issue ansible#319: have cfsetraw() generate sensible flags.

Attempting to fix issue on WSL.

Closes ansible#71

mitogen/parent.py

@@ -102,26 +102,23 @@ def is_immediate_child(msg, stream):
 def flags(names):
     """Return the result of ORing a set of (space separated) :py:mod:`termios`
     module constants together."""
-    return sum(getattr(termios, name) for name in names.split())
+    return sum(getattr(termios, name, 0)
+               for name in names.split())
 
 
 def cfmakeraw(tflags):
     """Given a list returned by :py:func:`termios.tcgetattr`, return a list
-    that has been modified in the same manner as the `cfmakeraw()` C library
-    function."""
+    modified in a manner similar to the `cfmakeraw()` C library function, but
+    additionally disabling local echo."""
+    # BSD: https://github.com/freebsd/freebsd/blob/master/lib/libc/gen/termios.c#L162
+    # Linux: https://github.com/lattera/glibc/blob/master/termios/cfmakeraw.c#L20
     iflag, oflag, cflag, lflag, ispeed, ospeed, cc = tflags
-    iflag &= ~flags('IGNBRK BRKINT PARMRK ISTRIP INLCR IGNCR ICRNL IXON')
-    oflag &= ~flags('OPOST IXOFF')
-    lflag &= ~flags('ECHO ECHOE ECHONL ICANON ISIG IEXTEN')
+    iflag &= ~flags('IMAXBEL IXOFF INPCK BRKINT PARMRK ISTRIP INLCR ICRNL IXON IGNPAR')
+    iflag &= ~flags('IGNBRK BRKINT PARMRK')
+    oflag &= ~flags('OPOST')
+    lflag &= ~flags('ECHO ECHOE ECHOK ECHONL ICANON ISIG IEXTEN NOFLSH TOSTOP PENDIN')
     cflag &= ~flags('CSIZE PARENB')
-    cflag |= flags('CS8')
-
-    # TODO: one or more of the above bit twiddles sets or omits a necessary
-    # flag. Forcing these fields to zero, as shown below, gets us what we want
-    # on Linux/OS X, but it is possibly broken on some other OS.
-    iflag = 0
-    oflag = 0
-    lflag = 0
+    cflag |= flags('CS8 CREAD')
     return [iflag, oflag, cflag, lflag, ispeed, ospeed, cc]