TEST-85-NETWORK: enable NetworkdSysctlTest

Note, each test case must be prefixed with 'test_'.

This also adds one more log check for issue #40051.

Follow-up for c78bcda461.

src/network/networkd-sysctl.c

@@ -53,6 +53,8 @@ static int sysctl_event_handler(void *ctx, void *data, size_t data_sz) {
                                          "Unexpected sysctl event, disabling sysctl monitoring: %d", we->version);
 
         if (we->errorcode != 0) {
+                /* The log message is checked in test-network/systemd-networkd-tests.py. Please update the
+                 * test when the log message is changed. */
                 log_warning_errno(we->errorcode, "Sysctl monitor BPF returned error: %m");
                 return 0;
         }
@@ -69,6 +71,8 @@ static int sysctl_event_handler(void *ctx, void *data, size_t data_sz) {
                 return 0;
 
         if (!strneq(value, we->newvalue, sizeof(we->newvalue)))
+                /* The log message is checked in test-network/systemd-networkd-tests.py. Please update the
+                 * test when the log message is changed. */
                 log_struct(LOG_WARNING,
                            LOG_MESSAGE_ID(SD_MESSAGE_SYSCTL_CHANGED_STR),
                            LOG_ITEM("OBJECT_PID=" PID_FMT, we->pid),

test/integration-tests/TEST-85-NETWORK/meson.build

@@ -22,6 +22,7 @@ foreach testcase : [
         'NetworkdDHCPPDTests',
         'NetworkdIPv6PrefixTests',
         'NetworkdMTUTests',
+        'NetworkdSysctlTest',
 ]
         integration_tests += [
                 integration_test_template + {

test/test-network/systemd-networkd-tests.py

@@ -9375,7 +9375,7 @@ class NetworkdSysctlTest(unittest.TestCase, Utilities):
         tear_down_common()
 
     @unittest.skipUnless(compare_kernel_version("6.12"), reason="On kernels <= 6.12, bpf_current_task_under_cgroup() isn't available for program types BPF_PROG_TYPE_CGROUP_SYSCTL")
-    def check_sysctl_watch(self):
+    def test_sysctl_monitor(self):
         copy_network_unit('12-dummy.network', '12-dummy.netdev', '12-dummy.link')
         start_networkd()
 
@@ -9398,6 +9398,7 @@ class NetworkdSysctlTest(unittest.TestCase, Utilities):
         self.assertRegex(log, r"Foreign process 'sysctl\[\d+\]' changed sysctl '/proc/sys/net/ipv6/conf/dummy98/proxy_ndp' from '0' to '1', conflicting with our setting to '0'")
         self.assertNotIn("changed sysctl '/proc/sys/net/ipv6/conf/dummy98/hop_limit'", log)
         self.assertNotIn("changed sysctl '/proc/sys/net/ipv6/conf/dummy98/max_addresses'", log)
+        self.assertNotIn("Sysctl monitor BPF returned error", log)
 
 if __name__ == '__main__':
     parser = argparse.ArgumentParser()