package/busybox: Add facility for DHCP hooks

The (u)dhcpc hook installed by the busybox package configures the
network and exits. If we want to do anything further with a DHCP lease,
we'd have to replace the script entirely.

This change introduces a .d directory for hooks (based on the script
filename), which are executed after the interface configuration. This
allows packages to drop a script file in the .d directory to perform
actions on DHCP events.

We'll use this in a later change to notify petitboot of DHCP boot
information.

[Thomas: update to latest Buildroot, fix indentation.]

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/busybox/busybox.mk

@@ -212,6 +212,8 @@ define BUSYBOX_INSTALL_TARGET_CMDS
 	$(BUSYBOX_MAKE_ENV) $(MAKE) $(BUSYBOX_MAKE_OPTS) -C $(@D) install
 	$(INSTALL) -m 0755 -D package/busybox/udhcpc.script \
 		$(TARGET_DIR)/usr/share/udhcpc/default.script
+	$(INSTALL) -m 0755 -d \
+		$(TARGET_DIR)/usr/share/udhcpc/default.script.d
 	$(BUSYBOX_INSTALL_MDEV_CONF)
 endef
 

package/busybox/udhcpc.script

@@ -64,4 +64,10 @@ case "$1" in
 		;;
 esac
 
+HOOK_DIR="$0.d"
+for hook in "${HOOK_DIR}/"*; do
+    [ -f "${hook}" -a -x "${hook}" ] || continue
+    "${hook}" "${@}"
+done
+
 exit 0