Minor bug fixes in gofer's BindAt mechanism.

- Allow lisafs client to open socket FDs. BindAt is now supported. So
  opening sockets over a connection should also be supported.
- Initialize socket's node with its name. Earlier, we were using the
  entire host path to init node's name.
- vfs.MknodOptions.Endpoint can be a connectionless endpoint, which does not
  implement transport.HostBoundEndpoint. In such a case, fallback to synthetic
  sockets.

PiperOrigin-RevId: 477212574

pkg/lisafs/handlers.go

@@ -524,7 +524,7 @@ func OpenAtHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32,
 		hostOpenFD int
 	)
 	if err := fd.safelyRead(func() error {
-		if fd.node.isDeleted() || !p9.CanOpen(p9.FileMode(fd.ftype)) {
+		if fd.node.isDeleted() || fd.IsSymlink() {
 			return unix.EINVAL
 		}
 		openFD, hostOpenFD, err = fd.impl.Open(req.Flags)

pkg/sentry/fsimpl/gofer/gofer.go

@@ -1628,7 +1628,7 @@ func (d *dentry) setStat(ctx context.Context, creds *auth.Credentials, opts *vfs
 // - d.isDir().
 // - fs.opts.lisaEnabled.
 func (d *dentry) mknodLisaLocked(ctx context.Context, name string, creds *auth.Credentials, opts vfs.MknodOptions, ds **[]*dentry) error {
-	if opts.Endpoint == nil {
+	if _, ok := opts.Endpoint.(transport.HostBoundEndpoint); !ok {
 		childInode, err := d.controlFDLisa.MknodAt(ctx, name, opts.Mode, lisafs.UID(creds.EffectiveKUID), lisafs.GID(creds.EffectiveKGID), opts.DevMinor, opts.DevMajor)
 		if err != nil {
 			return err

runsc/fsgofer/lisafs.go

@@ -756,7 +756,7 @@ func (fd *controlFDLisa) BindAt(name string, sockType uint32, mode linux.FileMod
 	}
 	cu.Release()
 
-	socketControlFD := newControlFDLisa(sockFD, fd, socketPath, linux.ModeSocket)
+	socketControlFD := newControlFDLisa(sockFD, fd, name, linux.ModeSocket)
 	boundSocketFD := &boundSocketFDLisa{
 		sock: os.NewFile(uintptr(sockFD), socketPath),
 	}