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 @@ class QemuSystemTest(QemuBaseTest):
             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 @@ class LinuxTest(LinuxSSHMixIn, QemuSystemTest):
 
     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 @@ from qemu.utils import get_info_usernet_hostfwd_port
 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 @@ class ReplayLinux(LinuxTest):
             '%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')