Since it's not strictly a uuid anymore

This allows event implementations to match on something other
than an object's uuid, like nodedev or interface objects which
don't have a uuid.

This should not have any functional difference, it's just a step
towards matching on non-uuid string keys

In every other instance virObjectEventCallbackPtr is named 'cb',
and in other code 'event' usually means a virObjectEventPtr

It's only used in object_event.c, so remove it from the header. We
need to move the _virObjectEventCallback definition earlier as a
result.

Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>

Filtering monitor events by name requires tracking the name for
the duration of the filtering.  In order to free the name, I
found it easiest to just piggyback on the user's freecb function,
which gets called when the event is deregistered.

For events without a name filter, we have the design of multiple
client registrations sharing a common server registration, because
the server side uses the same callback function and we reject
duplicate use of the same function.  But with events in the mix,
we want to be able to allow the same function pointer to be used
with more than one event name.  The solution is to tweak the
duplicate detection code to only act when there is no additional
filtering; if name filtering is in use, there is exactly one
client registration per server registration.  Yes, this means
that there is no longer a bound on the number of server
registrations possible, so a malicious client could repeatedly
register for the same name event to exhaust server memory.  On
the other hand, we already restricted monitor events to require
write access (compared to normal events only needing read access),
and separated it into the intentionally unsupported
libvirt-qemu.so, with documentation that using this function is
for debug purposes only; so it is not a security risk worth
worrying about a client trying to abuse multiple registrations.

* src/conf/domain_event.c (virDomainQemuMonitorEventData): New
struct.
(virDomainQemuMonitorEventFilter)
(virDomainQemuMonitorEventCleanup): New functions.
(virDomainQemuMonitorEventDispatchFunc)
(virDomainQemuMonitorEventStateRegisterID): Use new struct.
* src/conf/object_event.c (virObjectEventCallbackListCount)
(virObjectEventCallbackListAddID)
(virObjectEventCallbackListRemoveID)
(virObjectEventCallbackListMarkDeleteID): Drop duplicate detection
when filtering is in effect.
Signed-off-by: NEric Blake <eblake@redhat.com>

Any source file which calls the logging APIs now needs
to have a VIR_LOG_INIT("source.name") declaration at
the start of the file. This provides a static variable
of the virLogSource type.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

This fixes a possible double free. In virNetworkAssignDef() if
virBitmapNew() fails, then virNetworkObjFree(network) is called.
However, with network->def pointing to actual @def. So if caller
frees @def again, ...

Moreover, this fixes one possible memory leak too. In
virInterfaceAssignDef() if appending to the list of interfaces
fails, we ought to call virInterfaceObjFree() instead of bare
VIR_FREE().

Although, in order to do that some array size variables needs
to be turned into size_t rather than int.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

We want to convert over to server-side events, even for older
APIs.  To do that, the client side of the remote driver wants
to distinguish between legacy virConnectDomainEventRegister and
normal virConnectDomainEventRegisterAny, while knowing the
client callbackID and the server's serverID for both types of
registration.  The client also needs to probe whether the
server supports server-side filtering.  However, for ease of
review, we don't actually use the new RPCs until a later patch.

* src/conf/object_event_private.h (virObjectEventStateCallbackID):
Add parameter.
* src/conf/object_event.c (virObjectEventCallbackListAddID)
(virObjectEventStateRegisterID): Separate legacy from callbackID.
(virObjectEventStateCallbackID): Pass through parameter.
(virObjectEventCallbackLookup): Let legacy and global domain
lifecycle events share a common remoteID.
* src/conf/network_event.c (virNetworkEventStateRegisterID):
Update caller.
* src/conf/domain_event.c (virDomainEventStateRegister)
(virDomainEventStateRegisterID, virDomainEventStateDeregister):
Likewise.
(virDomainEventStateRegisterClient)
(virDomainEventStateCallbackID): Implement new functions.
* src/conf/domain_event.h (virDomainEventStateRegisterClient)
(virDomainEventStateCallbackID): New prototypes.
* src/remote/remote_driver.c (private_data): Add field.
(doRemoteOpen): Probe server feature.
(remoteConnectDomainEventRegister)
(remoteConnectDomainEventRegisterAny): Use new function.
Signed-off-by: NEric Blake <eblake@redhat.com>

Ever since ACL filtering was added in commit 76397360 (v1.1.1), a
user could still use event registration to obtain access to a
domain that they could not normally access via virDomainLookup*
or virConnectListAllDomains and friends.  We already have the
framework in the RPC generator for creating the filter, and
previous cleanup patches got us to the point that we can now
wire the filter through the entire object event stack.

Furthermore, whether or not domain:getattr is honored, use of
global events is a form of obtaining a list of networks, which
is covered by connect:search_domains added in a93cd08f (v1.1.0).
Ideally, we'd have a way to enforce connect:search_domains when
doing global registrations while omitting that check on a
per-domain registration.  But this patch just unconditionally
requires connect:search_domains, even when no list could be
obtained, based on the following observations:
1. Administrators are unlikely to grant domain:getattr for one
or all domains while still denying connect:search_domains - a
user that is able to manage domains will want to be able to
manage them efficiently, but efficient management includes being
able to list the domains they can access.  The idea of denying
connect:search_domains while still granting access to individual
domains is therefore not adding any real security, but just
serves as a layer of obscurity to annoy the end user.
2. In the current implementation, domain events are filtered
on the client; the server has no idea if a domain filter was
requested, and must therefore assume that all domain event
requests are global.  Even if we fix the RPC protocol to
allow for server-side filtering for newer client/server combos,
making the connect:serach_domains ACL check conditional on
whether the domain argument was NULL won't benefit older clients.
Therefore, we choose to document that connect:search_domains
is a pre-requisite to any domain event management.

Network events need the same treatment, with the obvious
change of using connect:search_networks and network:getattr.

* src/access/viraccessperm.h
(VIR_ACCESS_PERM_CONNECT_SEARCH_DOMAINS)
(VIR_ACCESS_PERM_CONNECT_SEARCH_NETWORKS): Document additional
effect of the permission.
* src/conf/domain_event.h (virDomainEventStateRegister)
(virDomainEventStateRegisterID): Add new parameter.
* src/conf/network_event.h (virNetworkEventStateRegisterID):
Likewise.
* src/conf/object_event_private.h (virObjectEventStateRegisterID):
Likewise.
* src/conf/object_event.c (_virObjectEventCallback): Track a filter.
(virObjectEventDispatchMatchCallback): Use filter.
(virObjectEventCallbackListAddID): Register filter.
* src/conf/domain_event.c (virDomainEventFilter): New function.
(virDomainEventStateRegister, virDomainEventStateRegisterID):
Adjust callers.
* src/conf/network_event.c (virNetworkEventFilter): New function.
(virNetworkEventStateRegisterID): Adjust caller.
* src/remote/remote_protocol.x
(REMOTE_PROC_CONNECT_DOMAIN_EVENT_REGISTER)
(REMOTE_PROC_CONNECT_DOMAIN_EVENT_REGISTER_ANY)
(REMOTE_PROC_CONNECT_NETWORK_EVENT_REGISTER_ANY): Generate a
filter, and require connect:search_domains instead of weaker
connect:read.
* src/test/test_driver.c (testConnectDomainEventRegister)
(testConnectDomainEventRegisterAny)
(testConnectNetworkEventRegisterAny): Update callers.
* src/remote/remote_driver.c (remoteConnectDomainEventRegister)
(remoteConnectDomainEventRegisterAny): Likewise.
* src/xen/xen_driver.c (xenUnifiedConnectDomainEventRegister)
(xenUnifiedConnectDomainEventRegisterAny): Likewise.
* src/vbox/vbox_tmpl.c (vboxDomainGetXMLDesc): Likewise.
* src/libxl/libxl_driver.c (libxlConnectDomainEventRegister)
(libxlConnectDomainEventRegisterAny): Likewise.
* src/qemu/qemu_driver.c (qemuConnectDomainEventRegister)
(qemuConnectDomainEventRegisterAny): Likewise.
* src/uml/uml_driver.c (umlConnectDomainEventRegister)
(umlConnectDomainEventRegisterAny): Likewise.
* src/network/bridge_driver.c
(networkConnectNetworkEventRegisterAny): Likewise.
* src/lxc/lxc_driver.c (lxcConnectDomainEventRegister)
(lxcConnectDomainEventRegisterAny): Likewise.
Signed-off-by: NEric Blake <eblake@redhat.com>

In order to mirror a server with per-object filtering, the client
needs to track which server callbackID is servicing the client
callback.  This patch introduces the notion of a serverID, as
well as the plumbing to use it for network events, although the
actual complexity of using per-object filtering in the remote
driver is deferred to a later patch.

* src/conf/object_event.h (virObjectEventStateEventID): Add parameter.
(virObjectEventStateQueueRemote, virObjectEventStateSetRemote):
New prototypes.
(virObjectEventStateRegisterID): Move...
* src/conf/object_event_private.h: ...here, and add parameter.
(_virObjectEvent): Add field.
* src/conf/network_event.h (virNetworkEventStateRegisterClient): New
prototype.
* src/conf/object_event.c (_virObjectEventCallback): Add field.
(virObjectEventStateSetRemote): New function.
(virObjectEventStateQueue): Make wrapper around...
(virObjectEventStateQueueRemote): New function.
(virObjectEventCallbackListCount): Tweak return count when remote
id matching is used.
(virObjectEventCallbackLookup, virObjectEventStateRegisterID):
Tweak registration when remote id matching will be used.
(virObjectEventNew): Default to no remote id.
(virObjectEventCallbackListAddID): Likewise, but set remote id
when one is available.
(virObjectEventCallbackListRemoveID)
(virObjectEventCallbackListMarkDeleteID): Adjust return value when
remote id was set.
(virObjectEventStateEventID): Query existing id.
(virObjectEventDispatchMatchCallback): Require matching event id.
(virObjectEventStateCallbackID): Adjust caller.
* src/conf/network_event.c (virNetworkEventStateRegisterClient): New
function.
(virNetworkEventStateRegisterID): Update caller.
* src/conf/domain_event.c (virDomainEventStateRegister)
(virDomainEventStateRegisterID): Update callers.
* src/remote/remote_driver.c
(remoteConnectNetworkEventRegisterAny)
(remoteConnectNetworkEventDeregisterAny)
(remoteConnectDomainEventDeregisterAny): Likewise.
(remoteEventQueue): Hoist earlier to avoid forward declaration,
and add parameter.  Adjust all callers.
* src/libvirt_private.syms (conf/object_event.h): Drop function.
Signed-off-by: NEric Blake <eblake@redhat.com>

Commit cfd62c1f was incomplete; I found more cases where error
messages were being overwritten, and where the code between
the three registration/deregistration APIs was not consistent.

Since it is fairly easy to trigger an attempt to deregister an
unregistered object through public API, I also changed the error
message from VIR_ERR_INTERNAL_ERROR to VIR_ERR_INVALID_ARG.

* src/conf/object_event.c (virObjectEventCallbackListEventID):
Inline...
(virObjectEventStateEventID): ...into lone caller, and report
error on failure.
(virObjectEventCallbackListAddID, virObjectEventStateCallbackID)
(virObjectEventCallbackListRemoveID)
(virObjectEventCallbackListMarkDeleteID): Tweak error category.
* src/remote/remote_driver.c (remoteConnectDomainEventRegister):
Don't leak registration on failure.
(remoteConnectDomainEventDeregisterAny)
(remoteConnectNetworkEventDeregisterAny): Don't overwrite error.
Signed-off-by: NEric Blake <eblake@redhat.com>

If a user registers for a domain event filtered to a particular
domain, but the persistent domain is offline at the time, then
the code silently failed to set up the filter.  As a result,
the event fires for all domains, rather than being filtered.
Network events were immune, since they always passed an id
0 argument.

The key to this patch is realizing that
virObjectEventDispatchMatchCallback() only cared about uuid;
so refusing to create a meta for a negative id is pointless,
and in fact, malloc'ing meta at all was overkill; instead,
just directly store a uuid and a flag of whether to filter.

Note that virObjectEventPtr still needs all fields of meta,
because this is how we reconstruct a virDomainPtr inside the
dispatch handler before calling the end user's callback
pointer with the correct object, even though only the uuid
portion of meta is used in deciding whether a callback
matches the given event.  So while uuid is optional for
callbacks, it is mandatory for events.

The change to testDomainCreateXMLMixed is merely on the setup
scenario (as you can't register for a domain unless it is either
running or persistent).  I actually first wrote that test for
this patch, then rebased it to also cover a prior patch (commit
4221d64f), but had to adjust it for that patch to use Create
instead of Define for setting up the domain long enough to
register the event in order to work around this bug.  But while
the setup is changed, the main body of the test is still about
whether creation events fire as expected.

* src/conf/object_event_private.h (_virObjectEventCallback):
Replace meta with uuid and flag.
(virObjectEventCallbackListAddID): Update signature.
* src/conf/object_event.h (virObjectEventStateRegisterID):
Likewise.
* src/conf/object_event_private.h (virObjectEventNew): Document
use of name and uuid in events.
* src/conf/object_event.c (virObjectEventCallbackListAddID): Drop
arguments that don't affect filtering.
(virObjectEventCallbackListRemoveID)
(virObjectEventDispatchMatchCallback)
(virObjectEventStateRegisterID): Update clients.
* src/conf/domain_event.c (virDomainEventCallbackListAdd)
(virDomainEventStateRegisterID): Likewise.
* src/conf/network_event.c (virNetworkEventStateRegisterID):
Likewise.
* tests/objecteventtest.c (testDomainCreateXMLMixed): Enhance test.
Signed-off-by: NEric Blake <eblake@redhat.com>

Consider these two calls, in either order:

id1 = virConnectDomainEventRegisterAny(conn, NULL,
   VIR_DOMAIN_EVENT_ID_LIFECYCLE,
   VIR_DOMAIN_EVENT_CALLBACK(callback), NULL, NULL);
virConnectDomainEventRegister(conn, callback, NULL, NULL);

Right now, the second call fails, because under the hood, the
old-style function registration is tightly coupled to the
new style lifecycle eventID, and the two calls both try
to register the same global eventID callback representation.

We've alreay documented that users should avoid old-style
registration and deregistration, so anyone heeding the advice
won't run into this situation.  But it would be even nicer if
we pretend the two interfaces are completely separate, and
disallow any cross-linking.  That is, a call to old-style
deregister should never remove a new-style callback even if it
is the same function pointer, and a call to new-style callback
using only callbackIDs obtained legitimately should never
remove an old-style callback (of course, since our callback
IDs are sequential, and there is still coupling under the
hood, you can easily guess the callbackID of an old style
registration and use new-style deregistration to nuke it - but
that starts to be blatantly bad coding on your part rather
than a surprising result on what looks like reasonable
stand-alone API).

With this patch, you can now register a global lifecycle event
handler twice, by using both old and new APIs; if such an event
occurs, your callback will be entered twice.  But that is not a
problem in practice, since it is already possible to use the
new API to register both a global and per-domain event handler
using the same function, which will likewise fire your callback
twice for that domain.  Duplicates are still prevented when
using the same API with same parameters twice (old-style twice,
new-style global twice, or new-style per-domain with same domain
twice), and things are still bounded (it is not possible to
register a single function pointer more than N+2 times per event
id, where N is the number of domains available on the connection).
Besides, it has always been possible to register as many
separate function pointers on the same event id as desired,
through either old or new style API, where the bound there is
the physical limitation of writing a program with enough
distinct function pointers.

Adding another event registration in the testsuite is sufficient
to cover this, where the test fails without the rest of the patch.

* src/conf/object_event.c (_virObjectEventCallback): Add field.
(virObjectEventCallbackLookup): Add argument.
(virObjectEventCallbackListAddID, virObjectEventStateCallbackID):
Adjust callers.
* tests/objecteventtest.c (testDomainCreateXMLMixed): Enhance test.
Signed-off-by: NEric Blake <eblake@redhat.com>

On the surface, this sequence of API calls should succeed:

id1 = virConnectDomainEventRegisterAny(..., VIR_DOMAIN_EVENT_ID_LIFECYCLE,...);
id2 = virConnectDomainEventRegisterAny(..., VIR_DOMAIN_EVENT_ID_RTC_CHANGE,...);
virConnectDomainEventDeregisterAny(id1);
id1 = virConnectDomainEventRegisterAny(..., VIR_DOMAIN_EVENT_ID_LIFECYCLE,...);

And for test:///default, it does.  But for qemu:///system, it fails:
libvirt: XML-RPC error : internal error: domain event 0 already registered

Looking closer, the bug is caused by miscommunication between
the object event engine and the client side of the remote driver.
In our implementation, we set up a single server-side event per
eventID, then the client side replicates that one event to all
callbacks that have been registered client side.  To know when
to turn the server side eventID on or off, the client side must
track how many events for the same eventID have been registered.
But while our code was filtering by eventID on event registration,
it did not filter on event deregistration.  So the above API calls
resulted in the deregister returning 1 instead of 0, so no RPC
deregister was issued, and the final register detects on the
server side that the server is already handling eventID 0.

Unfortunately, since the problem is only observable on remote
connections, it's not possible to enhance objecteventtest to
expose the semantics using only public API entry points.

* src/conf/object_event.c (virObjectEventCallbackListCount): New
function.
(virObjectEventCallbackListAddID)
(virObjectEventCallbackListRemoveID)
(virObjectEventCallbackListMarkDeleteID): Use it.
Signed-off-by: NEric Blake <eblake@redhat.com>

Tighten up scope after the previous patch avoided using
internals.  This will also make it easier to change
internal implementation without having to chase down quite
as many impacted callers or worrying about two files getting
implementations out of sync.

* src/conf/object_event_private.h
(virObjectEventCallbackListAddID, virObjectEventQueueClear)
(virObjectEventStateLock, virObjectEventStateUnlock)
(virObjectEventTimer): Drop prototype.
(_virObjectEventCallbackList, _virObjectEventState)
(_virObjectEventCallback): Move...
* src/conf/object_event.c: ...here.
(virObjectEventCallbackListAddID, virObjectEventQueueClear)
(virObjectEventStateLock, virObjectEventStateUnlock)
(virObjectEventTimer): Mark private.
Signed-off-by: NEric Blake <eblake@redhat.com>

Right now, the older virConnectDomainEventRegister (takes a
function pointer, returns 0 on success) and the newer
virConnectDomainEventRegisterID (takes an eventID, returns a
callbackID) share the underlying implementation (the older
API ends up consuming a callbackID for eventID 0 under the
hood).  We implemented that by a lot of copy and pasted
code between object_event.c and domain_event.c, according to
whether we are dealing with a function pointer or an eventID.
However, our copy and paste is not symmetric.  Consider this
sequence:

id1 = virConnectDomainEventRegisterAny(conn, dom,
   VIR_DOMAIN_EVENT_ID_LIFECYCLE,
   VIR_DOMAIN_EVENT_CALLBACK(callback), NULL, NULL);
virConnectDomainEventRegister(conn, callback, NULL, NULL);
virConnectDomainEventDeregister(conn, callback);
virConnectDomainEventDeregsiterAny(conn, id1);

the first three calls would succeed, but the third call ended
up nuking the id1 callbackID (the per-domain new-style handler),
then the fourth call failed with an error about an unknown
callbackID, leaving us with the global handler (old-style) still
live and receiving events.  It required another old-style
deregister to clean up the mess.  Root cause was that
virDomainEventCallbackList{Remove,MarkDelete} were only
checking for function pointer match, rather than also checking
for whether the registration was global.

Rather than playing with the guts of object_event ourselves
in domain_event, it is nicer to add a mapping function for the
internal callback id, then share common code for event removal.
For now, the function-to-id mapping is used only internally;
I thought about whether a new public API to let a user learn
the callback would be useful, but decided exposing this to the
user is probably a disservice, since we already publicly
document that they should avoid the old style, and since this
patch already demonstrates that older libvirt versions have
weird behavior when mixing old and new styles.

And like all good bug fix patches, I enhanced the testsuite,
validating that the changes in tests/ expose the failure
without the rest of the patch.

* src/conf/object_event.c (virObjectEventCallbackLookup)
(virObjectEventStateCallbackID): New functions.
(virObjectEventCallbackLookup): Use helper function.
* src/conf/object_event_private.h (virObjectEventStateCallbackID):
Declare new function.
* src/conf/domain_event.c (virDomainEventStateRegister)
(virDomainEventStateDeregister): Let common code handle the
complexity.
(virDomainEventCallbackListRemove)
(virDomainEventCallbackListMarkDelete)
(virDomainEventCallbackListAdd): Drop unused functions.
* tests/objecteventtest.c (testDomainCreateXMLMixed): New test.
Signed-off-by: NEric Blake <eblake@redhat.com>

We might as well take advantage of viralloc.h instead of open-coding
array management ourselves.  While at it, I simplified several
places that were doing repetitive pointer chasing to use an
intermediate variable for legibility (some other places remain,
but they will disapper in later refactoring patches).

* src/conf/object_event_private.h (_virObjectEventCallbackList):
Use size_t for count.
* src/conf/object_event.c (_virObjectEventQueue): Likewise.
(virObjectEventCallbackListRemoveID): Use VIR_DELETE_ELEMENT.
(virObjectEventQueuePush, virObjectEventCallbackListAddID): Use
VIR_APPEND_ELEMENT.
(virObjectEventCallbackListEventID)
(virObjectEventStateDispatchCallbacks): Simplify code.
Signed-off-by: NEric Blake <eblake@redhat.com>

No need to use an int that only ever stores 0 and 1.

* src/conf/object_event_private.h (_virObjectEventCallback):
Change deleted to bool.
* src/conf/object_event.c (virObjectEventDispatchMatchCallback):
Switch return type to bool.
(virObjectEventCallbackListMarkDeleteID): Update client.
* src/conf/domain_event.c (virDomainEventCallbackListMarkDelete):
Likewise.

Any file with access to object_event_private.h also has access to
the internals of virObjectEvent, without needing an accessor
function.  Not to mention the accessor function was doing type
checks that would always succeed.

* src/conf/object_event_private.h (virObjectEventGetEventID): Drop.
* src/conf/object_event.c (virObjectEventGetEventID): Drop.
(virObjectEventDispatchMatchCallback): Simplify caller.
* src/conf/domain_event.c (virDomainEventDispatchDefaultFunc):
Likewise.
Signed-off-by: NEric Blake <eblake@redhat.com>

While working on events, I found a number of minor issues; I'm
hoisting these to the front rather than doing it piecemeal in
the patches where I first noticed bad or missing documentation.

* src/conf/object_event.c: Fix grammar, document all parameters
of public functions, wrap some long lines.
* src/conf/object_event.h: Likewise.
* src/conf/network_event.c: Likewise.
* src/conf/domain_event.c: Likewise (except for the large number
of event creation functions).
* src/libvirt_private.cyms (conf/object_event.h): Split...
(conf/network_event.h): ...to account for new file.
Signed-off-by: NEric Blake <eblake@redhat.com>

Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

The event namespace concept is mostly redundant information.
With the re-written dispatcher, the namespace is only used
for equality comparisons between event IDs. This can be solved
by just comparing virClassPtr instances instead.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Instead of having the object event code have to know about each
type of event and their dispatch functions, associate a dispatch
function with the object instance. The dispatch code can thus be
significantly simplified.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

While running objecteventtest, it was found that valgrind pointed out the
following memory leak:

==13464== 5 bytes in 1 blocks are definitely lost in loss record 7 of 134
==13464==    at 0x4A0887C: malloc (vg_replace_malloc.c:270)
==13464==    by 0x341F485E21: strdup (strdup.c:42)
==13464==    by 0x4CAE28F: virStrdup (virstring.c:554)
==13464==    by 0x4CF3CBE: virObjectEventCallbackListAddID (object_event.c:286)
==13464==    by 0x4CF49CA: virObjectEventStateRegisterID (object_event.c:729)
==13464==    by 0x4CF73FE: virDomainEventStateRegisterID (domain_event.c:1424)
==13464==    by 0x4D7358F: testConnectDomainEventRegisterAny (test_driver.c:6032)
==13464==    by 0x4D600C8: virConnectDomainEventRegisterAny (libvirt.c:19128)
==13464==    by 0x402409: testDomainStartStopEvent (objecteventtest.c:232)
==13464==    by 0x403451: virtTestRun (testutils.c:138)
==13464==    by 0x402012: mymain (objecteventtest.c:395)
==13464==    by 0x403AF2: virtTestMain (testutils.c:593)
==13464==

Hitting this should be pretty rare, but at least developers will know
that they are providing a weird event ID. Otherwise for namespace that
are added in the normal way, gcc will raise a warning about unhandled
case in the switch.

Define the public API for (de-)registering network events
and the callbacks for receiving lifecycle events. The lifecycle
event includes a 'detail' parameter to match the domain lifecycle
event data, but this is currently unused.

The network events related code goes into its own set of internal
files src/conf/network_event.[ch]