Add utility library to do port forwarding

This will be useful for creating forwarding for
users.

confluent_server/confluent/forwarder.py

@@ -0,0 +1,78 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2017 Lenovo
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+#This handles port forwarding for web interfaces on management devices
+#It will also hijack port 3900 and do best effort..
+
+import eventlet
+import eventlet.green.select as select
+import eventlet.green.socket as socket
+forwarders = {}
+sockhandler = {}
+vidtarget = None
+vidforwarder = None
+
+def handle_connection(incoming, outgoing):
+    while True:
+        r, _, _ = select.select((incoming, outgoing), (), (), 60)
+        for mysock in r:
+            data = mysock.recv(32768)
+            if not data:
+                return
+            if mysock == incoming:
+                outgoing.sendall(data)
+            elif mysock == outgoing:
+                incoming.sendall(data)
+
+
+def forward_port(sock, target):
+    while True:
+        conn, _ = sock.accept()
+        try:
+            client = socket.create_connection((target, 443))
+        except Exception:
+            conn.close()
+            continue
+        eventlet.spawn_n(handle_connection, conn, client)
+
+
+def forward_video():
+    sock = eventlet.listen(('localhost', 3900, 0, 0), family=socket.AF_INET6)
+    while True:
+        conn, _ = sock.accept()
+        if vidtarget is None:
+            conn.close()
+            continue
+        try:
+            vidclient = socket.create_connection((vidtarget, 3900))
+        except Exception:
+            conn.close()
+            continue
+        eventlet.spawn_n(handle_connection, conn, vidclient)
+
+def get_port(addr):
+    global vidtarget
+    global vidforwarder
+    if addr not in forwarders:
+        newsock = eventlet.listen(('localhost', 0, 0, 0),
+                  family=socket.AF_INET6)
+        forwarders[addr] = newsock
+        sockhandler[newsock] = eventlet.spawn(forward_port, newsock, addr)
+        if not vidforwarder:
+            vidforwarder = eventlet.spawn(forward_video)
+    vidtarget = addr
+    return forwarders[addr].getsockname()[1]
+