selftests: drv-net: wait for iperf client to stop sending

A few packets may still be sent out during the termination of iperf
processes. These late packets cause failures in rss_ctx.py when they
arrive on queues expected to be empty.

Example failure observed:

  Check failed 2 != 0 traffic on inactive queues (context 1):
    [0, 0, 1, 1, 386385, 397196, 0, 0, 0, 0, ...]

  Check failed 4 != 0 traffic on inactive queues (context 2):
    [0, 0, 0, 0, 2, 2, 247152, 253013, 0, 0, ...]

  Check failed 2 != 0 traffic on inactive queues (context 3):
    [0, 0, 0, 0, 0, 0, 1, 1, 282434, 283070, ...]

To avoid such failures, wait until all client sockets for the requested
port are either closed or in the TIME_WAIT state.

Fixes: 847aa55 ("selftests: drv-net: rss_ctx: factor out send traffic and check")
Signed-off-by: Nimrod Oren <[email protected]>
Reviewed-by: Gal Pressman <[email protected]>
Reviewed-by: Carolina Jubran <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: nimrod-oren

tools/testing/selftests/drivers/net/lib/py/load.py

@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 
+import re
 import time
 
 from lib.py import ksft_pr, cmd, ip, rand_port, wait_port_listen
@@ -10,12 +11,11 @@ def __init__(self, env, port=None):
 
         self.env = env
 
-        if port is None:
-            port = rand_port()
-        self._iperf_server = cmd(f"iperf3 -s -1 -p {port}", background=True)
-        wait_port_listen(port)
+        self.port = rand_port() if port is None else port
+        self._iperf_server = cmd(f"iperf3 -s -1 -p {self.port}", background=True)
+        wait_port_listen(self.port)
         time.sleep(0.1)
-        self._iperf_client = cmd(f"iperf3 -c {env.addr} -P 16 -p {port} -t 86400",
+        self._iperf_client = cmd(f"iperf3 -c {env.addr} -P 16 -p {self.port} -t 86400",
                                  background=True, host=env.remote)
 
         # Wait for traffic to ramp up
@@ -56,3 +56,16 @@ def stop(self, verbose=None):
             ksft_pr(">> Server:")
             ksft_pr(self._iperf_server.stdout)
             ksft_pr(self._iperf_server.stderr)
+        self._wait_client_stopped()
+
+    def _wait_client_stopped(self, sleep=0.005, timeout=5):
+        end = time.monotonic() + timeout
+
+        live_port_pattern = re.compile(fr":{self.port:04X} 0[^6] ")
+
+        while time.monotonic() < end:
+            data = cmd("cat /proc/net/tcp*", host=self.env.remote).stdout
+            if not live_port_pattern.search(data):
+                return
+            time.sleep(sleep)
+        raise Exception(f"Waiting for client to stop timed out after {timeout}s")