driver/rawnetworkinterfacedriver: move timeout to tcpdump

Reworks the way that timeouts are handled so that instead of terminating
the process in stop_record, tcpdump will exit after a set time. This is
will allow for live streaming of packets in a future patch

Signed-off-by: Joshua Watt <[email protected]>
Signed-off-by: Bastian Krause <[email protected]>

Author: JoshuaWatt

helpers/labgrid-raw-interface

@@ -67,6 +67,14 @@ def main(program, options):
             args.append("-c")
             args.append(str(options.count))
 
+        if options.timeout:
+            # The timeout is implemented by specifying the number of seconds before rotating the
+            # dump file, but limiting the number of files to 1
+            args.append("-G")
+            args.append(str(options.timeout))
+            args.append("-W")
+            args.append("1")
+
     try:
         os.execvp(args[0], args)
     except FileNotFoundError as e:
@@ -82,6 +90,9 @@ if __name__ == "__main__":
     tcpdump_parser = subparsers.add_parser("tcpdump")
     tcpdump_parser.add_argument("ifname", type=str, help="interface name")
     tcpdump_parser.add_argument("count", type=int, default=None, help="amount of frames to capture while recording")
+    tcpdump_parser.add_argument(
+        "--timeout", type=int, default=None, help="Amount of time to capture while recording. 0 means capture forever"
+    )
 
     # tcpreplay
     tcpreplay_parser = subparsers.add_parser("tcpreplay")

labgrid/driver/rawnetworkinterfacedriver.py

@@ -53,14 +53,15 @@ def _stop(self, proc, *, timeout=None):
             )
 
     @Driver.check_active
-    @step(args=["filename", "count"])
-    def start_record(self, filename, *, count=None):
+    @step(args=["filename", "count", "timeout"])
+    def start_record(self, filename, *, count=None, timeout=None):
         """
         Starts tcpdump on bound network interface resource.
 
         Args:
             filename (str): name of a file to record to
             count (int): optional, exit after receiving this many number of packets
+            timeout (int): optional, number of seconds to capture packets before tcpdump exits
         Returns:
             Popen object of tcpdump process
         """
@@ -69,6 +70,9 @@ def start_record(self, filename, *, count=None):
         cmd = ["tcpdump", self.iface.ifname]
         if count is not None:
             cmd.append(str(count))
+        if timeout is not None:
+            cmd.append("--timeout")
+            cmd.append(str(timeout))
         cmd = self._wrap_command(cmd)
         with open(filename, "wb") as outdata:
             self._record_handle = subprocess.Popen(cmd, stdout=outdata, stderr=subprocess.PIPE)
@@ -99,15 +103,16 @@ def record(self, filename, *, count=None, timeout=None):
         Args:
             filename (str): name of a file to record to
             count (int): optional, exit after receiving this many number of packets
-            timeout (int): optional, maximum number of seconds to wait for the tcpdump process to
-                           terminate
+            timeout (int): optional, number of seconds to capture packets before tcpdump exits
+        Returns:
+            Popen object of tcpdump process.
         """
         assert count or timeout
 
         try:
-            yield self.start_record(filename, count=count)
+            yield self.start_record(filename, count=count, timeout=timeout)
         finally:
-            self.stop_record(timeout=timeout)
+            self.stop_record()
 
     @Driver.check_active
     @step(args=["filename"])