Make DHCP timeout configurable

As noted in the bug, there may be circumstances where a longer
timeout than the current default is needed.  This patch allows users
to tune this timeout for their environment if need be.

Change-Id: I173f3dad684894fbc3c27dece5ae15b5f63bae5a
Closes-Bug: 1654027

elements/dhcp-all-interfaces/README.rst

@@ -17,3 +17,13 @@ configured properly before networking services are started.
 On Gentoo based distributions we will install the dhcpcd package and
 ensure the service starts at boot.  This service automatically sets
 up all interfaces found via dhcp and/or dhcpv6 (or SLAAC).
+
+Environment Variables
+---------------------
+
+DIB_DHCP_TIMEOUT
+  :Required: No
+  :Default: 30
+  :Description: Amount of time in seconds that the systemd service will
+   wait to get an address.
+  :Example: DIB_DHCP_TIMEOUT=300

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

@@ -24,6 +24,7 @@ if [ "$DIB_INIT_SYSTEM" == "upstart" ]; then
 elif [ "$DIB_INIT_SYSTEM" == "systemd" ]; then
     install -D -g root -o root -m 0644 ${SCRIPTDIR}/dhcp-interface@.service /usr/lib/systemd/system/dhcp-interface@.service
     install -D -g root -o root -m 0644 ${SCRIPTDIR}/dhcp-all-interfaces-udev.rules /etc/udev/rules.d/99-dhcp-all-interfaces.rules
+    sed -i "s/TimeoutStartSec=DIB_DHCP_TIMEOUT/TimeoutStartSec=${DIB_DHCP_TIMEOUT:-30}s/" /usr/lib/systemd/system/dhcp-interface@.service
 elif [ "$DIB_INIT_SYSTEM" == "sysv" ]; then
     install -D -g root -o root -m 0755 ${SCRIPTDIR}/dhcp-all-interfaces.init /etc/init.d/dhcp-all-interfaces
     update-rc.d dhcp-all-interfaces defaults

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

@@ -15,7 +15,7 @@ User=root
 ExecStartPre=/usr/local/sbin/dhcp-all-interfaces.sh %I
 ExecStart=/sbin/ifup %I
 RemainAfterExit=true
-TimeoutStartSec=30s
+TimeoutStartSec=DIB_DHCP_TIMEOUT
 
 [Install]
 WantedBy=multi-user.target