 		"Path to the Uncloud configuration file. [$UNCLOUD_CONFIG]")
 	_ = cmd.MarkPersistentFlagFilename("uncloud-config", "yaml", "yml")

internal/cli/config/connection.go

@@ -23,6 +23,8 @@ type MachineConnection struct {
 	// TCP is the address and port of the machine's API server.
 	// The pointer is used to omit the field when not set. Otherwise, yaml marshalling includes an empty object.
 	TCP *netip.AddrPort `yaml:"tcp,omitempty"`
+	// Unix is the path to the machine's API unix socket.
+	Unix      string        `yaml:"unix,omitempty"`
 	Host      string        `yaml:"host,omitempty"`
 	PublicKey secret.Secret `yaml:"public_key,omitempty"`
 	MachineID string        `yaml:"machine_id,omitempty"`
@@ -35,6 +37,8 @@ func (c MachineConnection) String() string {
 		return "ssh+cli://" + string(c.SSHCLI)
 	} else if c.TCP != nil && c.TCP.IsValid() {
 		return fmt.Sprintf("tcp://%s", c.TCP)
+	} else if c.Unix != "" {
+		return fmt.Sprintf("unix://%s", c.Unix)
 	}
 	return "unknown connection"
 }
@@ -50,12 +54,15 @@ func (c *MachineConnection) Validate() error {
 	if c.TCP != nil && c.TCP.IsValid() {
 		setCount++
 	}
+	if c.Unix != "" {
+		setCount++
+	}
 
 	if setCount == 0 {
-		return errors.New("no connection method specified (ssh, ssh_cli, or tcp required)")
+		return errors.New("no connection method specified (ssh, ssh_cli, tcp, or unix required)")
 	}
 	if setCount > 1 {
-		return errors.New("only one connection method allowed per connection (ssh, ssh_cli, or tcp)")
+		return errors.New("only one connection method allowed per connection (ssh, ssh_cli, tcp, or unix)")
 	}
 
 	return nil

internal/cli/config/connection_test.go

@@ -53,6 +53,13 @@ func TestMachineConnection_String(t *testing.T) {
 			},
 			want: "tcp://10.0.0.1:8080",
 		},
+		{
+			name: "unix connection",
+			conn: MachineConnection{
+				Unix: "/run/uncloud/uncloud.sock",
+			},
+			want: "unix:///run/uncloud/uncloud.sock",
+		},
 		{
 			name: "no connection",
 			conn: MachineConnection{},
@@ -112,6 +119,13 @@ func TestMachineConnection_Validate(t *testing.T) {
 			},
 			wantErr: false,
 		},
+		{
+			name: "unix only - valid",
+			conn: MachineConnection{
+				Unix: "/path/to/socket",
+			},
+			wantErr: false,
+		},
 		{
 			name:    "no connection method - error",
 			conn:    MachineConnection{},
@@ -127,6 +141,15 @@ func TestMachineConnection_Validate(t *testing.T) {
 			wantErr: true,
 			errMsg:  "only one connection method allowed",
 		},
+		{
+			name: "ssh and unix - error",
+			conn: MachineConnection{
+				SSH:  "user@host",
+				Unix: "/path/to/socket",
+			},
+			wantErr: true,
+			errMsg:  "only one connection method allowed",
+		},
 		{
 			name: "ssh and tcp - error",
 			conn: MachineConnection{

internal/cli/connect.go

@@ -73,6 +73,8 @@ func connectCluster(ctx context.Context, conn config.MachineConnection) (*client
 		useSSHCLI = true
 	} else if conn.TCP != nil && conn.TCP.IsValid() {
 		return client.New(ctx, connector.NewTCPConnector(*conn.TCP))
+	} else if conn.Unix != "" {
+		return client.New(ctx, connector.NewUnixConnector(conn.Unix))
 	} else {
 		return nil, errors.New("connection configuration is invalid")
 	}

pkg/client/connector/unix.go

@@ -0,0 +1,41 @@
+package connector
+
+import (
+	"context"
+	"fmt"
+
+	"golang.org/x/net/proxy"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+)
+
+// UnixConnector establishes a connection to the machine API through a unix domain socket.
+type UnixConnector struct {
+	socketPath string
+}
+
+func NewUnixConnector(socketPath string) *UnixConnector {
+	return &UnixConnector{socketPath: socketPath}
+}
+
+func (c *UnixConnector) Connect(_ context.Context) (*grpc.ClientConn, error) {
+	// gRPC uses "unix:path" syntax for unix sockets.
+	target := "unix:" + c.socketPath
+
+	conn, err := grpc.NewClient(
+		target,
+		grpc.WithTransportCredentials(insecure.NewCredentials()),
+	)
+	if err != nil {
+		return nil, fmt.Errorf("create machine API client: %w", err)
+	}
+	return conn, nil
+}
+
+func (c *UnixConnector) Dialer() (proxy.ContextDialer, error) {
+	return nil, fmt.Errorf("proxy connections are not supported over a unix connection")
+}
+
+func (c *UnixConnector) Close() error {
+	return nil
+}