2:54 p.m.
This is a series of patches to implement DHCP IP & hostname mappings
for libvirt virtual networks.
** NOTE: This patch is not to be applied. There is some memory
corruption bug which I'm still tracking down.
What this patch allows you to do is to create a table of IP address to
host (defined by its hardware / MAC address) for each virtual network.
Optionally you can also assign a hostname. When a host starts up and
requests an IP address through DHCP, if it is in this table then it
gets the fixed IP address from the table and, optionally, a fixed
hostname.
Four new API calls are added. Two are required to list the contents
of the mapping table. Two more allow you to add and delete a mapping.
The mapping table is semi-permanent. It is stored in
/var/lib/libvirt/hosts-<networkname>.conf and survives across libvirtd
restarts.
The implementation simply uses dnsmasq's --dhcp-hostsfile flag. Refer
to the dnsmasq(1) manual page.
Rich.
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2:56 p.m.
New subject: [Libvir] 1/4 Additions to the public API
This just adds the four new functions to the public API.
Rich.
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4:13 p.m.
New subject: [Libvir] 1/4 Additions to the public API
On Thu, Feb 21, 2008 at 08:56:17PM +0000, Richard W.M. Jones wrote:
This just adds the four new functions to the public API.
[...]
+/**
+ * virNetworkDHCPHostMapping:
+ *
+ * hostname mappings are returned by virNetworkListDHCPHostMapping.
+ */
+typedef struct _virNetworkDHCPHostMapping {
+ char *hwaddr;
+ char *ipaddr;
+ char *hostname;
+} virNetworkDHCPHostMapping;
+
+typedef virNetworkDHCPHostMapping *virNetworkDHCPHostMappingPtr;
+
[...]
+int virNetworkListDHCPHostMappings
+ (virNetworkPtr network,
+ virNetworkDHCPHostMappingPtr *const mappings,
+ int maxmappings);
+int virNetworkFreeDHCPHostMappings
+ (virNetworkDHCPHostMappingPtr *const mappings,
+ int maxmappings);
Hum, do we really need to expose this structure at the API level, since we
use it only for listing. Since everything is provided as strings why not
use something like
int virNetworkListDHCPHostMappings (virNetworkPtr network,
int maxmappings,
char **hwaddrtab,
char **ipaddrtab,
char **hostnametab);
This also avoids the free function too, same functionality, quite a simpler
interface.
Also I don't understand the 'const' in that function and what
virNetworkFreeDHCPHostMappings is supposed to be used for. If mappings
is allocated by the user, it doesn't need a library deallocator, if it's
allocated by the library I can't see how it's const, the API confuses me
I must admit.
Daniel
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Daniel Veillard | virtualization library http://libvirt.org/
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4:21 p.m.
New subject: [Libvir] 1/4 Additions to the public API
On Thu, Feb 21, 2008 at 05:13:51PM -0500, Daniel Veillard wrote:
On Thu, Feb 21, 2008 at 08:56:17PM +0000, Richard W.M. Jones wrote:
> This just adds the four new functions to the public API.
[...]
> +/**
> + * virNetworkDHCPHostMapping:
> + *
> + * hostname mappings are returned by virNetworkListDHCPHostMapping.
> + */
> +typedef struct _virNetworkDHCPHostMapping {
> + char *hwaddr;
> + char *ipaddr;
> + char *hostname;
> +} virNetworkDHCPHostMapping;
> +
> +typedef virNetworkDHCPHostMapping *virNetworkDHCPHostMappingPtr;
> +
[...]
> +int virNetworkListDHCPHostMappings
> + (virNetworkPtr network,
> + virNetworkDHCPHostMappingPtr *const mappings,
> + int maxmappings);
> +int virNetworkFreeDHCPHostMappings
> + (virNetworkDHCPHostMappingPtr *const mappings,
> + int maxmappings);
Hum, do we really need to expose this structure at the API level, since we
use it only for listing. Since everything is provided as strings why not
use something like
int virNetworkListDHCPHostMappings (virNetworkPtr network,
int maxmappings,
char **hwaddrtab,
char **ipaddrtab,
char **hostnametab);
This also avoids the free function too, same functionality, quite a simpler
interface.
Simpler for who ? Apps using this data now have to pass around a whole
bunch of pointers, instead of a single virNetworkDHCPHostMapping. When
you map this API into higher level languages a struct is also going to be
a much nicer thing to represent.
Dan.
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4:39 p.m.
New subject: [Libvir] 1/4 Additions to the public API
On Thu, Feb 21, 2008 at 10:21:09PM +0000, Daniel P. Berrange wrote:
On Thu, Feb 21, 2008 at 05:13:51PM -0500, Daniel Veillard wrote:
> On Thu, Feb 21, 2008 at 08:56:17PM +0000, Richard W.M. Jones wrote:
> > This just adds the four new functions to the public API.
> [...]
> > +/**
> > + * virNetworkDHCPHostMapping:
> > + *
> > + * hostname mappings are returned by virNetworkListDHCPHostMapping.
> > + */
> > +typedef struct _virNetworkDHCPHostMapping {
> > + char *hwaddr;
> > + char *ipaddr;
> > + char *hostname;
> > +} virNetworkDHCPHostMapping;
> > +
> > +typedef virNetworkDHCPHostMapping *virNetworkDHCPHostMappingPtr;
> > +
> [...]
> > +int virNetworkListDHCPHostMappings
> > + (virNetworkPtr network,
> > + virNetworkDHCPHostMappingPtr *const mappings,
> > + int maxmappings);
> > +int virNetworkFreeDHCPHostMappings
> > + (virNetworkDHCPHostMappingPtr *const
mappings,
> > + int maxmappings);
>
> Hum, do we really need to expose this structure at the API level, since we
> use it only for listing. Since everything is provided as strings why not
> use something like
>
> int virNetworkListDHCPHostMappings (virNetworkPtr network,
> int maxmappings,
> char **hwaddrtab,
> char **ipaddrtab,
> char **hostnametab);
>
> This also avoids the free function too, same functionality, quite a simpler
> interface.
Simpler for who ? Apps using this data now have to pass around a whole
bunch of pointers, instead of a single virNetworkDHCPHostMapping. When
you map this API into higher level languages a struct is also going to be
a much nicer thing to represent.
if the struct was a simpler representation it would be used for Add too,
I don't think it's the case. Maybe the 3 arrays is not the nicest but
defining a public structure holding 3 strings feels strange to me,
especially when in the other place we use the 3 strings directly.
Having a deallocator but no allocator function looks strange to me too.
Daniel
--
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Daniel Veillard | virtualization library http://libvirt.org/
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3:37 a.m.
New subject: [Libvir] 1/4 Additions to the public API
[... Struct versus 3 arrays discussion snipped ...]
I think both representations have their merits, and DV's "3 arrays"
approach is much easier to marshal through the remote code, and
simpler to produce OCaml bindings for (no idea about Python).
The reason for using the struct was to provide extensibility. The
dnsmasq "--dhcp-hostfiles" file format is much richer than merely
(hwaddr, ipaddr [, hostname]) triplets. For example it can include
lease times and client IDs[1].
The API calls I chose give us the opportunity to extend the structure
with new elements in future. But to do this you have to provide a
deallocator (because additional elements may need to be freed), and
flags on the Add call.
If we agree that we won't / can't / don't want to extend this
structure, I'd be more than happy to use 3 arrays and lose the
deallocator. It will simplify the remote code considerably.
Rich.
[1] See the dnsmasq manual page for the full details. I'm not
convinced that the format is even well-specified by that manpage so
probably at some point we'll need to look at the source code.
--
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Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod
Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in
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3:51 a.m.
New subject: [Libvir] 1/4 Additions to the public API
On Fri, 2008-02-22 at 09:37 +0000, Richard W.M. Jones wrote:
The reason for using the struct was to provide extensibility.
Another reason for adding it via the network's XML definition rather
than an ABI/API ... isn't extensibility the reason we don't have e.g. an
API for listing, adding and removing domain network interfaces?
Cheers,
Mark.
4:16 a.m.
New subject: [Libvir] 1/4 Additions to the public API
On Fri, Feb 22, 2008 at 09:37:24AM +0000, Richard W.M. Jones wrote:
[... Struct versus 3 arrays discussion snipped ...]
First I should state it's a cool idea, even if I reacted to the
proposed API. I also agree to some extend with Mark, the on disk
storage should probably go in the network description. But that's
orthogonal to the API side :)
I think both representations have their merits, and DV's "3
arrays"
approach is much easier to marshal through the remote code, and
simpler to produce OCaml bindings for (no idea about Python).
For python we will need manually generated bindings anyway to
have something which looks nice from a python viewpoint, for example
the list would be nicer exported as a dictionary based on the host
names, and one or the other won't make it much different.
The reason for using the struct was to provide extensibility. The
dnsmasq "--dhcp-hostfiles" file format is much richer than merely
(hwaddr, ipaddr [, hostname]) triplets. For example it can include
lease times and client IDs[1].
Okay, then we probably need to abstract the notion of dhcp host
but I would not expose the structure then (which was my main beef
in the intial patch) let's keep the structure private and provide
accessors and lookups in the library, then we will be able to extend.
The API calls I chose give us the opportunity to extend the
structure
with new elements in future. But to do this you have to provide a
deallocator (because additional elements may need to be freed), and
flags on the Add call.
Agreed, but if you provide deallocator, provide allocators too,
and acessors.
If we agree that we won't / can't / don't want to extend
this
structure, I'd be more than happy to use 3 arrays and lose the
deallocator. It will simplify the remote code considerably.
Actually at the remote level we probably don't need to expose
the informations in the exact same way as in the public API, do we ?
The way things are exposed though the API opaque structure doesn't
have to match exactly the way it's done at the driver level, and
there we can shoot for the most convenient way (while trying to be
portable if we extend the set of informations).
[1] See the dnsmasq manual page for the full details. I'm not
convinced that the format is even well-specified by that manpage so
probably at some point we'll need to look at the source code.
heh
Daniel
--
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Daniel Veillard | virtualization library http://libvirt.org/
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http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/
4:47 a.m.
New subject: [Libvir] 1/4 Additions to the public API
On Fri, 2008-02-22 at 05:16 -0500, Daniel Veillard wrote:
I also agree to some extend with Mark, the on disk
storage should probably go in the network description. But that's
orthogonal to the API side :)
Heh, no it's not orthogonal ... XML *is* the API for this kind of stuff
across libvirt :-)
Cheers,
Mark.
5:07 a.m.
New subject: [Libvir] 1/4 Additions to the public API
On Fri, Feb 22, 2008 at 10:47:44AM +0000, Mark McLoughlin wrote:
On Fri, 2008-02-22 at 05:16 -0500, Daniel Veillard wrote:
> I also agree to some extend with Mark, the on disk
> storage should probably go in the network description. But that's
> orthogonal to the API side :)
Heh, no it's not orthogonal ... XML *is* the API for this kind of stuff
across libvirt :-)
Sort of. XML is used as a way to avoid making any ABI guarantees.
I had a look at the implementation of the network XML. There are
three calls which matter:
virNetworkDefineXML
Define the network from the XML definition, but don't start it up.
Saves the XML into a private directory so that it will be loaded
when libvirtd restarts (and depending on the autostart setting may
also be started up automatically).
The current implementation always completely recreates the
internal network definitions from scratch.
virNetworkCreateXML
Start up the network from the XML definition.
As far as I can see, this doesn't persist the XML so the network
will disappear after libvirtd is restarted.
The current implementation always completely recreates the
internal network definitions from scratch.
virNetworkUndefine
Stops the network.
Deletes the config file and autostart setting from the private
directory.
The first two calls need to be changed to look for incremental changes
in the XML, since its better to avoid fully restarting dnsmasq, and we
certainly don't want to try taking down the bridge.
Rich.
--
Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/
Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod
Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in
England and Wales under Company Registration No. 03798903
4:20 p.m.
New subject: [Libvir] 1/4 Additions to the public API
On Fri, Feb 22, 2008 at 11:07:15AM +0000, Richard W.M. Jones wrote:
On Fri, Feb 22, 2008 at 10:47:44AM +0000, Mark McLoughlin wrote:
> On Fri, 2008-02-22 at 05:16 -0500, Daniel Veillard wrote:
>
> > I also agree to some extend with Mark, the on disk
> > storage should probably go in the network description. But that's
> > orthogonal to the API side :)
>
> Heh, no it's not orthogonal ... XML *is* the API for this kind of stuff
> across libvirt :-)
Sort of. XML is used as a way to avoid making any ABI guarantees.
I had a look at the implementation of the network XML. There are
three calls which matter:
virNetworkDefineXML
Define the network from the XML definition, but don't start it up.
Saves the XML into a private directory so that it will be loaded
when libvirtd restarts (and depending on the autostart setting may
also be started up automatically).
The current implementation always completely recreates the
internal network definitions from scratch.
virNetworkCreateXML
Start up the network from the XML definition.
As far as I can see, this doesn't persist the XML so the network
will disappear after libvirtd is restarted.
The current implementation always completely recreates the
internal network definitions from scratch.
virNetworkUndefine
Stops the network.
Deletes the config file and autostart setting from the private
directory.
The first two calls need to be changed to look for incremental changes
in the XML, since its better to avoid fully restarting dnsmasq, and we
certainly don't want to try taking down the bridge.
We can't change the semantics of these calls. virNetworkDefineXML()
explicitly does not affect the current live config, saving the config
to take effect next time the network is started. This is the same semantics
as the virDomainDefineXML() call, and the virStoragePoolDefineXML()
calls.
To do live updates, we'd need API similar to the domain device hot attach
and detach APIs
Dan.
--
|=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=|
|=- Perl modules: http://search.cpan.org/~danberr/ -=|
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4:07 a.m.
New subject: [Libvir] 1/4 Additions to the public API
On Sun, Feb 24, 2008 at 10:20:24PM +0000, Daniel P. Berrange wrote:
We can't change the semantics of these calls.
virNetworkDefineXML()
explicitly does not affect the current live config, saving the config
to take effect next time the network is started. This is the same semantics
as the virDomainDefineXML() call, and the virStoragePoolDefineXML()
calls.
Understood.
To do live updates, we'd need API similar to the domain device
hot attach
and detach APIs
Well given that it sounds like the original implementation is just as
good. Any further comments on that?
(http://www.redhat.com/archives/libvir-list/2008-February/thread.html#00281)
Rich.
--
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7:10 a.m.
New subject: [Libvir] 1/4 Additions to the public API
On Mon, Feb 25, 2008 at 10:07:48AM +0000, Richard W.M. Jones wrote:
On Sun, Feb 24, 2008 at 10:20:24PM +0000, Daniel P. Berrange wrote:
> We can't change the semantics of these calls. virNetworkDefineXML()
> explicitly does not affect the current live config, saving the config
> to take effect next time the network is started. This is the same semantics
> as the virDomainDefineXML() call, and the virStoragePoolDefineXML()
> calls.
Understood.
> To do live updates, we'd need API similar to the domain device hot attach
> and detach APIs
Well given that it sounds like the original implementation is just as
good. Any further comments on that?
(http://www.redhat.com/archives/libvir-list/2008-February/thread.html#00281)
I'm fine with your original proposal, or DV's suggestion to use 3 separate
arrays instead of the struct.
Dan.
--
|=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=|
|=- Perl modules: http://search.cpan.org/~danberr/ -=|
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2:57 p.m.
New subject: [Libvir] 2/4 QEMU driver
This patch implements the QEMU driver part of the change.
We run dnsmasq with the extra --dhcp-hostsfile=... parameter, and then
include functions to read and write this file.
When the file changes we send SIGHUP to dnsmasq.
Rich.
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2:58 p.m.
New subject: [Libvir] 3/4 Remote driver
This implements the changes in the client & server ends of the remote
driver.
Rich.
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Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod
Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in
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2:59 p.m.
New subject: [Libvir] 4/4 virsh
This adds four new subcommands to virsh allowing you to control the
new functionality.
Rich.
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Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod
Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in
England and Wales under Company Registration No. 03798903
2:04 a.m.
Hi Rich,
On Thu, 2008-02-21 at 20:54 +0000, Richard W.M. Jones wrote:
What this patch allows you to do is to create a table of IP address
to
host (defined by its hardware / MAC address) for each virtual network.
Optionally you can also assign a hostname. When a host starts up and
requests an IP address through DHCP, if it is in this table then it
gets the fixed IP address from the table and, optionally, a fixed
hostname.
Four new API calls are added. Two are required to list the contents
of the mapping table. Two more allow you to add and delete a mapping.
The mapping table is semi-permanent. It is stored in
/var/lib/libvirt/hosts-<networkname>.conf and survives across libvirtd
restarts.
Cool stuff, but why isn't this just an addition to the network's XML
definition?
Cheers,
Mark.
3:38 a.m.
On Fri, Feb 22, 2008 at 08:04:26AM +0000, Mark McLoughlin wrote:
On Thu, 2008-02-21 at 20:54 +0000, Richard W.M. Jones wrote:
> What this patch allows you to do is to create a table of IP address to
> host (defined by its hardware / MAC address) for each virtual network.
> Optionally you can also assign a hostname. When a host starts up and
> requests an IP address through DHCP, if it is in this table then it
> gets the fixed IP address from the table and, optionally, a fixed
> hostname.
>
> Four new API calls are added. Two are required to list the contents
> of the mapping table. Two more allow you to add and delete a mapping.
>
> The mapping table is semi-permanent. It is stored in
> /var/lib/libvirt/hosts-<networkname>.conf and survives across libvirtd
> restarts.
Cool stuff, but why isn't this just an addition to the network's XML
definition?
Well indeed. It's essentially because this implementation was thought
to be easier. I haven't tried the other implementation so I'm not
categorically sure that is true.
Rich.
--
Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/
Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod
Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in
England and Wales under Company Registration No. 03798903
4:17 p.m.
On Fri, Feb 22, 2008 at 08:04:26AM +0000, Mark McLoughlin wrote:
Hi Rich,
On Thu, 2008-02-21 at 20:54 +0000, Richard W.M. Jones wrote:
> What this patch allows you to do is to create a table of IP address to
> host (defined by its hardware / MAC address) for each virtual network.
> Optionally you can also assign a hostname. When a host starts up and
> requests an IP address through DHCP, if it is in this table then it
> gets the fixed IP address from the table and, optionally, a fixed
> hostname.
>
> Four new API calls are added. Two are required to list the contents
> of the mapping table. Two more allow you to add and delete a mapping.
>
> The mapping table is semi-permanent. It is stored in
> /var/lib/libvirt/hosts-<networkname>.conf and survives across libvirtd
> restarts.
Cool stuff, but why isn't this just an addition to the network's XML
definition?
It is possible, but tricky to get the on-the-fly updates when the semantics
of the APIs for creating/definging networks.
If you call 'virNetworkDefine' with a new XML doc, it loads the new config
into memory, but does not apply the config until you destroy & restart
the network in question. We can't destroy & restart the network since this
would break networking for any live guests attached to the network.
So if we wanted to represent this in the master XML for a network we'd have
to follow the example of domain device hotplug, and have APIs to add/remove
a snippet of XML describing the new entry.
virNetworkAddHostMapping(virNetworkPtr net, char *xml);
virNetworkRemoveHostMapping(virNetworkPtr net, char *xml);
Where the XML was:
'<mapping hostname="foo"
mac="00:33:22:55:44:11"/>'
Dan.
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18 comments
4 participants
participants (4)
-
Daniel P. Berrange -
Daniel Veillard -
Mark McLoughlin -
Richard W.M. Jones