From 935cd0c56643d28a5c60ff6658b16bd4c2fd920c Mon Sep 17 00:00:00 2001

From: Laine Stump <laine@laine.org>

Date: Wed, 10 Sep 2014 13:10:45 -0400

Subject: [PATCH] network: try to eliminate default network conflict during

 package install

Sometimes libvirt is installed on a host that is already using the

network 192.168.122.0/24. If the libvirt-daemon-config-network package

is installed, this creates a conflict, since that package has been

hard-coded to create a virtual network that also uses

192.168.122.0/24. In the past libvirt has attempted to warn of /

remediate this situation by checking for conflicting routes when the

network is started, but it turns out that isn't always useful (for

example in the case that the *other* interface/network creating the

conflict hasn't yet been started at the time libvirtd start its own

networks).

This patch attempts to catch the problem earlier - at install

time. During the %post install script for

libvirt-daemon-config-network, we use a case statement to look through

the output of "ip route show" for a route that exactly matches

192.168.122.0/24, and if found we search for a similar route that

*doesn't* match (e.g. 192.168.124.0/24) (note that the search starts

with "124" instead of 123 because of reports of people already

modifying their L1 host's network to 192.168.123.0/24 in an attempt to

solve exactly the problem we are also trying to solve).  When we find

an available route, we just replace all occurrences of "122" in the

default.xml that is being created with the newly found 192.168

subnet. This could obviously be made more complicated - examine the

template defaul.xml to automatically determine the existing network

address and mask rather than hard coding it in the specfile, etc, but

this scripting is simpler and gets the job done as long as we continue

to use 192.168.122.0/24 in the template. (If anyone with mad bash

skillz wants to suggest something to do that, by all means please do).

This is intended to at least "further reduce" occurrence of the

problems detailed in:

  https://bugzilla.redhat.com/show_bug.cgi?id=811967

(cherry picked from commit 5f71959667e4902d738a849e7c9391e794fccf22)

---

 libvirt.spec.in | 31 ++++++++++++++++++++++++++++++-

 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/libvirt.spec.in b/libvirt.spec.in

index 4dc801b..75a91f5 100644

--- a/libvirt.spec.in

+++ b/libvirt.spec.in

@@ -1732,8 +1732,37 @@ fi

     %if %{with_network}

 %post daemon-config-network

 if test $1 -eq 1 && test ! -f %{_sysconfdir}/libvirt/qemu/networks/default.xml ; then

+    # see if the network used by default network creates a conflict,

+    # and try to resolve it

+    # NB: 192.168.122.0/24 is used in the default.xml template file;

+    # do not modify any of those values here without also modifying

+    # them in the template.

+    orig_sub=122

+    sub=${orig_sub}

+    nl='

+'

+    routes="${nl}$(ip route show | cut -d' ' -f1)"

+    case ${routes} in

+      *"${nl}192.168.${orig_sub}.0/24${nl}"*)

+        # there was a match, so we need to look for an unused subnet

+        for new_sub in $(seq 124 254); do

+          case ${routes} in

+          *"${nl}192.168.${new_sub}.0/24${nl}"*)

+            ;;

+          *)

+            sub=$new_sub

+            break;

+            ;;

+          esac

+        done

+        ;;

+      *)

+        ;;

+    esac

+

     UUID=`/usr/bin/uuidgen`

-    sed -e "s,</name>,</name>\n  <uuid>$UUID</uuid>," \

+    sed -e "s/${orig_sub}/${sub}/g" \

+        -e "s,</name>,</name>\n  <uuid>$UUID</uuid>," \

          < %{_datadir}/libvirt/networks/default.xml \

          > %{_sysconfdir}/libvirt/qemu/networks/default.xml

     ln -s ../default.xml %{_sysconfdir}/libvirt/qemu/networks/autostart/default.xml