selftests: drv-net: add a TCP ping test case (and useful helpers)

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().

The test itself uses socat, which insists on v6 addresses
being wrapped in [], it's not the only command which requires
this format, so add the wrapped address to env. The hope
is to save test code from checking if address is v6.

Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20240420025237.3309296-7-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -110,6 +110,11 @@ class NetDrvEpEnv:
         self.addr = self.v6 if self.v6 else self.v4
         self.remote_addr = self.remote_v6 if self.remote_v6 else self.remote_v4
 
+        self.addr_ipver = "6" if self.v6 else "4"
+        # Bracketed addresses, some commands need IPv6 to be inside []
+        self.baddr = f"[{self.v6}]" if self.v6 else self.v4
+        self.remote_baddr = f"[{self.remote_v6}]" if self.remote_v6 else self.remote_v4
+
         self.ifname = self.dev['ifname']
         self.ifindex = self.dev['ifindex']
 

tools/testing/selftests/drivers/net/ping.py

@@ -2,8 +2,9 @@
 # SPDX-License-Identifier: GPL-2.0
 
 from lib.py import ksft_run, ksft_exit
+from lib.py import ksft_eq
 from lib.py import NetDrvEpEnv
-from lib.py import cmd
+from lib.py import bkg, cmd, wait_port_listen, rand_port
 
 
 def test_v4(cfg) -> None:
@@ -16,6 +17,24 @@ def test_v6(cfg) -> None:
     cmd(f"ping -c 1 -W0.5 {cfg.v6}", host=cfg.remote)
 
 
+def test_tcp(cfg) -> None:
+    port = rand_port()
+    listen_cmd = f"socat -{cfg.addr_ipver} -t 2 -u TCP-LISTEN:{port},reuseport STDOUT"
+
+    with bkg(listen_cmd, exit_wait=True) as nc:
+        wait_port_listen(port)
+
+        cmd(f"echo ping | socat -t 2 -u STDIN TCP:{cfg.baddr}:{port}",
+            shell=True, host=cfg.remote)
+    ksft_eq(nc.stdout.strip(), "ping")
+
+    with bkg(listen_cmd, host=cfg.remote, exit_wait=True) as nc:
+        wait_port_listen(port, host=cfg.remote)
+
+        cmd(f"echo ping | socat -t 2 -u STDIN TCP:{cfg.remote_baddr}:{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, ))

tools/testing/selftests/net/lib/py/utils.py

@@ -1,7 +1,11 @@
 # SPDX-License-Identifier: GPL-2.0
 
 import json as _json
+import random
+import re
 import subprocess
+import time
+
 
 class cmd:
     def __init__(self, comm, shell=True, fail=True, ns=None, background=False, host=None):
@@ -38,6 +42,20 @@ class cmd:
                             (self.proc.args, stdout, stderr))
 
 
+class bkg(cmd):
+    def __init__(self, comm, shell=True, fail=True, ns=None, host=None,
+                 exit_wait=False):
+        super().__init__(comm, background=True,
+                         shell=shell, fail=fail, ns=ns, host=host)
+        self.terminate = not exit_wait
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, ex_type, ex_value, ex_tb):
+        return self.process(terminate=self.terminate)
+
+
 def ip(args, json=None, ns=None, host=None):
     cmd_str = "ip "
     if json:
@@ -47,3 +65,28 @@ def ip(args, json=None, ns=None, host=None):
     if json:
         return _json.loads(cmd_obj.stdout)
     return cmd_obj
+
+
+def rand_port():
+    """
+    Get unprivileged port, for now just random, one day we may decide to check if used.
+    """
+    return random.randint(1024, 65535)
+
+
+def wait_port_listen(port, proto="tcp", ns=None, host=None, sleep=0.005, deadline=5):
+    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)