coredevice: simplify/cleanup network connection code

This removes:
* host-side keepalive, which turns out not to be required
* custom connection timeout (the default is OK)
* SSH tunneling support (doesn't seem to be actually used anywhere)

artiq/coredevice/comm.py

@@ -1,37 +0,0 @@
-import sys
-import socket
-import logging
-
-
-logger = logging.getLogger(__name__)
-
-
-def set_keepalive(sock, after_idle, interval, max_fails):
-    if sys.platform.startswith("linux"):
-        sock.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
-        sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPIDLE, after_idle)
-        sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPINTVL, interval)
-        sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPCNT, max_fails)
-    elif sys.platform.startswith("win") or sys.platform.startswith("cygwin"):
-        # setting max_fails is not supported, typically ends up being 5 or 10
-        # depending on Windows version
-        sock.ioctl(socket.SIO_KEEPALIVE_VALS,
-                   (1, after_idle*1000, interval*1000))
-    else:
-        logger.warning("TCP keepalive not supported on platform '%s', ignored",
-                       sys.platform)
-
-
-def initialize_connection(host, port, ssh_transport=None):
-    if ssh_transport is None:
-        sock = socket.create_connection((host, port), 5.0)
-        sock.settimeout(None)
-        set_keepalive(sock, 3, 2, 3)
-        logger.debug("connected to %s:%d", host, port)
-    else:
-        sock = ssh_transport.open_channel("direct-tcpip", (host, port),
-                                          ("localhost", 9999), timeout=5.0)
-        ssh_transport.set_keepalive(2)
-        logger.debug("connected to %s:%d via SSH transport to %s:%d",
-                     host, port, *ssh_transport.getpeername())
-    return sock

artiq/coredevice/comm_kernel.py

@@ -2,12 +2,12 @@ import struct
 import logging
 import traceback
 import numpy
+import socket
 from enum import Enum
 from fractions import Fraction
 from collections import namedtuple
 
 from artiq.coredevice import exceptions
-from artiq.coredevice.comm import initialize_connection
 from artiq import __version__ as software_version
 
 
@@ -78,10 +78,11 @@ class CommKernel:
         self.host = host
         self.port = port
 
-    def open(self, **kwargs):
+    def open(self):
         if hasattr(self, "socket"):
             return
-        self.socket = initialize_connection(self.host, self.port, **kwargs)
+        self.socket = socket.create_connection((self.host, self.port))
+        logger.debug("connected to %s:%d", self.host, self.port)
         self.socket.sendall(b"ARTIQ coredev\n")
 
     def close(self):

artiq/coredevice/comm_mgmt.py

@@ -3,8 +3,6 @@ import logging
 import socket
 import struct
 
-from artiq.coredevice.comm import initialize_connection
-
 
 logger = logging.getLogger(__name__)
 
@@ -59,10 +57,11 @@ class CommMgmt:
         self.host = host
         self.port = port
 
-    def open(self, **kwargs):
+    def open(self):
         if hasattr(self, "socket"):
             return
-        self.socket = initialize_connection(self.host, self.port, **kwargs)
+        self.socket = socket.create_connection((self.host, self.port))
+        logger.debug("connected to %s:%d", self.host, self.port)
         self.socket.sendall(b"ARTIQ management\n")
 
     def close(self):