File libvirt-network-only-prevent-forwarding-of-DNS-requests-for-unqualified-names.patch of Package libvirt
From 1da44d851ea2d37baeea1c655d83abeacadf530d Mon Sep 17 00:00:00 2001
Message-Id: <1da44d851ea2d37baeea1c655d83abeacadf530d@dist-git>
From: Laine Stump <laine@laine.org>
Date: Mon, 10 Feb 2014 06:59:50 -0500
Subject: [PATCH] network: only prevent forwarding of DNS requests for
unqualified names
https://bugzilla.redhat.com/show_bug.cgi?id=1062708 (RHEL6.5.z)
https://bugzilla.redhat.com/show_bug.cgi?id=1037741 (RHEL6.6)
https://bugzilla.redhat.com/show_bug.cgi?id=928638 (RHEL6.5)
In commit f386825 we began adding the options
--domain-needed
--local=/$mydomain/
to all dnsmasq commandlines with the stated reason of preventing
forwarding of DNS queries for names that weren't fully qualified
domain names ("FQDN", i.e. a name that included some "."s and a domain
name). This was later changed to
domain-needed
local=/$mydomain/
when we moved the options from the dnsmasq commandline to a conf file.
The original patch on the list, and discussion about it, is here:
https://www.redhat.com/archives/libvir-list/2012-August/msg01594.html
When a domain name isn't specified (mydomain == ""), the addition of
"domain-needed local=//" will prevent forwarding of domain-less
requests to the virtualization host's DNS resolver, but if a domain
*is* specified, the addition of "local=/domain/" will prevent
forwarding of any requests for *qualified* names within that domain
that aren't resolvable by libvirt's dnsmasq itself.
An example of the problems this causes - let's say a network is
defined with:
<domain name='example.com'/>
<dhcp>
..
<host mac='52:54:00:11:22:33' ip='1.2.3.4' name='myguest'/>
</dhcp>
This results in "local=/example.com/" being added to the dnsmasq options.
If a guest requests "myguest" or "myguest.example.com", that will be
resolved by dnsmasq. If the guest asks for "www.example.com", dnsmasq
will not know the answer, but instead of forwarding it to the host, it
will return NOT FOUND to the guest. In most cases that isn't the
behavior an admin is looking for.
A later patch (commit 4f595ba) attempted to remedy this by adding a
"forwardPlainNames" attribute to the <dns> element. The idea was that
if forwardPlainNames='yes' (default is 'no'), we would allow
unresolved names to be forwarded. However, that patch was botched, in
that it only removed the "domain-needed" option when
forwardPlainNames='yes', and left the "local=/mydomain/".
Really we should have been just including the option "--domain-needed
--local=//" (note the lack of domain name) regardless of the
configured domain of the network, so that requests for names without a
domain would be treated as "local to dnsmasq" and not forwarded, but
all others (including those in the network's configured domain) would
be forwarded. We also shouldn't include *either* of those options if
forwardPlainNames='yes'. This patch makes those corrections.
This patch doesn't remedy the fact that default behavior was changed
by the addition of this feature. That will be handled in a subsequent
patch.
(cherry-picked from upstream commit
f69a6b987d616cf2679ec551a8b905b6a2aace6d)
Conflicts:
src/network/bridge_driver.c
- upstream has switched from creating a dnsmasq commandline, to
setting up a dnsmasq conf file. Also some options in the context
don't exist on this branch.
tests/networkxml2confdata/dhcp6-network.conf
tests/networkxml2confdata/nat-network-dns-forwarders.conf
- these tests were added upstream after this branch was created.
tests/networkxml2confdata/nat-network-dns-hosts.conf
tests/networkxml2confdata/netboot-network.conf
tests/networkxml2confdata/netboot-proxy-network.conf
- these tests are on the branch, but use a .argv file instead of
.conf
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
---
src/network/bridge_driver.c | 7 +------
tests/networkxml2argvdata/nat-network-dns-hosts.argv | 2 +-
tests/networkxml2argvdata/netboot-network.argv | 2 +-
tests/networkxml2argvdata/netboot-proxy-network.argv | 2 +-
4 files changed, 4 insertions(+), 9 deletions(-)
diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c
index 2989c00..0c493ad 100644
--- a/src/network/bridge_driver.c
+++ b/src/network/bridge_driver.c
@@ -608,13 +608,8 @@ networkBuildDnsmasqArgv(virNetworkObjPtr network,
if (network->def->domain)
virCommandAddArgPair(cmd, "--domain", network->def->domain);
/* need to specify local even if no domain specified */
- if (network->def->domain ||
- !(network->def->dns && network->def->dns->forwardPlainNames)) {
- virCommandAddArgFormat(cmd, "--local=/%s/",
- network->def->domain ? network->def->domain : "");
- }
if (!(network->def->dns && network->def->dns->forwardPlainNames))
- virCommandAddArg(cmd, "--domain-needed");
+ virCommandAddArgList(cmd, "--local=//", "--domain-needed", NULL);
if (pidfile)
virCommandAddArgPair(cmd, "--pid-file", pidfile);
diff --git a/tests/networkxml2argvdata/nat-network-dns-hosts.argv b/tests/networkxml2argvdata/nat-network-dns-hosts.argv
index 431e987..ece404a 100644
--- a/tests/networkxml2argvdata/nat-network-dns-hosts.argv
+++ b/tests/networkxml2argvdata/nat-network-dns-hosts.argv
@@ -1,5 +1,5 @@
@DNSMASQ@ --strict-order --domain=example.com \
---local=/example.com/ --domain-needed \
+--local=// --domain-needed \
--conf-file= \
--except-interface lo --bind-dynamic --interface virbr0 \
--expand-hosts --addn-hosts=/var/lib/libvirt/dnsmasq/default.addnhosts\
diff --git a/tests/networkxml2argvdata/netboot-network.argv b/tests/networkxml2argvdata/netboot-network.argv
index 0e17a71..0b3d441 100644
--- a/tests/networkxml2argvdata/netboot-network.argv
+++ b/tests/networkxml2argvdata/netboot-network.argv
@@ -1,5 +1,5 @@
@DNSMASQ@ --strict-order --domain=example.com \
---local=/example.com/ --domain-needed --conf-file= \
+--local=// --domain-needed --conf-file= \
--except-interface lo --bind-interfaces --listen-address 192.168.122.1 \
--dhcp-range 192.168.122.2,192.168.122.254 \
--dhcp-leasefile=/var/lib/libvirt/dnsmasq/netboot.leases \
diff --git a/tests/networkxml2argvdata/netboot-proxy-network.argv b/tests/networkxml2argvdata/netboot-proxy-network.argv
index 8764ef5..5916955 100644
--- a/tests/networkxml2argvdata/netboot-proxy-network.argv
+++ b/tests/networkxml2argvdata/netboot-proxy-network.argv
@@ -1,5 +1,5 @@
@DNSMASQ@ --strict-order --domain=example.com \
---local=/example.com/ --domain-needed --conf-file= \
+--local=// --domain-needed --conf-file= \
--except-interface lo --bind-interfaces \
--listen-address 192.168.122.1 \
--dhcp-range 192.168.122.2,192.168.122.254 \
--
1.9.1
