Implement dhcp-all-interfaces for systemd.

Includes:

 * Enhancements to the generate-interfaces-file.sh script
 so that it generates ifcfg network-scripts for
 distros like Fedora/RHEL.

 * Includes a new dhcp-all-interfaces.service systemd
 script which ensures network interfaces get generated
 before the network service starts on Fedora.

 * Add a new disable_interface function to
 generate-interfaces-file.sh which (on Fedora)
 will delete the ifcfg config for an interface which
 isn't plugged in.
 This is important because ifcfg-eth0 exists by default
 and we want to remove it if the NIC isn't connected.
 Previous behaviour on Ubuntu is unchanged and the
 generate-interfaces-file.sh just logs it as skipped.

 * General doc updates...

I tested this on a multi-nic machine w/ Fedora where the first NIC
exists but was not connected.

Change-Id: Ia99e312539da43caefd72aa60398d43dac5dcc8f
Closes-Bug: 1239880

elements/dhcp-all-interfaces/README.md

@@ -8,7 +8,4 @@ boot.
 
 The script /usr/local/sbin/generate-interfaces-file.sh will be called
 early in each boot and will scan available network interfaces and
-ensure they are all present in /etc/network/interfaces.
-
-Note that this element is only expected to be useful on Debian-derived
-distributions, currently.
+ensure they are configured properly before networking services are started.

elements/dhcp-all-interfaces/install.d/50-dhcp-all-interfaces

@@ -1,16 +1,14 @@
 #!/bin/bash
-
 set -x
 
-# Prepare the target system for regenerating /etc/network/interfaces
-# on its first boot.
-
 SCRIPTDIR=$(dirname $0)
 
-# Currently only installed on Debian-derived distributions
-# Installing these on Fedora causes problems with os-svc-daemon
-# https://bugs.launchpad.net/tripleo/+bug/1239880
-if [ -d /etc/init ] ; then
 install -D -g root -o root -m 0755 ${SCRIPTDIR}/generate-interfaces-file.sh /usr/local/sbin/generate-interfaces-file.sh
+
+DIB_INIT_SYSTEM=$(dib-init-system)
+if [ "$DIB_INIT_SYSTEM" == "upstart" ]; then
     install -D -g root -o root -m 0755 ${SCRIPTDIR}/dhcp-all-interfaces.conf /etc/init/dhcp-all-interfaces.conf
+elif [ "$DIB_INIT_SYSTEM" == "systemd" ]; then
+    install -D -g root -o root -m 0755 ${SCRIPTDIR}/dhcp-all-interfaces.service /usr/lib/systemd/system/dhcp-all-interfaces.service
+    systemctl enable dhcp-all-interfaces.service
 fi

elements/dhcp-all-interfaces/install.d/dhcp-all-interfaces.service

@@ -0,0 +1,14 @@
+[Unit]
+Description=DHCP All Interfaces Service
+Wants=local-fs.target systemd-udev-settle.service
+After=local-fs.target systemd-udev-settle.service
+Before=network.service
+
+[Service]
+Type=oneshot
+ExecStart=/usr/local/sbin/generate-interfaces-file.sh
+RemainAfterExit=yes
+
+[Install]
+WantedBy=multi-user.target
+Alias=dhcp-all-interfaces.service

elements/dhcp-all-interfaces/install.d/generate-interfaces-file.sh

@@ -1,21 +1,55 @@
 #!/bin/bash
 
-# Generate $INTERFACES_FILE on first boot
-# This will add any unconfigured network interfaces to /etc/network/interfaces
-#  and configure them for DHCP
+ENI_FILE="/etc/network/interfaces"
 
-INTERFACES_FILE="/etc/network/interfaces"
+if [ -d "/etc/network" ]; then
+    CONF_TYPE="eni"
+elif [ -d "/etc/sysconfig/network-scripts/" ]; then
+    CONF_TYPE="netscripts"
+else
+    echo "Unsupported network configuration type!"
+    exit 1
+fi
 
+if [ "$CONF_TYPE" == "eni" ]; then
     # Serialize runs so that we don't miss hot-add interfaces
     FLOCK=${1:-}
     if [ -z "$FLOCK" ] ; then
-    exec flock -x $INTERFACES_FILE $0 flocked
+        exec flock -x $ENI_FILE $0 flocked
+    fi
 fi
 
 function get_if_link() {
   cat /sys/class/net/${1}/carrier
 }
 
+function enable_interface() {
+  local interface=$1
+
+  if [ "$CONF_TYPE" == "eni" ]; then
+      printf "auto $interface\niface $interface inet dhcp\n\n" >>$ENI_FILE
+  elif [ "$CONF_TYPE" == "netscripts" ]; then
+      printf "DEVICE=\"$interface\"\nBOOTPROTO=\"dhcp\"\nONBOOT=\"yes\"\nTYPE=\"Ethernet\"" >"/etc/sysconfig/network-scripts/ifcfg-$interface"
+  fi
+  echo "Configured $1"
+
+}
+
+function disable_interface() {
+  local interface=$1
+
+  if [ "$CONF_TYPE" == "netscripts" ]; then
+      local IFCFG_FILE="/etc/sysconfig/network-scripts/ifcfg-$interface"
+      if [ -f "$IFCFG_FILE" ]; then
+          rm $IFCFG_FILE
+      else
+          echo "No link detected, skipping"
+      fi
+  else
+      echo "No link detected, skipping"
+  fi
+}
+
 for interface in $(ls /sys/class/net | grep -v ^lo$) ; do
   echo -n "Inspecting interface: $interface..."
   if ifquery $interface >/dev/null 2>&1 ; then
@@ -35,10 +69,9 @@ for interface in $(ls /sys/class/net | grep -v ^lo$) ; do
       TRIES=$(( TRIES - 1 ))
     done
     if [ "$HAS_LINK" == "1" ] ; then
-      printf "auto $interface\niface $interface inet dhcp\n\n" >>$INTERFACES_FILE
-      echo "Configured"
+      enable_interface "$interface"
     else
-      echo "No link detected, skipping"
+      disable_interface "$interface"
     fi
   fi
 done