[openwrt/openwrt] netifd: add udhcpc link check to dhcp shell handler script

[LEDE Commits]

dedeckeh pushed a commit to openwrt/openwrt.git, branch master:
https://git.lede-project.org/175b2623288957dc7087278d1e78a7eedb077f8f

commit 175b2623288957dc7087278d1e78a7eedb077f8f
Author: Hans Dedecker <dedeckeh at gmail.com>
AuthorDate: Thu Mar 1 18:38:55 2018 +0100

    netifd: add udhcpc link check to dhcp shell handler script
    
    Fixes the assumption the busybox udhcpc applet is always enabled; in case
    the symbolic link check fails the DHCP shell handler script will exit and
    as result the DHCP protocol handler will not be registered in netifd.
    
    Signed-off-by: Hans Dedecker <dedeckeh at gmail.com>
---
 package/network/config/netifd/Makefile                       | 2 +-
 package/network/config/netifd/files/lib/netifd/proto/dhcp.sh | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/package/network/config/netifd/Makefile b/package/network/config/netifd/Makefile
index 6e208dd..8b5d2f8 100644
--- a/package/network/config/netifd/Makefile
+++ b/package/network/config/netifd/Makefile
@@ -1,7 +1,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=netifd
-PKG_RELEASE:=4
+PKG_RELEASE:=5
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL=$(PROJECT_GIT)/project/netifd.git
diff --git a/package/network/config/netifd/files/lib/netifd/proto/dhcp.sh b/package/network/config/netifd/files/lib/netifd/proto/dhcp.sh
index afcfba9..a2b0cce 100755
--- a/package/network/config/netifd/files/lib/netifd/proto/dhcp.sh
+++ b/package/network/config/netifd/files/lib/netifd/proto/dhcp.sh
@@ -1,5 +1,7 @@
 #!/bin/sh
 
+[ -L /sbin/udhcpc ] || exit 0
+
 . /lib/functions.sh
 . ../netifd-proto.sh
 init_proto "$@"