Merge ~andreserl/maas:workaround_lp1711760 into maas:master

[Andres Rodriguez]

LP: #1711760 - Workaround bug in resolvconf where nameservers are not populated in ephemeral environments

[Lee Trager (ltrager)]

I havn't tested this but it looks good.

review: Approve

[MAAS Lander (maas-lander)]

LANDING
-b workaround_lp1711760 lp:~andreserl/maas into -b master lp:~maas-committers/maas

STATUS: FAILED BUILD
LOG: http://maas-ci-jenkins.internal:8080/job/maas/job/branch-tester/448/consoleText

[Scott Moser (smoser)]

I realize this is just a quick hack/workaround.
but something I think is probably better woudl be to just read the values in /run/net-*

i'd be kind of afraid of dhclient downing the interface (especially if for some reason it failed to get a lease).

maybe:

for i in /run/net-*.conf; do
   [ -f "$f" ] || continue
   # use a subshell to avoid contaminating this environment
   ( . "$f"
     for ns in "$IPV4DNS0" "$IPV4DNS1" "$IPV6DNS0" "$IPV6DNS1"; do
       [ -z "$ns" -o "$ns" = "0.0.0.0" ] && continue
       echo "nameserver $ns" >> /etc/resolv.conf
   )
done

diff --git a/src/metadataserver/user_data/templates/base_user_data.sh b/src/metadataserver/user_data/templates/base_user_data.sh
index e152a38..2a8e911 100644
--- a/src/metadataserver/user_data/templates/base_user_data.sh
+++ b/src/metadataserver/user_data/templates/base_user_data.sh
@@ -12,6 +12,30 @@ export PATH="$BIN_D:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
 
 mkdir -p "$BIN_D"
 
+#### FIXME: Remove work around when the issue is fixed in resolvconf ###
+#
+# LP: #1711760
+# Work around issue where resolv.conf is not set on the  ephemeral environment
+#
+# First check if a nameserver is set in resolv.conf
+if ! echo /etc/resolv.conf | grep -qs "nameserver"; then
+    # If it is not, obtain the MAC address of the PXE boot interface
+    mac_address=$(cat /proc/cmdline | grep -o -E '([[:xdigit:]]{1,2}:){5}[[:xdigit:]]{1,2}')
+
+    # Search for the NIC name of the PXE boot interface
+    for nic in /sys/class/net/*; do
+        nic_mac=$(cat $nic/address)
+        if [ "$nic_mac" == "$mac_address" ]; then
+            # Get the interface name and ask dhclient to refresh the lease
+            interface=$(echo $nic | cut -d'/' -f5)
+            dhclient $interface || true
+            break
+        fi
+    done
+fi
+
+######################
+
 # Ensure that invocations of apt-get are not interactive by default,
 # here and in all subprocesses.
 export DEBIAN_FRONTEND=noninteractive