Missing semicolon at the end of macros can confuse some analyzers
(like cppcheck <filename>), and we have a mix of semicolon and
non-semicolon usage through the code. Let's standardize on using
a semicolon for VIR_ENUM_DECL calls.
Drop the semicolon from the final statement of the macro, so
the compiler will require callers to add a semicolon.
Reviewed-by: John Ferlan <jferlan@redhat.com>
Signed-off-by: Cole Robinson <crobinso@redhat.com>
Since we're setting the zone anyway, it will be useful to allow
setting a different (custom) zone for each network. This will be done
by adding a "zone" attribute to the "bridge" element, e.g.:
...
<bridge name='virbr0' zone='myzone'/>
...
If a zone is specified in the config and it can't be honored, this
will be an error.
Signed-off-by: Laine Stump <laine@laine.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Require that all headers are guarded by a symbol named
LIBVIRT_$FILENAME
where $FILENAME is the uppercased filename, with all characters
outside a-z changed into '_'.
Note we do not use a leading __ because that is technically a
namespace reserved for the toolchain.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
In many files there are header comments that contain an Author:
statement, supposedly reflecting who originally wrote the code.
In a large collaborative project like libvirt, any non-trivial
file will have been modified by a large number of different
contributors. IOW, the Author: comments are quickly out of date,
omitting people who have made significant contribitions.
In some places Author: lines have been added despite the person
merely being responsible for creating the file by moving existing
code out of another file. IOW, the Author: lines give an incorrect
record of authorship.
With this all in mind, the comments are useless as a means to identify
who to talk to about code in a particular file. Contributors will always
be better off using 'git log' and 'git blame' if they need to find the
author of a particular bit of code.
This commit thus deletes all Author: comments from the source and adds
a rule to prevent them reappearing.
The Copyright headers are similarly misleading and inaccurate, however,
we cannot delete these as they have legal meaning, despite being largely
inaccurate. In addition only the copyright holder is permitted to change
their respective copyright statement.
Reviewed-by: Erik Skultety <eskultet@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Right-aligning backslashes when defining macros or using complex
commands in Makefiles looks cute, but as soon as any changes is
required to the code you end up with either distractingly broken
alignment or unnecessarily big diffs where most of the changes
are just pushing all backslashes a few characters to one side.
Generated using
$ git grep -El '[[:blank:]][[:blank:]]\\$' | \
grep -E '*\.([chx]|am|mk)$$' | \
while read f; do \
sed -Ei 's/[[:blank:]]*[[:blank:]]\\$/ \\/g' "$f"; \
done
Signed-off-by: Andrea Bolognani <abologna@redhat.com>
In an effort to be consistent with the source module, alter the function
prototypes to follow the similar style of source with the "type" on one
line followed by the function name and arguments on subsequent lines with
with argument getting it's own line.
Move all the virNetworkObj related API/data structures into their own
modules virnetworkobj.{c,h} from the network_conf.{c,h}
Purely code motion at this point plus adjustments to cleanly build
Proposed formal coding conventions encourage defining typedefs for
vir[Blah] and vir[Blah]Ptr separately from the associated struct named
_vir[Blah]:
typedef struct _virBlah virBlah;
typedef virBlah *virBlahPtr;
struct _virBlah {
...
};
At some point in the past, I had submitted several patches using a
more compact style that I prefer, and they were accepted:
typedef struct _virBlah {
...
} virBlah, *virBlahPtr;
Since these are by far a minority among all struct definitions, this
patch changes all those definitions to reflect the style prefered by
the proposal so that there is 100% consistency.
Example:
<network>
...
<mtu size='9000'/>
...
If mtu is unset, it's assumed that we want the default for whatever is
the underlying transport (usually this is 1500).
This setting isn't yet wired in, so it will have no effect.
This partially resolves: https://bugzilla.redhat.com/1224348
Similarly to localOnly DNS domain, localPtr attribute can be used to
tell the DNS server not to forward reverse lookups for unknown IPs which
belong to the virtual network.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Now that we have a module that's able to track
<domain, mac addres list> pairs, hook it up into
our network driver.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
For some unknown reason the original implementation of the <forwarder>
element only took advantage of part of the functionality in the
dnsmasq feature it exposes - it allowed specifying the ip address of a
DNS server which *all* DNS requests would be forwarded to, like this:
<forwarder addr='192.168.123.25'/>
This is a frontend for dnsmasq's "server" option, which also allows
you to specify a domain that must be matched in order for a request to
be forwarded to a particular server. This patch adds support for
specifying the domain. For example:
<forwarder domain='example.com' addr='192.168.1.1'/>
<forwarder domain='www.example.com'/>
<forwarder domain='travesty.org' addr='10.0.0.1'/>
would forward requests for bob.example.com, ftp.example.com and
joe.corp.example.com all to the DNS server at 192.168.1.1, but would
forward requests for travesty.org and www.travesty.org to
10.0.0.1. And due to the second line, requests for www.example.com,
and odd.www.example.com would be resolved by the libvirt network's own
DNS server (i.e. thery wouldn't be immediately forwarded) even though
they also match 'example.com' - the match is given to the entry with
the longest matching domain. DNS requests not matching any of the
entries would be resolved by the libvirt network's own DNS server.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1331796
If you define a libvirt virtual network with one or more IP addresses,
it starts up an instance of dnsmasq. It's always been possible to
avoid dnsmasq's dhcp server (simply don't include a <dhcp> element),
but until now it wasn't possible to avoid having the DNS server
listening; even if the network has no <dns> element, it is started
using default settings.
This patch adds a new attribute to <dns>: enable='yes|no'. For
backward compatibility, it defaults to 'yes', but if you don't want a
DNS server created for the network, you can simply add:
<dns enable='no'/>
to the network configuration, and next time the network is started
there will be no dns server created (if there is dhcp configuration,
dnsmasq will be started with "port=0" which disables the DNS server;
if there is no dhcp configuration, dnsmasq won't be started at all).
The new forward mode 'open' is just like mode='route', except that no
firewall rules are added to assure that any traffic does or doesn't
pass. It is assumed that either they aren't necessary, or they will be
setup outside the scope of libvirt.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=846810
These functions all need to be called from a utility function that
must be located in the util directory, so we move them all into
util/virnetdevip.[ch] now that it exists.
Function and struct names were appropriately changed for the new
location, but all code is unchanged aside from motion and renaming.
I'm tired of mistyping this all the time, so let's do it the same all
the time (similar to how we changed all "Pci" to "PCI" awhile back).
(NB: I've left alone some things in the esx and vbox drivers because
I'm unable to compile them and they weren't obviously *not* a part of
some API. I also didn't change a couple of variables named,
e.g. "somethingIptables", because they were derived from the name of
the "iptables" command)
We had both and the only difference was that the latter also included
information about multifunction setting. The problem with that was that
we couldn't use functions made for only one of the structs (e.g.
parsing). To consolidate those two structs, use the one in virpci.h,
include that in domain_conf.h and add the multifunction member in it.
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
While trying to build with -Os I've encountered some build
failures.
util/vircommand.c: In function 'virCommandAddEnvFormat':
util/vircommand.c:1257:1: error: inlining failed in call to 'virCommandAddEnv': call is unlikely and code size would grow [-Werror=inline]
virCommandAddEnv(virCommandPtr cmd, char *env)
^
util/vircommand.c:1308:5: error: called from here [-Werror=inline]
virCommandAddEnv(cmd, env);
^
This function is big enough for the compiler to be not inlined.
This is the error message I'm seeing:
Then virDomainNumatuneNodeSpecified is exported and called from
other places. It shouldn't be inlined then.
In file included from network/bridge_driver_platform.h:30:0,
from network/bridge_driver_platform.c:26:
network/bridge_driver_linux.c: In function 'networkRemoveRoutingFirewallRules':
./conf/network_conf.h:350:1: error: inlining failed in call to 'virNetworkDefForwardIf.constprop': call is unlikely and code size would grow [-Werror=inline]
virNetworkDefForwardIf(const virNetworkDef *def, size_t n)
^
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
We already check that any auto-assigned bridge device name for a
virtual network (e.g. "virbr1") doesn't conflict with the bridge name
for any existing libvirt network (via virNetworkSetBridgeName() in
conf/network_conf.c).
We also want to check that the name doesn't conflict with any bridge
device created on the host system outside the control of libvirt
(history: possibly due to the ploriferation of references to libvirt's
bridge devices in HOWTO documents all around the web, it is not
uncommon for an admin to manually create a bridge in their host's
system network config and name it "virbrX"). To add such a check to
virNetworkBridgeInUse() (which is called by virNetworkSetBridgeName())
we would have to call virNetDevExists() (from util/virnetdev.c); this
function calls ioctl(SIOCGIFFLAGS), which everyone on the mailing list
agreed should not be done from an XML parsing function in the conf
directory.
To remedy that problem, this patch removes virNetworkSetBridgeName()
from conf/network_conf.c and puts an identically functioning
networkBridgeNameValidate() in network/bridge_driver.c (because it's
reasonable for the bridge driver to call virNetDevExists(), although
we don't do that yet because I wanted this patch to have as close to 0
effect on function as possible).
There are a couple of inevitable changes though:
1) We no longer check the bridge name during
virNetworkLoadConfig(). Close examination of the code shows that
this wasn't necessary anyway - the only *correct* way to get XML
into the config files is via networkDefine(), and networkDefine()
will always call networkValidate(), which previously called
virNetworkSetBridgeName() (and now calls
networkBridgeNameValidate()). This means that the only way the
bridge name can be unset during virNetworkLoadConfig() is if
someone edited the config file on disk by hand (which we explicitly
prohibit).
2) Just on the off chance that somebody *has* edited the file by hand,
rather than crashing when they try to start their malformed
network, a check for non-NULL bridge name has been added to
networkStartNetworkVirtual().
(For those wondering why I don't instead call
networkValidateBridgeName() there to set a bridge name if one
wasn't present - the problem is that during
networkStartNetworkVirtual(), the lock for the network being
started has already been acquired, but the lock for the network
list itself *has not* (because we aren't adding/removing a
network). But virNetworkBridgeInuse() iterates through *all*
networks (including this one) and locks each network as it is
checked for a duplicate entry; it is necessary to lock each network
even before checking if it is the designated "skip" network because
otherwise some other thread might acquire the list lock and delete
the very entry we're examining. In the end, permitting a setting of
the bridge name during network start would require that we lock the
entire network list during any networkStartNetwork(), which
eliminates a *lot* of parallelism that we've worked so hard to
achieve (it can make a huge difference during libvirtd startup). So
rather than try to adjust for someone playing against the rules, I
choose to instead give them the error they deserve.)
3) virNetworkAllocateBridge() (now removed) would leak any "template"
string set as the bridge name. Its replacement
networkFindUnusedBridgeName() doesn't leak the template string - it
is properly freed.
This function does not make any sense now, that network driver is
(almost) dropped. I mean, previously, when threads were
serialized, this function was there to check, if no other network
with the same name or UUID exists. However, nowadays that threads
can run more in parallel, this function is useless, in fact it
gives misleading return values. Consider the following scenario.
Two threads, both trying to define networks with same name but
different UUID (e.g. because it was generated during XML parsing
phase, whatever). Lets assume that both threads are about to call
networkValidate() which immediately calls
virNetworkObjIsDuplicate().
T1: calls virNetworkObjIsDuplicate() and since no network with
given name or UUID exist, success is returned.
T2: calls virNetworkObjIsDuplicate() and since no network with
given name or UUID exist, success is returned.
T1: calls virNetworkAssignDef() and successfully places its
network into the virNetworkObjList.
T2: calls virNetworkAssignDef() and since network with the same
name exists, the network definition is replaced.
Okay, this is mainly because virNetworkAssignDef() does not check
whether name and UUID matches. Well, lets make it so! And drop
useless function too.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
This is going to be needed later, when some functions already
have the virNetworkObjList object already locked and need to
lookup a object to work on. As an example of such function is
virNetworkAssignDef(). The other use case might be in
virNetworkObjListForEach() callback.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
This is practically copy of qemuDomObjEndAPI. The reason why is
it so widely available is to avoid code duplication, since the
function is going to be called from our bridge driver, test
driver and parallels driver too.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
So far it's just a structure which happens to have 'Obj' in its
name, but otherwise it not related to virObject at all. No
reference counting, not virObjectLock(), nothing.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Well, one day this will be self-locking object, but not today.
But lets prepare the code for that! Moreover,
virNetworkObjListFree() is no longer needed, so turn it into
virNetworkObjListDispose().
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
This API will be used in the future to call passed callback over
each network object in the list. It's slightly different to its
virDomainObjListForEach counterpart, because virDomainObjList
uses a hash table to store domain object, while virNetworkObjList
uses an array.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Instead of copying the whole object onto stack when calling the
function, just pass the pointer to the object and save up some
space on the stack. Moreover, this prepares the code to hide the
virNetworkObjList structure into network_conf.c and use accessors
only.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
This is probably a copy-paste error from virDomainObj*
counterpart. But when speaking of virNetworkObj we should use
variable @nets for an array of networks, rather than @doms. It's
just confusing.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
This adds a new "localOnly" attribute on the domain element of the
network xml. With this set to "yes", DNS requests under that domain
will only be resolved by libvirt's dnsmasq, never forwarded upstream.
This was how it worked before commit f69a6b987d, and I found that
functionality useful. For example, I have my host's NetworkManager
dnsmasq configured to forward that domain to libvirt's dnsmasq, so I can
easily resolve guest names from outside. But if libvirt's dnsmasq
doesn't know a name and forwards it to the host, I'd get an endless
forwarding loop. Now I can set localOnly="yes" to prevent the loop.
Signed-off-by: Josh Stone <jistone@redhat.com>
Moving code for parsing and formatting network routes to
networkcommon_conf helps reusing those routes for domains. The route
definition has been hidden to help reducing the number of unnecessary
checks in the format function.
The macTableManager attribute of a network's bridge subelement tells
libvirt how the bridge's MAC address table (used to determine the
egress port for packets) is managed. In the default mode, "kernel",
management is left to the kernel, which usually determines entries in
part by turning on promiscuous mode on all ports of the bridge,
flooding packets to all ports when the correct destination is unknown,
and adding/removing entries to the fdb as it sees incoming traffic
from particular MAC addresses. In "libvirt" mode, libvirt turns off
learning and flooding on all the bridge ports connected to guest
domain interfaces, and adds/removes entries according to the MAC
addresses in the domain interface configurations. A side effect of
turning off learning and unicast_flood on the ports of a bridge is
that (with Linux kernel 3.17 and newer), the kernel can automatically
turn off promiscuous mode on one or more of the bridge's ports
(usually only the one interface that is used to connect the bridge to
the physical network). The result is better performance (because
packets aren't being flooded to all ports, and can be dropped earlier
when they are of no interest) and slightly better security (a guest
can still send out packets with a spoofed source MAC address, but will
only receive traffic intended for the guest interface's configured MAC
address).
The attribute looks like this in the configuration:
<network>
<name>test</name>
<bridge name='br0' macTableManager='libvirt'/>
...
This patch only adds the config knob, documentation, and test
cases. The functionality behind this knob is added in later patches.
This new attribute will control whether or not libvirt will pay
attention to guest notifications about changes to network device mac
addresses and receive filters. The default for this is 'no' (for
security reasons). If it is set to 'yes' *and* the specified device
model and connection support it (currently only macvtap+virtio) then
libvirt will watch for NIC_RX_FILTER_CHANGED events, and when it
receives one, it will issue a query-rx-filter command, retrieve the
result, and modify the host-side macvtap interface's mac address and
unicast/multicast filters accordingly.
The functionality behind this attribute will be in a later patch. This
patch merely adds the attribute to the top-level of a domain's
<interface> as well as to <network> and <portgroup>, and adds
documentation and schema/xml2xml tests. Rather than adding even more
test files, I've just added the net attribute in various applicable
places of existing test files.
In "src/conf/" there are many enumeration (enum) declarations.
Similar to the recent cleanup to "src/util" directory, it's
better to use a typedef for variable types, function types and
other usages. Other enumeration and folders will be changed to
typedef's in the future. Most of the files changed in this commit
are reltaed to Network (network_conf.* and interface_conf.*) enums.
Signed-off-by: Julio Faracco <jcfaracco@gmail.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Experimentation showed that if virNetworkCreateXML() was called for a
network that was already defined, and then the network was
subsequently shutdown, the network would continue to be persistent
after the shutdown (expected/desired), but the original config would
be lost in favor of the transient config sent in with
virNetworkCreateXML() (which would then be the new persistent config)
(obviously unexpected/not desired).
To fix this, virNetworkObjAssignDef() has been changed to
1) properly save/free network->def and network->newDef for all the
various combinations of live/active/persistent, including some
combinations that were previously considered to be an error but didn't
need to be (e.g. setting a "live" config for a network that isn't yet
active but soon will be - that was previously considered an error,
even though in practice it can be very useful).
2) automatically set the persistent flag whenever a new non-live
config is assigned to the network (and clear it when the non-live
config is set to NULL). the libvirt network driver no longer directly
manipulates network->persistent, but instead relies entirely on
virNetworkObjAssignDef() to do the right thing automatically.
After this patch, the following sequence will behave as expected:
virNetworkDefineXML(X)
virNetworkCreateXML(X') (same name but some config different)
virNetworkDestroy(X)
At the end of these calls, the network config will remain as it was
after the initial virNetworkDefine(), whereas previously it would take
on the changes given during virNetworkCreateXML().
Another effect of this tighter coupling between a) setting a !live def
and b) setting/clearing the "persistent" flag, is that future patches
which change the details of network lifecycle management
(e.g. upcoming patches to fix detection of "active" networks when
libvirtd is restarted) will find it much more difficult to break
persistence functionality.
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: Michal Privoznik <mprivozn@redhat.com>
Basically, the idea is copied from domain code, where tainting
exists for a while. Currently, only one taint reason exists -
VIR_NETWORK_TAINT_HOOK to mark those networks which caused invoking
of hook script.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
In the next patch I'm going to need the network format function that
takes virBuffer as argument. However, slightly change of name is more
appropriate then: virNetworkDefFormatBuf to match the rest of functions
that format an object to buffer.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
The previous patch fixed "forwardPlainNames" so that it really is
doing only what is intended, but left the default to be
"forwardPlainNames='no'". Discussion around the initial version of
that patch led to the decision that the default should instead be
"forwardPlainNames='yes'" (i.e. the original behavior before commit
f3886825). This patch makes that change to the default.
'const fooPtr' is the same as 'foo * const' (the pointer won't
change, but it's contents can). But in general, if an interface
is trying to be const-correct, it should be using 'const foo *'
(the pointer is to data that can't be changed).
Fix up remaining offenders in src/conf, and their fallout.
* src/conf/snapshot_conf.h (virDomainSnapshotAssignDef)
(virDomainSnapshotFindByName): Drop attempt at const.
* src/conf/interface_conf.h (virInterfaceObjIsActive)
(virInterfaceDefFormat): Use intended type.
(virInterfaceFindByMACString, virInterfaceFindByName)
(virInterfaceAssignDef, virInterfaceRemove): Drop attempt at
const.
* src/conf/network_conf.h (virNetworkObjIsActive)
(virNetworkDefFormat, virNetworkDefForwardIf)
(virNetworkDefGetIpByIndex, virNetworkIpDefPrefix)
(virNetworkIpDefNetmask): Use intended type.
(virNetworkFindByUUID, virNetworkFindByName, virNetworkAssignDef)
(virNetworkObjAssignDef, virNetworkRemoveInactive)
(virNetworkBridgeInUse, virNetworkSetBridgeName)
(virNetworkAllocateBridge): Drop attempt at const.
* src/conf/netdev_vlan_conf.h (virNetDevVlanFormat): Make
const-correct.
* src/conf/node_device_conf.h (virNodeDeviceHasCap)
(virNodeDeviceDefFormat): Use intended type.
(virNodeDeviceFindByName, virNodeDeviceFindBySysfsPath)
(virNodeDeviceAssignDef, virNodeDeviceObjRemove)
(virNodeDeviceGetParentHost): Drop attempt at const.
* src/conf/secret_conf.h (virSecretDefFormat): Use intended type.
* src/conf/snapshot_conf.c (virDomainSnapshotAssignDef)
(virDomainSnapshotFindByName): Fix fallout.
* src/conf/interface_conf.c (virInterfaceBridgeDefFormat)
(virInterfaceBondDefFormat, virInterfaceVlanDefFormat)
(virInterfaceProtocolDefFormat, virInterfaceDefDevFormat)
(virInterfaceDefFormat, virInterfaceFindByMACString)
(virInterfaceFindByName, virInterfaceAssignDef)
(virInterfaceRemove): Likewise.
* src/conf/network_conf.c
(VIR_ENUM_IMPL, virNetworkFindByName, virNetworkObjAssignDef)
(virNetworkAssignDef, virNetworkRemoveInactive)
(virNetworkDefGetIpByIndex, virNetworkIpDefPrefix)
(virNetworkIpDefNetmask, virNetworkDHCPHostDefParseXML)
(virNetworkIpDefFormat, virNetworkRouteDefFormat)
(virPortGroupDefFormat, virNetworkForwardNatDefFormat)
(virNetworkDefFormatInternal, virNetworkBridgeInUse)
(virNetworkAllocateBridge, virNetworkSetBridgeName)
(virNetworkDNSDefFormat, virNetworkDefFormat): Likewise.
* src/conf/netdev_vlan_conf.c (virNetDevVlanFormat): Likewise.
* src/conf/node_device_conf.c (virNodeDeviceHasCap)
(virNodeDeviceFindBySysfsPath, virNodeDeviceFindByName)
(virNodeDeviceAssignDef, virNodeDeviceObjRemove)
(virNodeDeviceDefFormat, virNodeDeviceGetParentHost): Likewise.
* src/conf/secret_conf.c (virSecretDefFormatUsage)
(virSecretDefFormat): Likewise.
Signed-off-by: Eric Blake <eblake@redhat.com>
Useful to set custom forwarders instead of using the contents of
/etc/resolv.conf. It helps me to setup dnsmasq as local nameserver to
resolve VM domain names from domain 0, when domain option is used.
Signed-off-by: Diego Woitasen <diego.woitasen@vhgroup.net>
Signed-off-by: Eric Blake <eblake@redhat.com>
This resolves the issue that prompted the filing of
https://bugzilla.redhat.com/show_bug.cgi?id=928638
(although the request there is for something much larger and more
general than this patch).
commit f3868259ca disabled the
forwarding to upstream DNS servers of unresolved DNS requests for
names that had no domain, but were just simple host names (no "."
character anywhere in the name). While this behavior is frowned upon
by DNS root servers (that's why it was changed in libvirt), it is
convenient in some cases, and since dnsmasq can be configured to allow
it, it must not be strictly forbidden.
This patch restores the old behavior, but since it is usually
undesirable, restoring it requires specification of a new option in
the network config. Adding the attribute "forwardPlainNames='yes'" to
the <dns> elemnt does the trick - when that attribute is added to a
network config, any simple hostnames that can't be resolved by the
network's dnsmasq instance will be forwarded to the DNS servers listed
in the host's /etc/resolv.conf for an attempt at resolution (just as
any FQDN would be forwarded).
When that attribute *isn't* specified, unresolved simple names will
*not* be forwarded to the upstream DNS server - this is the default
behavior.
