[libvirt] [PATCHv3 1/3] v2.0: allow guest to guest IPv6 without gateway definition
Gene Czarcinski
gene at czarc.net
Mon Dec 3 16:13:36 UTC 2012
This patch adds the capability for virtual guests to do IPv6
communication via a virtual network interface with no IPv6
(gateway) addresses specified. This capability currently
exists for IPv4.
This patch allows creation of a completely isolated IPv6 network.
Note that virtual guests cannot communication with the virtualization
host via this interface. Also note that:
net.ipv6.conf.<interface_name>.disable_ipv6 = 1
Also not that starting libvirtd has set the following:
net.bridge.bridge-nf-call-arptables = 1
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
although /etc/syslog.conf has them all set to 0.
To control this behavior so that it is not enabled by default, the parameter
ipv6='yes' on the <network> statement has been added.
Documentation related to this patch has been updated.
The network schema has also been updated.
---
docs/formatnetwork.html.in | 28 +++++++++++++++++++++++++++-
docs/schemas/network.rng | 10 ++++++++++
src/conf/network_conf.c | 8 ++++++++
src/conf/network_conf.h | 5 +++++
src/network/bridge_driver.c | 25 ++++++++++++++++++++-----
5 files changed, 70 insertions(+), 6 deletions(-)
diff --git a/docs/formatnetwork.html.in b/docs/formatnetwork.html.in
index 49206dd..a3a5ced 100644
--- a/docs/formatnetwork.html.in
+++ b/docs/formatnetwork.html.in
@@ -33,7 +33,7 @@
</p>
<pre>
- <network>
+ <network ipv6='yes'>
<name>default</name>
<uuid>3e3fce45-4f53-4fa7-bb32-11f34168b82b</uuid>
...</pre>
@@ -52,6 +52,12 @@
The format must be RFC 4122 compliant, eg <code>3e3fce45-4f53-4fa7-bb32-11f34168b82b</code>.
If omitted when defining/creating a new network, a random
UUID is generated. <span class="since">Since 0.3.0</span></dd>
+ <dt><code>ipv6='yes'</code></dt>
+ <dd>The new, optional parameter <code>ipv6='yes'</code> enables
+ a network definition with no IPv6 gateway addresses specified
+ to have guest-to-guest communications. For further information,
+ see the example below for the example with no gateway addresses.
+ <span class="since">Since 1.0.1</span></dd>
</dl>
<h3><a name="elementsConnect">Connectivity</a></h3>
@@ -773,5 +779,25 @@
</forward>
</network></pre>
+ <h3><a name="examplesNoGateway">Network config with no gateway addresses</a></h3>
+
+ <p>
+ A valid network definition can contain no IPv4 or IPv6 addresses. Such a definition
+ can be used for a "very private" or "very isolated" network since it will not be
+ possible to communicate with the virtualization host via this network. However,
+ this virtual network interface can be used for communication between virtual guest
+ systems. This works for IPv4 and <span class="since">(Since 1.0.1)</span> IPv6.
+ However, the new ipv6='yes' must be added for guest-to-guest IPv6
+ communication.
+ </p>
+
+ <pre>
+ <network ipv6='yes'>
+ <name>nogw</name>
+ <uuid>7a3b7497-1ec7-8aef-6d5c-38dff9109e93</uuid>
+ <bridge name="virbr2" stp="on" delay="0" />
+ <mac address='00:16:3E:5D:C7:9E'/>
+ </network></pre>
+
</body>
</html>
diff --git a/docs/schemas/network.rng b/docs/schemas/network.rng
index 4abfd91..0d67f7f 100644
--- a/docs/schemas/network.rng
+++ b/docs/schemas/network.rng
@@ -17,6 +17,16 @@
<data type="unsignedInt"/>
</attribute>
</optional>
+ <!-- Enables IPv6 guest-to-guest communications on a network
+ with no gateways addresses specified -->
+ <optional>
+ <attribute name="ipv6">
+ <choice>
+ <value>yes</value>
+ <value>no</value>
+ </choice>
+ </attribute>
+ </optional>
<interleave>
<!-- The name of the network, used to refer to it through the API
diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c
index 6ce2e63..3f9e13c 100644
--- a/src/conf/network_conf.c
+++ b/src/conf/network_conf.c
@@ -1264,6 +1264,12 @@ virNetworkDefParseXML(xmlXPathContextPtr ctxt)
def->uuid_specified = true;
}
+ /* check if definitions with no IPv6 gateway addresses is to
+ * allow guest-to-guest communications.
+ */
+ if (virXPathBoolean("boolean(./@ipv6)", ctxt) == 1)
+ def->ipv6nogw = true;
+
/* Parse network domain information */
def->domain = virXPathString("string(./domain[1]/@name)", ctxt);
@@ -1839,6 +1845,8 @@ char *virNetworkDefFormat(const virNetworkDefPtr def, unsigned int flags)
if (!(flags & VIR_NETWORK_XML_INACTIVE) && (def->connections > 0)) {
virBufferAsprintf(&buf, " connections='%d'", def->connections);
}
+ if (def->ipv6nogw)
+ virBufferAddLit(&buf, " ipv6='yes'");
virBufferAddLit(&buf, ">\n");
virBufferAdjustIndent(&buf, 2);
virBufferEscapeString(&buf, "<name>%s</name>\n", def->name);
diff --git a/src/conf/network_conf.h b/src/conf/network_conf.h
index 3e46304..949b3d2 100644
--- a/src/conf/network_conf.h
+++ b/src/conf/network_conf.h
@@ -184,6 +184,11 @@ struct _virNetworkDef {
virMacAddr mac; /* mac address of bridge device */
bool mac_specified;
+ /* specified if ip6tables rules added
+ * when no ipv6 gateway addresses specified.
+ */
+ bool ipv6nogw;
+
int forwardType; /* One of virNetworkForwardType constants */
int managed; /* managed attribute for hostdev mode */
diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c
index 75f3c3a..cb2997d 100644
--- a/src/network/bridge_driver.c
+++ b/src/network/bridge_driver.c
@@ -1617,13 +1617,18 @@ networkRemoveRoutingIptablesRules(struct network_driver *driver,
}
}
-/* Add all once/network rules required for IPv6 (if any IPv6 addresses are defined) */
+/* Add all once/network rules required for IPv6.
+ * If no IPv6 addresses are defined and <network ipv6='yes'> is
+ * specified, then allow IPv6 commuinications between virtual systems.
+ * If any IPv6 addresses are defined, then add the rules for regular operation.
+ */
static int
networkAddGeneralIp6tablesRules(struct network_driver *driver,
virNetworkObjPtr network)
{
- if (!virNetworkDefGetIpByIndex(network->def, AF_INET6, 0))
+ if (!virNetworkDefGetIpByIndex(network->def, AF_INET6, 0) &&
+ !network->def->ipv6nogw)
return 0;
/* Catch all rules to block forwarding to/from bridges */
@@ -1653,6 +1658,10 @@ networkAddGeneralIp6tablesRules(struct network_driver *driver,
goto err3;
}
+ /* if no IPv6 addresses are defined, we are done. */
+ if (!virNetworkDefGetIpByIndex(network->def, AF_INET6, 0))
+ return 0;
+
/* allow DNS over IPv6 */
if (iptablesAddTcpInput(driver->iptables, AF_INET6,
network->def->bridge, 53) < 0) {
@@ -1689,11 +1698,17 @@ static void
networkRemoveGeneralIp6tablesRules(struct network_driver *driver,
virNetworkObjPtr network)
{
- if (!virNetworkDefGetIpByIndex(network->def, AF_INET6, 0))
+ if (!virNetworkDefGetIpByIndex(network->def, AF_INET6, 0) &&
+ !network->def->ipv6nogw)
return;
+ if (virNetworkDefGetIpByIndex(network->def, AF_INET6, 0)) {
+ iptablesRemoveUdpInput(driver->iptables, AF_INET6, network->def->bridge, 53);
+ iptablesRemoveTcpInput(driver->iptables, AF_INET6, network->def->bridge, 53);
+ }
- iptablesRemoveUdpInput(driver->iptables, AF_INET6, network->def->bridge, 53);
- iptablesRemoveTcpInput(driver->iptables, AF_INET6, network->def->bridge, 53);
+ /* the following rules are there if no IPv6 address has been defined
+ * but network->def->ipv6nogw == true
+ */
iptablesRemoveForwardAllowCross(driver->iptables, AF_INET6, network->def->bridge);
iptablesRemoveForwardRejectIn(driver->iptables, AF_INET6, network->def->bridge);
iptablesRemoveForwardRejectOut(driver->iptables, AF_INET6, network->def->bridge);
--
1.7.11.7
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