From 6fd75a18de9c5cf8886e9b974b91edbdf31e7b96 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Graber?= <stgraber@ubuntu.com>
Date: Tue, 3 Nov 2015 11:42:58 -0500
Subject: Allocate new lxcbr0 subnet at startup time

---
 config/init/common/lxc-net.in | 100 +++++++++++++++++++++++++++++++---
 1 file changed, 91 insertions(+), 9 deletions(-)

diff --git a/config/init/common/lxc-net.in b/config/init/common/lxc-net.in
index 4985be958..6396e8f32 100644
--- a/config/init/common/lxc-net.in
+++ b/config/init/common/lxc-net.in
@@ -23,6 +23,85 @@ LXC_IPV6_MASK=""
 LXC_IPV6_NETWORK=""
 LXC_IPV6_NAT="false"
 
+write_lxc_net()
+{
+    local i=$1
+    cat >>  $distrosysconfdir/lxc-net << EOF
+# Leave USE_LXC_BRIDGE as "true" if you want to use lxcbr0 for your
+# containers.  Set to "false" if you'll use virbr0 or another existing
+# bridge, or mavlan to your host's NIC.
+USE_LXC_BRIDGE="true"
+
+# If you change the LXC_BRIDGE to something other than lxcbr0, then
+# you will also need to update your /etc/lxc/default.conf as well as the
+# configuration (/var/lib/lxc/<container>/config) for any containers
+# already created using the default config to reflect the new bridge
+# name.
+# If you have the dnsmasq daemon installed, you'll also have to update
+# /etc/dnsmasq.d/lxc and restart the system wide dnsmasq daemon.
+LXC_BRIDGE="lxcbr0"
+LXC_ADDR="10.0.$i.1"
+LXC_NETMASK="255.255.255.0"
+LXC_NETWORK="10.0.$i.0/24"
+LXC_DHCP_RANGE="10.0.$i.2,10.0.$i.254"
+LXC_DHCP_MAX="253"
+# Uncomment the next line if you'd like to use a conf-file for the lxcbr0
+# dnsmasq.  For instance, you can use 'dhcp-host=mail1,10.0.3.100' to have
+# container 'mail1' always get ip address 10.0.3.100.
+#LXC_DHCP_CONFILE=/etc/lxc/dnsmasq.conf
+
+# Uncomment the next line if you want lxcbr0's dnsmasq to resolve the .lxc
+# domain.  You can then add "server=/lxc/10.0.$i.1' (or your actual \$LXC_ADDR)
+# to your system dnsmasq configuration file (normally /etc/dnsmasq.conf,
+# or /etc/NetworkManager/dnsmasq.d/lxc.conf on systems that use NetworkManager).
+# Once these changes are made, restart the lxc-net and network-manager services.
+# 'container1.lxc' will then resolve on your host.
+#LXC_DOMAIN="lxc"
+EOF
+}
+
+configure_lxcbr0()
+{
+    local i=3
+    cat >  $distrosysconfdir/lxc-net << EOF
+# This file is auto-generated by lxc.postinst if it does not
+# exist.  Customizations will not be overridden.
+EOF
+    # if lxcbr0 exists, keep using the same network
+    if  ip addr show lxcbr0 > /dev/null 2>&1 ; then
+        i=`ip addr show lxcbr0 | grep "inet\>" | awk '{ print $2 }' | awk -F. '{ print $3 }'`
+        write_lxc_net $i
+        return
+    fi
+    # if no lxcbr0, find an open 10.0.a.0 network
+    for l in `ip addr show | grep "inet\>" |awk '{ print $2 }' | grep '^10\.0\.' | sort -n`; do
+            j=`echo $l | awk -F. '{ print $3 }'`
+            if [ $j -gt $i ]; then
+                write_lxc_net $i
+                return
+            fi
+            i=$((j+1))
+    done
+    if [ $i -ne 254 ]; then
+        write_lxc_net $i
+    fi
+}
+
+update_lxcnet_config()
+{
+    local i=3
+    # if lxcbr0 exists, keep using the same network
+    if  ip addr show lxcbr0 > /dev/null 2>&1 ; then
+        return
+    fi
+    # our LXC_NET conflicts with an existing interface.  Probably first
+    # run after system install with package pre-install.  Find a new subnet
+    configure_lxcbr0
+
+    # and re-load the newly created config
+    [ ! -f $distrosysconfdir/lxc-net ] || . $distrosysconfdir/lxc-net
+}
+
 [ ! -f $distrosysconfdir/lxc ] || . $distrosysconfdir/lxc
 
 use_iptables_lock="-w"
@@ -50,7 +129,19 @@ _ifup() {
     ip link set dev ${LXC_BRIDGE} up
 }
 
+cleanup() {
+    set +e
+    if [ "$FAILED" = "1" ]; then
+        echo "Failed to setup lxc-net." >&2
+        stop force
+        exit 1
+    fi
+}
+
 start() {
+
+    [ ! -f $distrosysconfdir/lxc-net ] && update_lxcnet_config
+
     [ "x$USE_LXC_BRIDGE" = "xtrue" ] || { exit 0; }
 
     [ ! -f "${varrun}/network_up" ] || { echo "lxc-net is already running"; exit 1; }
@@ -61,15 +152,6 @@ start() {
 
     FAILED=1
 
-    cleanup() {
-        set +e
-        if [ "$FAILED" = "1" ]; then
-            echo "Failed to setup lxc-net." >&2
-            stop force
-            exit 1
-        fi
-    }
-
     trap cleanup EXIT HUP INT TERM
     set -e