os-net-config: add configure_safe_defaults

This patch adds a new configure_safe_defaults function that
is called on EXIT. If the exit code is non-zero the function
executes code to configure DHCP on all active interfaces.

Since DHCP is used to initially bootstrap all TripleO instances
via the provisioning network this should always be a safe default
and allow communication with Heat to persist if an invalid
(breaking) network configuration change is pushed out. This would
facilitate immediate Heat notification of the failure and subsequent
Heat updates to potentially help correct the invalid network
configuration.

Change-Id: Ibccba1ee77aa13c85a78a75d2e6cd179f87d7d16
Depends-on: Ibe0e32bc09979bc68b92a722b2bfa383e77502a9

elements/os-net-config/os-refresh-config/configure.d/20-os-net-config

@@ -48,9 +48,58 @@ function ping_metadata_ip() {
   fi
 }
 
+function configure_safe_defaults() {
+
+[[ $? == 0 ]] && return 0
+
+cat > /etc/os-net-config/dhcp_all_interfaces.yaml <<EOF_CAT
+# This file is an autogenerated safe defaults file for os-net-config
+# which runs DHCP on all discovered interfaces to ensure connectivity
+# back to the undercloud for updates
+network_config:
+EOF_CAT
+
+    for iface in $(ls /sys/class/net | grep -v ^lo$); do
+        local mac_addr_type="$(cat /sys/class/net/${iface}/addr_assign_type)"
+        if [ "$mac_addr_type" != "0" ]; then
+            echo "Device has generated MAC, skipping."
+        else
+            ip link set dev $iface up &>/dev/null
+            HAS_LINK="$(cat /sys/class/net/${iface}/carrier)"
+
+            TRIES=10
+            while [ "$HAS_LINK" == "0" -a $TRIES -gt 0 ]; do
+                HAS_LINK="$(cat /sys/class/net/${iface}/carrier)"
+                if [ "$HAS_LINK" == "1" ]; then
+                    break
+                else
+                    sleep 1
+                fi
+                TRIES=$(( TRIES - 1 ))
+            done
+            if [ "$HAS_LINK" == "1" ] ; then
+cat >> /etc/os-net-config/dhcp_all_interfaces.yaml <<EOF_CAT
+  -
+    type: interface
+    name: $iface
+    use_dhcp: true
+EOF_CAT
+            fi
+        fi
+    done
+    os-net-config -c /etc/os-net-config/dhcp_all_interfaces.yaml -v --detailed-exit-codes --cleanup
+    RETVAL=$?
+    if [[ $RETVAL == 2 ]]; then
+        ping_metadata_ip
+    elif [[ $RETVAL != 0 ]]; then
+        echo "ERROR: configuration of safe defaults failed."
+    fi
+}
+
 NET_CONFIG=$(os-apply-config --key os_net_config --type raw --key-default '')
 
 if [ -n "$NET_CONFIG" ]; then
+    trap configure_safe_defaults EXIT
     os-net-config -c /etc/os-net-config/config.json -v --detailed-exit-codes
     RETVAL=$?
     if [[ $RETVAL == 2 ]]; then