skytools.sockutil: separate module for low-level socket stuff

Move set_tcp_keepalive() here, plus set_nonblocking() and
set_cloexec().

1 files changed, 131 insertions, 0 deletions

diff --git a/python/skytools/sockutil.py b/python/skytools/sockutil.py
new file mode 100644
index 00000000..f950f5a0
--- /dev/null
+++ b/python/skytools/sockutil.py
@@ -0,0 +1,131 @@
+"""Various low-level utility functions for sockets."""
+
+__all__ = ['set_tcp_keepalive', 'set_nonblocking', 'set_cloexec']
+
+import sys
+import os
+import socket
+
+try:
+    import fcntl
+except ImportError:
+    pass
+
+__all__ = ['set_tcp_keepalive', 'set_nonblocking', 'set_cloexec']
+
+def set_tcp_keepalive(fd, keepalive = True,
+                     tcp_keepidle = 4 * 60,
+                     tcp_keepcnt = 4,
+                     tcp_keepintvl = 15):
+    """Turn on TCP keepalive.  The fd can be either numeric or socket
+    object with 'fileno' method.
+
+    OS defaults for SO_KEEPALIVE=1:
+     - Linux: (7200, 9, 75) - can configure all.
+     - MacOS: (7200, 8, 75) - can configure only tcp_keepidle.
+     - Win32: (7200, 5|10, 1) - can configure tcp_keepidle and tcp_keepintvl.
+       Python needs SIO_KEEPALIVE_VALS support in socket.ioctl to enable it.
+
+    Our defaults: (240, 4, 15).
+
+    >>> import socket
+    >>> s = socket.socket()
+    >>> set_tcp_keepalive(s)
+    """
+
+    # usable on this OS?
+    if not hasattr(socket, 'SO_KEEPALIVE') or not hasattr(socket, 'fromfd'):
+        return
+
+    # get numeric fd and cast to socket
+    if hasattr(fd, 'fileno'):
+        fd = fd.fileno()
+    s = socket.fromfd(fd, socket.AF_INET, socket.SOCK_STREAM)
+
+    # skip if unix socket
+    if type(s.getsockname()) != type(()):
+        return
+
+    # turn on keepalive on the connection
+    if keepalive:
+        s.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
+        if hasattr(socket, 'TCP_KEEPCNT'):
+            s.setsockopt(socket.IPPROTO_TCP, getattr(socket, 'TCP_KEEPIDLE'), tcp_keepidle)
+            s.setsockopt(socket.IPPROTO_TCP, getattr(socket, 'TCP_KEEPCNT'), tcp_keepcnt)
+            s.setsockopt(socket.IPPROTO_TCP, getattr(socket, 'TCP_KEEPINTVL'), tcp_keepintvl)
+        elif hasattr(socket, 'TCP_KEEPALIVE'):
+            s.setsockopt(socket.IPPROTO_TCP, getattr(socket, 'TCP_KEEPALIVE'), tcp_keepidle)
+        elif sys.platform == 'darwin':
+            TCP_KEEPALIVE = 0x10
+            s.setsockopt(socket.IPPROTO_TCP, TCP_KEEPALIVE, tcp_keepidle)
+        elif sys.platform == 'win32':
+            #s.ioctl(SIO_KEEPALIVE_VALS, (1, tcp_keepidle*1000, tcp_keepintvl*1000))
+            pass
+    else:
+        s.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 0)
+
+
+def set_nonblocking(fd, onoff=True):
+    """Toggle the O_NONBLOCK flag.
+
+    If onoff==None then return current setting.
+
+    Actual sockets from 'socket' module should use .setblocking() method,
+    this is for situations where it is not available.  Eg. pipes
+    from 'subprocess' module.
+
+    >>> import socket
+    >>> s = socket.socket()
+    >>> set_nonblocking(s, None)
+    False
+    >>> set_nonblocking(s, 1)
+    >>> set_nonblocking(s, None)
+    True
+    """
+
+    flags = fcntl.fcntl(fd, fcntl.F_GETFL)
+    if onoff is None:
+        return (flags & os.O_NONBLOCK) > 0
+    if onoff:
+        flags |= os.O_NONBLOCK
+    else:
+        flags &= ~os.O_NONBLOCK
+    fcntl.fcntl(fd, fcntl.F_SETFL, flags)
+
+def set_cloexec(fd, onoff=True):
+    """Toggle the FD_CLOEXEC flag.
+
+    If onoff==None then return current setting.
+
+    Some libraries do it automatically (eg. libpq).
+    Others do not (Python stdlib).
+
+    >>> import os
+    >>> f = open(os.devnull, 'rb')
+    >>> set_cloexec(f, None)
+    False
+    >>> set_cloexec(f, True)
+    >>> set_cloexec(f, None)
+    True
+    >>> import socket
+    >>> s = socket.socket()
+    >>> set_cloexec(s, None)
+    False
+    >>> set_cloexec(s)
+    >>> set_cloexec(s, None)
+    True
+    """
+
+    flags = fcntl.fcntl(fd, fcntl.F_GETFD)
+    if onoff is None:
+        return (flags & fcntl.FD_CLOEXEC) > 0
+    if onoff:
+        flags |= fcntl.FD_CLOEXEC
+    else:
+        flags &= ~fcntl.FD_CLOEXEC
+    fcntl.fcntl(fd, fcntl.F_SETFD, flags)
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()
+