Merge ~juliank/ubuntu/+source/systemd:lp1805183 into ~ubuntu-core-dev/ubuntu/+source/systemd:ubuntu-disco

[Julian Andres Klode]

[Julian Andres Klode (juliank)]

The trick here with the md5sum and redirecting stderr to stdout means we easily handle newly created and absent files too, and don't have to worry about this, while keeping it short.

Unmerged commits

16d761d... by Julian Andres Klode on 2018-12-17

Only restart resolved on changes in dhclient enter hook

This prevents spurious restarts of resolved on rebounds when
the addresses did not change.

LP: #1805183

diff --git a/debian/extra/dhclient-enter-resolved-hook b/debian/extra/dhclient-enter-resolved-hook
index b504f5b..c2d59e4 100755
--- a/debian/extra/dhclient-enter-resolved-hook
+++ b/debian/extra/dhclient-enter-resolved-hook
@@ -28,6 +28,9 @@ if [ -x /lib/systemd/systemd-resolved ] ; then
               fi
               statedir="/run/systemd/resolved.conf.d"
               mkdir -p $statedir
+
+              oldstate="$(mktemp)"
+              md5sum $statedir/isc-dhcp-v4-$interface.conf $statedir/isc-dhcp-v6-$interface.conf &> $oldstate
               if [ -n "$new_domain_name_servers" ] ; then
                   cat <<EOF >$statedir/isc-dhcp-v4-$interface.conf
 [Resolve]
@@ -50,7 +53,12 @@ Domains=$new_dhcp6_domain_search
 EOF
                   fi
               fi
-              systemctl try-reload-or-restart systemd-resolved.service
+
+              if ! cmp --quiet $oldstate <(md5sum $statedir/isc-dhcp-v4-$interface.conf $statedir/isc-dhcp-v6-$interface.conf 2>&1); then
+                  systemctl try-reload-or-restart systemd-resolved.service
+              fi
+
+              rm $oldstate
           }
                 ;;