This is yet another refinement to the fix for CVE-2012-3411:
https://bugzilla.redhat.com/show_bug.cgi?id=833033
It turns out that it would be very intrusive to correctly backport the
entire --bind-dynamic option to older dnsmasq versions
(e.g. dnsmasq-2.48 that is used on RHEL6.x and CentOS 6.x), but very
simple to patch those versions to just use SO_BINDTODEVICE on all
their listening sockets (SO_BINDTODEVICE also has the desired effect
of permitting only traffic that was received on the interface(s) where
dnsmasq was set to listen.)
This patch modifies the dnsmasq capabilities detection to detect the
string:
--bind-interfaces with SO_BINDTODEVICE
in the output of "dnsmasq --version", and in that case realize that
using the old --bind-interfaces option is just as safe as
--bind-dynamic (and therefore *not* forbid creation of networks that
use public IP address ranges).
If -bind-dynamic is available, it is still preferred over
--bind-interfaces.
Note that this patch does no harm in upstream, or in any distro's
downstream if it happens to end up there, but builds for distros that
have a new enough dnsmasq to support --bind-dynamic do *NOT* need to
specifically backport this patch; it's only required for distro
releases that have dnsmasq too old to have --bind-dynamic (and those
distros will need to add the SO_BINDTODEVICE patch to dnsmasq,
*including the extra string in the --version output*, as well.
Somehow I managed to push the changes to this file with improper
indentation. This patch just re-indents, reformats the comment lines,
and re-groups a couple of multi-line strings so that they fit within
80 columns. The resulting binary should be identical.
A forgotten "!" in recently-modified code at the top of
networkRefreshDaemon() meant an improper early return, which led to 1)
dnsmasq config files not being updated from the newly modified config,
and 2) dnsmasq not being sent a SIGHUP so that it could learn about
the changes to the config.
virNetworkDefGetIpByIndex() returns NULL if there are no ip objects of
the requested type, and if there are no IP elements, then dnsmasq
shouldn't be running, so we can return early. Otherwise we should
rewrite the config files and send a SIGHUP.
This patch resolves the problem reported in:
https://bugzilla.redhat.com/show_bug.cgi?id=886663
The source of the problem was the fix for CVE 2011-3411:
https://bugzilla.redhat.com/show_bug.cgi?id=833033
which was originally committed upstream in commit
753ff83a50. That commit improperly
removed the "--except-interface lo" from dnsmasq commandlines when
--bind-dynamic was used (based on comments in the latter bug).
It turns out that the problem reported in the CVE could be eliminated
without removing "--except-interface lo", and removing it actually
caused each instance of dnsmasq to listen on localhost on port 53,
which created a new problem:
If another instance of dnsmasq using "bind-interfaces" (instead of
"bind-dynamic") had already been started (or if another instance
started later used "bind-dynamic"), this wouldn't have any immediately
visible ill effects, but if you tried to start another dnsmasq
instance using "bind-interfaces" *after* starting any libvirt
networks, the new dnsmasq would fail to start, because there was
already another process listening on port 53.
(Subsequent to the CVE fix, another patch changed the network driver
to put dnsmasq options in a conf file rather than directly on the
dnsmasq commandline, but preserved the same options.)
This patch changes the network driver to *always* add
"except-interface=lo" to dnsmasq conf files, regardless of whether we use
bind-dynamic or bind-interfaces. This way no libvirt dnsmasq instances
are listening on localhost (and the CVE is still fixed).
The actual code change is miniscule, but must be propogated through all
of the test files as well.
I noticed that /var/lib/libvirt/dnsmasq/*.conf used the wrong word;
it was intended to match the wording in src/util/xml.c.
* src/network/bridge_driver.c (networkDnsmasqConfContents): Fix typo.
* tests/networkxml2confdata/*.conf: Update accordingly.
Currently, we are only keeping a inactive XML configuration
in status dir. This is no longer enough as we need to keep
this class_id attribute so we don't overwrite old entries
when the daemon restarts. However, since there has already
been release which has just <network/> as root element,
and we want to keep things compatible, detect that loaded
status file is older one, and don't scream about it.
Network should be notified if we plug in or unplug an
interface, so it can perform some action, e.g. set/unset
network part of QoS. However, we are doing this in very
early stage, so iface->ifname isn't filled in yet. So
whenever we want to report an error, we must use a different
identifier, e.g. the MAC address.
These classes can borrow unused bandwidth. Basically,
only egress qdsics can have classes, therefore we can
do this kind of traffic shaping only on host's outgoing,
that is domain's incoming traffic.
This patch changes how parameters are passed to dnsmasq. Instead of
being on the command line, the parameters are put into a file (one
parameter per line) and a commandline --conf-file= specifies the
location of the file. The file is located in the same directory as
the leases file.
Putting the dnsmasq parameters into a configuration file
allows them to be examined and more easily understood than
examining the command lines displayed by "ps ax". This is
especially true when a number of networks have been started.
When the use of dnsmasq was originally done, the required command line
was simple, but it has gotten more complicated over time and will
likely become even more complicated in the future.
Note: The test conf files have all been renamed .conf instead of
.argv, and tests/networkxml2xmlargvdata was moved to
tests/networkxml2xmlconfdata.
The DHCPv6 support includes IPV6 dhcp-range and dhcp-host for one
IPv6 subnetwork on one interface. This support will only work
if dnsmasq version >= 2.64; otherwise an error occurs if
dhcp-range or dhcp-host is specified for an IPv6 address.
Essentially, this change provides the same DHCP support for IPv6
that has been available for IPv4.
With dnsmasq >= 2.64, support for the RA service is also now provided
by dnsmasq (radvd is no longer used/started). (Although at least one
version of dnsmasq prior to 2.64 "supported" IPv6 Router
Advertisement, there were bugs (fixed in 2.64) that rendered it
unusable.)
Documentation and the network schema has been updated
to reflect the new support.
The attributes of a <network> element's <forward> element were
previously stored directly in the virNetworkDef object, but
virNetworkUpdateForward() needs to operate on a <forward> in
isolation, so this patchs pulls out all those attributes into a
separate virNetworkForwardDef struct (and shortens their names
appropriately). This new object is contained in the virNetworkDef, not
pointed to by it, so there is no extra memory management.
This patch makes no functional changes, it only changes, e.g.,
"nForwardIfs" to "forward.nifs".
Since there is only a single virNetworkDNSDef for any virNetworkDef,
and it's trivial to determine whether or not it contains any real
data, it's much simpler (and fits more uniformly with the parse
function calling sequence of the parsers for many other objects that
are subordinates of virNetworkDef) if virNetworkDef *contains* an
virNetworkDNSDef rather than pointing to one.
Since it is now just a part of another object rather than its own
object, it no longer makes sense to have a *Free() function, so that
is changed to a *Clear() function.
More importantly though, ParseXML and Clear functions are needed for
the individual items contained in a virNetworkDNSDef (srv, txt, and
host records), but none of them have a *Clear(), and only two of the
three had *ParseXML() functions (both of which used a non-uniform
arglist). Those problems are cleared up by this patch - it splits the
higher-level Clear function into separate functions for each of the
three, creates a parse for txt records, and cleans up the srv and host
parsers, so we now have all the utility functions necessary to
implement virNetworkDefUpdateDNS(Host|Srv|Txt).
This shortens the name of the structs for srv and txt, and their
instances in virNetworkDNSDef, to be more compact and uniform with the
naming of the dns host array. It also changes the type of ntxts, etc
from unsigned int to size_t, so that they can be used directly as args
to VIR_*_ELEMENT.
This resolves: https://bugzilla.redhat.com/show_bug.cgi?id=767057
It was possible to define a network with <forward mode='bridge'> that
had both a bridge device and a forward device defined. These two are
mutually exclusive by definition (if you are using a bridge device,
then this is a host bridge, and if you have a forward dev defined,
this is using macvtap). It was also possible to put <ip>, <dns>, and
<domain> elements in this definition, although those aren't supported
by the current driver (although it's conceivable that some other
driver might support that).
The items that are invalid by definition, are now checked in the XML
parser (since they will definitely *always* be wrong), and the others
are checked in networkValidate() in the network driver (since, as
mentioned, it's possible that some other network driver, or even this
one, could some day support setting those).
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 has always been enabled by
default for IPv4, but disabled for IPv6 for security concerns, and
because it requires the ip6tables command to be operational (which
isn't the case on a system with the ipv6 module completely disabled).
This patch adds a new attribute "ipv6" at the toplevel of a <network>
object. If ipv6='yes', the extra ip6tables rules required to permite
inter-guest communications are added when the network is started. If
it is 'no', or not present, those rules will not be added; thus the
default behavior doesn't change, so there should be no compatibility
issues with any existing installations.
Note that virtual guests cannot communication with the virtualization
host via this interface, because the following kernel tunable has
been set:
net.ipv6.conf.<bridge_interface_name>.disable_ipv6 = 1
This assures that the bridge interface will not have an IPv6
link-local (fe80::) address.
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.
Currently to deal with auto-shutdown libvirtd must periodically
poll all stateful drivers. Thus sucks because it requires
acquiring both the driver lock and locks on every single virtual
machine. Instead pass in a "inhibit" callback to virStateInitialize
which drivers can invoke whenever they want to inhibit shutdown
due to existance of active VMs.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
The only important state that should prevent libvirtd shutdown
is from running VMs. Networks, host devices, network filters
and storage pools are all long lived resources that have no
significant in-memory state. They should not block shutdown.
This bug resolves CVE-2012-3411, which is described in the following
bugzilla report:
https://bugzilla.redhat.com/show_bug.cgi?id=833033
The following report is specifically for libvirt on Fedora:
https://bugzilla.redhat.com/show_bug.cgi?id=874702
In short, a dnsmasq instance run with the intention of listening for
DHCP/DNS requests only on a libvirt virtual network (which is
constructed using a Linux host bridge) would also answer queries sent
from outside the virtualization host.
This patch takes advantage of a new dnsmasq option "--bind-dynamic",
which will cause the listening socket to be setup such that it will
only receive those requests that actually come in via the bridge
interface. In order for this behavior to actually occur, not only must
"--bind-interfaces" be replaced with "--bind-dynamic", but also all
"--listen-address" options must be replaced with a single
"--interface" option. Fully:
--bind-interfaces --except-interface lo --listen-address x.x.x.x ...
(with --listen-address possibly repeated) is replaced with:
--bind-dynamic --interface virbrX
Of course libvirt can't use this new option if the host's dnsmasq
doesn't have it, but we still want libvirt to function (because the
great majority of libvirt installations, which only have mode='nat'
networks using RFC1918 private address ranges (e.g. 192.168.122.0/24),
are immune to this vulnerability from anywhere beyond the local subnet
of the host), so we use the new dnsmasqCaps API to check if dnsmasq
supports the new option and, if not, we use the "old" option style
instead. In order to assure that this permissiveness doesn't lead to a
vulnerable system, we do check for non-private addresses in this case,
and refuse to start the network if both a) we are using the old-style
options, and b) the network has a publicly routable IP
address. Hopefully this will provide the proper balance of not being
disruptive to those not practically affected, and making sure that
those who *are* affected get their dnsmasq upgraded.
(--bind-dynamic was added to dnsmasq in upstream commit
54dd393f3938fc0c19088fbd319b95e37d81a2b0, which was included in
dnsmasq-2.63)
In order to optionally take advantage of new features in dnsmasq when
the host's version of dnsmasq supports them, but still be able to run
on hosts that don't support the new features, we need to be able to
detect the version of dnsmasq running on the host, and possibly
determine from the help output what options are in this dnsmasq.
This patch implements a greatly simplified version of the capabilities
code we already have for qemu. A dnsmasqCaps device can be created and
populated either from running a program on disk, reading a file with
the concatenated output of "dnsmasq --version; dnsmasq --help", or
examining a buffer in memory that contains the concatenated output of
those two commands. Simple functions to retrieve capabilities flags,
the version number, and the path of the binary are also included.
bridge_driver.c creates a single dnsmasqCaps object at driver startup,
and disposes of it at driver shutdown. Any time it must be used, the
dnsmasqCapsRefresh method is called - it checks the mtime of the
binary, and re-runs the checks if the binary has changed.
networkxml2argvtest.c creates 2 "artificial" dnsmasqCaps objects at
startup - one "restricted" (doesn't support --bind-dynamic) and one
"full" (does support --bind-dynamic). Some of the test cases use one
and some the other, to make sure both code pathes are tested.
The virStateInitialize method and several cgroups methods were
using an 'int privileged' parameter or similar for dual-state
values. These are better represented with the bool type.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
The libvirt coding standard is to use 'function(...args...)'
instead of 'function (...args...)'. A non-trivial number of
places did not follow this rule and are fixed in this patch.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
When assigning the new persistent definition for a transient network
(thus making it persistent) the network needs to be marked persistent
before actually atempting to assign the definition.
Until now, the network undefine API was able to undefine only inactive
networks. The restriction doesn't make sense any more so this patch
implements changing networks to transient.
When a transient network was created some of the checks weren't run on
the definition allowing to start invalid networks.
This patch splits out code to the network validation function and
re-uses that code when creating transient networks.
The network driver didn't care about config files when a network was
destroyed, just when it was undefined leaving behind files for transient
networks.
This patch splits out the cleanup code to a helper function that handles
the cleanup if the inactive network object is being removed and re-uses
this code when getting rid of inactive networks.
The hosts file was created in the network definition function. This
patch moves the place the file is being created to the point where
dnsmasq is being started.
Three FORWARD chain rules are added and two INPUT chain rules
are added when a network is started but only the FORWARD chain
rules are removed when the network is destroyed.
This was found during testing of the fix for:
https://bugzilla.redhat.com/show_bug.cgi?id=868483
networkValidate was supposed to check for the existence of multiple
portgroups and report an error if this was encountered. It did, but
there were two problems:
1) even though it logged an error, it still returned success, allowing
the operation to continue.
2) It could exit the portgroup checking loop early (or possibly not
even do it once) if a vlan tag was supplied in the base network config
or one of the portgroups.
This patch fixes networkValidate to return failure in addition to
logging the error, and also changes it to not exit the portgroup
checking loop early. The logic was a bit off in the checking for vlan
anyway, and it's intertwined with fixing the early loop exit, so I
fixed that as well. Now it correctly checks for combinations where a
<virtualport> is specified in the base network def and <vlan> is given
in a portgroup, as well as the opposite (<vlan> in base network def
and <virtualport> in portgroup), and ignores the case of a disallowed
vlan when using *no* portgroup if there is a default portgroup (since
in that case there is no way to not use any portgroup).
This resolves: https://bugzilla.redhat.com/show_bug.cgi?id=868483
virNetworkUpdate, virNetworkDefine, and virNetworkCreate all three
allow network definitions to contain multiple <portgroup> elements
with default='yes'. Only a single default portgroup should be allowed
for each network.
This patch updates networkValidate() (called by both
virNetworkCreate() and virNetworkDefine()) and
virNetworkDefUpdatePortGroup (called by virNetworkUpdate() to not
allow multiple default portgroups.
This fixes the problem reported in:
https://bugzilla.redhat.com/show_bug.cgi?id=868389
Previously, the dnsmasq hosts file (used for static dhcp entries, and
addnhosts file (used for additional dns host entries) were only
created/referenced on the dnsmasq commandline if there was something
to put in them at the time the network was started. Once we can update
a network definition while it's active (which is now possible with
virNetworkUpdate), this is no longer a valid strategy - if there were
0 dhcp static hosts (resulting in no reference to the hosts file on the
commandline), then one was later added, the commandline wouldn't have
linked dnsmasq up to the file, so even though we create it, dnsmasq
doesn't pay any attention.
The solution is to just always create these files and reference them
on the dnsmasq commandline (almost always, anyway). That way dnsmasq
can notice when a new entry is added at runtime (a SIGHUP is sent to
dnsmasq by virNetworkUdpate whenever a host entry is added or removed)
The exception to this is that the dhcp static hosts file isn't created
if there are no lease ranges *and* no static hosts. This is because in
this case dnsmasq won't be setup to listen for dhcp requests anyway -
in that case, if the count of dhcp hosts goes from 0 to 1, dnsmasq
will need to be restarted anyway (to get it listening on the dhcp
port). Likewise, if the dhcp hosts count goes from 1 to 0 (and there
are no dhcp ranges) we need to restart dnsmasq so that it will stop
listening on port 67. These special situations are handled in the
bridge driver's networkUpdate() by checking for ((bool)
nranges||nhosts) both before and after the update, and triggering a
dnsmasq restart if the before and after don't match.
https://bugzilla.redhat.com/show_bug.cgi?id=866364
pointed out a crash due to virNetworkObjAssignDef free'ing
network->newDef without NULLing it afterward. A fix for this is in
upstream commit b7e9202401. While the
NULLing of newDef was a legitimate fix, newDef should have already
been empty (NULL) anyway (as indicated in the comment that was deleted
by that commit).
The reason that newDef had a non-NULL value (i.e. the root cause) was
that networkStartNetwork() had failed after populating
network->newDef, but then neglected to free/NULL newDef in the
cleanup.
(A bit of background here: network->newDef should contain the
persistent config of a network when a network is active (and of course
only when it is persisten), and NULL at all other times. There is also
a network->def which should contain the persistent definition of the
network when it is inactive, and the current live state at all other
times. The idea is that you can make changes to network->newDef which
will take effect the next time the network is restarted, but won't
mess with the current state of the network (virDomainObj has a similar
pair of virDomainDefs that behave in the same fashion). Personally I
think there should be a network->live and network->config, and the
location of the persistent config should *always* be in
network->config, but that's for a later cleanup).
Since I love things to be symmetric, I created a new function called
virNetworkObjUnsetDefTransient(), which reverses the effects of
virNetworkObjSetDefTransient(). I don't really like the name of the
new function, but then I also didn't really like the name of the old
one either (it's just named that way to match a similar function in
the domain conf code).
This function really should have been taking virDevicePCIAddress*
instead of the inefficient virDevicePCIAddress (results in copying two
entire structs onto the stack rather than just two pointers), and
returning a bool true/false (not matching is not necessarily a
"failure", as a -1 return would imply, and also using "if
(!virDevicePCIAddressEqual(x, y))" to mean "if x == y" is just a bit
counterintuitive).
I hit this problem recently when trying to create a bridge with an IPv6
address on a 3.2 kernel: dnsmasq (and, further, radvd) would not bind to
the given address, waiting 20s and then giving up with -EADDRNOTAVAIL
(resp. exiting immediately with "error parsing or activating the config
file", without libvirt noticing it, BTW). This can be reproduced with (I
think) any kernel >= 2.6.39 and the following XML (to be used with
"virsh net-create"):
<network>
<name>test-bridge</name>
<bridge name='testbr0' />
<ip family='ipv6' address='fd00::1' prefix='64'>
</ip>
</network>
(it happens even when you have an IPv4, too)
The problem is that since commit [1] (which, ironically, was made to
“help IPv6 autoconfiguration”) the linux bridge code makes bridges
behave like “real” devices regarding carrier detection. This makes the
bridges created by libvirt, which are started without any up devices,
stay with the NO-CARRIER flag set, and thus prevents DAD (Duplicate
address detection) from happening, thus letting the IPv6 address flagged
as “tentative”. Such addresses cannot be bound to (see RFC 2462), so
dnsmasq fails binding to it (for radvd, it detects that "interface XXX
is not RUNNING", thus that "interface XXX does not exist, ignoring the
interface" (sic)). It seems that this behavior was enhanced somehow with
commit [2] by avoiding setting NO-CARRIER on empty bridges, but I
couldn't reproduce this behavior on my kernel. Anyway, with the “dummy
tap to set MAC address” trick, this wouldn't work.
To fix this, the idea is to get the bridge's attached device to be up so
that DAD can happen (deactivating DAD altogether is not a good idea, I
think). Currently, libvirt creates a dummy TAP device to set the MAC
address of the bridge, keeping it down. But even if we set this device
up, it is not RUNNING as soon as the tap file descriptor attached to it
is closed, thus still preventing DAD. So, we must modify the API a bit,
so that we can get the fd, keep the tap device persistent, run the
daemons, and close it after DAD has taken place. After that, the bridge
will be flagged NO-CARRIER again, but the daemons will be running, even
if not happy about the device's state (but we don't really care about
the bridge's daemons doing anything when no up interface is connected to
it).
Other solutions that I envisioned were:
* Keeping the *-nic interface up: this would waste an fd for each
bridge during all its life. May be acceptable, I don't really
know.
* Stop using the dummy tap trick, and set the MAC address directly
on the bridge: it is possible since quite some time it seems,
even if then there is the problem of the bridge not being
RUNNING when empty, contrary to what [2] says, so this will need
fixing (and this fix only happened in 3.1, so it wouldn't work
for 2.6.39)
* Using the --interface option of dnsmasq, but I saw somewhere
that it's not used by libvirt for backward compatibility. I am
not sure this would solve this problem, though, as I don't know
how dnsmasq binds itself to it with this option.
This is why this patch does what's described earlier.
This patch also makes radvd start even if the interface is
“missing” (i.e. it is not RUNNING), as it daemonizes before binding to
it, and thus sometimes does it after the interface has been brought down
by us (by closing the tap fd), and then originally stops. This also
makes it stop yelling about it in the logs when the interface is down at
a later time.
[1]
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=1faa4356a3bd89ea11fb92752d897cff3a20ec0e
[2]
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=b64b73d7d0c480f75684519c6134e79d50c1b341
The bridge driver implementation of virNetworkUpdate() removes and
re-adds iptables rules any time a network has an <ip>, <forward>, or
<forward>/<interface> element updated. There are some types of
networks that have those elements and yet have no iptables rules
associated with them, and unfortunately the functions that remove/add
iptables rules don't check the type of network before attempting to
remove/add the rules, sometimes leading to an erroneous failure of the
entire update operation.
Under normal circumstances I would refactor the lower level functions
to be more robust, but to avoid code churn as much as possible, I've
just added extra checks directly to networkUpdate().
https://www.gnu.org/licenses/gpl-howto.html recommends that
the 'If not, see <url>.' phrase be a separate sentence.
* tests/securityselinuxhelper.c: Remove doubled line.
* tests/securityselinuxtest.c: Likewise.
* globally: s/; If/. If/
Two changes are introduced in this patch:
- The first change removes ATTRIBUTE_RETURN_CHECK from
virNetDevBandwidthClear, because it was called with ignore_value
always, anyway. The function is used even when it's not necessary
to call it, just for cleanup purposes.
- The second change is added ignoring of the command's exit status,
since it may report an error even when run just as "to be sure we
clean up" function. No libvirt errors are suppresed by this.
A user on IRC had accidentally killed all of his libvirt-started
dnsmasq instances (due to a buggy dnsmasq service script in Fedora
16), and had hoped that libvirtd would notice this on restart and
reload all the dnsmasq daemons (as it does with iptables
rules). Unfortunately this was not the case - as long as the network
object had a pid registered for dnsmasq and/or radvd, it assumed that
the processes were running.
This patch takes advantage of the new utility functions in
bridge_driver.c to do a "refresh" of all radvd and dnsmasq processes
started by libvirt each time libvirtd is restarted - this function
attempts to do a SIGHUP of each existing process, and if that fails,
it restarts the process, rebuilding all the associated config files
and commandline parameters in the process. This normally has no
effect, but will be useful in solving the occasional "odd situation"
without needing to take the drastic step of destroying/re-starting the
network.
Call the network_conf function that modifies the live/persistent/both
config, then refresh/restart dnsmasq/radvd if necessary, and finally
save the config in the proper place(s).
This patch also needed to uncomment a few utility functions that were
added inside #if 0 in the previous commit (to avoid compiler errors
due to unreferenced static functions).
This patch splits the starting of dnsmasq and radvd into multiple
files, and adds new networkRefreshXX() and networkRestartXX()
functions for each. These new functions are currently commented out
because they won't be used until the next commit, and the compile options
require all static functions to be used.
networkRefreshXX() - rewrites any file-based config for dnsmasq/radvd,
and sends SIGHUP to the process to make it reread its config. If the
program isn't already running, it's just started.
networkRestartXX() - kills the given program, waits for it to exit
(see the comments in the function networkKillDaemon()), then calls
networkStartXX().
This commit is here mostly as a checkpoint to verify no change in
functional behavior after refactoring networkStartXX() functions to
fit in with these new functions.
These new functions are highly inspired by those in domain_conf.c (but
not identical), and are intended to make it simpler to update the
various combinations of live/persistent network configs.
The network driver wasn't previously as careful about the separation
between the live "status" in network->def and the persistent "config"
in network->newDef (or sometimes in network->def). This series
attempts to remedy some of that, but probably doesn't go all the way
(enough to get these functions working and enable continued work on
virNetworkUpdate though).
bridge_driver.c and test_driver.c were updated in a few places to take
advantage of the new functions and/or account for changes in argument
lists.
