[libvirt] [PATCH] bridge: Add --dhcp-no-override option to dnsmasq

[Jiri Denemark]

> > Are we guaranteed that --dhcp-no-override is supported as far back as
> > the earliest version of dnsmasq that we claim to run with, or do we need
> > to add some --help parsing?
> 
> Hmm, good point. The option was added into dnsmasq-2.41 released on
> 12-Feb-2008. I'm not sure what version we claim to run with (libvirt.spec just
> requires dnsmasq without any version restrictions) so it might be worth
> parsing --help for that. What others think about the dnsmasq version we
> support?

As confirmed on irc, the oldest distros we care about are RHEL-5 and Debian
stable and both have dnsmasq-2.45. Requiring 2.41 is fine then. Given the
conditional ACK from Eric, I'm going to push the following patch soon:

bridge: Add --dhcp-no-override option to dnsmasq

--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.
---
 libvirt.spec.in             |    4 ++--
 src/network/bridge_driver.c |    3 +++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/libvirt.spec.in b/libvirt.spec.in
index c666a70..cc3e8e2 100644
--- a/libvirt.spec.in
+++ b/libvirt.spec.in
@@ -200,7 +200,7 @@ Requires: %{name}-client = %{version}-%{release}
 Requires: bridge-utils
 %endif
 %if %{with_network}
-Requires: dnsmasq
+Requires: dnsmasq >= 2.41
 Requires: iptables
 %endif
 %if %{with_nwfilter}
@@ -298,7 +298,7 @@ BuildRequires: avahi-devel
 BuildRequires: libselinux-devel
 %endif
 %if %{with_network}
-BuildRequires: dnsmasq
+BuildRequires: dnsmasq >= 2.41
 %endif
 BuildRequires: bridge-utils
 %if %{with_sasl}
diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c
index f247a0f..d6d3068 100644
--- a/src/network/bridge_driver.c
+++ b/src/network/bridge_driver.c
@@ -427,6 +427,8 @@ networkBuildDnsmasqArgv(virNetworkObjPtr network,
         (2 * network->def->nranges) + /* --dhcp-range 10.0.0.2,10.0.0.254 */
         /* --dhcp-lease-max=xxx if needed */
         (network->def->nranges ? 1 : 0) +
+        /* --dhcp-no-override if needed */
+        (network->def->nranges ? 1 : 0) +
         /* --dhcp-hostsfile=/var/lib/dnsmasq/$NAME.hostsfile */
         (network->def->nhosts > 0 ? 1 : 0) +
         /* --enable-tftp --tftp-root /srv/tftp */
@@ -497,6 +499,7 @@ networkBuildDnsmasqArgv(virNetworkObjPtr network,
     if (network->def->nranges > 0) {
         snprintf(buf, sizeof(buf), "--dhcp-lease-max=%d", nbleases);
         APPEND_ARG(*argv, i++, buf);
+        APPEND_ARG(*argv, i++, "--dhcp-no-override");
     }
 
     if (network->def->nhosts > 0) {
-- 
1.7.2