This is detailed in:
https://bugzilla.redhat.com/show_bug.cgi?id=688957
Since radvd is executed by daemonizing it, the attempt to exec the
radvd binary doesn't happen until after libvirtd has already received
an exit code from the intermediate forked process, so no error is
detected or logged by __virExec().
We can't require radvd as a prerequisite for the libvirt package (many
installations don't use IPv6, so they don't need it), so instead we
add in a check to verify there is an executable radvd binary prior to
trying to exec it.
Normally dnsmasq will send a default route (the address of the host in
the network definition) to any client requesting an address via
DHCP. On an isolated network this makes no sense, as we have iptables
to prevent any traffic going out via that interface, so anything sent
that way would be dropped anyway.
This extra/unusable default route becomes problematic if you have
setup a guest with multiple network interfaces, with one connected to
an isolated network and another that provides connectivity to the
outside (example - one interface directly connecting to a physical
interface via macvtap, with a second connected to an isolated network
so that the host and guest can communicate (macvtap doesn't support
guest<->host communication without an external switch that supports
vepa, or reflecting all traffic back)). In this case, if the guest
chooses the default route of the isolated network, the guest will not
be able to get network traffic beyond the host.
To prevent dnsmasq from sending a default route, you can tell it to
send 0 bytes of data for the default route option (option number 3)
with --dhcp-option=3 (normally the data to send for the option would
follow the option number; no extra data means "don't send this option").
I have checked on RHEL5 (a good representative of the oldest supported
libvirt platforms) and its version of dnsmasq (2.45) does support
--dhcp-option, so this shouldn't create any compatibility problems.
By default, all dnsmasq processes share the same leases file. libvirt
also uses the --dhcp-lease-max option to control the maximum number of
leases allowed. The problem is that libvirt puts in a number equal to
the number of addresses in the range for the one network handled by a
single instance of dnsmasq, but dnsmasq checks the total number of
leases in the file (which could potentially contain many more).
The solution is to tell each instance of dnsmasq to create and use its
own leases file. (/var/lib/libvirt/network/<net-name>.leases).
This file is created by dnsmasq when it starts, but not deleted when
it exists. This is fine when the network is just being stopped, but if
the leases file was left around when a network was undefined, we could
end up with an ever-increasing number of dead files - instead, we
explicitly unlink the leases file when a network is undefined.
Note that Ubuntu carries a patch against an older version of libvirt for this:
hhttps://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/713071
ttp://bazaar.launchpad.net/~serge-hallyn/ubuntu/maverick/libvirt/bugall/revision/109
I was certain I'd also seen discussion of this on libvir-list or
libvirt-users, but couldn't find it.
This fixes a regression introduced in commit ad48df, and reported on
the libvirt-users list:
https://www.redhat.com/archives/libvirt-users/2011-March/msg00018.html
The problem in that commit was that we began searching a list of ip
address definitions (rather than just having one) to look for a dhcp
range or static host; when we didn't find any, our pointer (ipdef) was
left at NULL, and when ipdef was NULL, we returned without starting up
dnsmasq.
Previously dnsmasq was started even without any dhcp ranges or static
entries, because it's still useful for DNS services.
Another problem I noticed while investigating was that, if there are
IPv6 addresses, but no IPv4 addresses of any kind, we would jump out
at an ever higher level in the call chain.
This patch does the following:
1) networkBuildDnsmasqArgv() = all uses of ipdef are protected from
NULL dereference. (this patch doesn't change indentation, to make
review easier. The next patch will change just the
indentation). ipdef is intended to point to the first IPv4 address
with DHCP info (or the first IPv4 address if none of them have any
dhcp info).
2) networkStartDhcpDaemon() = if the loop looking for an ipdef with
DHCP info comes up empty, we then grab the first IPv4 def from the
list. Also, instead of returning if there are no IPv4 defs, we just
return if there are no IP defs at all (either v4 or v6). This way a
network that is IPv6-only will still get dnsmasq listening for DNS
queries.
3) in networkStartNetworkDaemon() - we will startup dhcp not just if there
are any IPv4 addresses, but also if there are any IPv6 addresses.
This fixes https://bugzilla.redhat.com/show_bug.cgi?id=609463
The problem was that, since a bridge always acquires the MAC address
of the connected interface with the numerically lowest MAC, as guests
are started and stopped, it was possible for the MAC address to change
over time, and this change in the network was being detected by
Windows 7 (it sees the MAC of the default route change), so on each
reboot it would bring up a dialog box asking about this "new network".
The solution is to create a dummy tap interface with a MAC guaranteed
to be lower than any guest interface's MAC, and attach that tap to the
bridge as soon as it's created. Since all guest MAC addresses start
with 0xFE, we can just generate a MAC with the standard "0x52, 0x54,
0" prefix, and it's guaranteed to always win (physical interfaces are
never connected to these bridges, so we don't need to worry about
competing numerically with them).
Note that the dummy tap is never set to IFF_UP state - that's not
necessary in order for the bridge to take its MAC, and not setting it
to UP eliminates the clutter of having an (eg) "virbr0-nic" displayed
in the output of the ifconfig command.
I chose to not auto-generate the MAC address in the network XML
parser, as there are likely to be consumers of that API that don't
need or want to have a MAC address associated with the
bridge.
Instead, in bridge_driver.c when the network is being defined, if
there is no MAC, one is generated. To account for virtual network
configs that already exist when upgrading from an older version of
libvirt, I've added a %post script to the specfile that searches for
all network definitions in both the config directory
(/etc/libvirt/qemu/networks) and the state directory
(/var/lib/libvirt/network) that are missing a mac address, generates a
random address, and adds it to the config (and a matching address to
the state file, if there is one).
docs/formatnetwork.html.in: document <mac address.../>
docs/schemas/network.rng: add nac address to schema
libvirt.spec.in: %post script to update existing networks
src/conf/network_conf.[ch]: parse and format <mac address.../>
src/libvirt_private.syms: export a couple private symbols we need
src/network/bridge_driver.c:
auto-generate mac address when needed,
create dummy interface if mac address is present.
tests/networkxml2xmlin/isolated-network.xml
tests/networkxml2xmlin/routed-network.xml
tests/networkxml2xmlout/isolated-network.xml
tests/networkxml2xmlout/routed-network.xml: add mac address to some tests
I added a host definition to a network definition:
<network>
<name>Lokal</name>
<uuid>2074f379-b82c-423f-9ada-305d8088daaa</uuid>
<bridge name='virbr1' stp='on' delay='0' />
<ip address='192.168.180.1' netmask='255.255.255.0'>
<dhcp>
<range start='192.168.180.128' end='192.168.180.254' />
<host mac='23:74:00:03:42:02' name='somevm' ip='192.168.180.10' />
</dhcp>
</ip>
</network>
But due to the wrong if-statement the argument --dhcp-hostsfile doesn't get
added to the dnsmasq command. The patch below fixes it for me.
Running an instance of the router advertisement daemon (radvd) allows
guests using the virtual network to automatically acquire an IPv6
address and default route. Note that acquiring an address only works
for networks with a prefix length of exactly 64 - radvd is still run
in other circumstances, and still advertises routes, but autoconf will
not work because it requires exactly 64 bits of address info from the
network prefix.
This patch avoids a race condition with the pidfile by manually
daemonizing radvd rather than allowing it to daemonize itself, then
creating our own pidfile (in addition to radvd's own file, which is
unnecessary, but there is no way to tell radvd to not create it). This
is accomplished by exec'ing it with "--debug 1" in the commandline,
and using virCommand's features to fork, create a pidfile, and detach
from the newly forked process.
At this point everything is already in place to make IPv6 happen, we just
need to add a few rules, remove some checks for IPv4-only, and document
the changes to the XML on the website.
All of the iptables functions eventually call down to a single
bottom-level function, and fortunately, ip6tables syntax (for all the
args that we use) is identical to iptables format (except the
addresses), so all we need to do is:
1) Get an address family down to the lowest level function in each
case, either implied through an address, or explicitly when no
address is in the parameter list, and
2) At the lowest level, just decide whether to call "iptables" or
"ip6tables" based on the family.
The location of the ip6tables binary is determined at build time by
autoconf. If a particular target system happens to not have ip6tables
installed, any attempts to run it will generate an error, but that
won't happen unless someone tries to define an IPv6 address for a
network. This is identical behavior to IPv4 addresses and iptables.
This patch reorganizes the code in bridge_driver.c to account for the
concept of a single network with multiple IP addresses, without adding
in the extra variable of IPv6. A small bit of code has been
temporarily added that checks all given addresses to verify they are
IPv4 - this will be removed when full IPv6 support is turned on.
This commit adds support for IPv6 parsing and formatting to the
virtual network XML parser, including moving around data definitions
to allow for multiple <ip> elements on a single network, but only
changes the consumers of this API to accommodate for the changes in
API/structure, not to add any actual IPv6 functionality. That will
come in a later patch - this patch attempts to maintain the same final
functionality in both drivers that use the network XML parser - vbox
and "bridge" (the Linux bridge-based driver used by the qemu
hypervisor driver).
* src/libvirt_private.syms: Add new private API functions.
* src/conf/network_conf.[ch]: Change C data structure and
parsing/formatting.
* src/network/bridge_driver.c: Update to use new parser/formatter.
* src/vbox/vbox_tmpl.c: update to use new parser/formatter
* docs/schemas/network.rng: changes to the schema -
* there can now be more than one <ip> element.
* ip address is now an ip-addr (ipv4 or ipv6) rather than ipv4-addr
* new optional "prefix" attribute that can be used in place of "netmask"
* new optional "family" attribute - "ipv4" or "ipv6"
(will default to ipv4)
* define data types for the above
* tests/networkxml2xml(in|out)/nat-network.xml: add multiple <ip> elements
(including IPv6) to a single network definition to verify they are being
correctly parsed and formatted.
brSetInetAddress can only set a single IP address on the bridge, and
uses a method (ioctl(SIOCSETIFADDR)) that only works for IPv4. Replace
it and brSetInetNetmask with a single function that uses the external
"ip addr add" command to add an address/prefix to the interface - this
supports IPv6, and allows adding multiple addresses to the interface.
Although it isn't currently used in the code, we also add a
brDelInetAddress for completeness' sake.
Also, while we're modifying bridge.c, we change brSetForwardDelay and
brSetEnableSTP to use the new virCommand API rather than the
deprecated virRun, and also log an error message in bridge_driver.c if
either of those fail (previously the failure would be completely
silent).
IPv6 will use prefix exclusively, and IPv4 will also optionally be
able to use it, and the iptables functions really need a prefix
anyway, so use the new virNetworkDefPrefix() function to send prefixes
into iptables functions instead of netmasks.
Also, in a couple places where a netmask is actually needed, use the
new private API function for it rather than getting it directly. This
will allow for cases where no netmask or prefix is specified (it
returns the default for the current class of network.)
Some functions in this file were returning 1 on success and 0 on
failure, and others were returning 0 on success and -1 on
failure. Switch them all to return the libvirt-preferred 0/-1.
The functions in iptables.c all return -1 on failure, but all their
callers (which all happen to be in bridge_driver.c) assume that they
are returning an errno, and the logging is done accordingly. This
patch fixes all the error checking and logging to assume < 0 is an
error, and nothing else.
While not technically a double free (since VIR_FREE NULLs the
pointer), this is unnecessary extra code.
This crept in when the function was converted from virRun to virCommand.
The AUTHORS file has also been updated.
This is pretty straightforward - even though dnsmasq gets daemonized
and uses a pid file, those things are both handled by the dnsmasq
binary itself. And libvirt doesn't need any of the output of the
dnsmasq command either, so we just setup the args and call
virRun(). Mainly it was just a (mostly) mechanical job of replacing
the APPEND_ARG() macro (and some other *printfs()) with
virCommandAddArg*().
This patch adds a mode_t parameter to virFileWriteStr().
If mode is different from 0, virFileWriteStr() will try
to create the file if it doesn't exist.
* src/util/util.h (virFileWriteStr): Alter signature.
* src/util/util.c (virFileWriteStr): Allow file creation.
* src/network/bridge_driver.c (networkEnableIpForwarding)
(networkDisableIPV6): Adjust clients.
* src/node_device/node_device_driver.c
(nodeDeviceVportCreateDelete): Likewise.
* src/util/cgroup.c (virCgroupSetValueStr): Likewise.
* src/util/pci.c (pciBindDeviceToStub, pciUnBindDeviceFromStub):
Likewise.
During virtual network startup, the iptables rule that allows tftp
traffic is only added if network->def->tftproot is non-empty, but when
the virtual network is destroyed, we had been unconditionally trying
to delete the rule. This was harmless, except that it created a bogus
error message.
This patch conditionalizes the delete command in the same manner that
the insert command is already conditionalized.
When failing to start a virtual network, we have to cleanup,
tearing down any iptables rules. If the iptables rules were
not present yet though, this raises an error, which squashes
the original error we were handling.
* src/network/bridge_driver.c: When failing to start a virtual
network, don't squash the original error in cleanup
The network address was being set to 192.168.122.0 instead
of 192.168.122.0/24. Fix this by removing the unneccessary
'network' field from virNetworkDef and just pass the
network address and netmask into the iptables APIs directly.
* src/conf/network_conf.h, src/conf/network_conf.c: Remove
the 'network' field from virNEtworkDef.
* src/network/bridge_driver.c: Update for iptables API changes
* src/util/iptables.c, src/util/iptables.h: Require the
network address + netmask pair to be passed in
Instead of storing the IP address string in virNetwork related
structs, store the parsed virSocketAddr. This will make it
easier to add IPv6 support in the future, by letting driver
code directly check what address family is present
* src/conf/network_conf.c, src/conf/network_conf.h,
src/network/bridge_driver.c: Convert to use virSocketAddr
in virNetwork, instead of char *.
* src/util/bridge.c, src/util/bridge.h,
src/util/dnsmasq.c, src/util/dnsmasq.h,
src/util/iptables.c, src/util/iptables.h: Convert to
take a virSocketAddr instead of char * for any IP
address parameters
* src/util/network.h: Add macros to determine if an address
is set, and what address family is set.
The virSocketParse method was not doing any error reporting
which meant the true cause of the problem was lost. Remove
all error reporting from callers, and push it into virSocketParse
* src/util/network.c: Add error reporting to virSocketParse
* src/conf/domain_conf.c, src/conf/network_conf.c,
src/network/bridge_driver.c: Remove error reporting in
callers of virSocketParse
The virSocketParseAddr function was accepting any AF_* constant
and using that to set the ai_flags field in struct addrinfo.
This is invalid, since address families must go in the ai_family
field of the struct.
* src/util/network.c: Fix handling of address family
* src/conf/network_conf.c, src/network/bridge_driver.c: Pass
AF_UNSPEC instead of relying on it being 0.
Some operations on socket addresses need to know the length of
the sockaddr struct for the particular address family. This
info was being discarded when passing around virSocketAddr
instances. Turn it from a union into a struct containing
union+socklen_t fields, so length is always kept around.
* src/util/network.h: Add socklen_t field to virSocketAddr
* src/util/network.c, src/network/bridge_driver.c,
src/conf/domain_conf.c: Update to take account of new
struct definition.
For static-only DHCP, i.e. with no <range> but at least one <host>
element within <dhcp> element, we have to add "--dhcp-range IP,static"
option to dnsmasq to actually enable the service. Without this option,
dnsmasq will not respond to DHCP requests.
--dhcp-no-override description from dnsmasq man page:
Disable re-use of the DHCP servername and filename fields as
extra option space. If it can, dnsmasq moves the boot server and
filename information (from dhcp-boot) out of their dedicated
fields into DHCP options. This make extra space available in the
DHCP packet for options but can, rarely, confuse old or broken
clients. This flag forces "simple and safe" behaviour to avoid
problems in such a case.
It seems some virtual network card ROMs are this old/buggy so let's add
--dhcp-no-override as a workaround for them. We don't use extra DHCP
options so this should be safe. The option was added in dnsmasq-2.41,
which becomes the minimum required version.
We add --dhcp-lease-max=xxx argument when network->def->nranges > 0 but
we only allocate space for in the opposite case :-) I guess we are lucky
enough to miscount somewhere else so that we actually allocate more
space than we need since no-one has hit this bug so far.
This patch attempts to take advantage of a newly added netfilter
module to correct for a problem with some guest DHCP client
implementations when used in conjunction with a DHCP server run on the
host systems with packet checksum offloading enabled.
The problem is that, when the guest uses a RAW socket to read the DHCP
response packets, the checksum hasn't yet been fixed by the IP stack,
so it is incorrect.
The fix implemented here is to add a rule to the POSTROUTING chain of
the mangle table in iptables that fixes up the checksum for packets on
the virtual network's bridge that are destined for the bootpc port (ie
"dhcpc", ie port 68) port on the guest.
Only very new versions of iptables will have this support (it will be
in the next upstream release), so a failure to add this rule only
results in a warning message. The iptables patch is here:
http://patchwork.ozlabs.org/patch/58525/
A corresponding kernel module patch is also required (the backend of
the iptables patch) and that will be in the next release of the
kernel.
IPtables will seek to preserve the source port unchanged when
doing masquerading, if possible. NFS has a pseudo-security
option where it checks for the source port <= 1023 before
allowing a mount request. If an admin has used this to make the
host OS trusted for mounts, the default iptables behaviour will
potentially allow NAT'd guests access too. This needs to be
stopped.
With this change, the iptables -t nat -L -n -v rules for the
default network will be
Chain POSTROUTING (policy ACCEPT 95 packets, 9163 bytes)
pkts bytes target prot opt in out source destination
14 840 MASQUERADE tcp -- * * 192.168.122.0/24 !192.168.122.0/24 masq ports: 1024-65535
75 5752 MASQUERADE udp -- * * 192.168.122.0/24 !192.168.122.0/24 masq ports: 1024-65535
0 0 MASQUERADE all -- * * 192.168.122.0/24 !192.168.122.0/24
* src/network/bridge_driver.c: Add masquerade rules for TCP
and UDP protocols
* src/util/iptables.c, src/util/iptables.c: Add source port
mappings for TCP & UDP protocols when masquerading.
add iptables rules to allow TFTP from the virtual network if <tftp>
element is defined in the network definition.
Fedora bz#580215
* src/network/bridge_driver.c: open UDP port 69 for TFTP traffic if
tftproot is defined
The network driver is not doing correct checking for
duplicate UUID/name values. This introduces a new method
virNetworkObjIsDuplicate, based on the previously
written virDomainObjIsDuplicate.
* src/conf/network_conf.c, src/conf/network_conf.c,
src/libvirt_private.syms: Add virNetworkObjIsDuplicate,
* src/network/bridge_driver.c: Call virNetworkObjIsDuplicate
for checking uniqueness of uuid/names
Fedora bug https://bugzilla.redhat.com/show_bug.cgi?id=235961
If using the default virtual network, an easy way to lose guest network
connectivity is to install libvirt inside the VM. The autostarted
default network inside the guest collides with host virtual network
routing. This is a long standing issue that has caused users quite a
bit of pain and confusion.
On network startup, parse /proc/net/route and compare the requested
IP+netmask against host routing destinations: if any matches are found,
refuse to start the network.
v2: Drop sscanf, fix a comment typo, comment that function could use
libnl instead of /proc
v3: Consider route netmask. Compare binary data rather than convert to
string.
v4: Return to using sscanf, drop inet functions in favor of virSocket,
parsing safety checks. Don't make parse failures fatal, in case
expected format changes.
v5: Try and continue if we receive unexpected. Delimit parsed lines to
prevent scanning past newline
Approximately 60 messages were marked. Since these diagnostics are
intended solely for developers and maintainers, encouraging translation
is deemed to be counterproductive:
http://thread.gmane.org/gmane.comp.emulators.libvirt/25050/focus=25052
Run this command:
git grep -l VIR_WARN|xargs perl -pi -e \
's/(VIR_WARN0?)\s*\(_\((".*?")\)/$1($2/'
use /var/lib/libvirt/dnsmasq since /var/lib/libvirt/network is
unreadable by the dnsmasq binary
* src/network/bridge_driver.c: update DNSMASQ_STATE_DIR
* src/Makefile.am: create it on make install
* libvirt.spec.in: take the new directory into account
This patch makes libvirtd start the dnsmasq daemon with a
--dhcp-hostsfile option instead of --dhcp-host options for each
'//ip/dhcp/host' entries defined in network xml file.
the dnsmasq host file is stored into /var/lib/libvirt/network
* src/network/bridge_driver.c: define the directory for the hostfiles
and save/delete them to be used by dnsmasq
