per-test logfiles

The new --log-dir option creates a directory with one log file for every test
(plus main.log for the oft script). It takes precedence over the --log-file
option if both are specified.

The --log-append option and the ability to pass "-" or "stderr" to --log-file
have been removed.
diff --git a/src/python/oftest/__init__.py b/src/python/oftest/__init__.py
index 9199b1a..c78bb67 100644
--- a/src/python/oftest/__init__.py
+++ b/src/python/oftest/__init__.py
@@ -1,5 +1,7 @@
 '''Docstring to silence pylint; ignores --ignore option for __init__.py'''
 import sys
+import os
+import logging
 
 # Global config dictionary
 # Populated by oft.
@@ -8,3 +10,31 @@
 # Global DataPlane instance used by all tests.
 # Populated by oft.
 dataplane_instance = None
+
+def open_logfile(name):
+    """
+    (Re)open logfile
+
+    When using a log directory a new logfile is created for each test. The same
+    code is used to implement a single logfile in the absence of --log-dir.
+    """
+
+    _format = "%(asctime)s.%(msecs)03d  %(name)-10s: %(levelname)-8s: %(message)s"
+    _datefmt = "%H:%M:%S"
+
+    if config["log_dir"] != None:
+        filename = os.path.join(config["log_dir"], name) + ".log"
+    else:
+        filename = config["log_file"]
+
+    logger = logging.getLogger()
+
+    # Remove any existing handlers
+    for handler in logger.handlers:
+        logger.removeHandler(handler)
+        handler.close()
+
+    # Add a new handler
+    handler = logging.FileHandler(filename, mode='a')
+    handler.setFormatter(logging.Formatter(_format, _datefmt))
+    logger.addHandler(handler)
diff --git a/src/python/oftest/base_tests.py b/src/python/oftest/base_tests.py
index a1eec43..3b59bc1 100644
--- a/src/python/oftest/base_tests.py
+++ b/src/python/oftest/base_tests.py
@@ -14,13 +14,25 @@
 import oftest.dataplane as dataplane
 import ofp
 
-class SimpleProtocol(unittest.TestCase):
+class BaseTest(unittest.TestCase):
+    def __str__(self):
+        return self.id().replace('.runTest', '')
+
+    def setUp(self):
+        oftest.open_logfile(str(self))
+        logging.info("** START TEST CASE " + str(self))
+
+    def tearDown(self):
+        logging.info("** END TEST CASE " + str(self))
+
+class SimpleProtocol(BaseTest):
     """
     Root class for setting up the controller
     """
 
     def setUp(self):
-        logging.info("** START TEST CASE " + str(self))
+        BaseTest.setUp(self)
+
         self.controller = controller.Controller(
             switch=config["switch_ip"],
             host=config["controller_host"],
@@ -73,10 +85,10 @@
         self.supported_actions = parent.supported_actions
         
     def tearDown(self):
-        logging.info("** END TEST CASE " + str(self))
         self.controller.shutdown()
         self.controller.join()
         del self.controller
+        BaseTest.tearDown(self)
 
     def assertTrue(self, cond, msg):
         if not cond:
@@ -102,20 +114,17 @@
         self.dataplane = parent.dataplane
 
     def tearDown(self):
-        logging.info("Teardown for simple dataplane test")
         SimpleProtocol.tearDown(self)
-        logging.info("Teardown done")
 
-class DataPlaneOnly(unittest.TestCase):
+class DataPlaneOnly(BaseTest):
     """
     Root class that sets up only the dataplane
     """
 
     def setUp(self):
-        logging.info("** START DataPlaneOnly CASE " + str(self))
+        BaseTest.setUp(self)
         self.dataplane = oftest.dataplane_instance
         self.dataplane.flush()
 
     def tearDown(self):
-        logging.info("Teardown for simple dataplane test")
-        logging.info("Teardown done")
+        BaseTest.tearDown(self)