qemu: Avoid using ".(null)" in UNIX socket path

The code which generates paths for UNIX socket blindly used target name
without checking if it was set. Thus for the following device XML

    <channel type='unix'>
      <source mode='bind'/>
      <target type='virtio'/>
    </channel>

we would generate "/var/lib/libvirt/qemu/channel/target/NAME.(null)"
path which works but is not really correct. Let's not use the
".target_name" suffix at all if target name is not set.

https://bugzilla.redhat.com/show_bug.cgi?id=1226854

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>

src/qemu/qemu_domain.c

@@ -1249,11 +1249,23 @@ qemuDomainDeviceDefPostParse(virDomainDeviceDefPtr dev,
         dev->data.chr->deviceType == VIR_DOMAIN_CHR_DEVICE_TYPE_CHANNEL &&
         dev->data.chr->targetType == VIR_DOMAIN_CHR_CHANNEL_TARGET_TYPE_VIRTIO &&
         dev->data.chr->source.type == VIR_DOMAIN_CHR_TYPE_UNIX &&
-        !dev->data.chr->source.data.nix.path && cfg) {
-        if (virAsprintf(&dev->data.chr->source.data.nix.path, "%s/%s.%s",
-                        cfg->channelTargetDir,
-                        def->name, dev->data.chr->target.name) < 0)
+        !dev->data.chr->source.data.nix.path) {
+        if (!cfg) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("cannot generate UNIX socket path"));
             goto cleanup;
+        }
+
+        if (dev->data.chr->target.name) {
+            if (virAsprintf(&dev->data.chr->source.data.nix.path, "%s/%s.%s",
+                            cfg->channelTargetDir,
+                            def->name, dev->data.chr->target.name) < 0)
+                goto cleanup;
+        } else {
+            if (virAsprintf(&dev->data.chr->source.data.nix.path, "%s/%s",
+                            cfg->channelTargetDir, def->name) < 0)
+                goto cleanup;
+        }
 
         dev->data.chr->source.data.nix.listen = true;
     }

tests/qemuxml2argvdata/qemuxml2argv-channel-virtio-unix.args

@@ -0,0 +1,19 @@
+LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test QEMU_AUDIO_DRV=none \
+/usr/bin/qemu -S -M pc -m 214 -smp 1 -nographic -nodefconfig -nodefaults \
+-chardev socket,id=charmonitor,path=/tmp/test-monitor,server,nowait \
+-mon chardev=charmonitor,id=monitor,mode=readline \
+-no-acpi \
+-boot c \
+-device virtio-serial-pci,id=virtio-serial1,bus=pci.0,addr=0xa \
+-device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x3 \
+-usb \
+-hda /dev/HostVG/QEMUGuest1 \
+-chardev socket,id=charchannel0,path=\
+/tmp/QEMUGuest1.org.qemu.guest_agent.0,server,nowait \
+-device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,\
+name=org.qemu.guest_agent.0 \
+-chardev socket,id=charchannel1,path=/tmp/QEMUGuest1,server,nowait \
+-device virtserialport,bus=virtio-serial0.0,nr=2,chardev=charchannel1,id=channel1 \
+-chardev socket,id=charchannel2,path=/tmp/QEMUGuest1.ble,server,nowait \
+-device virtserialport,bus=virtio-serial0.0,nr=3,chardev=charchannel2,id=channel2,\
+name=ble

tests/qemuxml2argvdata/qemuxml2argv-channel-virtio-unix.xml

@@ -0,0 +1,37 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <vcpu placement='static' cpuset='1-4,8-20,525'>1</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu</emulator>
+    <disk type='block' device='disk'>
+      <source dev='/dev/HostVG/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='virtio-serial' index='1'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/>
+    </controller>
+    <channel type='unix'>
+      <target type='virtio' name='org.qemu.guest_agent.0'/>
+    </channel>
+    <channel type='unix'>
+      <target type='virtio'/>
+    </channel>
+    <channel type='unix'>
+      <target type='virtio' name='ble'/>
+    </channel>
+    <memballoon model='none'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -519,6 +519,9 @@ mymain(void)
     driver.config->spiceTLS = 1;
     if (VIR_STRDUP_QUIET(driver.config->spicePassword, "123456") < 0)
         return EXIT_FAILURE;
+    VIR_FREE(driver.config->channelTargetDir);
+    if (VIR_STRDUP_QUIET(driver.config->channelTargetDir, "/tmp") < 0)
+        return EXIT_FAILURE;
 
 # define DO_TEST_FULL(name, migrateFrom, migrateFd, flags, ...)         \
     do {                                                                \
@@ -1113,6 +1116,8 @@ mymain(void)
     DO_TEST("channel-virtio-default",
             QEMU_CAPS_DEVICE, QEMU_CAPS_CHARDEV, QEMU_CAPS_NODEFCONFIG,
             QEMU_CAPS_SPICE, QEMU_CAPS_CHARDEV_SPICEVMC);
+    DO_TEST("channel-virtio-unix",
+            QEMU_CAPS_DEVICE, QEMU_CAPS_CHARDEV, QEMU_CAPS_NODEFCONFIG);
 
     DO_TEST("smartcard-host",
             QEMU_CAPS_CHARDEV, QEMU_CAPS_DEVICE,