dial: add the ability to connect via socket fd

This patch introduces `FdDialer`, which connects to Tarantool
using an existing socket file descriptor.

`FdDialer` is not authenticated when creating a connection.

Closes #321

.gitignore

@@ -4,3 +4,4 @@
 work_dir*
 .rocks
 bench*
+testdata/sidecar

dial.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"os"
 	"strings"
 	"time"
 
@@ -267,6 +268,61 @@ func (d OpenSslDialer) Dial(ctx context.Context, opts DialOpts) (Conn, error) {
 	return conn, nil
 }
 
+type FdDialer struct {
+	// Fd is a socket file descrpitor.
+	Fd uintptr
+	// RequiredProtocol contains minimal protocol version and
+	// list of protocol features that should be supported by
+	// Tarantool server. By default, there are no restrictions.
+	RequiredProtocolInfo ProtocolInfo
+}
+
+type fdAddr struct {
+	fd uintptr
+}
+
+func (a fdAddr) Network() string {
+	return "fd"
+}
+
+func (a fdAddr) String() string {
+	return fmt.Sprintf("fd://%d", a.fd)
+}
+
+type fdConn struct {
+	fd uintptr
+	net.Conn
+}
+
+func (c *fdConn) LocalAddr() net.Addr {
+	return fdAddr{fd: c.fd}
+}
+
+// Dial makes FdDialer satisfy the Dialer interface.
+func (d FdDialer) Dial(ctx context.Context, opts DialOpts) (Conn, error) {
+	file := os.NewFile(d.Fd, "")
+	c, err := net.FileConn(file)
+	if err != nil {
+		return nil, fmt.Errorf("failed to dial: %w", err)
+	}
+
+	conn := new(tntConn)
+	conn.isLocal = true
+	conn.net = &fdConn{fd: d.Fd, Conn: c}
+
+	dc := &deadlineIO{to: opts.IoTimeout, c: conn.net}
+	conn.reader = bufio.NewReaderSize(dc, bufSize)
+	conn.writer = bufio.NewWriterSize(dc, bufSize)
+
+	_, err = rawDial(conn, d.RequiredProtocolInfo)
+	if err != nil {
+		conn.net.Close()
+		return nil, err
+	}
+
+	return conn, nil
+}
+
 // Addr makes tntConn satisfy the Conn interface.
 func (c *tntConn) Addr() net.Addr {
 	if c.isLocal {

dial_test.go

@@ -425,10 +425,11 @@ func assertRequest(t *testing.T, r io.Reader, expected []byte) {
 }
 
 type testDialOpts struct {
-	errGreeting   bool
-	errId         bool
-	errAuth       bool
-	idUnsupported bool
+	errGreeting    bool
+	errId          bool
+	errAuth        bool
+	idUnsupported  bool
+	authNoRequired bool
 }
 
 func testDialAccept(t *testing.T, ch chan struct{}, opts testDialOpts, l net.Listener) {
@@ -458,6 +459,9 @@ func testDialAccept(t *testing.T, ch chan struct{}, opts testDialOpts, l net.Lis
 		client.Write(idResponse)
 	}
 
+	if opts.authNoRequired {
+		return
+	}
 	// Check Auth request.
 	assertRequest(t, client, authRequestExpected)
 	if opts.errAuth {
@@ -566,3 +570,47 @@ func TestOpenSslDialer_Dial(t *testing.T) {
 		testDialer(t, l, dialer)
 	}
 }
+
+func TestFdDialer_Dial(t *testing.T) {
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	require.NoError(t, err)
+	addr := l.Addr().String()
+
+	for _, cs := range testDialCases {
+		opts := cs.opts
+		if opts.errAuth {
+			// No need to test FdDialer for auth errors.
+			continue
+		}
+		// FdDialer doesn't make auth requests.
+		opts.authNoRequired = true
+
+		t.Run(cs.name, func(t *testing.T) {
+			ch := make(chan struct{})
+			go testDialAccept(t, ch, opts, l)
+
+			sock, err := net.Dial("tcp", addr)
+			require.NoError(t, err)
+			f, err := sock.(*net.TCPConn).File()
+			require.NoError(t, err)
+
+			dialer := tarantool.FdDialer{
+				Fd: f.Fd(),
+			}
+			ctx, cancel := test_helpers.GetConnectContext()
+			defer cancel()
+			conn, err := dialer.Dial(ctx, tarantool.DialOpts{
+				IoTimeout: time.Second * 2,
+			})
+			<-ch
+			if cs.wantErr {
+				require.Error(t, err)
+				return
+			}
+			require.NoError(t, err)
+			require.Equal(t, cs.protocolInfo, conn.ProtocolInfo())
+			require.Equal(t, cs.version, []byte(conn.Greeting().Version))
+			conn.Close()
+		})
+	}
+}

example_test.go

@@ -3,6 +3,7 @@ package tarantool_test
 import (
 	"context"
 	"fmt"
+	"net"
 	"time"
 
 	"github.com/tarantool/go-iproto"
@@ -1337,3 +1338,33 @@ func ExampleWatchOnceRequest() {
 		fmt.Println(resp.Data)
 	}
 }
+
+// This example demonstrates how to use an existing socket file descriptor
+// to establish a connection with Tarantool. This can be useful if the socket fd
+// was inherited from the Tarantool process itself.
+// For details, please see TestFdDialer.
+func ExampleFdDialer() {
+	addr := dialer.Address
+	c, err := net.Dial("tcp", addr)
+	if err != nil {
+		fmt.Printf("can't establish connection: %v\n", err)
+		return
+	}
+	f, err := c.(*net.TCPConn).File()
+	if err != nil {
+		fmt.Printf("unexpected error: %v\n", err)
+	}
+	dialer := tarantool.FdDialer{
+		Fd: f.Fd(),
+	}
+	// Use an existing socket fd to create connection with Tarantool.
+	conn, err := tarantool.Connect(context.Background(), dialer, opts)
+	if err != nil {
+		fmt.Printf("connect error: %v\n", err)
+		return
+	}
+	resp, err := conn.Do(tarantool.NewPingRequest()).Get()
+	fmt.Println(resp.Code, err)
+	// Output:
+	// 0 <nil>
+}

tarantool_test.go

@@ -8,6 +8,8 @@ import (
 	"log"
 	"math"
 	"os"
+	"os/exec"
+	"path/filepath"
 	"reflect"
 	"runtime"
 	"strings"
@@ -76,6 +78,7 @@ func (m *Member) DecodeMsgpack(d *msgpack.Decoder) error {
 }
 
 var server = "127.0.0.1:3013"
+var fdDialerTestServer = "127.0.0.1:3014"
 var spaceNo = uint32(617)
 var spaceName = "test"
 var indexNo = uint32(0)
@@ -3950,6 +3953,85 @@ func TestConnect_context_cancel(t *testing.T) {
 	}
 }
 
+func buildSidecar(dir string) error {
+	goPath, err := exec.LookPath("go")
+	if err != nil {
+		return err
+	}
+	cmd := exec.Command(goPath, "build", "sidecar.go")
+	cmd.Dir = filepath.Join(dir, "testdata")
+	return cmd.Run()
+}
+
+func TestFdDialer(t *testing.T) {
+	isLess, err := test_helpers.IsTarantoolVersionLess(3, 0, 0)
+	if err != nil || isLess {
+		t.Skip("box.session.new present in Tarantool since version 3.0")
+	}
+
+	wd, err := os.Getwd()
+	require.NoError(t, err)
+
+	err = buildSidecar(wd)
+	require.NoErrorf(t, err, "failed to build sidecar: %v", err)
+
+	instOpts := startOpts
+	instOpts.Listen = fdDialerTestServer
+	inst, err := test_helpers.StartTarantool(instOpts, TtDialer{
+		Address:  fdDialerTestServer,
+		User:     "test",
+		Password: "test",
+	})
+	require.NoError(t, err)
+	defer test_helpers.StopTarantoolWithCleanup(inst)
+
+	conn := test_helpers.ConnectWithValidation(t, dialer, opts)
+	defer conn.Close()
+
+	sidecarExe := filepath.Join(wd, "testdata", "sidecar")
+
+	evalBody := fmt.Sprintf(`
+		local socket = require('socket')
+		local popen = require('popen')
+		local os = require('os')
+		local s1, s2 = socket.socketpair('AF_UNIX', 'SOCK_STREAM', 0)
+
+		--[[ Tell sidecar which fd use to connect. --]]
+		os.setenv('SOCKET_FD', tostring(s2:fd()))
+
+		box.session.new({
+			type = 'binary',
+			fd = s1:fd(),
+			user = 'test',
+		})
+		s1:detach()
+
+		local ph, err = popen.new({'%s'}, {
+			stdout = popen.opts.PIPE,
+			stderr = popen.opts.PIPE,
+			inherit_fds = {s2:fd()},
+		})
+
+		if err ~= nil then
+			return 1, err
+		end
+
+		ph:wait()
+
+		local status_code = ph:info().status.exit_code
+		local stderr = ph:read({stderr=true}):rstrip()
+		local stdout = ph:read({stdout=true}):rstrip()
+		return status_code, stderr, stdout
+	`, sidecarExe)
+
+	var resp []interface{}
+	err = conn.EvalTyped(evalBody, []interface{}{}, &resp)
+	require.NoError(t, err)
+	require.Equal(t, "", resp[1], resp[1])
+	require.Equal(t, "", resp[2], resp[2])
+	require.Equal(t, int8(0), resp[0])
+}
+
 // runTestMain is a body of TestMain function
 // (see https://pkg.go.dev/testing#hdr-Main).
 // Using defer + os.Exit is not works so TestMain body

testdata/sidecar.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"context"
+	"os"
+	"strconv"
+
+	"github.com/tarantool/go-tarantool/v2"
+)
+
+func main() {
+	fd, err := strconv.Atoi(os.Getenv("SOCKET_FD"))
+	if err != nil {
+		panic(err)
+	}
+	dialer := tarantool.FdDialer{
+		Fd: uintptr(fd),
+	}
+	conn, err := tarantool.Connect(context.Background(), dialer, tarantool.Opts{})
+	if err != nil {
+		panic(err)
+	}
+	if _, err := conn.Do(tarantool.NewPingRequest()).
+		Get(); err != nil {
+		panic(err)
+	}
+	// Insert new tuple.
+	if _, err := conn.Do(tarantool.NewInsertRequest("test").
+		Tuple([]interface{}{239})).Get(); err != nil {
+		panic(err)
+	}
+	// Delete inserted tuple.
+	if _, err := conn.Do(tarantool.NewDeleteRequest("test").
+		Index("primary").
+		Key([]interface{}{239})).Get(); err != nil {
+		panic(err)
+	}
+}