10:04 a.m.
I just wrote this to assist some Red Hat folks understanding
what libvirt does with iptables, and thought it is useful info
for the whole libvirt community. When I have time I'll adjust
this content so that it can fit into the website in relevant
pages/places.
Firewall / network filtering in libvirt
=======================================
There are three pieces of libvirt functionality which do network
filtering of some type. At a high level they are:
- The virtual network driver.
This provides a isolated bridge device (ie no physical NICs
enslaved). Guest TAP devices are attached to this bridge.
Guests can talk to each other & the host, and optionally the
wider world.
- The QEMU driver MAC filtering
This provides a generic filtering of MAC addresses to prevent
the guest spoofing its MAC address. This is mostly obsoleted by
the next item, so won't be discussed further.
- The network filter driver
This provides fully configurable, arbitrary network filtering
of traffic on guest NICs. Generic rulesets are defined at the
host level to control traffic in some manner. Rules sets are
then associated with individual NICs of a guest. While not as
expressive as directly using iptables/ebtables, this can still
do nearly everything you would want to on a guest NIC filter.
The virtual network driver
==========================
The typical configuration for guests is to use bridging of the
physical NIC on the host to connect the guest directly to the LAN.
In RHEL6 there is also the possibility of using macvtap/sr-iov
and VEPA connectivity. None of this stuff plays nicely with wireless
NICs, since they will typically silently drop any traffic with a
MAC address that doesn't match that of the physical NIC.
Thus the virtual network driver in libvirt was invented. This takes
the form of an isolated bridge device (ie one with no physical NICs
enslaved). The TAP devices associated with the guest NICs are attached
to the bridge device. This immediately allows guests on a single host
to talk to each other and to the host OS (modulo host IPtables rules).
libvirt then uses iptables to control what further connectivity is
available. There are three configurations possible for a virtual
network at time of writing
- isolated: all off-node traffic is completely blocked
- nat: outbound traffic to the LAN is allowed, but MASQUERADED
- forward: outbound traffic to the LAN is allowed
The latter 'forward' case requires the virtual network be on a
separate sub-net from the main LAN, and that the LAN admin has
configured routing for this subnet. In the future we intend to
add support for IP subnetting and/or proxy-arp. This allows for
the virtual network to use the same subnet as the main LAN &
should avoid need for the LAN admin to configure special routing.
Libvirt will optionally also provide DHCP services to the virtual
network using DNSMASQ. In all cases, we need to allow DNS/DHCP
queries to the host OS. Since we can't predict whether the host
firewall setup is already allowing this, we insert 4 rules into
the head of the INPUT chain
target prot opt in out source destination
ACCEPT udp -- virbr0 * 0.0.0.0/0 0.0.0.0/0 udp dpt:53
ACCEPT tcp -- virbr0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:53
ACCEPT udp -- virbr0 * 0.0.0.0/0 0.0.0.0/0 udp dpt:67
ACCEPT tcp -- virbr0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:67
Note we have restricted our rules to just the bridge associated
with the virutal network, to avoid opening undesirable holes in
the host firewall wrt the LAN/WAN.
The next rules depend on the type of connectivity allowed, and go
in the main FORWARD chain:
type=isolated
-------------
Allow traffic between guests. Deny inbound. Deny outbound.
target prot opt in out source destination
ACCEPT all -- virbr1 virbr1 0.0.0.0/0 0.0.0.0/0
REJECT all -- * virbr1 0.0.0.0/0 0.0.0.0/0 reject-with
icmp-port-unreachable
REJECT all -- virbr1 * 0.0.0.0/0 0.0.0.0/0 reject-with
icmp-port-unreachable
type=nat
--------
Allow inbound related to an established connection. Allow
outbound, but only from our expected subnet. Allow traffic
between guests. Deny all other inbound. Deny all other outbound.
target prot opt in out source destination
ACCEPT all -- * virbr0 0.0.0.0/0 192.168.122.0/24 state
RELATED,ESTABLISHED
ACCEPT all -- virbr0 * 192.168.122.0/24 0.0.0.0/0
ACCEPT all -- virbr0 virbr0 0.0.0.0/0 0.0.0.0/0
REJECT all -- * virbr0 0.0.0.0/0 0.0.0.0/0 reject-with
icmp-port-unreachable
REJECT all -- virbr0 * 0.0.0.0/0 0.0.0.0/0 reject-with
icmp-port-unreachable
type=routed
-----------
Allow inbound, but only to our expected subnet. Allow
outbound, but only from our expected subnet. Allow traffic
between guests. Deny all other inbound. Deny all other outbound.
target prot opt in out source destination
ACCEPT all -- * virbr2 0.0.0.0/0 192.168.124.0/24
ACCEPT all -- virbr2 * 192.168.124.0/24 0.0.0.0/0
ACCEPT all -- virbr2 virbr2 0.0.0.0/0 0.0.0.0/0
REJECT all -- * virbr2 0.0.0.0/0 0.0.0.0/0 reject-with
icmp-port-unreachable
REJECT all -- virbr2 * 0.0.0.0/0 0.0.0.0/0 reject-with
icmp-port-unreachable
Finally, with type=nat, there is also an entry in the POSTROUTING
chain to apply masquerading
target prot opt in out source destination
MASQUERADE all -- * * 192.168.122.0/24 !192.168.122.0/24
The network filter driver
=========================
This driver provides a fully configurable network filtering capability
that leverages ebtables, iptables and ip6tables. This was written by
the libvirt guys at IBM and although its XML schema is defined by libvirt,
the conceptual model is closely aligned with the DMTF CIM schema for
network filtering
http://www.dmtf.org/standards/cim/cim_schema_v2230/CIM_Network.pdf
The filters are managed in libvirt as a top level, standalone object.
This allows the filters to then be referenced by any libvirt object
that requires their functionality, instead tieing them only to use
by guest NICs. In the current implementation, filters can be associated
with individual guest NICs via the libvirt domain XML format. In the
future we might allow filters to be associated with the virtual network
objects. Further we're expecting to define a new 'virtual switch' object
to remove the complexity of configuring bridge/sriov/vepa networking
modes. This make also end up making use of network filters.
There are a new set of virsh commands for managing network filters
virsh nwfilter-define define or update a network filter from an XML file
virsh nwfilter-undefine undefine a network filter
virsh nwfilter-dumpxml network filter information in XML
virsh nwfilter-list list network filters
virsh nwfilter-edit edit XML configuration for a network filter
There are equivalently named C APIs for each of these commands.
As with all objects libvirt manages, network filters are configured
using an XML format. At a high level the format looks like this:
<filter name='no-spamming' chain='XXXX'>
<uuid>d217f2d7-5a04-0e01-8b98-ec2743436b74</uuid>
<rule ...>
....
</rule>
<filterref filter='XXXX'/>
</filter>
Every filter has a name and UUID which serve as unique identifiers.
A filter can have zero-or-more <rule> elements which are used to
actually define network controls. Filters can be arranged into a
DAG, so zero-or-more <filterref/> elements are also allowed. Cycles
in the graph are not allowed.
The <rule> element is where all the interesting stuff happens. It
has three attributes, an action, a traffic direction and an optional
priority. eg
<rule action='drop' direction='out' priority='500'>
Within the rule there are a wide variety of elements allowed, which
do protocol specific matching. Supported protocols currently include
'mac', 'arp', 'rarp', 'ip', 'ipv6',
'tcp/ip', 'icmp/ip', 'igmp/ip',
'udp/ip', 'udplite/ip' 'esp/ip', 'ah/ip',
'sctp/ip', 'tcp/ipv6',
'icmp/ipv6', 'igmp/ipv6', 'udp/ipv6', 'udplite/ipv6',
'esp/ipv6',
'ah/ipv6', 'sctp/ipv6'. Each protocol defines what is valid inside
the <rule> element, the general pattern though is
<protocol match='yes|no' attribute1='value1'
attribute2='value2'/>
so, eg a TCP protocol, matching ports 0-1023 would be expressed
as:
<tcp match='yes' srcportstart='0' srcportend='1023'/>
Attributes can included references to variables defined by the
object using the rule. So the guest XML format allows each NIC
to have a MAC address and IP address defined. These are made
available to filters via the variables $IP and $MAC.
So to define a filter the prevents IP address spoofing we can
simply match on source IP address != $IP
<filter name='no-ip-spoofing' chain='ipv4'>
<rule action='drop' direction='out'>
<ip match='no' srcipaddr='$IP' />
</rule>
</filter>
I'm not going to go into details on all the other protocol
matches you can do, because it'll take far too much space.
You can read about the options here
http://libvirt.org/formatnwfilter.html#nwfelemsRulesProto
Out of the box in RHEL6/Fedora rawhide, libvirt ships with a
set of default useful rules
# virsh nwfilter-list
UUID Name
----------------------------------------------------------------
15b1ab2b-b1ac-1be2-ed49-2042caba4abb allow-arp
6c51a466-8d14-6d11-46b0-68b1a883d00f allow-dhcp
7517ad6c-bd90-37c8-26c9-4eabcb69848d allow-dhcp-server
3d38b406-7cf0-8335-f5ff-4b9add35f288 allow-incoming-ipv4
5ff06320-9228-2899-3db0-e32554933415 allow-ipv4
db0b1767-d62b-269b-ea96-0cc8b451144e clean-traffic
f88f1932-debf-4aa1-9fbe-f10d3aa4bc95 no-arp-spoofing
772f112d-52e4-700c-0250-e178a3d91a7a no-ip-multicast
7ee20370-8106-765d-f7ff-8a60d5aaf30b no-ip-spoofing
d5d3c490-c2eb-68b1-24fc-3ee362fc8af3 no-mac-broadcast
fb57c546-76dc-a372-513f-e8179011b48a no-mac-spoofing
dba10ea7-446d-76de-346f-335bd99c1d05 no-other-l2-traffic
f5c78134-9da4-0c60-a9f0-fb37bc21ac1f no-other-rarp-traffic
7637e405-4ccf-42ac-5b41-14f8d03d8cf3 qemu-announce-self
9aed52e7-f0f3-343e-fe5c-7dcb27b594e5 qemu-announce-self-rarp
Most of these are just building blocks. The interesting one here
is 'clean-traffic'. This pulls together all the building blocks
into one filter that you can then associate with a guest NIC.
This stops the most common bad things a guest might try, IP
spoofing, arp spoofing and MAC spoofing. To look at the rules for
any of these just do
virsh nwfilter-dumpxml FILTERNAME|UUID
They are all stored in /etc/libvirt/nwfilter, but don't edit
files there directly. Use 'virsh nwfilter-define' to update
them. This ensures the guests have their iptables/ebtables
rules recreated.
To associate the clean-trafffic filter with a guest, edit the
guest XML config and change the <interface> element to include
a <filterref> and also specify the whitelisted <ip addres/> the
guest is allowed to use
<interface type='bridge'>
<mac address='52:54:00:56:44:32'/>
<source bridge='br1'/>
<ip address='10.33.8.131'/>
<target dev='vnet0'/>
<model type='virtio'/>
<filterref filter='clean-traffic'/>
</interface>
If no <ip address> is included, the network filter driver will
activate its 'learning mode'. This uses libpcap to snoop on
network traffic the guest sends and attempts to identify the
first IP address it uses. It then locks traffic to this address.
Obviously this isn't entirely secure, but it does offer some
protection against the guest being trojaned once up & running.
In the future we intend to enhance the learning mode so that it
looks for DHCPOFFERS from a trusted DHCP server and only allows
the offered IP address to be used.
Now, how is all this implemented... The network filter driver
uses a combination of ebtables, iptables and ip6tables, depending
on which protocols are referenced in a filter. The out of the box
'clean-traffic' filter rules only require use of ebtables. If you
want to do matching at tcp/udp/etc protocols (eg to add a new
filter 'no-email-spamming' to block port 25), then iptables will
also be used.
The driver attempts to keep its rules separate from those that
the host admin might already have configured. So the first thing
it does with ebtables, is to add two hooks in POSTROUTING &
PREROUTING chains, to redirect traffic to custom chains. These
hooks match on the TAP device name of the guest NIC, so they
should not interact badly with any administrator defined rules
Bridge chain: PREROUTING, entries: 1, policy: ACCEPT
-i vnet0 -j libvirt-I-vnet0
Bridge chain: POSTROUTING, entries: 1, policy: ACCEPT
-o vnet0 -j libvirt-O-vnet0
To keep things managable & easy to follow, the driver will then
create further sub-chains for each protocol then it needs to match
against:
Bridge chain: libvirt-I-vnet0, entries: 5, policy: ACCEPT
-p IPv4 -j I-vnet0-ipv4
-p ARP -j I-vnet0-arp
-p 0x8035 -j I-vnet0-rarp
-p 0x835 -j ACCEPT
-j DROP
Bridge chain: libvirt-O-vnet0, entries: 4, policy: ACCEPT
-p IPv4 -j O-vnet0-ipv4
-p ARP -j O-vnet0-arp
-p 0x8035 -j O-vnet0-rarp
-j DROP
Finally, come the actual implementation of the filters. These
example is showing the 'clean-traffic' filter implementation.
I'm not going to explain what this is doing now :-)
Bridge chain: I-vnet0-ipv4, entries: 2, policy: ACCEPT
-s ! 52:54:0:56:44:32 -j DROP
-p IPv4 --ip-src ! 10.33.8.131 -j DROP
Bridge chain: O-vnet0-ipv4, entries: 1, policy: ACCEPT
-j ACCEPT
Bridge chain: I-vnet0-arp, entries: 6, policy: ACCEPT
-s ! 52:54:0:56:44:32 -j DROP
-p ARP --arp-mac-src ! 52:54:0:56:44:32 -j DROP
-p ARP --arp-ip-src ! 10.33.8.131 -j DROP
-p ARP --arp-op Request -j ACCEPT
-p ARP --arp-op Reply -j ACCEPT
-j DROP
Bridge chain: O-vnet0-arp, entries: 5, policy: ACCEPT
-p ARP --arp-op Reply --arp-mac-dst ! 52:54:0:56:44:32 -j DROP
-p ARP --arp-ip-dst ! 10.33.8.131 -j DROP
-p ARP --arp-op Request -j ACCEPT
-p ARP --arp-op Reply -j ACCEPT
-j DROP
Bridge chain: I-vnet0-rarp, entries: 2, policy: ACCEPT
-p 0x8035 -s 52:54:0:56:44:32 -d Broadcast --arp-op Request_Reverse --arp-ip-src 0.0.0.0
--arp-ip-dst 0.0.0.0 --arp-mac-src 52:54:0:56:44:32 --arp-mac-dst 52:54:0:56:44:32 -j
ACCEPT
-j DROP
Bridge chain: O-vnet0-rarp, entries: 2, policy: ACCEPT
-p 0x8035 -d Broadcast --arp-op Request_Reverse --arp-ip-src 0.0.0.0 --arp-ip-dst
0.0.0.0 --arp-mac-src 52:54:0:56:44:32 --arp-mac-dst 52:54:0:56:44:32 -j ACCEPT
-j DROP
NB, we would have liked to include the prefix 'libvirt-' in all
of our chain names, but unfortunately the kernel limits names
to a very short maximum length. So only the first two custom
chains can include that prefix. The others just include the
TAP device name + protocol name.
If I define a new filter 'no-spamming' and then add this to the
'clean-traffic' filter, I can illustrate how iptables usage works.
# cat > /root/spamming.xml <<EOF
<filter name='no-spamming' chain='root'>
<uuid>d217f2d7-5a04-0e01-8b98-ec2743436b74</uuid>
<rule action='drop' direction='out' priority='500'>
<tcp dstportstart='25' dstportend='25'/>
</rule>
</filter>
EOF
# virsh nwfilter-define /root/spamming.xml
# virsh nwfilter-edit clean-traffic
...add <filterref filter='no-spamming'/>
All active guests immediately have their iptables/ebtables rules
rebuilt.
The network filter driver deals with iptables in a very similar
way. First it separates out its rules from those the admin may
have defined, by adding a couple of hooks into the INPUT/FORWARD
chains
Chain INPUT (policy ACCEPT 13M packets, 21G bytes)
target prot opt in out source destination
libvirt-host-in all -- * * 0.0.0.0/0 0.0.0.0/0
Chain FORWARD (policy ACCEPT 5532K packets, 3010M bytes)
target prot opt in out source destination
libvirt-in all -- * * 0.0.0.0/0 0.0.0.0/0
libvirt-out all -- * * 0.0.0.0/0 0.0.0.0/0
libvirt-in-post all -- * * 0.0.0.0/0 0.0.0.0/0
These custom chains, then do matching based on the TAP device
name, so they won't open holes in the admin defined matches for
the LAN/WAN (if any).
Chain libvirt-host-in (1 references)
target prot opt in out source destination
HI-vnet0 all -- * * 0.0.0.0/0 0.0.0.0/0 [goto]
PHYSDEV match --physdev-in vnet0
Chain libvirt-in (1 references)
target prot opt in out source destination
FI-vnet0 all -- * * 0.0.0.0/0 0.0.0.0/0 [goto]
PHYSDEV match --physdev-in vnet0
Chain libvirt-in-post (1 references)
target prot opt in out source destination
ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 PHYSDEV
match --physdev-in vnet0
Chain libvirt-out (1 references)
target prot opt in out source destination
FO-vnet0 all -- * * 0.0.0.0/0 0.0.0.0/0 [goto]
PHYSDEV match --physdev-out vnet0
Finally, we can see the interesting bit which is the actual
implementation of my filter to block port 25 access:
Chain FI-vnet0 (1 references)
target prot opt in out source destination
DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:25
Chain FO-vnet0 (1 references)
target prot opt in out source destination
DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp spt:25
Chain HI-vnet0 (1 references)
target prot opt in out source destination
DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:25
One thing in looking at this that you may notice is that if there
are many guests all using the same filters, we will be duplicating
the iptables rules over & over for each guest. This is merely a
limitation of the current rules engine implementation. At the libvirt
object modelling level you can clearly see we've designed the model
so that filter rules are define in one place, and indirectly referenced
by guests. Thus it should be possible to change the impl in the future
so that we can share the actual iptables/ebtables rules for each
guest to create a more scalable system. The stuff in current libvirt
is more or less the very first working impl we've had of this stuff,
so there's not been much optimization work yet.
Also notice that at the XML level we don't expose the fact that we
are using iptables or ebtables at all. The rule definition is done in
terms of network protocols. Thus if we ever find a need, we could
plug in an alternative implementation that calls out to a different
firewall implementation instead of ebtables/iptables (providing that
impl was suitably expressive of course)
Finally, in terms of problems we have in deployment. The biggest
problem is that if the admin does 'service iptables restart' all
our work gets blown away. We've experimented with using lokkit
to record our custom rules in a persistent config file, but that
caused different problem. Admins who were not using lokkit for
their config found that all their own rules got blown away. So
we threw away our lokkit code. Instead we document that if you
run 'service iptables restart', you need to send SIGHUP to libvirt
to make it recreate its rules.
Finally a reminder, that the main documentation we have on this
is online at http://libvirt.org/formatnwfilter.html
Regards,
Daniel
--
|: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :|
|: http://libvirt.org -o- http://virt-manager.org -o- http://deltacloud.org :|
|: http://autobuild.org -o- http://search.cpan.org/~danberr/ :|
|: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|
10:13 a.m.
New subject: [libvirt] FYI: a short guide to libvirt & network filtering iptables/ebtables use
On 07/01/2010 01:04 AM, Daniel P. Berrange wrote:
I just wrote this to assist some Red Hat folks understanding
what libvirt does with iptables, and thought it is useful info
for the whole libvirt community. When I have time I'll adjust
this content so that it can fit into the website in relevant
pages/places.
Do you want me to transfer this to the wiki?
Thinking it might take a while, but maybe it'll help me learn the stuff
as I go through it and it'll let you focus on other stuff?
Regards and best wishes,
Justin Clift
--
Salasaga - Open Source eLearning IDE
http://www.salasaga.org
10:22 a.m.
New subject: [libvirt] FYI: a short guide to libvirt & network filtering iptables/ebtables use
On 06/30/2010 09:13 AM, Justin Clift wrote:
On 07/01/2010 01:04 AM, Daniel P. Berrange wrote:
> I just wrote this to assist some Red Hat folks understanding
> what libvirt does with iptables, and thought it is useful info
> for the whole libvirt community. When I have time I'll adjust
> this content so that it can fit into the website in relevant
> pages/places.
Do you want me to transfer this to the wiki?
Thinking it might take a while, but maybe it'll help me learn the stuff
as I go through it and it'll let you focus on other stuff?
Absolutely - that would be a useful task to take on. If you need help
with any particular aspect, give us a shout.
--
Eric Blake eblake(a)redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org
10:30 a.m.
New subject: [libvirt] FYI: a short guide to libvirt & network filtering iptables/ebtables use
On Thu, Jul 01, 2010 at 01:13:20AM +1000, Justin Clift wrote:
On 07/01/2010 01:04 AM, Daniel P. Berrange wrote:
>I just wrote this to assist some Red Hat folks understanding
>what libvirt does with iptables, and thought it is useful info
>for the whole libvirt community. When I have time I'll adjust
>this content so that it can fit into the website in relevant
>pages/places.
Do you want me to transfer this to the wiki?
I'd rather this content were in the appropriate pages in the main
website rather than the wiki, because the wiki pages never fit into
the site navigation well & this content is relevant for several of
the existing pages on the site.
I'm thinking a new page under 'Documentation -> Deployment -> Firewall'
with info that's relevant to administrators. Cross-referencing from
the driver pages for QEMU, Networking where appropriate. Also need
to add content about firewall needs for guest migration, and VNC access
Regards,
Daniel
--
|: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :|
|: http://libvirt.org -o- http://virt-manager.org -o- http://deltacloud.org :|
|: http://autobuild.org -o- http://search.cpan.org/~danberr/ :|
|: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|
10:33 a.m.
New subject: [libvirt] FYI: a short guide to libvirt & network filtering iptables/ebtables use
On 07/01/2010 01:30 AM, Daniel P. Berrange wrote:
<snip>
I'd rather this content were in the appropriate pages in the
main
website rather than the wiki, because the wiki pages never fit into
the site navigation well& this content is relevant for several of
the existing pages on the site.
I'm thinking a new page under 'Documentation -> Deployment ->
Firewall'
with info that's relevant to administrators. Cross-referencing from
the driver pages for QEMU, Networking where appropriate. Also need
to add content about firewall needs for guest migration, and VNC access
No worries. I'll submit an initial bulk patch that gets this info in
place in a new something.html.in file, and you can massage that as needed?
+ Justin
--
Salasaga - Open Source eLearning IDE
http://www.salasaga.org
6:58 p.m.
New subject: [libvirt] [PATCH] html docs: added firewall explanation page by daniel berrange
---
Daniel, how's this as a first go?
It's just your content converted to HTML in the same style as the other
pages, with the occasional typo fix. If this is workable, then I'll create
another patch after this to hook it into the overall website menu structure.
docs/firewall.html.in | 477 +++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 477 insertions(+), 0 deletions(-)
create mode 100644 docs/firewall.html.in
diff --git a/docs/firewall.html.in b/docs/firewall.html.in
new file mode 100644
index 0000000..a6dbec2
--- /dev/null
+++ b/docs/firewall.html.in
@@ -0,0 +1,477 @@
+<?xml version="1.0"?>
+<html>
+ <body>
+ <h1 >Firewall / network filtering in libvirt</h1>
+ <p>There are three pieces of libvirt functionality which do network
+ filtering of some type.
+ <br /><br />
+ At a high level they are:
+ </p>
+ <ul>
+ <li>The virtual network driver
+ <br /><br />
+ This provides a isolated bridge device (ie no physical NICs
+ enslaved). Guest TAP devices are attached to this bridge.
+ Guests can talk to each other and the host, and optionally the
+ wider world.
+ <br /><br />
+ </li>
+ <li>The QEMU driver MAC filtering
+ <br /><br />
+ This provides a generic filtering of MAC addresses to prevent
+ the guest spoofing its MAC address. This is mostly obsoleted by
+ the next item, so won't be discussed further.
+ <br /><br />
+ </li>
+ <li>The network filter driver
+ <br /><br />
+ This provides fully configurable, arbitrary network filtering
+ of traffic on guest NICs. Generic rulesets are defined at the
+ host level to control traffic in some manner. Rules sets are
+ then associated with individual NICs of a guest. While not as
+ expressive as directly using iptables/ebtables, this can still
+ do nearly everything you would want to on a guest NIC filter.
+ </li>
+ </ul>
+
+ <h3><a name="name-fw-virtual-network-driver"
+ id="id-fw-virtual-network-driver">The virtual network
driver</a>
+ </h3>
+ <p>The typical configuration for guests is to use bridging of the
+ physical NIC on the host to connect the guest directly to the LAN.
+ In RHEL6 there is also the possibility of using macvtap/sr-iov
+ and VEPA connectivity. None of this stuff plays nicely with wireless
+ NICs, since they will typically silently drop any traffic with a
+ MAC address that doesn't match that of the physical NIC.
+ </p>
+ <p>Thus the virtual network driver in libvirt was invented. This takes
+ the form of an isolated bridge device (ie one with no physical NICs
+ enslaved). The TAP devices associated with the guest NICs are attached
+ to the bridge device. This immediately allows guests on a single host
+ to talk to each other and to the host OS (modulo host IPtables rules).
+ </p>
+ <p>libvirt then uses iptables to control what further connectivity is
+ available. There are three configurations possible for a virtual
+ network at time of writing:
+ </p>
+ <ul>
+ <li>isolated: all off-node traffic is completely blocked</li>
+ <li>nat: outbound traffic to the LAN is allowed, but MASQUERADED</li>
+ <li>forward: outbound traffic to the LAN is allowed</li>
+ </ul>
+ <p>The latter 'forward' case requires the virtual network be on a
+ separate sub-net from the main LAN, and that the LAN admin has
+ configured routing for this subnet. In the future we intend to
+ add support for IP subnetting and/or proxy-arp. This allows for
+ the virtual network to use the same subnet as the main LAN and
+ should avoid need for the LAN admin to configure special routing.
+ </p>
+ <p>Libvirt will optionally also provide DHCP services to the virtual
+ network using DNSMASQ. In all cases, we need to allow DNS/DHCP
+ queries to the host OS. Since we can't predict whether the host
+ firewall setup is already allowing this, we insert 4 rules into
+ the head of the INPUT chain
+ </p>
+ <pre>
+target prot opt in out source destination
+ACCEPT udp -- virbr0 * 0.0.0.0/0 0.0.0.0/0 udp dpt:53
+ACCEPT tcp -- virbr0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:53
+ACCEPT udp -- virbr0 * 0.0.0.0/0 0.0.0.0/0 udp dpt:67
+ACCEPT tcp -- virbr0 * 0.0.0.0/0 0.0.0.0/0 tcp
dpt:67</pre>
+ <p>Note we have restricted our rules to just the bridge associated
+ with the virtual network, to avoid opening undesirable holes in
+ the host firewall wrt the LAN/WAN.
+ </p>
+ <p>The next rules depend on the type of connectivity allowed, and go
+ in the main FORWARD chain:
+ </p>
+ <ul>
+ <li>type=isolated
+ <br /><br />
+Allow traffic between guests. Deny inbound. Deny outbound.
+ <pre>
+target prot opt in out source destination
+ACCEPT all -- virbr1 virbr1 0.0.0.0/0 0.0.0.0/0
+REJECT all -- * virbr1 0.0.0.0/0 0.0.0.0/0 reject-with
icmp-port-unreachable
+REJECT all -- virbr1 * 0.0.0.0/0 0.0.0.0/0 reject-with
icmp-port-unreachable</pre>
+ </li>
+ <li>type=nat
+ <br /><br />
+Allow inbound related to an established connection. Allow
+outbound, but only from our expected subnet. Allow traffic
+between guests. Deny all other inbound. Deny all other outbound.
+ <pre>
+target prot opt in out source destination
+ACCEPT all -- * virbr0 0.0.0.0/0 192.168.122.0/24 state
RELATED,ESTABLISHED
+ACCEPT all -- virbr0 * 192.168.122.0/24 0.0.0.0/0
+ACCEPT all -- virbr0 virbr0 0.0.0.0/0 0.0.0.0/0
+REJECT all -- * virbr0 0.0.0.0/0 0.0.0.0/0 reject-with
icmp-port-unreachable
+REJECT all -- virbr0 * 0.0.0.0/0 0.0.0.0/0 reject-with
icmp-port-unreachable</pre>
+ </li>
+ <li>type=routed
+ <br /><br />
+Allow inbound, but only to our expected subnet. Allow
+outbound, but only from our expected subnet. Allow traffic
+between guests. Deny all other inbound. Deny all other outbound.
+ <pre>
+target prot opt in out source destination
+ACCEPT all -- * virbr2 0.0.0.0/0 192.168.124.0/24
+ACCEPT all -- virbr2 * 192.168.124.0/24 0.0.0.0/0
+ACCEPT all -- virbr2 virbr2 0.0.0.0/0 0.0.0.0/0
+REJECT all -- * virbr2 0.0.0.0/0 0.0.0.0/0 reject-with
icmp-port-unreachable
+REJECT all -- virbr2 * 0.0.0.0/0 0.0.0.0/0 reject-with
icmp-port-unreachable</pre>
+ </li>
+ <li>Finally, with type=nat, there is also an entry in the POSTROUTING
+chain to apply masquerading:
+ <pre>
+target prot opt in out source destination
+MASQUERADE all -- * * 192.168.122.0/24 !192.168.122.0/24</pre>
+ </li>
+ </ul>
+
+ <h3><a name="name-fw-network-filter-driver"
+ id="id-fw-network-filter-driver">The network filter
driver</a>
+ </h3>
+ <p>This driver provides a fully configurable network filtering capability
+ that leverages ebtables, iptables and ip6tables. This was written by
+ the libvirt guys at IBM and although its XML schema is defined by libvirt,
+ the conceptual model is closely aligned with the DMTF CIM schema for
+ network filtering:
+ </p>
+ <p><a
href="http://www.dmtf.org/standards/cim/cim_schema_v2230/CIM_Network...
+ <p>The filters are managed in libvirt as a top level, standalone object.
+ This allows the filters to then be referenced by any libvirt object
+ that requires their functionality, instead tieing them only to use
+ by guest NICs. In the current implementation, filters can be associated
+ with individual guest NICs via the libvirt domain XML format. In the
+ future we might allow filters to be associated with the virtual network
+ objects. Further we're expecting to define a new 'virtual switch'
object
+ to remove the complexity of configuring bridge/sriov/vepa networking
+ modes. This make also end up making use of network filters.
+ </p>
+ <p>There are a new set of virsh commands for managing network
filters:</p>
+ <ul>
+ <li>virsh nwfilter-define
+ <br /><br />
+ define or update a network filter from an XML file
+ <br /><br />
+ </li>
+ <li>virsh nwfilter-undefine
+ <br /><br />
+ undefine a network filter
+ <br /><br />
+ </li>
+ <li>virsh nwfilter-dumpxml
+ <br /><br />
+ network filter information in XML
+ <br /><br />
+ </li>
+ <li>virsh nwfilter-list
+ <br /><br />
+ list network filters
+ <br /><br />
+ </li>
+ <li>virsh nwfilter-edit
+ <br /><br />
+ edit XML configuration for a network filter
+ </li>
+ </ul>
+ <p>There are equivalently named C APIs for each of these commands.</p>
+ <p>As with all objects libvirt manages, network filters are configured
+using an XML format. At a high level the format looks like this:
+ </p>
+<pre>
+<filter name='no-spamming' chain='XXXX'>
+ <uuid>d217f2d7-5a04-0e01-8b98-ec2743436b74</uuid>
+
+ <rule ...>
+ ....
+ </rule>
+
+ <filterref filter='XXXX'/>
+</filter></pre>
+ <p>Every filter has a name and UUID which serve as unique identifiers.
+ A filter can have zero-or-more <code><rule></code>
elements which
+ are used to actually define network controls. Filters can be arranged
+ into a DAG, so zero-or-more <code><filterref/></code>
elements are
+ also allowed. Cycles in the graph are not allowed.
+ </p>
+ <p>The <code><rule></code> element is where all the
interesting stuff
+ happens. It has three attributes, an action, a traffic direction and an
+ optional priority. eg:
+ </p>
+ <pre><rule action='drop' direction='out'
priority='500'></pre>
+ <p>Within the rule there are a wide variety of elements allowed, which
+ do protocol specific matching. Supported protocols currently include
+ <code>mac</code>, <code>arp</code>,
<code>rarp</code>, <code>ip</code>,
+ <code>ipv6</code>, <code>tcp/ip</code>,
<code>icmp/ip</code>,
+ <code>igmp/ip</code>, <code>udp/ip</code>,
<code>udplite/ip</code>,
+ <code>esp/ip</code>, <code>ah/ip</code>,
<code>sctp/ip</code>,
+ <code>tcp/ipv6</code>, <code>icmp/ipv6</code>,
<code>igmp/ipv6</code>,
+ <code>udp/ipv6</code>, <code>udplite/ipv6</code>,
<code>esp/ipv6</code>,
+ <code>ah/ipv6</code>, <code>sctp/ipv6</code>. Each
protocol defines what
+ is valid inside the <rule> element. The general pattern though is:
+ </p>
+ <pre>
+<protocol match='yes|no' attribute1='value1'
attribute2='value2'/></pre>
+ <p>So, eg a TCP protocol, matching ports 0-1023 would be expressed
as:</p>
+ <pre><tcp match='yes' srcportstart='0'
srcportend='1023'/></pre>
+ <p>Attributes can included references to variables defined by the
+ object using the rule. So the guest XML format allows each NIC
+ to have a MAC address and IP address defined. These are made
+ available to filters via the variables
<code><b>$IP</b></code> and
+ <code><b>$MAC</b></code>.
+ </p>
+ <p>So to define a filter that prevents IP address spoofing we can
+ simply match on source IP address <code>!= $IP</code> like this:
+ </p>
+ <pre>
+<filter name='no-ip-spoofing' chain='ipv4'>
+ <rule action='drop' direction='out'>
+ <ip match='no' srcipaddr='<b>$IP</b>' />
+ </rule>
+</filter></pre>
+ <p>I'm not going to go into details on all the other protocol
+ matches you can do, because it'll take far too much space.
+ You can read about the options
+ <a
href="http://libvirt.org/formatnwfilter.html#nwfelemsRulesProto"...;.
+ </p>
+ <p>Out of the box in RHEL6/Fedora rawhide, libvirt ships with a
+ set of default useful rules:
+ </p>
+ <pre>
+# virsh nwfilter-list
+UUID Name
+----------------------------------------------------------------
+15b1ab2b-b1ac-1be2-ed49-2042caba4abb allow-arp
+6c51a466-8d14-6d11-46b0-68b1a883d00f allow-dhcp
+7517ad6c-bd90-37c8-26c9-4eabcb69848d allow-dhcp-server
+3d38b406-7cf0-8335-f5ff-4b9add35f288 allow-incoming-ipv4
+5ff06320-9228-2899-3db0-e32554933415 allow-ipv4
+db0b1767-d62b-269b-ea96-0cc8b451144e clean-traffic
+f88f1932-debf-4aa1-9fbe-f10d3aa4bc95 no-arp-spoofing
+772f112d-52e4-700c-0250-e178a3d91a7a no-ip-multicast
+7ee20370-8106-765d-f7ff-8a60d5aaf30b no-ip-spoofing
+d5d3c490-c2eb-68b1-24fc-3ee362fc8af3 no-mac-broadcast
+fb57c546-76dc-a372-513f-e8179011b48a no-mac-spoofing
+dba10ea7-446d-76de-346f-335bd99c1d05 no-other-l2-traffic
+f5c78134-9da4-0c60-a9f0-fb37bc21ac1f no-other-rarp-traffic
+7637e405-4ccf-42ac-5b41-14f8d03d8cf3 qemu-announce-self
+9aed52e7-f0f3-343e-fe5c-7dcb27b594e5 qemu-announce-self-rarp</pre>
+ <p>Most of these are just building blocks. The interesting one here
+ is 'clean-traffic'. This pulls together all the building blocks
+ into one filter that you can then associate with a guest NIC.
+ This stops the most common bad things a guest might try, IP
+ spoofing, arp spoofing and MAC spoofing. To look at the rules for
+ any of these just do:
+ </p>
+ <pre>virsh nwfilter-dumpxml FILTERNAME|UUID</pre>
+ <p>They are all stored in <code>/etc/libvirt/nwfilter</code>, but
don't
+ edit the files there directly. Use <code>virsh nwfilter-define</code>
+ to update them. This ensures the guests have their iptables/ebtables
+ rules recreated.
+ </p>
+ <p>To associate the clean-trafffic filter with a guest, edit the
+ guest XML config and change the <code><interface></code>
element
+ to include a <code><filterref></code> and also specify
the
+ whitelisted <code><ip address/></code> the guest is
allowed to
+ use:
+ </p>
+ <pre>
+<interface type='bridge'>
+ <mac address='52:54:00:56:44:32'/>
+ <source bridge='br1'/>
+ <ip address='10.33.8.131'/>
+ <target dev='vnet0'/>
+ <model type='virtio'/>
+ <filterref filter='clean-traffic'/>
+</interface></pre>
+ <p>If no <code><ip address></code> is included, the
network filter
+ driver will activate its 'learning mode'. This uses libpcap to snoop on
+ network traffic the guest sends and attempts to identify the
+ first IP address it uses. It then locks traffic to this address.
+ Obviously this isn't entirely secure, but it does offer some
+ protection against the guest being trojaned once up and running.
+ In the future we intend to enhance the learning mode so that it
+ looks for DHCPOFFERS from a trusted DHCP server and only allows
+ the offered IP address to be used.
+ </p>
+ <p>Now, how is all this implemented...?</p>
+ <p>The network filter driver uses a combination of ebtables, iptables and
+ ip6tables, depending on which protocols are referenced in a filter. The
+ out of the box 'clean-traffic' filter rules only require use of
+ ebtables. If you want to do matching at tcp/udp/etc protocols (eg to add
+ a new filter 'no-email-spamming' to block port 25), then iptables will
+ also be used.
+ </p>
+ <p>The driver attempts to keep its rules separate from those that
+ the host admin might already have configured. So the first thing
+ it does with ebtables, is to add two hooks in POSTROUTING and
+ PREROUTING chains, to redirect traffic to custom chains. These
+ hooks match on the TAP device name of the guest NIC, so they
+ should not interact badly with any administrator defined rules:
+ </p>
+ <pre>
+Bridge chain: PREROUTING, entries: 1, policy: ACCEPT
+-i vnet0 -j libvirt-I-vnet0
+
+Bridge chain: POSTROUTING, entries: 1, policy: ACCEPT
+-o vnet0 -j libvirt-O-vnet0</pre>
+ <p>To keep things managable and easy to follow, the driver will then
+ create further sub-chains for each protocol then it needs to match
+ against:
+ </p>
+ <pre>
+Bridge chain: libvirt-I-vnet0, entries: 5, policy: ACCEPT
+-p IPv4 -j I-vnet0-ipv4
+-p ARP -j I-vnet0-arp
+-p 0x8035 -j I-vnet0-rarp
+-p 0x835 -j ACCEPT
+-j DROP
+
+Bridge chain: libvirt-O-vnet0, entries: 4, policy: ACCEPT
+-p IPv4 -j O-vnet0-ipv4
+-p ARP -j O-vnet0-arp
+-p 0x8035 -j O-vnet0-rarp
+-j DROP</pre>
+ <p>Finally, here comes the actual implementation of the filters. This
+ example shows the 'clean-traffic' filter implementation.
+ I'm not going to explain what this is doing now. :-)
+ </p>
+ <pre>
+Bridge chain: I-vnet0-ipv4, entries: 2, policy: ACCEPT
+-s ! 52:54:0:56:44:32 -j DROP
+-p IPv4 --ip-src ! 10.33.8.131 -j DROP
+
+Bridge chain: O-vnet0-ipv4, entries: 1, policy: ACCEPT
+-j ACCEPT
+
+Bridge chain: I-vnet0-arp, entries: 6, policy: ACCEPT
+-s ! 52:54:0:56:44:32 -j DROP
+-p ARP --arp-mac-src ! 52:54:0:56:44:32 -j DROP
+-p ARP --arp-ip-src ! 10.33.8.131 -j DROP
+-p ARP --arp-op Request -j ACCEPT
+-p ARP --arp-op Reply -j ACCEPT
+-j DROP
+
+Bridge chain: O-vnet0-arp, entries: 5, policy: ACCEPT
+-p ARP --arp-op Reply --arp-mac-dst ! 52:54:0:56:44:32 -j DROP
+-p ARP --arp-ip-dst ! 10.33.8.131 -j DROP
+-p ARP --arp-op Request -j ACCEPT
+-p ARP --arp-op Reply -j ACCEPT
+-j DROP
+
+Bridge chain: I-vnet0-rarp, entries: 2, policy: ACCEPT
+-p 0x8035 -s 52:54:0:56:44:32 -d Broadcast --arp-op Request_Reverse --arp-ip-src 0.0.0.0
--arp-ip-dst 0.0.0.0 --arp-mac-src 52:54:0:56:44:32 --arp-mac-dst 52:54:0:56:44:32 -j
ACCEPT
+-j DROP
+
+Bridge chain: O-vnet0-rarp, entries: 2, policy: ACCEPT
+-p 0x8035 -d Broadcast --arp-op Request_Reverse --arp-ip-src 0.0.0.0 --arp-ip-dst 0.0.0.0
--arp-mac-src 52:54:0:56:44:32 --arp-mac-dst 52:54:0:56:44:32 -j ACCEPT
+-j DROP</pre>
+ <p>NB, we would have liked to include the prefix 'libvirt-' in all
+ of our chain names, but unfortunately the kernel limits names
+ to a very short maximum length. So only the first two custom
+ chains can include that prefix. The others just include the
+ TAP device name + protocol name.
+ </p>
+ <p>If I define a new filter 'no-spamming' and then add this to the
+ 'clean-traffic' filter, I can illustrate how iptables usage works:
+ </p>
+ <pre>
+# cat > /root/spamming.xml <<EOF
+<filter name='no-spamming' chain='root'>
+ <uuid>d217f2d7-5a04-0e01-8b98-ec2743436b74</uuid>
+ <rule action='drop' direction='out'
priority='500'>
+ <tcp dstportstart='25' dstportend='25'/>
+ </rule>
+</filter>
+EOF
+# virsh nwfilter-define /root/spamming.xml
+# virsh nwfilter-edit clean-traffic</pre>
+
+ <p>...add <code><filterref
filter='no-spamming'/></code></p>
+ <p>All active guests immediately have their iptables/ebtables rules
+ rebuilt.
+ </p>
+ <p>The network filter driver deals with iptables in a very similar
+ way. First it separates out its rules from those the admin may
+ have defined, by adding a couple of hooks into the INPUT/FORWARD
+ chains:
+ </p>
+ <pre>
+Chain INPUT (policy ACCEPT 13M packets, 21G bytes)
+target prot opt in out source destination
+libvirt-host-in all -- * * 0.0.0.0/0 0.0.0.0/0
+
+Chain FORWARD (policy ACCEPT 5532K packets, 3010M bytes)
+target prot opt in out source destination
+libvirt-in all -- * * 0.0.0.0/0 0.0.0.0/0
+libvirt-out all -- * * 0.0.0.0/0 0.0.0.0/0
+libvirt-in-post all -- * * 0.0.0.0/0 0.0.0.0/0</pre>
+ <p>These custom chains then do matching based on the TAP device
+ name, so they won't open holes in the admin defined matches for
+ the LAN/WAN (if any).
+ </p>
+ <pre>
+Chain libvirt-host-in (1 references)
+ target prot opt in out source destination
+ HI-vnet0 all -- * * 0.0.0.0/0 0.0.0.0/0 [goto]
PHYSDEV match --physdev-in vnet0
+
+Chain libvirt-in (1 references)
+ target prot opt in out source destination
+ FI-vnet0 all -- * * 0.0.0.0/0 0.0.0.0/0 [goto]
PHYSDEV match --physdev-in vnet0
+
+Chain libvirt-in-post (1 references)
+ target prot opt in out source destination
+ ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 PHYSDEV
match --physdev-in vnet0
+
+Chain libvirt-out (1 references)
+ target prot opt in out source destination
+ FO-vnet0 all -- * * 0.0.0.0/0 0.0.0.0/0 [goto]
PHYSDEV match --physdev-out vnet0</pre>
+ <p>Finally, we can see the interesting bit which is the actual
+ implementation of my filter to block port 25 access:
+ </p>
+ <pre>
+Chain FI-vnet0 (1 references)
+ target prot opt in out source destination
+ DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:25
+
+Chain FO-vnet0 (1 references)
+ target prot opt in out source destination
+ DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp spt:25
+
+Chain HI-vnet0 (1 references)
+ target prot opt in out source destination
+ DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp
dpt:25</pre>
+ <p>One thing in looking at this you may notice is that if there
+ are many guests all using the same filters, we will be duplicating
+ the iptables rules over and over for each guest. This is merely a
+ limitation of the current rules engine implementation. At the libvirt
+ object modelling level you can clearly see we've designed the model
+ so filter rules are defined in one place, and indirectly referenced
+ by guests. Thus it should be possible to change the implementation in
+ the future so we can share the actual iptables/ebtables rules for
+ each guest to create a more scalable system. The stuff in current libvirt
+ is more or less the very first working implementation we've had of this,
+ so there's not been much optimization work done yet.
+ </p>
+ <p>Also notice that at the XML level we don't expose the fact we
+ are using iptables or ebtables at all. The rule definition is done in
+ terms of network protocols. Thus if we ever find a need, we could
+ plug in an alternative implementation that calls out to a different
+ firewall implementation instead of ebtables/iptables (providing that
+ implementation was suitably expressive of course)
+ </p>
+ <p>Finally, in terms of problems we have in deployment. The biggest
+ problem is that if the admin does <code>service iptables
restart</code>
+ all our work gets blown away. We've experimented with using lokkit
+ to record our custom rules in a persistent config file, but that
+ caused different problem. Admins who were not using lokkit for
+ their config found that all their own rules got blown away. So
+ we threw away our lokkit code. Instead we document that if you
+ run <code>service iptables restart</code>, you need to send SIGHUP to
+ libvirt to make it recreate its rules.
+ </p>
+ <p>More in depth documentation on this is <a
href="http://libvirt.org/formatnwfilter.html">here</a>...
+ </body>
+</html>
--
1.7.0.1
5:46 a.m.
New subject: [libvirt] [PATCH] html docs: added firewall explanation page by daniel berrange
On Fri, Jul 02, 2010 at 09:58:17AM +1000, Justin Clift wrote:
---
Daniel, how's this as a first go?
It's just your content converted to HTML in the same style as the other
pages, with the occasional typo fix. If this is workable, then I'll create
another patch after this to hook it into the overall website menu structure.
docs/firewall.html.in | 477 +++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 477 insertions(+), 0 deletions(-)
create mode 100644 docs/firewall.html.in
Looks fine to me - just add it to docs/sitemap.html.in
diff --git a/docs/firewall.html.in b/docs/firewall.html.in
new file mode 100644
index 0000000..a6dbec2
--- /dev/null
+++ b/docs/firewall.html.in
+ </p>
+ <p>More in depth documentation on this is <a
href="http://libvirt.org/formatnwfilter.html">here</a>...
+ </body>
+</html>
Just use a relative link here so it works offline
Regards,
Daniel
--
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|: http://libvirt.org -o- http://virt-manager.org -o- http://deltacloud.org :|
|: http://autobuild.org -o- http://search.cpan.org/~danberr/ :|
|: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|
7:48 a.m.
New subject: [libvirt] [PATCH] html docs: added firewall explanation page by daniel berrange
On 07/08/2010 08:46 PM, Daniel P. Berrange wrote:
<snip
> docs/firewall.html.in | 477
+++++++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 477 insertions(+), 0 deletions(-)
> create mode 100644 docs/firewall.html.in
Looks fine to me - just add it to docs/sitemap.html.in
Done, and pushed, with the internal links made into relative links.
I'll look for opportunities to cross-reference from the QEMU and
Networking pages appropriately, as you mentioned in a follow up email.
Will email through a patch submission for them.
Regards and best wishes,
Justin Clift
1:40 p.m.
On Wed, 2010-06-30 at 16:04 +0100, Daniel P. Berrange wrote:
I just wrote this to assist some Red Hat folks understanding
what libvirt does with iptables, and thought it is useful info
for the whole libvirt community. When I have time I'll adjust
this content so that it can fit into the website in relevant
pages/places.
Wow. That was insanely useful, thanks Dan.
Jon.
5:57 a.m.
On 06/30/2010 11:04 AM, Daniel P. Berrange wrote:
One thing in looking at this that you may notice is that if there
are many guests all using the same filters, we will be duplicating
the iptables rules over& over for each guest. This is merely a
One comment here: An optimization would be (easier, if at all)
implementable if there was no priority field in the rules that allows
the rules of different filters to be interleaved with each other.
Stefan
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Daniel P. Berrange -
Eric Blake -
Jon Masters -
Justin Clift -
Justin Clift -
Stefan Berger