tests/avocado: Do not run tests that require libslirp if it is not available

Some avocado tests blindly assume that QEMU has been compiled with libslirp
enabled and fail badly if it is missing. Add a proper check to cancel the
tests in this case.

Message-Id: <20220824151122.704946-6-thuth@redhat.com>
Acked-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/avocado/avocado_qemu/__init__.py

@@ -299,6 +299,12 @@ def require_accelerator(self, accelerator):
             self.cancel("%s accelerator does not seem to be "
                         "available" % accelerator)
 
+    def require_netdev(self, netdevname):
+        netdevhelp = run_cmd([self.qemu_bin,
+                             '-M', 'none', '-netdev', 'help'])[0];
+        if netdevhelp.find('\n' + netdevname + '\n') < 0:
+            self.cancel('no support for user networking')
+
     def _new_vm(self, name, *args):
         self._sd = tempfile.TemporaryDirectory(prefix="avo_qemu_sock_")
         vm = QEMUMachine(self.qemu_bin, base_temp_dir=self.workdir,
@@ -550,6 +556,7 @@ def _set_distro(self):
 
     def setUp(self, ssh_pubkey=None, network_device_type='virtio-net'):
         super().setUp()
+        self.require_netdev('user')
         self._set_distro()
         self.vm.add_args('-smp', self.smp)
         self.vm.add_args('-m', self.memory)

tests/avocado/info_usernet.py

@@ -16,6 +16,7 @@
 class InfoUsernet(QemuSystemTest):
 
     def test_hostfwd(self):
+        self.require_netdev('user')
         self.vm.add_args('-netdev', 'user,id=vnet,hostfwd=:127.0.0.1:0-:22')
         self.vm.launch()
         res = self.vm.command('human-monitor-command',

tests/avocado/replay_linux.py

@@ -55,6 +55,7 @@ def vm_add_disk(self, vm, path, id, device):
             '%s,drive=disk%s-rr%s' % (device, id, bus_string))
 
     def launch_and_wait(self, record, args, shift):
+        self.require_netdev('user')
         vm = self.get_vm()
         vm.add_args('-smp', '1')
         vm.add_args('-m', '1024')