[PATCH net-next v3 8/8] selftests: drv-net: add a TCP ping test case (and useful helpers)

[Jakub Kicinski <kuba@kernel.org>]

More complex tests often have to spawn a background process,
like a server which will respond to requests or tcpdump.

Add support for creating such processes using the with keyword:

  with bkg("my-daemon", ..):
     # my-daemon is alive in this block

My initial thought was to add this support to cmd() directly
but it runs the command in the constructor, so by the time
we __enter__ it's too late to make sure we used "background=True".

Second useful helper transplanted from net_helper.sh is
wait_port_listen().

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 tools/testing/selftests/drivers/net/ping.py | 24 +++++++++++++--
 tools/testing/selftests/net/lib/py/utils.py | 33 +++++++++++++++++++++
 2 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/drivers/net/ping.py b/tools/testing/selftests/drivers/net/ping.py
index 58aefd3e740f..8532e3be72ba 100755
--- a/tools/testing/selftests/drivers/net/ping.py
+++ b/tools/testing/selftests/drivers/net/ping.py
@@ -1,9 +1,12 @@
 #!/usr/bin/env python3
 # SPDX-License-Identifier: GPL-2.0
 
-from lib.py import ksft_run, ksft_exit, KsftXfailEx
+import random
+
+from lib.py import ksft_run, ksft_exit
+from lib.py import ksft_eq, KsftXfailEx
 from lib.py import NetDrvEpEnv
-from lib.py import cmd
+from lib.py import bkg, cmd, wait_port_listen
 
 
 def test_v4(cfg) -> None:
@@ -22,6 +25,23 @@ from lib.py import cmd
     cmd(f"ping -c 1 -W0.5 {cfg.v6}", host=cfg.remote)
 
 
+def test_tcp(cfg) -> None:
+    port = random.randrange(1024 + (1 << 15))
+    with bkg(f"nc -l {cfg.addr} {port}") as nc:
+        wait_port_listen(port)
+
+        cmd(f"echo ping | nc {cfg.addr} {port}",
+            shell=True, host=cfg.remote)
+    ksft_eq(nc.stdout.strip(), "ping")
+
+    port = random.randrange(1024 + (1 << 15))
+    with bkg(f"nc -l {cfg.remote_addr} {port}", host=cfg.remote) as nc:
+        wait_port_listen(port, host=cfg.remote)
+
+        cmd(f"echo ping | nc {cfg.remote_addr} {port}", shell=True)
+    ksft_eq(nc.stdout.strip(), "ping")
+
+
 def main() -> None:
     with NetDrvEpEnv(__file__) as cfg:
         ksft_run(globs=globals(), case_pfx={"test_"}, args=(cfg, ))
diff --git a/tools/testing/selftests/net/lib/py/utils.py b/tools/testing/selftests/net/lib/py/utils.py
index e80fea9f6562..6bacdc99d21b 100644
--- a/tools/testing/selftests/net/lib/py/utils.py
+++ b/tools/testing/selftests/net/lib/py/utils.py
@@ -1,7 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0
 
 import json as _json
+import re
 import subprocess
+import time
+
 
 class cmd:
     def __init__(self, comm, shell=True, fail=True, ns=None, background=False, host=None):
@@ -38,6 +41,18 @@ import subprocess
                             (self.proc.args, stdout, stderr))
 
 
+class bkg(cmd):
+    def __init__(self, comm, shell=True, fail=True, ns=None, host=None):
+        super().__init__(comm, background=True,
+                         shell=shell, fail=fail, ns=ns, host=host)
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, ex_type, ex_value, ex_tb):
+        return self.process()
+
+
 def ip(args, json=None, ns=None, host=None):
     cmd_str = "ip "
     if json:
@@ -47,3 +62,21 @@ import subprocess
     if json:
         return _json.loads(cmd_obj.stdout)
     return cmd_obj
+
+
+def wait_port_listen(port, proto="tcp", ns=None, host=None, sleep=0.005, deadline=1):
+    end = time.monotonic() + deadline
+
+    pattern = f":{port:04X} .* "
+    if proto == "tcp": # for tcp protocol additionally check the socket state
+        pattern += "0A"
+    pattern = re.compile(pattern)
+
+    while True:
+        data = cmd(f'cat /proc/net/{proto}*', ns=ns, host=host, shell=True).stdout
+        for row in data.split("\n"):
+            if pattern.search(row):
+                return
+        if time.monotonic() > end:
+            raise Exception("Waiting for port listen timed out")
+        time.sleep(sleep)
-- 
2.44.0