Only match FIFOs by name, not everything

Before this change we over-estimated IPC connectivity on Linux (at least) by
blindly assuming that everything named the same with opposing access was an IPC
channel.

With this change in place we only do that for FIFOs, which is how the comments
in the code say things should work.

px/px_ipc_map.py

@@ -59,7 +59,7 @@ def _create_indices(self):
         self._plain_name_to_pids = {}
         self._name_to_files = {}
         self._device_number_to_files = {}
-        self._name_and_access_to_pids = {}
+        self._fifo_name_and_access_to_pids = {}
         for file in self.files:
             if file.device is not None:
                 add_arraymapping(self._device_to_pids, file.device, file.pid)
@@ -71,8 +71,9 @@ def _create_indices(self):
             if file.device_number is not None:
                 add_arraymapping(self._device_number_to_files, file.device_number, file)
 
-            if file.access is not None:
-                add_arraymapping(self._name_and_access_to_pids, file.name + file.access, file.pid)
+            if file.access is not None and file.type == 'FIFO':
+                add_arraymapping(self._fifo_name_and_access_to_pids,
+                                 file.name + file.access, file.pid)
 
     def _get_other_end_pids(self, file):
         """Locate the other end of a pipe / domain socket"""
@@ -108,12 +109,12 @@ def _get_other_end_pids(self, file):
                 if candidate.name == file.name:
                     pids.add(candidate.pid)
 
-        if file.access:
+        if file.access and file.type == 'FIFO':
             # On Linux, this is how we identify named FIFOs
             opposing_access = {'r': 'w', 'w': 'r'}.get(file.access)
             if opposing_access:
                 name_and_opposing_access = file.name + opposing_access
-                matching_pids = self._name_and_access_to_pids.get(name_and_opposing_access)
+                matching_pids = self._fifo_name_and_access_to_pids.get(name_and_opposing_access)
                 if matching_pids:
                     pids.update(matching_pids)