set preferred port for networkserialport

This allows for specifying a start port and a range up from that to be
used when looking for a free port to use with ser2net when creating a
networkserialport resource. This can be helpful on networks where access
to ports on the network is limited.

Signed-off-by: Benjamin B. Frost <[email protected]>

Author: benjamin1313

labgrid/remote/exporter.py

@@ -235,7 +235,7 @@ def _start(self, start_params):
         assert self.local.avail
         assert self.child is None
         assert start_params["path"].startswith("/dev/")
-        self.port = get_free_port()
+        self.port = get_free_port(os.environ.get("LG_PREFERRED_NETWORKSERIAL_PORT", None))
 
         # Ser2net has switched to using YAML format at version 4.0.0.
         result = subprocess.run([self.ser2net_bin, "-v"], capture_output=True, text=True)

labgrid/util/helper.py

@@ -15,10 +15,23 @@
 
 re_vt100 = re.compile(r"(\x1b\[|\x9b)[^@-_a-z]*[@-_a-z]|\x1b[@-_a-z]")
 
-def get_free_port():
+def get_free_port(prefered_port=None):
     """Helper function to always return an unused port."""
     with closing(socket(AF_INET, SOCK_STREAM)) as s:
-        s.bind(('', 0))
+        if prefered_port is not None:
+            port_range = [int(i) for i in prefered_port.split(':')]
+            port = port_range[0]
+            max_range = port_range[1] if len(port_range) > 1 else 10
+            max_no_of_ports = port + max_range
+            while port <= max_no_of_ports:
+                try:
+                    s.bind(('', port))
+                except Exception as e:
+                    port += 1
+                else:
+                    break
+        else:
+            s.bind(('', 0))
         return s.getsockname()[1]
 
 

man/labgrid-exporter.1

@@ -104,6 +104,10 @@ The following environment variable can be used to configure labgrid\-exporter.
 .sp
 This variable can be used to set the default coordinator in the format
 \fBHOST[:PORT]\fP (instead of using the \fB\-x\fP option).
+.SS LG_PREFERRED_NETWORKSERIAL_PORT
+.sp
+Set a preferred port to be used with NetworkSerialPort resources.
+Specify a port and a optional range counting up using the format \fBPORT[:RANGE]\fP
 .SH EXAMPLES
 .sp
 Start the exporter with the configuration file \fImy\-config.yaml\fP:

man/labgrid-exporter.rst

@@ -96,6 +96,13 @@ LG_COORDINATOR
 This variable can be used to set the default coordinator in the format
 ``HOST[:PORT]`` (instead of using the ``-x`` option).
 
+LG_PREFERRED_NETWORKSERIAL_PORT
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Set a preferred port to be used with NetworkSerialPort resources.
+Specify a port and a optional range counting up using the format ``PORT[:RANGE]``
+
+
+
 EXAMPLES
 --------