NuKVM/libvirt
3
0
Fork 0
mirror of https://github.com/libvirt/libvirt.git synced 2025-02-25 18:55:26 -06:00
Code Issues Packages Projects Releases Wiki Activity

Support for static routes on a virtual bridge

Browse Source 
network: static route support for <network>

This patch adds the <route> subelement of <network> to define a static
route.  the address and prefix (or netmask) attribute identify the
destination network, and the gateway attribute specifies the next hop
address (which must be directly reachable from the containing
<network>) which is to receive the packets destined for
"address/(prefix|netmask)".

These attributes are translated into an "ip route add" command that is
executed when the network is started. The command used is of the
following form:

  ip route add <address>/<prefix> via <gateway> \
               dev <virbr-bridge> proto static metric <metric>

Tests are done to validate that the input data are correct.  For
example, for a static route ip definition, the address must be a
network address and not a host address.  Additional checks are added
to ensure that the specified gateway is directly reachable via this
network (i.e. that the gateway IP address is in the same subnet as one
of the IP's defined for the network).

prefix='0' is supported for both family='ipv4' address='0.0.0.0'
netmask='0.0.0.0' or prefix='0', and for family='ipv6' address='::',
prefix=0', although care should be taken to not override a desired
system default route.

Anytime an attempt is made to define a static route which *exactly*
duplicates an existing static route (for example, address=::,
prefix=0, metric=1), the following error message will be sent to
syslog:

    RTNETLINK answers: File exists

This can be overridden by decreasing the metric value for the route
that should be preferred, or increasing the metric for the route that
shouldn't be preferred (and is thus in place only in anticipation that
the preferred route may be removed in the future).  Caution should be
used when manipulating route metrics, especially for a default route.

Note: The use of the command-line interface should be replaced by
direct use of libnl so that error conditions can be handled better.  But,
that is being left as an exercise for another day.

Signed-off-by: Gene Czarcinski <gene@czarc.net>
Signed-off-by: Laine Stump <laine@laine.org>
This commit is contained in:
Gene Czarcinski
2013-05-07 13:42:55 -04:00
committed by Laine Stump
parent 84f3777a79
commit ccff335f83
10 changed files with 606 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

84
docs/formatnetwork.html.in
View File

@@ -546,6 +546,62 @@
starting.
</p>
<h5><a name="elementsStaticroute">Static Routes</a></h5>
<p>
Static route definitions are used to provide routing information
to the virtualization host for networks which are not directly
reachable from the virtualization host, but *are* reachable from
a guest domain that is itself reachable from the
host <span class="since">since 1.0.6</span>.
</p>
<p>
As shown in <a href="formatnetwork.html#examplesNoGateway">this
example</a>, it is possible to define a virtual network
interface with no IPv4 or IPv6 addresses. Such networks are
useful to provide host connectivity to networks which are only
reachable via a guest. A guest with connectivity both to the
guest-only network and to another network that is directly
reachable from the host can act as a gateway between the
networks. A static route added to the "host-visible" network
definition provides the routing information so that IP packets
can be sent from the virtualization host to guests on the hidden
network.
</p>
<p>
Here is a fragment of a definition which shows the static
route specification as well as the IPv4 and IPv6 definitions
for network addresses which are referred to in the
<code>gateway</code> gateway address specifications. Note
that the third static route specification includes the
<code>metric</code> attribute specification with a value of 2.
This particular route would *not* be preferred if there was
another existing rout on the system with the same address and
prefix but with a lower value for the metric. If there is a
route in the host system configuration that should be overriden
by a route in a virtual network whenever the virtual network is
running, the configuration for the system-defined route should
be modified to have a higher metric, and the route on the
virtual network given a lower metric (for example, the default
metric of "1").
</p>
<pre>
...
&lt;ip address="192.168.122.1" netmask="255.255.255.0"&gt;
&lt;dhcp&gt;
&lt;range start="192.168.122.128" end="192.168.122.254" /&gt;
&lt;/dhcp&gt;
&lt;/ip&gt;
&lt;route address="192.168.222.0" prefix="24" gateway="192.168.122.2" /&gt;
&lt;ip family="ipv6" address="2001:db8:ca2:2::1" prefix="64" /&gt;
&lt;route family="ipv6" address="2001:db8:ca2:3::" prefix="64" gateway="2001:db8:ca2:2::2"/&gt;
&lt;route family="ipv6" address="2001:db9:4:1::" prefix="64" gateway="2001:db8:ca2:2::3" metric='2'&gt;
&lt;/route&gt;
...
</pre>
<h3><a name="elementsAddress">Addressing</a></h3>
<p>
@@ -577,6 +633,7 @@
&lt;/dhcp&gt;
&lt;/ip&gt;
&lt;ip family="ipv6" address="2001:db8:ca2:2::1" prefix="64" /&gt;
&lt;route family="ipv6" address="2001:db9:ca1:1::" prefix="64" gateway="2001:db8:ca2:2::2" /&gt;
&lt;/network&gt;</pre>
<dl>
@@ -826,6 +883,33 @@
&lt;/ip&gt;
&lt;/network&gt;</pre>
<p>
Below is yet another IPv6 variation. This variation has only
IPv6 defined with DHCPv6 on the primary IPv6 network. A static
link if defined for a second IPv6 network which will not be
directly visible on the bridge interface but there will be a
static route defined for this network via the specified
gateway. Note that the gateway address must be directly
reachable via (on the same subnet as) one of the &lt;ip&gt;
addresses defined for this &lt;network&gt;.
<span class="since">Since 1.0.6</span>
</p>
<pre>
&lt;network&gt;
&lt;name&gt;net7&lt;/name&gt;
&lt;bridge name="virbr7" /&gt;
&lt;forward mode="route"/&gt;
&lt;ip family="ipv6" address="2001:db8:ca2:7::1" prefix="64" &gt;
&lt;dhcp&gt;
&lt;range start="2001:db8:ca2:7::100" end="2001:db8:ca2::1ff" /&gt;
&lt;host id="0:4:7e:7d:f0:7d:a8:bc:c5:d2:13:32:11:ed:16:ea:84:63" name="lucas" ip="2001:db8:ca2:2:3::4" /&gt;
&lt;/dhcp&gt;
&lt;/ip&gt;
&lt;route family="ipv6" address="2001:db8:ca2:8::" prefix="64" gateway="2001:db8:ca2:7::4" &gt;
&lt;/route&gt;
&lt;/network&gt;</pre>
<h3><a name="examplesPrivate">Isolated network config</a></h3>
<p>

22
docs/schemas/network.rng
View File

@@ -316,6 +316,28 @@
</optional>
</element>
</zeroOrMore>
<!-- <route> element -->
<zeroOrMore>
<!-- The (static) route element specifies a network address and gateway
address to access that network. Both the network address and
the gateway address must be specified. -->
<element name="route">
<optional>
<attribute name="family"><ref name="addr-family"/></attribute>
</optional>
<attribute name="address"><ref name="ipAddr"/></attribute>
<optional>
<choice>
<attribute name="netmask"><ref name="ipv4Addr"/></attribute>
<attribute name="prefix"><ref name="ipPrefix"/></attribute>
</choice>
</optional>
<attribute name="gateway"><ref name="ipAddr"/></attribute>
<optional>
<attribute name="metric"><ref name="unsignedInt"/></attribute>
</optional>
</element>
</zeroOrMore>
</interleave>
</element>
</define>