guest: Add default virtio-rng /dev/urandom (bz 1212082)

For guests that support it, per libosinfo, and new enough libvirt
to handle /dev/urandom. See the bug for discussion

https://bugzilla.redhat.com/show_bug.cgi?id=1212082

tests/cli-test-xml/compare/virt-install-f21-kvm-remote.xml

@@ -63,5 +63,8 @@
     </video>
     <redirdev bus="usb" type="spicevmc"/>
     <redirdev bus="usb" type="spicevmc"/>
+    <rng model="virtio">
+      <backend model="random">/dev/urandom</backend>
+    </rng>
   </devices>
 </domain>

tests/cli-test-xml/compare/virt-install-kvm-f14-url.xml

@@ -55,6 +55,9 @@
     <video>
       <model type="qxl"/>
     </video>
+    <rng model="virtio">
+      <backend model="random">/dev/urandom</backend>
+    </rng>
   </devices>
 </domain>
 <domain type="kvm">
@@ -111,5 +114,8 @@
     <video>
       <model type="qxl"/>
     </video>
+    <rng model="virtio">
+      <backend model="random">/dev/urandom</backend>
+    </rng>
   </devices>
 </domain>

tests/cli-test-xml/compare/virt-install-kvm-session-defaults.xml

@@ -72,6 +72,9 @@
     </video>
     <redirdev bus="usb" type="spicevmc"/>
     <redirdev bus="usb" type="spicevmc"/>
+    <rng model="virtio">
+      <backend model="random">/dev/urandom</backend>
+    </rng>
   </devices>
 </domain>
 <domain type="kvm">
@@ -144,5 +147,8 @@
     </video>
     <redirdev bus="usb" type="spicevmc"/>
     <redirdev bus="usb" type="spicevmc"/>
+    <rng model="virtio">
+      <backend model="random">/dev/urandom</backend>
+    </rng>
   </devices>
 </domain>

tests/cli-test-xml/compare/virt-install-qemu-32-on-64.xml

@@ -45,5 +45,8 @@
       <source mode="bind"/>
       <target type="virtio" name="org.qemu.guest_agent.0"/>
     </channel>
+    <rng model="virtio">
+      <backend model="random">/dev/urandom</backend>
+    </rng>
   </devices>
 </domain>

tests/cli-test-xml/compare/virt-install-spice-gl.xml

@@ -63,5 +63,8 @@
     </video>
     <redirdev bus="usb" type="spicevmc"/>
     <redirdev bus="usb" type="spicevmc"/>
+    <rng model="virtio">
+      <backend model="random">/dev/urandom</backend>
+    </rng>
   </devices>
 </domain>

virtinst/cli.py

@@ -2359,6 +2359,7 @@ class ParserRNG(VirtCLIParser):
     cli_arg_name = "rng"
     objclass = VirtualRNGDevice
     remove_first = "type"
+    stub_none = False
 
     def set_hosts_cb(self, inst, val, virtarg):
         namemap = {}
@@ -2386,6 +2387,10 @@ class ParserRNG(VirtCLIParser):
             inst.cli_backend_type = val
 
     def _parse(self, inst):
+        if self.optstr == "none":
+            self.guest.skip_default_rng = True
+            return
+
         inst.cli_backend_mode = "connect"
         inst.cli_backend_type = "udp"
 

virtinst/guest.py

@@ -39,6 +39,7 @@ from .devicedisk import VirtualDisk
 from .devicegraphics import VirtualGraphics
 from .deviceinput import VirtualInputDevice
 from .deviceredirdev import VirtualRedirDevice
+from .devicerng import VirtualRNGDevice
 from .devicevideo import VirtualVideoDevice
 from .distroinstaller import DistroInstaller
 from .domainblkiotune import DomainBlkiotune
@@ -124,6 +125,7 @@ class Guest(XMLBuilder):
         self.skip_default_sound = False
         self.skip_default_usbredir = False
         self.skip_default_graphics = False
+        self.skip_default_rng = False
         self.x86_cpu_default = self.cpu.SPECIAL_MODE_HOST_MODEL_ONLY
 
         self.__os_object = None
@@ -641,6 +643,25 @@ class Guest(XMLBuilder):
             return
         self.add_device(VirtualGraphics(self.conn))
 
+    def add_default_rng(self):
+        if self.skip_default_rng:
+            return
+        if self.get_devices("rng"):
+            return
+        if not self.os.is_x86():
+            # Not strictly x86 specific, but some other archs like
+            # arm have limited virtio options in some situations, so
+            # it needs more work there.
+            return
+
+        if (self.conn.is_qemu() and
+            self._os_object.supports_virtiorng() and
+            self.conn.check_support(self.conn.SUPPORT_CONN_RNG_URANDOM)):
+            dev = VirtualRNGDevice(self.conn)
+            dev.type = "random"
+            dev.device = "/dev/urandom"
+            self.add_device(dev)
+
     def add_default_devices(self):
         self.add_default_graphics()
         self.add_default_video_device()
@@ -648,6 +669,7 @@ class Guest(XMLBuilder):
         self.add_default_console_device()
         self.add_default_usb_controller()
         self.add_default_channels()
+        self.add_default_rng()
 
     def _add_install_cdrom(self):
         if self._install_cdrom_device:

virtinst/osdict.py

@@ -494,6 +494,18 @@ class _OsVariant(object):
 
         return False
 
+    def supports_virtiorng(self):
+        if self._os:
+            fltr = libosinfo.Filter()
+            fltr.add_constraint("class", "rng")
+            devs = self._os.get_all_devices(fltr)
+            for dev in range(devs.get_length()):
+                d = devs.get_nth(dev)
+                if d.get_name() == "virtio-rng":
+                    return True
+
+        return False
+
     def supports_qemu_ga(self):
         return self._is_related_to(["debian8", "fedora18", "rhel6.0", "sles11sp4"])
 

virtinst/support.py

@@ -320,6 +320,7 @@ SUPPORT_CONN_SPICE_RENDERNODE = _make(version="3.1.0",
 SUPPORT_CONN_VIDEO_VIRTIO_ACCEL3D = _make(version="1.3.0",
     hv_version={"qemu": "2.5.0", "test": 0})
 SUPPORT_CONN_GRAPHICS_LISTEN_NONE = _make(version="2.0.0")
+SUPPORT_CONN_RNG_URANDOM = _make(version="1.3.4")
 
 
 # This is for disk <driver name=qemu>. xen supports this, but it's