Implement AF_UNIX sockets on Windows

See moby/moby#36442

Signed-off-by: Marat Radchenko <[email protected]>

sockets/sockets.go

@@ -2,13 +2,19 @@
 package sockets
 
 import (
+	"context"
 	"errors"
+	"fmt"
 	"net"
 	"net/http"
+	"syscall"
 	"time"
 )
 
-const defaultTimeout = 10 * time.Second
+const (
+	defaultTimeout        = 10 * time.Second
+	maxUnixSocketPathSize = len(syscall.RawSockaddrUnix{}.Path)
+)
 
 // ErrProtocolNotAvailable is returned when a given transport protocol is not provided by the operating system.
 var ErrProtocolNotAvailable = errors.New("protocol not available")
@@ -35,3 +41,18 @@ func ConfigureTransport(tr *http.Transport, proto, addr string) error {
 	}
 	return nil
 }
+
+func configureUnixTransport(tr *http.Transport, proto, addr string) error {
+	if len(addr) > maxUnixSocketPathSize {
+		return fmt.Errorf("Unix socket path %q is too long", addr)
+	}
+	// No need for compression in local communications.
+	tr.DisableCompression = true
+	dialer := &net.Dialer{
+		Timeout: defaultTimeout,
+	}
+	tr.DialContext = func(ctx context.Context, _, _ string) (net.Conn, error) {
+		return dialer.DialContext(ctx, proto, addr)
+	}
+	return nil
+}

sockets/sockets_unix.go

@@ -3,31 +3,12 @@
 package sockets
 
 import (
-	"context"
-	"fmt"
 	"net"
 	"net/http"
 	"syscall"
 	"time"
 )
 
-const maxUnixSocketPathSize = len(syscall.RawSockaddrUnix{}.Path)
-
-func configureUnixTransport(tr *http.Transport, proto, addr string) error {
-	if len(addr) > maxUnixSocketPathSize {
-		return fmt.Errorf("unix socket path %q is too long", addr)
-	}
-	// No need for compression in local communications.
-	tr.DisableCompression = true
-	dialer := &net.Dialer{
-		Timeout: defaultTimeout,
-	}
-	tr.DialContext = func(ctx context.Context, _, _ string) (net.Conn, error) {
-		return dialer.DialContext(ctx, proto, addr)
-	}
-	return nil
-}
-
 func configureNpipeTransport(tr *http.Transport, proto, addr string) error {
 	return ErrProtocolNotAvailable
 }

sockets/sockets_windows.go

@@ -9,10 +9,6 @@ import (
 	"github.com/Microsoft/go-winio"
 )
 
-func configureUnixTransport(tr *http.Transport, proto, addr string) error {
-	return ErrProtocolNotAvailable
-}
-
 func configureNpipeTransport(tr *http.Transport, proto, addr string) error {
 	// No need for compression in local communications.
 	tr.DisableCompression = true

sockets/unix_socket.go

@@ -1,5 +1,3 @@
-//go:build !windows
-
 /*
 Package sockets is a simple unix domain socket wrapper.
 
@@ -90,22 +88,7 @@ func NewUnixSocketWithOpts(path string, opts ...SockOption) (net.Listener, error
 		return nil, err
 	}
 
-	// net.Listen does not allow for permissions to be set. As a result, when
-	// specifying custom permissions ("WithChmod()"), there is a short time
-	// between creating the socket and applying the permissions, during which
-	// the socket permissions are Less restrictive than desired.
-	//
-	// To work around this limitation of net.Listen(), we temporarily set the
-	// umask to 0777, which forces the socket to be created with 000 permissions
-	// (i.e.: no access for anyone). After that, WithChmod() must be used to set
-	// the desired permissions.
-	//
-	// We don't use "defer" here, to reset the umask to its original value as soon
-	// as possible. Ideally we'd be able to detect if WithChmod() was passed as
-	// an option, and skip changing umask if default permissions are used.
-	origUmask := syscall.Umask(0o777)
-	l, err := net.Listen("unix", path)
-	syscall.Umask(origUmask)
+	l, err := listenUnix(path)
 	if err != nil {
 		return nil, err
 	}

sockets/unix_socket_test.go

@@ -1,12 +1,9 @@
-//go:build !windows
-
 package sockets
 
 import (
 	"fmt"
 	"net"
 	"os"
-	"syscall"
 	"testing"
 )
 
@@ -52,26 +49,16 @@ func TestNewUnixSocket(t *testing.T) {
 }
 
 func TestUnixSocketWithOpts(t *testing.T) {
-	uid, gid := os.Getuid(), os.Getgid()
-	perms := os.FileMode(0o660)
-	path := "/tmp/test.sock"
-	echoStr := "hello"
-	l, err := NewUnixSocketWithOpts(path, WithChown(uid, gid), WithChmod(perms))
+	socketFile, err := os.CreateTemp("", "test*.sock")
 	if err != nil {
 		t.Fatal(err)
 	}
+	socketFile.Close()
+	defer os.Remove(socketFile.Name())
+
+	l := createTestUnixSocket(t, socketFile.Name())
 	defer l.Close()
-	p, err := os.Stat(path)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if p.Mode().Perm() != perms {
-		t.Fatalf("unexpected file permissions: expected: %#o, got: %#o", perms, p.Mode().Perm())
-	}
-	if stat, ok := p.Sys().(*syscall.Stat_t); ok {
-		if stat.Uid != uint32(uid) || stat.Gid != uint32(gid) {
-			t.Fatalf("unexpected file ownership: expected: %d:%d, got: %d:%d", uid, gid, stat.Uid, stat.Gid)
-		}
-	}
-	runTest(t, path, l, echoStr)
+
+	echoStr := "hello"
+	runTest(t, socketFile.Name(), l, echoStr)
 }

sockets/unix_socket_test_unix.go

@@ -0,0 +1,32 @@
+//go:build !windows
+
+package sockets
+
+import (
+	"net"
+	"os"
+	"syscall"
+	"testing"
+)
+
+func createTestUnixSocket(t *testing.T, path string) (listener net.Listener) {
+	uid, gid := os.Getuid(), os.Getgid()
+	perms := os.FileMode(0660)
+	l, err := NewUnixSocketWithOpts(path, WithChown(uid, gid), WithChmod(perms))
+	if err != nil {
+		t.Fatal(err)
+	}
+	p, err := os.Stat(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if p.Mode().Perm() != perms {
+		t.Fatalf("unexpected file permissions: expected: %#o, got: %#o", perms, p.Mode().Perm())
+	}
+	if stat, ok := p.Sys().(*syscall.Stat_t); ok {
+		if stat.Uid != uint32(uid) || stat.Gid != uint32(gid) {
+			t.Fatalf("unexpected file ownership: expected: %d:%d, got: %d:%d", uid, gid, stat.Uid, stat.Gid)
+		}
+	}
+	return l
+}

sockets/unix_socket_test_windows.go

@@ -0,0 +1,14 @@
+package sockets
+
+import (
+	"net"
+	"testing"
+)
+
+func createTestUnixSocket(t *testing.T, path string) (listener net.Listener) {
+	l, err := NewUnixSocketWithOpts(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return l
+}

sockets/unix_socket_unix.go

@@ -0,0 +1,28 @@
+//go:build !windows
+
+package sockets
+
+import (
+	"net"
+	"syscall"
+)
+
+func listenUnix(path string) (net.Listener, error) {
+	// net.Listen does not allow for permissions to be set. As a result, when
+	// specifying custom permissions ("WithChmod()"), there is a short time
+	// between creating the socket and applying the permissions, during which
+	// the socket permissions are Less restrictive than desired.
+	//
+	// To work around this limitation of net.Listen(), we temporarily set the
+	// umask to 0777, which forces the socket to be created with 000 permissions
+	// (i.e.: no access for anyone). After that, WithChmod() must be used to set
+	// the desired permissions.
+	//
+	// We don't use "defer" here, to reset the umask to its original value as soon
+	// as possible. Ideally we'd be able to detect if WithChmod() was passed as
+	// an option, and skip changing umask if default permissions are used.
+	origUmask := syscall.Umask(0o777)
+	l, err := net.Listen("unix", path)
+	syscall.Umask(origUmask)
+	return l, err
+}

sockets/unix_socket_windows.go

@@ -0,0 +1,7 @@
+package sockets
+
+import "net"
+
+func listenUnix(path string) (net.Listener, error) {
+	return net.Listen("unix", path)
+}