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[libvirt] [PATCH v2 2/4] conf: support configuring mtu size in a virtual network



Example:

  <network>
     ...
     <mtu size='9000'/>
     ...

If mtu is unset, it's assumed that we want the default for whatever is
the underlying transport (usually this is 1500).

This setting isn't yet wired in, so it will have no effect.

This partially resolves: https://bugzilla.redhat.com/1224348
---

Change from V1:

* switch from <bridge .... mtu='9000'/> to <mtu size='9000'/> for
  consistency and to allow for potentially setting an MTU on a network
  that doesn't have a <bridge> element.

* use Michal's mtu element definition from networkcommon.rng rather
  than rolling my own.


 docs/formatnetwork.html.in          | 19 ++++++++++++++++++-
 docs/news.xml                       |  5 +++--
 docs/schemas/network.rng            |  5 +++++
 src/conf/network_conf.c             | 31 ++++++++++++++++++++++++++++++-
 src/conf/network_conf.h             |  1 +
 tests/networkxml2xmlin/set-mtu.xml  | 12 ++++++++++++
 tests/networkxml2xmlout/set-mtu.xml | 12 ++++++++++++
 tests/networkxml2xmltest.c          |  1 +
 8 files changed, 82 insertions(+), 4 deletions(-)
 create mode 100644 tests/networkxml2xmlin/set-mtu.xml
 create mode 100644 tests/networkxml2xmlout/set-mtu.xml

diff --git a/docs/formatnetwork.html.in b/docs/formatnetwork.html.in
index 8638df9..777c341 100644
--- a/docs/formatnetwork.html.in
+++ b/docs/formatnetwork.html.in
@@ -93,6 +93,7 @@
     <pre>
 ...
 &lt;bridge name="virbr0" stp="on" delay="5" macTableManager="libvirt"/&gt;
+&lt;mtu size="9000"/&gt;
 &lt;domain name="example.com" localOnly="no"/&gt;
 &lt;forward mode="nat" dev="eth0"/&gt;
 ...</pre>
@@ -151,9 +152,25 @@
           <span class="since">Since 1.2.11, requires kernel 3.17 or
           newer</span>
         </p>
+      </dd>
 
-
+      <dt><code>mtu</code></dt>
+      <dd>
+        The <code>size</code> attribute of the <code>mtu></code>
+        element specifies the Maximum Transmission Unit (MTU) for the
+        network. <span class="since">Since 3.1.0</span>. In the case
+        of a libvirt-managed network (one with forward mode
+        of <code>nat</code>, <code>route</code>, <code>open</code>, or
+        no <code>forward</code> element (i.e. an isolated network),
+        this will be the MTU assigned to the bridge device when
+        libvirt creates it, and thereafter also assigned to all tap
+        devices created to connect guest interfaces. Network types not
+        specifically mentioned here don't support having an MTU set in
+        the libvirt network config. If mtu size is unspecified, the
+        default setting for the type of device being used is assumed
+        (usually 1500).
       </dd>
+
       <dt><code>domain</code></dt>
       <dd>
         The <code>name</code> attribute on the <code>domain</code>
diff --git a/docs/news.xml b/docs/news.xml
index f408293..8f0d3d6 100644
--- a/docs/news.xml
+++ b/docs/news.xml
@@ -36,10 +36,11 @@
       </change>
       <change>
         <summary>
-          Introduce MTU to domain &lt;interface/&gt;
+          Introduce MTU to domain &lt;interface/&gt; and &lt;network&gt;
         </summary>
         <description>
-          Allow setting MTU size for some types of domain interface.
+          Allow setting MTU size for some types of domain interface
+          and network.
         </description>
       </change>
     </section>
diff --git a/docs/schemas/network.rng b/docs/schemas/network.rng
index 8f0a61b..1048dab 100644
--- a/docs/schemas/network.rng
+++ b/docs/schemas/network.rng
@@ -79,6 +79,11 @@
           </element>
         </optional>
 
+        <!-- <mtu> element -->
+        <optional>
+          <ref name="mtu"/>
+        </optional>
+
         <!-- <mac> element -->
         <optional>
           <element name="mac">
diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c
index 86ce311..0e20dac 100644
--- a/src/conf/network_conf.c
+++ b/src/conf/network_conf.c
@@ -2242,6 +2242,17 @@ virNetworkDefParseXML(xmlXPathContextPtr ctxt)
         def->mac_specified = true;
     }
 
+    tmp = virXPathString("string(./mtu/@size)", ctxt);
+    if (tmp) {
+        if (virStrToLong_ui(tmp, NULL, 10, &def->mtu) < 0) {
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("Invalid mtu size '%s' in network '%s'"),
+                           tmp, def->name);
+            goto error;
+        }
+    }
+    VIR_FREE(tmp);
+
     dnsNode = virXPathNode("./dns", ctxt);
     if (dnsNode != NULL &&
         virNetworkDNSDefParseXML(def->name, dnsNode, ctxt, &def->dns) < 0) {
@@ -2435,7 +2446,9 @@ virNetworkDefParseXML(xmlXPathContextPtr ctxt)
     case VIR_NETWORK_FORWARD_BRIDGE:
         if (def->delay || stp) {
             virReportError(VIR_ERR_XML_ERROR,
-                           _("bridge delay/stp options only allowed in route, nat, and isolated mode, not in %s (network '%s')"),
+                           _("bridge delay/stp options only allowed in "
+                             "route, nat, and isolated mode, not in %s "
+                             "(network '%s')"),
                            virNetworkForwardTypeToString(def->forward.type),
                            def->name);
             goto error;
@@ -2454,6 +2467,19 @@ virNetworkDefParseXML(xmlXPathContextPtr ctxt)
 
     VIR_FREE(stp);
 
+    if (def->mtu &&
+        (def->forward.type != VIR_NETWORK_FORWARD_NONE &&
+         def->forward.type != VIR_NETWORK_FORWARD_NAT &&
+         def->forward.type != VIR_NETWORK_FORWARD_ROUTE &&
+         def->forward.type != VIR_NETWORK_FORWARD_OPEN)) {
+        virReportError(VIR_ERR_XML_ERROR,
+                       _("mtu size only allowed in open, route, nat, "
+                         "and isolated mode, not in %s (network '%s')"),
+                       virNetworkForwardTypeToString(def->forward.type),
+                       def->name);
+        goto error;
+    }
+
     /* Extract custom metadata */
     if ((metadataNode = virXPathNode("./metadata[1]", ctxt)) != NULL) {
         def->metadata = xmlCopyNode(metadataNode, 1);
@@ -2964,6 +2990,9 @@ virNetworkDefFormatBuf(virBufferPtr buf,
         virBufferAddLit(buf, "/>\n");
     }
 
+    if (def->mtu)
+        virBufferAsprintf(buf, "<mtu size='%u'/>\n", def->mtu);
+
     if (def->mac_specified) {
         char macaddr[VIR_MAC_STRING_BUFLEN];
         virMacAddrFormat(&def->mac, macaddr);
diff --git a/src/conf/network_conf.h b/src/conf/network_conf.h
index b5c9ea2..9e4ae71 100644
--- a/src/conf/network_conf.h
+++ b/src/conf/network_conf.h
@@ -240,6 +240,7 @@ struct _virNetworkDef {
     int domainLocalOnly; /* enum virTristateBool: yes disables dns forwarding */
     unsigned long delay;   /* Bridge forward delay (ms) */
     bool stp; /* Spanning tree protocol */
+    unsigned int mtu; /* MTU for bridge, 0 means "default" i.e. unset in config */
     virMacAddr mac; /* mac address of bridge device */
     bool mac_specified;
 
diff --git a/tests/networkxml2xmlin/set-mtu.xml b/tests/networkxml2xmlin/set-mtu.xml
new file mode 100644
index 0000000..d1ef32a
--- /dev/null
+++ b/tests/networkxml2xmlin/set-mtu.xml
@@ -0,0 +1,12 @@
+<network ipv6='no'>
+  <name>private</name>
+  <uuid>81ff0d90-c91e-6742-64da-4a736edb9a9b</uuid>
+  <bridge name='virbr2'/>
+  <mtu size='9000'/>
+  <mac address='52:54:00:17:3F:37'/>
+  <ip address="192.168.152.1" netmask="255.255.255.0">
+    <dhcp>
+      <range start="192.168.152.2" end="192.168.152.254"/>
+    </dhcp>
+  </ip>
+</network>
diff --git a/tests/networkxml2xmlout/set-mtu.xml b/tests/networkxml2xmlout/set-mtu.xml
new file mode 100644
index 0000000..10e8155
--- /dev/null
+++ b/tests/networkxml2xmlout/set-mtu.xml
@@ -0,0 +1,12 @@
+<network>
+  <name>private</name>
+  <uuid>81ff0d90-c91e-6742-64da-4a736edb9a9b</uuid>
+  <bridge name='virbr2' stp='on' delay='0'/>
+  <mtu size='9000'/>
+  <mac address='52:54:00:17:3f:37'/>
+  <ip address='192.168.152.1' netmask='255.255.255.0'>
+    <dhcp>
+      <range start='192.168.152.2' end='192.168.152.254'/>
+    </dhcp>
+  </ip>
+</network>
diff --git a/tests/networkxml2xmltest.c b/tests/networkxml2xmltest.c
index 01cd6f7..cfaf718 100644
--- a/tests/networkxml2xmltest.c
+++ b/tests/networkxml2xmltest.c
@@ -158,6 +158,7 @@ mymain(void)
     DO_TEST_PARSE_ERROR("hostdev-duplicate");
     DO_TEST_PARSE_ERROR("passthrough-duplicate");
     DO_TEST("metadata");
+    DO_TEST("set-mtu");
 
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }
-- 
2.9.3


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