qemu: implement QEMU NBD source reconnect delay attribute

Currently it's only possible to set this parameter during domain
creation via QEMU commandline passthrough feature.
With the new delay attribute it's also possible to set this
parameter if you want to attach a new NBD disk
using "virsh attach-device domain device.xml" e.g.:

  <disk type='network' device='disk'>
    <driver name='qemu' type='raw'/>
    <source protocol='nbd' name='foo'>
      <host name='example.org' port='6000'/>
      <reconnect delay='10'/>
    </source>
    <target dev='vdb' bus='virtio'/>
  </disk>

Signed-off-by: Christian Nautze <christian.nautze@exoscale.ch>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

docs/formatdomain.rst

@@ -2956,13 +2956,20 @@ paravirtualized driver is specified via the ``disk`` element.
       are intended to be default, then the entire element may be omitted.
    ``reconnect``
       For disk type ``vhostuser`` configures reconnect timeout if the connection
-      is lost. It has two mandatory attributes:
+      is lost. This is set with the two mandatory attributes ``enabled`` and
+      ``timeout``.
+      For disk type ``network`` and protocol ``nbd`` the QEMU NBD reconnect delay
+      can be set via attribute ``delay``:
 
       ``enabled``
          If the reconnect feature is enabled, accepts ``yes`` and ``no``
       ``timeout``
          The amount of seconds after which hypervisor tries to reconnect.
-
+      ``delay``
+         Only for NBD hosts. The amount of seconds during which all requests are
+         paused and will be rerun after a successful reconnect. After that time, any
+         delayed requests and all future requests before a successful reconnect
+         will immediately fail. If not set the default QEMU value is 0.
 
    For a "file" or "volume" disk type which represents a cdrom or floppy (the
    ``device`` attribute), it is possible to define policy what to do with the

src/conf/domain_conf.c

@@ -7166,6 +7166,15 @@ virDomainDiskSourceNetworkParse(xmlNodePtr node,
         src->tlsFromConfig = !!value;
     }
 
+    if (src->protocol == VIR_STORAGE_NET_PROTOCOL_NBD) {
+        xmlNodePtr cur;
+        if ((cur = virXPathNode("./reconnect", ctxt))) {
+            if (virXMLPropUInt(cur, "delay", 10, VIR_XML_PROP_NONE,
+                               &src->reconnectDelay) < 0)
+                return -1;
+        }
+    }
+
     /* for historical reasons we store the volume and image name in one XML
      * element although it complicates thing when attempting to access them. */
     if (src->path &&
@@ -22146,6 +22155,9 @@ virDomainDiskSourceFormatNetwork(virBuffer *attrBuf,
         virBufferAddLit(childBuf, "/>\n");
     }
 
+    if (src->reconnectDelay) {
+        virBufferAsprintf(childBuf, "<reconnect delay='%u'/>\n", src->reconnectDelay);
+    }
 
     virBufferEscapeString(childBuf, "<snapshot name='%s'/>\n", src->snapshot);
     virBufferEscapeString(childBuf, "<config file='%s'/>\n", src->configFile);

src/conf/schemas/domaincommon.rng

@@ -2205,6 +2205,9 @@
         </optional>
         <ref name="diskSourceCommon"/>
         <ref name="diskSourceNetworkHost"/>
+        <optional>
+          <ref name="reconnect"/>
+        </optional>
         <optional>
           <ref name="encryption"/>
         </optional>

src/conf/schemas/storagecommon.rng

@@ -55,6 +55,8 @@
 
   <define name="reconnect">
     <element name="reconnect">
+      <choice>
+        <group>
           <attribute name="enabled">
             <ref name="virYesNo"/>
           </attribute>
@@ -63,6 +65,11 @@
               <ref name="unsignedInt"/>
             </attribute>
           </optional>
+        </group>
+        <attribute name="delay">
+          <ref name="unsignedInt"/>
+        </attribute>
+      </choice>
     </element>
   </define>
 

src/conf/storage_source_conf.c

@@ -811,6 +811,7 @@ virStorageSourceCopy(const virStorageSource *src,
     def->sslverify = src->sslverify;
     def->readahead = src->readahead;
     def->timeout = src->timeout;
+    def->reconnectDelay = src->reconnectDelay;
     def->metadataCacheMaxSize = src->metadataCacheMaxSize;
 
     /* storage driver metadata are not copied */

src/conf/storage_source_conf.h

@@ -312,6 +312,10 @@ struct _virStorageSource {
     unsigned long long readahead; /* size of the readahead buffer in bytes */
     unsigned long long timeout; /* connection timeout in seconds */
 
+    /* NBD QEMU reconnect-delay option,
+     * 0 as default value */
+    unsigned int reconnectDelay;
+
     virStorageSourceNVMeDef *nvme; /* type == VIR_STORAGE_TYPE_NVME */
 
     virDomainChrSourceDef *vhostuser; /* type == VIR_STORAGE_TYPE_VHOST_USER */

src/qemu/qemu_block.c

@@ -529,6 +529,7 @@ qemuBlockStorageSourceGetNBDProps(virStorageSource *src,
                               "S:export", src->path,
                               "S:tls-creds", tlsAlias,
                               "S:tls-hostname", tlsHostname,
+                              "p:reconnect-delay", src->reconnectDelay,
                               NULL) < 0)
         return NULL;
 
@@ -1848,7 +1849,8 @@ qemuBlockGetBackingStoreString(virStorageSource *src,
             src->ncookies == 0 &&
             src->sslverify == VIR_TRISTATE_BOOL_ABSENT &&
             src->timeout == 0 &&
-            src->readahead == 0) {
+            src->readahead == 0 &&
+            src->reconnectDelay == 0) {
 
             switch ((virStorageNetProtocol) src->protocol) {
             case VIR_STORAGE_NET_PROTOCOL_NBD:

src/qemu/qemu_domain.c

@@ -5063,6 +5063,15 @@ qemuDomainValidateStorageSource(virStorageSource *src,
         }
     }
 
+    if (src->reconnectDelay > 0) {
+        if (actualType != VIR_STORAGE_TYPE_NETWORK ||
+            src->protocol != VIR_STORAGE_NET_PROTOCOL_NBD) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("reconnect delay is supported only with NBD protocol"));
+            return -1;
+        }
+    }
+
     if (src->query &&
         (actualType != VIR_STORAGE_TYPE_NETWORK ||
          (src->protocol != VIR_STORAGE_NET_PROTOCOL_HTTPS &&

tests/qemuxml2argvdata/disk-network-nbd.x86_64-latest.args

@@ -27,21 +27,24 @@ XDG_CONFIG_HOME=/var/lib/libvirt/qemu/domain--1-QEMUGuest1/.config \
 -no-shutdown \
 -boot strict=on \
 -device '{"driver":"piix3-usb-uhci","id":"usb","bus":"pci.0","addr":"0x1.0x2"}' \
--blockdev '{"driver":"nbd","server":{"type":"inet","host":"example.org","port":"6000"},"node-name":"libvirt-5-storage","auto-read-only":true,"discard":"unmap"}' \
+-blockdev '{"driver":"nbd","server":{"type":"inet","host":"example.org","port":"6000"},"node-name":"libvirt-6-storage","auto-read-only":true,"discard":"unmap"}' \
+-blockdev '{"node-name":"libvirt-6-format","read-only":false,"driver":"raw","file":"libvirt-6-storage"}' \
+-device '{"driver":"virtio-blk-pci","bus":"pci.0","addr":"0x2","drive":"libvirt-6-format","id":"virtio-disk0","bootindex":1}' \
+-blockdev '{"driver":"nbd","server":{"type":"inet","host":"example.org","port":"6000"},"export":"bar","node-name":"libvirt-5-storage","auto-read-only":true,"discard":"unmap"}' \
 -blockdev '{"node-name":"libvirt-5-format","read-only":false,"driver":"raw","file":"libvirt-5-storage"}' \
--device '{"driver":"virtio-blk-pci","bus":"pci.0","addr":"0x2","drive":"libvirt-5-format","id":"virtio-disk0","bootindex":1}' \
+-device '{"driver":"virtio-blk-pci","bus":"pci.0","addr":"0x3","drive":"libvirt-5-format","id":"virtio-disk1"}' \
--blockdev '{"driver":"nbd","server":{"type":"inet","host":"example.org","port":"6000"},"export":"bar","node-name":"libvirt-4-storage","auto-read-only":true,"discard":"unmap"}' \
+-blockdev '{"driver":"nbd","server":{"type":"inet","host":"::1","port":"6000"},"node-name":"libvirt-4-storage","auto-read-only":true,"discard":"unmap"}' \
 -blockdev '{"node-name":"libvirt-4-format","read-only":false,"driver":"raw","file":"libvirt-4-storage"}' \
--device '{"driver":"virtio-blk-pci","bus":"pci.0","addr":"0x3","drive":"libvirt-4-format","id":"virtio-disk1"}' \
+-device '{"driver":"virtio-blk-pci","bus":"pci.0","addr":"0x4","drive":"libvirt-4-format","id":"virtio-disk2"}' \
--blockdev '{"driver":"nbd","server":{"type":"inet","host":"::1","port":"6000"},"node-name":"libvirt-3-storage","auto-read-only":true,"discard":"unmap"}' \
+-blockdev '{"driver":"nbd","server":{"type":"inet","host":"::1","port":"6000"},"export":"bar","node-name":"libvirt-3-storage","auto-read-only":true,"discard":"unmap"}' \
 -blockdev '{"node-name":"libvirt-3-format","read-only":false,"driver":"raw","file":"libvirt-3-storage"}' \
--device '{"driver":"virtio-blk-pci","bus":"pci.0","addr":"0x4","drive":"libvirt-3-format","id":"virtio-disk2"}' \
+-device '{"driver":"virtio-blk-pci","bus":"pci.0","addr":"0x5","drive":"libvirt-3-format","id":"virtio-disk3"}' \
--blockdev '{"driver":"nbd","server":{"type":"inet","host":"::1","port":"6000"},"export":"bar","node-name":"libvirt-2-storage","auto-read-only":true,"discard":"unmap"}' \
+-blockdev '{"driver":"nbd","server":{"type":"unix","path":"/var/run/nbdsock"},"export":"bar","node-name":"libvirt-2-storage","auto-read-only":true,"discard":"unmap"}' \
 -blockdev '{"node-name":"libvirt-2-format","read-only":false,"driver":"raw","file":"libvirt-2-storage"}' \
--device '{"driver":"virtio-blk-pci","bus":"pci.0","addr":"0x5","drive":"libvirt-2-format","id":"virtio-disk3"}' \
+-device '{"driver":"virtio-blk-pci","bus":"pci.0","addr":"0x6","drive":"libvirt-2-format","id":"virtio-disk4"}' \
--blockdev '{"driver":"nbd","server":{"type":"unix","path":"/var/run/nbdsock"},"export":"bar","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \
+-blockdev '{"driver":"nbd","server":{"type":"inet","host":"example.org","port":"6000"},"export":"foo","reconnect-delay":10,"node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \
 -blockdev '{"node-name":"libvirt-1-format","read-only":false,"driver":"raw","file":"libvirt-1-storage"}' \
--device '{"driver":"virtio-blk-pci","bus":"pci.0","addr":"0x6","drive":"libvirt-1-format","id":"virtio-disk4"}' \
+-device '{"driver":"virtio-blk-pci","bus":"pci.0","addr":"0x7","drive":"libvirt-1-format","id":"virtio-disk5"}' \
 -audiodev '{"id":"audio1","driver":"none"}' \
 -sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
 -msg timestamp=on

tests/qemuxml2argvdata/disk-network-nbd.xml

@@ -49,6 +49,14 @@
       </source>
       <target dev='vde' bus='virtio'/>
     </disk>
+    <disk type='network' device='disk'>
+      <driver name='qemu' type='raw'/>
+      <source protocol='nbd' name='foo'>
+        <host name='example.org' port='6000'/>
+        <reconnect delay='10'/>
+      </source>
+      <target dev='vdf' bus='virtio'/>
+    </disk>
     <controller type='usb' index='0'/>
     <controller type='ide' index='0'/>
     <controller type='pci' index='0' model='pci-root'/>

tests/qemuxml2xmloutdata/disk-network-nbd.xml

@@ -54,6 +54,15 @@
       <target dev='vde' bus='virtio'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
     </disk>
+    <disk type='network' device='disk'>
+      <driver name='qemu' type='raw'/>
+      <source protocol='nbd' name='foo'>
+        <host name='example.org' port='6000'/>
+        <reconnect delay='10'/>
+      </source>
+      <target dev='vdf' bus='virtio'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
+    </disk>
     <controller type='usb' index='0'>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
     </controller>