container-tests: add multi-container network

checks/container/default.nix

@@ -3,17 +3,42 @@
   {
     name = "container";
 
-    nodes.machine =
+    nodes.machine1 =
       { ... }:
       {
-        networking.hostName = "machine";
+        networking.hostName = "machine1";
         services.openssh.enable = true;
         services.openssh.startWhenNeeded = false;
       };
+
+    nodes.machine2 =
+      { ... }:
+      {
+        networking.hostName = "machine2";
+        services.openssh.enable = true;
+        services.openssh.startWhenNeeded = false;
+      };
+
     testScript = ''
+      import subprocess
       start_all()
-      machine.succeed("systemctl status sshd")
-      machine.wait_for_unit("sshd")
+      machine1.succeed("systemctl status sshd")
+      machine2.succeed("systemctl status sshd")
+      machine1.wait_for_unit("sshd")
+      machine2.wait_for_unit("sshd")
+
+      p1 = subprocess.run(["ip", "a"], check=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+      assert p1.returncode == 0
+      bridge_output = p1.stdout.decode("utf-8")
+      assert "br0" in bridge_output, f"bridge not found in ip a output: {bridge_output}"
+
+      for m in [machine1, machine2]:
+          out = machine1.succeed("ip addr show eth1")
+          assert "UP" in out, f"UP not found in ip addr show output: {out}"
+          assert "inet" in out, f"inet not found in ip addr show output: {out}"
+          assert "inet6" in out, f"inet6 not found in ip addr show output: {out}"
+
+      machine1.succeed("ping -c 1 machine2")
     '';
   }
 )