Rawnetworkinterface stream

helpers/labgrid-raw-interface

@@ -32,18 +32,18 @@ def get_denylist():
     return denylist
 
 
-def main(program, ifname, count):
-    if not ifname:
+def main(program, options):
+    if not options.ifname:
         raise ValueError("Empty interface name.")
-    if any((c == "/" or c.isspace()) for c in ifname):
-        raise ValueError(f"Interface name '{ifname}' contains invalid characters.")
-    if len(ifname) > 16:
-        raise ValueError(f"Interface name '{ifname}' is too long.")
+    if any((c == "/" or c.isspace()) for c in options.ifname):
+        raise ValueError(f"Interface name '{options.ifname}' contains invalid characters.")
+    if len(options.ifname) > 16:
+        raise ValueError(f"Interface name '{options.ifname}' is too long.")
 
     denylist = get_denylist()
 
-    if ifname in denylist:
-        raise ValueError(f"Interface name '{ifname}' is denied in denylist.")
+    if options.ifname in denylist:
+        raise ValueError(f"Interface name '{options.ifname}' is denied in denylist.")
 
     programs = ["tcpreplay", "tcpdump"]
     if program not in programs:
@@ -54,18 +54,30 @@ def main(program, ifname, count):
     ]
 
     if program == "tcpreplay":
-        args.append(f"--intf1={ifname}")
-        args.append('-')
+        args.append(f"--intf1={options.ifname}")
+        args.append("-")
 
     if program == "tcpdump":
         args.append("-n")
-        args.append(f"--interface={ifname}")
+        args.append(f"--interface={options.ifname}")
+        # Write out each packet as it is received
+        args.append("--packet-buffered")
+        # Capture complete packets (for compatibility with older tcpdump versions)
+        args.append("--snapshot-length=0")
         args.append("-w")
-        args.append('-')
+        args.append("-")
 
-        if count:
+        if options.count:
             args.append("-c")
-            args.append(str(count))
+            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)
@@ -75,22 +87,28 @@ def main(program, ifname, count):
 
 if __name__ == "__main__":
     parser = argparse.ArgumentParser()
-    parser.add_argument(
-        '-d',
-        '--debug',
-        action='store_true',
-        default=False,
-        help="enable debug mode"
+    parser.add_argument("-d", "--debug", action="store_true", default=False, help="enable debug mode")
+    subparsers = parser.add_subparsers(dest="program", help="program to run")
+
+    # tcpdump
+    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"
     )
-    parser.add_argument('program', type=str, help='program to run, either tcpreplay or tcpdump')
-    parser.add_argument('interface', type=str, help='interface name')
-    parser.add_argument('count', nargs="?", type=int, default=None, help='amount of frames to capture while recording')
+
+    # tcpreplay
+    tcpreplay_parser = subparsers.add_parser("tcpreplay")
+    tcpreplay_parser.add_argument("ifname", type=str, help="interface name")
+
     args = parser.parse_args()
     try:
-        main(args.program, args.interface, args.count)
+        main(args.program, args)
     except Exception as e:  # pylint: disable=broad-except
         if args.debug:
             import traceback
+
             traceback.print_exc(file=sys.stderr)
         print(f"ERROR: {e}", file=sys.stderr)
         exit(1)

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
+            filename (str): name of a file to record to, or None to record to stdout
             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
         """
@@ -69,9 +70,15 @@ 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)
+        if filename is None:
+            self._record_handle = subprocess.Popen(cmd, stdout=subprocess.PIPE)
+        else:
+            with open(filename, "wb") as outdata:
+                self._record_handle = subprocess.Popen(cmd, stdout=outdata, stderr=subprocess.PIPE)
         return self._record_handle
 
     @Driver.check_active
@@ -86,6 +93,11 @@ def stop_record(self, *, timeout=None):
         """
         try:
             self._stop(self._record_handle, timeout=timeout)
+        except subprocess.TimeoutExpired:
+            # If live streaming packets, there is no reason to wait for tcpdump
+            # to finish, so expect a timeout if piping to stdout
+            if self._record_handle.stdout is None:
+                raise
         finally:
             self._record_handle = None
 
@@ -97,17 +109,18 @@ def record(self, filename, *, count=None, timeout=None):
         Either count or timeout must be specified.
 
         Args:
-            filename (str): name of a file to record to
+            filename (str): name of a file to record to, or None to live stream packets
             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. If filename is None, packets can be read from stdout
         """
         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(timeout=0 if filename is None else None)
 
     @Driver.check_active
     @step(args=["filename"])
@@ -170,12 +183,7 @@ def get_statistics(self):
         """
         Returns basic interface statistics of bound network interface resource.
         """
-        cmd = self.iface.command_prefix + [
-            "ip",
-            "--json",
-            "-stats", "-stats",
-            "link", "show",
-            self.iface.ifname]
+        cmd = self.iface.command_prefix + ["ip", "--json", "-stats", "-stats", "link", "show", self.iface.ifname]
         output = processwrapper.check_output(cmd)
         return json.loads(output)[0]