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[libvirt] [PATCH 3/9] conf: new network bridge device attribute promiscLinks



The promiscLinks attribute of a network's bridge subelement is used as
a single switch to simultaneously turn on/off several options related
to a bridge and its attached devices. When this is done, as many of
the links to the bridge as possible have promiscuous mode turned off
and/or flooding turned on. The result is better performance (because
packets aren't being flooded to all ports, and can be dropped earlier
when they are of no interest) and better security (since a guest will
only receive traffic intended for the guest interface's configured MAC
address).

The attribute looks like this in the configuration:

  <network>
    <name>test</name>
    <bridge name='br0' promiscLinks='no'/>
    ...

In order to preserve operational backward compatibility, the default
for promiscLinks will be considered to be "yes" (although that won't
be automatically stored in the XML, to allow for existing
installations to automatically take advantage of this performance
improvement in the future if we ever decide that it is safe to turn on
everywhere).

The details of what is turned on/off will be described in a later
enabling patch. This patch only adds the config knob, documentation,
and test cases.
---
 docs/formatnetwork.html.in                         | 36 ++++++++++++++---
 docs/schemas/network.rng                           |  5 +++
 src/conf/network_conf.c                            | 47 +++++++++++++++++-----
 src/conf/network_conf.h                            |  1 +
 tests/networkxml2xmlin/host-bridge-no-flood.xml    |  6 +++
 .../nat-network-explicit-flood.xml                 | 21 ++++++++++
 tests/networkxml2xmlout/host-bridge-no-flood.xml   |  6 +++
 .../nat-network-explicit-flood.xml                 | 23 +++++++++++
 tests/networkxml2xmltest.c                         |  2 +
 9 files changed, 130 insertions(+), 17 deletions(-)
 create mode 100644 tests/networkxml2xmlin/host-bridge-no-flood.xml
 create mode 100644 tests/networkxml2xmlin/nat-network-explicit-flood.xml
 create mode 100644 tests/networkxml2xmlout/host-bridge-no-flood.xml
 create mode 100644 tests/networkxml2xmlout/nat-network-explicit-flood.xml

diff --git a/docs/formatnetwork.html.in b/docs/formatnetwork.html.in
index dc438ae..82bdc88 100644
--- a/docs/formatnetwork.html.in
+++ b/docs/formatnetwork.html.in
@@ -81,7 +81,7 @@
 
     <pre>
         ...
-        &lt;bridge name="virbr0" stp="on" delay="5"/&gt;
+        &lt;bridge name="virbr0" stp="on" delay="5" promiscLinks="no"/&gt;
         &lt;domain name="example.com"/&gt;
         &lt;forward mode="nat" dev="eth0"/&gt;
         ...</pre>
@@ -92,18 +92,42 @@
         defines the name of a bridge device which will be used to construct
         the virtual network. The virtual machines will be connected to this
         bridge device allowing them to talk to each other. The bridge device
-        may also be connected to the LAN. It is recommended that bridge
-        device names started with the prefix <code>vir</code>, but the name
-        <code>virbr0</code> is reserved for the "default" virtual
-        network.  This element should always be provided when defining
+        may also be connected to the LAN. When defining
         a new network with a <code>&lt;forward&gt;</code> mode of
+
         "nat" or "route" (or an isolated network with
-        no <code>&lt;forward&gt;</code> element).
+        no <code>&lt;forward&gt;</code> element), libvirt will
+        automatically generate a unique name for the bridge device if
+        none is given, and this name will be permanently stored in the
+        network configuration so that that the same name will be used
+        every time the network is started. For these types of networks
+        (nat, routed, and isolated), a bridge name beginning with the
+        prefix "virbr" is recommended (and that is what is
+        auto-generated), but not enforced.
         Attribute <code>stp</code> specifies if Spanning Tree Protocol
         is 'on' or 'off' (default is
         'on'). Attribute <code>delay</code> sets the bridge's forward
         delay value in seconds (default is 0).
         <span class="since">Since 0.3.0</span>
+
+        <p>
+          The <code>promiscLinks</code> attribute of the bridge
+          element is used to tell libvirt whether or not to attempt a
+          bridge configuration which disables flooding and turns off
+          promiscuous mode on as many ports as possible (this is done
+          by turning off each tap device's learning and unicast_flood
+          settings, and manually managing the bridge's forwarding
+          databas). It can be set to 'yes' or 'no' (defaults to 'yes'
+          to preserve backward compatibility). Turning off promiscuous
+          mode on the links to a bridge can improve performance and
+          provide better security, but can also cause some networking
+          setups to stop working (e.g. vlan tagging, multicast) and is
+          not supported by older kernels.
+          <span class="since">Since 1.2.11, requires kernel 3.17 or
+          newer</span>
+        </p>
+
+
       </dd>
       <dt><code>domain</code></dt>
       <dd>
diff --git a/docs/schemas/network.rng b/docs/schemas/network.rng
index 4546f80..5c57165 100644
--- a/docs/schemas/network.rng
+++ b/docs/schemas/network.rng
@@ -64,6 +64,11 @@
                 <data type="unsignedLong"/>
               </attribute>
             </optional>
+            <optional>
+              <attribute name="promiscLinks">
+                <ref name="virYesNo"/>
+              </attribute>
+            </optional>
 
           </element>
         </optional>
diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c
index 067334e..d6ecc51 100644
--- a/src/conf/network_conf.c
+++ b/src/conf/network_conf.c
@@ -2108,6 +2108,18 @@ virNetworkDefParseXML(xmlXPathContextPtr ctxt)
     }
     VIR_FREE(tmp);
 
+    tmp = virXPathString("string(./bridge[1]/@promiscLinks)", ctxt);
+    if (tmp) {
+        if ((def->promiscLinks
+             = virTristateBoolTypeFromString(tmp)) <= 0) {
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("Invalid promiscLinks setting '%s' "
+                             "in network '%s'"), tmp, def->name);
+            goto error;
+        }
+        VIR_FREE(tmp);
+    }
+
     tmp = virXPathString("string(./mac[1]/@address)", ctxt);
     if (tmp) {
         if (virMacAddrParse(tmp, &def->mac) < 0) {
@@ -2290,6 +2302,14 @@ virNetworkDefParseXML(xmlXPathContextPtr ctxt)
                            def->name);
             goto error;
         }
+        if (def->promiscLinks) {
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("bridge promiscLinks setting not allowed "
+                             "in %s mode (network '%s')"),
+                           virNetworkForwardTypeToString(def->forward.type),
+                           def->name);
+            goto error;
+        }
         /* fall through to next case */
     case VIR_NETWORK_FORWARD_BRIDGE:
         if (def->delay || stp) {
@@ -2783,22 +2803,27 @@ virNetworkDefFormatBuf(virBufferPtr buf,
             virBufferAddLit(buf, "</forward>\n");
     }
 
+
     if (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_NAT ||
+        def->forward.type == VIR_NETWORK_FORWARD_ROUTE ||
+        def->bridge || def->promiscLinks) {
 
         virBufferAddLit(buf, "<bridge");
-        if (def->bridge)
-            virBufferEscapeString(buf, " name='%s'", def->bridge);
-        virBufferAsprintf(buf, " stp='%s' delay='%ld'/>\n",
-                          def->stp ? "on" : "off",
-                          def->delay);
-    } else if (def->forward.type == VIR_NETWORK_FORWARD_BRIDGE &&
-               def->bridge) {
-        virBufferEscapeString(buf, "<bridge name='%s'/>\n", def->bridge);
+        virBufferEscapeString(buf, " name='%s'", def->bridge);
+        if (def->forward.type == VIR_NETWORK_FORWARD_NONE ||
+            def->forward.type == VIR_NETWORK_FORWARD_NAT ||
+            def->forward.type == VIR_NETWORK_FORWARD_ROUTE) {
+            virBufferAsprintf(buf, " stp='%s' delay='%ld'",
+                              def->stp ? "on" : "off", def->delay);
+        }
+        if (def->promiscLinks) {
+            virBufferAsprintf(buf, " promiscLinks='%s'",
+                             virTristateBoolTypeToString(def->promiscLinks));
+        }
+        virBufferAddLit(buf, "/>\n");
     }
 
-
     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 660cd2d..0d4aa2e 100644
--- a/src/conf/network_conf.h
+++ b/src/conf/network_conf.h
@@ -231,6 +231,7 @@ struct _virNetworkDef {
     int   connections; /* # of guest interfaces connected to this network */
 
     char *bridge;       /* Name of bridge device */
+    int  promiscLinks; /* enum virTristateBool - default is YES */
     char *domain;
     unsigned long delay;   /* Bridge forward delay (ms) */
     bool stp; /* Spanning tree protocol */
diff --git a/tests/networkxml2xmlin/host-bridge-no-flood.xml b/tests/networkxml2xmlin/host-bridge-no-flood.xml
new file mode 100644
index 0000000..a5378c8
--- /dev/null
+++ b/tests/networkxml2xmlin/host-bridge-no-flood.xml
@@ -0,0 +1,6 @@
+<network>
+  <name>host-bridge-net</name>
+  <uuid>81ff0d90-c91e-6742-64da-4a736edb9a8e</uuid>
+  <forward mode="bridge"/>
+  <bridge name="br0" promiscLinks='no'/>
+</network>
diff --git a/tests/networkxml2xmlin/nat-network-explicit-flood.xml b/tests/networkxml2xmlin/nat-network-explicit-flood.xml
new file mode 100644
index 0000000..a0f79ff
--- /dev/null
+++ b/tests/networkxml2xmlin/nat-network-explicit-flood.xml
@@ -0,0 +1,21 @@
+<network>
+  <name>default</name>
+  <uuid>81ff0d90-c91e-6742-64da-4a736edb9a9b</uuid>
+  <bridge name="virbr0" promiscLinks='yes'/>
+  <forward mode="nat" dev="eth1"/>
+  <ip address="192.168.122.1" netmask="255.255.255.0">
+    <dhcp>
+      <range start="192.168.122.2" end="192.168.122.254"/>
+      <host mac="00:16:3e:77:e2:ed" name="a.example.com" ip="192.168.122.10"/>
+      <host mac="00:16:3e:3e:a9:1a" name="b.example.com" ip="192.168.122.11"/>
+    </dhcp>
+  </ip>
+  <ip family="ipv4" address="192.168.123.1" netmask="255.255.255.0">
+  </ip>
+  <ip family="ipv6" address="2001:db8:ac10:fe01::1" prefix="64">
+  </ip>
+  <ip family="ipv6" address="2001:db8:ac10:fd01::1" prefix="64">
+  </ip>
+  <ip family="ipv4" address="10.24.10.1">
+  </ip>
+</network>
diff --git a/tests/networkxml2xmlout/host-bridge-no-flood.xml b/tests/networkxml2xmlout/host-bridge-no-flood.xml
new file mode 100644
index 0000000..f8f1ced
--- /dev/null
+++ b/tests/networkxml2xmlout/host-bridge-no-flood.xml
@@ -0,0 +1,6 @@
+<network>
+  <name>host-bridge-net</name>
+  <uuid>81ff0d90-c91e-6742-64da-4a736edb9a8e</uuid>
+  <forward mode='bridge'/>
+  <bridge name='br0' promiscLinks='no'/>
+</network>
diff --git a/tests/networkxml2xmlout/nat-network-explicit-flood.xml b/tests/networkxml2xmlout/nat-network-explicit-flood.xml
new file mode 100644
index 0000000..ffca9af
--- /dev/null
+++ b/tests/networkxml2xmlout/nat-network-explicit-flood.xml
@@ -0,0 +1,23 @@
+<network>
+  <name>default</name>
+  <uuid>81ff0d90-c91e-6742-64da-4a736edb9a9b</uuid>
+  <forward dev='eth1' mode='nat'>
+    <interface dev='eth1'/>
+  </forward>
+  <bridge name='virbr0' stp='on' delay='0' promiscLinks='yes'/>
+  <ip address='192.168.122.1' netmask='255.255.255.0'>
+    <dhcp>
+      <range start='192.168.122.2' end='192.168.122.254'/>
+      <host mac='00:16:3e:77:e2:ed' name='a.example.com' ip='192.168.122.10'/>
+      <host mac='00:16:3e:3e:a9:1a' name='b.example.com' ip='192.168.122.11'/>
+    </dhcp>
+  </ip>
+  <ip family='ipv4' address='192.168.123.1' netmask='255.255.255.0'>
+  </ip>
+  <ip family='ipv6' address='2001:db8:ac10:fe01::1' prefix='64'>
+  </ip>
+  <ip family='ipv6' address='2001:db8:ac10:fd01::1' prefix='64'>
+  </ip>
+  <ip family='ipv4' address='10.24.10.1'>
+  </ip>
+</network>
diff --git a/tests/networkxml2xmltest.c b/tests/networkxml2xmltest.c
index 65ac591..34a5211 100644
--- a/tests/networkxml2xmltest.c
+++ b/tests/networkxml2xmltest.c
@@ -120,6 +120,8 @@ mymain(void)
     DO_TEST("hostdev");
     DO_TEST_FULL("hostdev-pf", VIR_NETWORK_XML_INACTIVE);
     DO_TEST("passthrough-address-crash");
+    DO_TEST("nat-network-explicit-flood");
+    DO_TEST("host-bridge-no-flood");
 
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }
-- 
1.9.3


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