diff --git a/pipe.go b/pipe.go index 806fd342..d99eedb6 100644 --- a/pipe.go +++ b/pipe.go @@ -15,7 +15,6 @@ import ( //sys connectNamedPipe(pipe syscall.Handle, o *syscall.Overlapped) (err error) = ConnectNamedPipe //sys createNamedPipe(name string, flags uint32, pipeMode uint32, maxInstances uint32, outSize uint32, inSize uint32, defaultTimeout uint32, sa *syscall.SecurityAttributes) (handle syscall.Handle, err error) [failretval==syscall.InvalidHandle] = CreateNamedPipeW //sys createFile(name string, access uint32, mode uint32, sa *syscall.SecurityAttributes, createmode uint32, attrs uint32, templatefile syscall.Handle) (handle syscall.Handle, err error) [failretval==syscall.InvalidHandle] = CreateFileW -//sys waitNamedPipe(name string, timeout uint32) (err error) = WaitNamedPipeW //sys getNamedPipeInfo(pipe syscall.Handle, flags *uint32, outSize *uint32, inSize *uint32, maxInstances *uint32) (err error) = GetNamedPipeInfo //sys getNamedPipeHandleState(pipe syscall.Handle, state *uint32, curInstances *uint32, maxCollectionCount *uint32, collectDataTimeout *uint32, userName *uint16, maxUserNameSize uint32) (err error) = GetNamedPipeHandleStateW //sys localAlloc(uFlags uint32, length uint32) (ptr uintptr) = LocalAlloc @@ -139,12 +138,14 @@ func (s pipeAddress) String() string { } // DialPipe connects to a named pipe by path, timing out if the connection -// takes longer than the specified duration. If timeout is nil, then the timeout -// is the default timeout established by the pipe server. +// takes longer than the specified duration. If timeout is nil, then we use +// a default timeout of 5 seconds. (We do not use WaitNamedPipe.) func DialPipe(path string, timeout *time.Duration) (net.Conn, error) { var absTimeout time.Time if timeout != nil { absTimeout = time.Now().Add(*timeout) + } else { + absTimeout = time.Now().Add(time.Second * 2) } var err error var h syscall.Handle @@ -153,22 +154,13 @@ func DialPipe(path string, timeout *time.Duration) (net.Conn, error) { if err != cERROR_PIPE_BUSY { break } - now := time.Now() - var ms uint32 - if absTimeout.IsZero() { - ms = cNMPWAIT_USE_DEFAULT_WAIT - } else if now.After(absTimeout) { - ms = cNMPWAIT_NOWAIT - } else { - ms = uint32(absTimeout.Sub(now).Nanoseconds() / 1000 / 1000) - } - err = waitNamedPipe(path, ms) - if err != nil { - if err == cERROR_SEM_TIMEOUT { - return nil, ErrTimeout - } - break + if time.Now().After(absTimeout) { + return nil, ErrTimeout } + + // Wait 10 msec and try again. This is a rather simplistic + // view, as we always try each 10 milliseconds. + time.Sleep(time.Millisecond * 10) } if err != nil { return nil, &os.PathError{Op: "open", Path: path, Err: err} @@ -349,13 +341,23 @@ func ListenPipe(path string, c *PipeConfig) (net.Listener, error) { if err != nil { return nil, err } - // Immediately open and then close a client handle so that the named pipe is - // created but not currently accepting connections. + // Create a client handle and connect it. This results in the pipe + // instance always existing, so that clients see ERROR_PIPE_BUSY + // rather than ERROR_FILE_NOT_FOUND. This ties the first instance + // up so that no other instances can be used. This would have been + // cleaner if the Win32 API matched CreateFile with ConnectNamedPipe + // instead of CreateNamedPipe. (Apparently created named pipes are + // considered to be in listening state regardless of whether any + // active calls to ConnectNamedPipe are outstanding.) h2, err := createFile(path, 0, 0, nil, syscall.OPEN_EXISTING, cSECURITY_SQOS_PRESENT|cSECURITY_ANONYMOUS, 0) if err != nil { syscall.Close(h) return nil, err } + // Close the client handle. The server side of the instance will + // still be busy, leading to ERROR_PIPE_BUSY instead of + // ERROR_NOT_FOUND, as long as we don't close the server handle, + // or disconnect the client with DisconnectNamedPipe. syscall.Close(h2) l := &win32PipeListener{ firstHandle: h,