While the default iptables setup used by Fedora/RHEL distros
only restricts traffic on the INPUT and/or FORWARD rules,
some users might have custom firewalls that restrict the
OUTPUT rules too.
These can prevent DHCP/DNS/TFTP responses from dnsmasq
from reaching the guest VMs. We should thus whitelist
these protocols in the OUTPUT chain, as well as the
INPUT chain.
Signed-off-by: Malina Salina <malina.salina@protonmail.com>
Initial patch then modified to add unit tests and IPv6
support
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
During startup libvirtd creates top level chains for both ipv4
and ipv6 protocols. If this fails for any reason then startup
of virtual networks is blocked.
The default virtual network, however, only requires use of ipv4
and some servers have ipv6 disabled so it is expected that ipv6
chain creation will fail. There could equally be servers with
no ipv4, only ipv6.
This patch thus makes error reporting a little more fine grained
so that it works more sensibly when either ipv4 or ipv6 is
disabled on the server. Only the protocols that are actually
used by the virtual network have errors reported.
Reviewed-by: Andrea Bolognani <abologna@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Historically firewall rules for virtual networks were added straight
into the base chains. This works but has a number of bugs and design
limitations:
- It is inflexible for admins wanting to add extra rules ahead
of libvirt's rules, via hook scripts.
- It is not clear to the admin that the rules were created by
libvirt
- Each rule must be deleted by libvirt individually since they
are all directly in the builtin chains
- The ordering of rules in the forward chain is incorrect
when multiple networks are created, allowing traffic to
mistakenly flow between networks in one direction.
To address all of these problems, libvirt needs to move to creating
rules in its own private chains. In the top level builtin chains,
libvirt will add links to its own private top level chains.
Addressing the traffic ordering bug requires some extra steps. With
everything going into the FORWARD chain there was interleaving of rules
for outbound traffic and inbound traffic for each network:
-A FORWARD -d 192.168.3.0/24 -o virbr1 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -s 192.168.3.0/24 -i virbr1 -j ACCEPT
-A FORWARD -i virbr1 -o virbr1 -j ACCEPT
-A FORWARD -o virbr1 -j REJECT --reject-with icmp-port-unreachable
-A FORWARD -i virbr1 -j REJECT --reject-with icmp-port-unreachable
-A FORWARD -d 192.168.2.0/24 -o virbr0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -s 192.168.2.0/24 -i virbr0 -j ACCEPT
-A FORWARD -i virbr0 -o virbr0 -j ACCEPT
-A FORWARD -o virbr0 -j REJECT --reject-with icmp-port-unreachable
-A FORWARD -i virbr0 -j REJECT --reject-with icmp-port-unreachable
The rule allowing outbound traffic from virbr1 would mistakenly
allow packets from virbr1 to virbr0, before the rule denying input
to virbr0 gets a chance to run.
What we really need todo is group the forwarding rules into three
distinct sets:
* Cross rules - LIBVIRT_FWX
-A FORWARD -i virbr1 -o virbr1 -j ACCEPT
-A FORWARD -i virbr0 -o virbr0 -j ACCEPT
* Incoming rules - LIBVIRT_FWI
-A FORWARD -d 192.168.3.0/24 -o virbr1 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o virbr1 -j REJECT --reject-with icmp-port-unreachable
-A FORWARD -d 192.168.2.0/24 -o virbr0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o virbr0 -j REJECT --reject-with icmp-port-unreachable
* Outgoing rules - LIBVIRT_FWO
-A FORWARD -s 192.168.3.0/24 -i virbr1 -j ACCEPT
-A FORWARD -i virbr1 -j REJECT --reject-with icmp-port-unreachable
-A FORWARD -s 192.168.2.0/24 -i virbr0 -j ACCEPT
-A FORWARD -i virbr0 -j REJECT --reject-with icmp-port-unreachable
There is thus no risk of outgoing rules for one network mistakenly
allowing incoming traffic for another network, as all incoming rules
are evalated first.
With this in mind, we'll thus need three distinct chains linked from
the FORWARD chain, so we end up with:
INPUT --> LIBVIRT_INP (filter)
OUTPUT --> LIBVIRT_OUT (filter)
FORWARD +-> LIBVIRT_FWX (filter)
+-> LIBVIRT_FWO
\-> LIBVIRT_FWI
POSTROUTING --> LIBVIRT_PRT (nat & mangle)
Signed-off-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>
Update the iptablesXXXX methods so that instead of directly
executing iptables commands, they populate rules in an
instance of virFirewallPtr. The bridge driver can thus
construct the ruleset and then invoke it in one operation
having rollback handled automatically.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
When the host is configured with very restrictive firewall (default policy
is DROP for all chains, including OUTPUT), the bridge driver for Linux
adds netfilter entries to allow DHCP and DNS requests to go from the VM
to the dnsmasq of the host.
The issue that this commit fixes is the fact that a DROP policy on the OUTPUT
chain blocks the DHCP replies from the host’s dnsmasq to the VM.
As DHCP replies are sent in UDP, they are not caught by any --ctstate ESTABLISHED
rule and so, need to be explicitly allowed.
Signed-off-by: Lénaïc Huard <lenaic@lhuard.fr.eu.org>
The functions
- iptablesAddForwardDontMasquerade(),
- iptablesRemoveForwardDontMasquerade
handle exceptions in the masquerading implemented in the POSTROUTING chain
of the "nat" table. Such exceptions should be added as chronologically
latest, logically top-most rules.
The bridge driver will call these functions beginning with the next patch:
some special destination IP addresses always refer to the local
subnetwork, even though they don't match any practical subnetwork's
netmask. Packets from virbrN targeting such IP addresses are never routed
outwards, but the current rules treat them as non-virbrN-destined packets
and masquerade them. This causes problems for some receivers on virbrN.
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
iptablesContext holds only 4 pairs of iptables
(table, chain) and there's no need to pass
it around.
This is a first step towards separating bridge_driver.c
in platform-specific parts.
We pass over the address/port start/end values many times so we put
them in structs.
Signed-off-by: Natanael Copa <ncopa@alpinelinux.org>
Signed-off-by: Laine Stump <laine@laine.org>
Let users set the port range to be used for forward mode NAT:
...
<forward mode='nat'>
<nat>
<port start='1024' end='65535'/>
</nat>
</forward>
...
Signed-off-by: Natanael Copa <ncopa@alpinelinux.org>
Signed-off-by: Laine Stump <laine@laine.org>
Support setting which public ip to use for NAT via attribute
address in subelement <nat> in <forward>:
...
<forward mode='nat'>
<address start='1.2.3.4' end='1.2.3.10'/>
</forward>
...
This will construct an iptables line using:
'-j SNAT --to-source <start>-<end>'
instead of:
'-j MASQUERADE'
Signed-off-by: Natanael Copa <ncopa@alpinelinux.org>
Signed-off-by: Laine Stump <laine@laine.org>
