feat: read the host's listening sockets through napalm-device-types

LinuxDriver mixes in ListeningSocketsMixin (napalm-device-types 2.4.0) and
supplies its transport: privileged readings go through _run_privileged --
as they are for a root login, through sudo with a password, sudo -n
without one -- and the rest through _send. The command arrives as one
sh -c argument, so sudo covers the whole script; when sudo refuses, the
mixin reads again without it.

OpenMediaVault and QNAP QTS inherit it; a host without ss raises
ListeningSocketsUnavailable.

For netOrk#658.

tests/test_linux.py

@@ -1555,3 +1555,65 @@ class TestRebootHost:
 
         with pytest.raises(RuntimeError):
             driver.reboot_host()
+
+
+# ---------------------------------------------------------------------------
+# Listening sockets: ss and the processes' cgroups, as root when it can
+# ---------------------------------------------------------------------------
+
+_SOCKETS = (
+    "SOCK_BEGIN\n[ss]\n"
+    'tcp LISTEN 0 128 0.0.0.0:5432 0.0.0.0:* users:(("postgres",pid=812,fd=6))\n'
+    "__SS_RC=0\n[cgroups]\n"
+    "812 0::/system.slice/system-postgresql.slice/postgresql@16-main.service\n"
+    "SOCK_END\n"
+)
+
+
+class TestGetListeningSockets:
+    def _sent(self, driver) -> list[str]:
+        return [c[0][0] for c in driver._device.send_command.call_args_list]
+
+    def test_it_reads_with_the_shared_command(self, driver):
+        from napalm_device_types import ListeningSocketsMixin
+
+        assert isinstance(driver, ListeningSocketsMixin)
+        driver._root = True
+        driver._device.send_command.return_value = _SOCKETS
+
+        reading = driver.get_listening_sockets()
+
+        assert reading["attributed"] is True
+        [socket] = reading["sockets"]
+        assert (socket["port"], socket["unit"]) == (5432, "postgresql@16-main")
+        assert self._sent(driver)[0].startswith("sh -c '")
+
+    def test_without_a_sudo_password_the_whole_script_runs_under_sudo_n(self, driver):
+        driver._root = False
+        driver._device.send_command.return_value = _SOCKETS
+
+        driver.get_listening_sockets()
+
+        assert self._sent(driver)[0].startswith("sudo -n sh -c '")
+
+    def test_with_a_sudo_password_it_goes_through_sudo(self, driver):
+        driver._root = False
+        driver._sudo_password = "pw"  # noqa: S105
+        driver._device.send_command.return_value = _SOCKETS
+
+        driver.get_listening_sockets()
+
+        sent = self._sent(driver)[0]
+        assert sent.startswith("echo pw | sudo -S")
+        assert "sh -c '" in sent
+
+    def test_when_sudo_refuses_it_reads_what_the_user_may_see(self, driver):
+        driver._root = False
+        driver._device.send_command.side_effect = ["sudo: a password is required", _SOCKETS]
+
+        reading = driver.get_listening_sockets()
+
+        assert reading["attributed"] is False
+        refused, plain = self._sent(driver)
+        assert refused.startswith("sudo -n sh -c '")
+        assert plain.startswith("sh -c '")