[source] gre: Support fqdn as remote tunnel endpoint

[LEDE Commits]

blogic pushed a commit to source.git, branch master:
https://git.lede-project.org/a79f3d11b3d7e4441544a2401f129bd055e84034

commit a79f3d11b3d7e4441544a2401f129bd055e84034
Author: Hans Dedecker <dedeckeh at gmail.com>
AuthorDate: Mon Oct 3 10:56:45 2016 +0200

    gre: Support fqdn as remote tunnel endpoint
    
    Signed-off-by: Hans Dedecker <dedeckeh at gmail.com>
---
 package/network/config/gre/Makefile     |  6 +++---
 package/network/config/gre/files/gre.sh | 30 ++++++++++++++++++++++++++++--
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/package/network/config/gre/Makefile b/package/network/config/gre/Makefile
index 12257a8..2e05ffc 100644
--- a/package/network/config/gre/Makefile
+++ b/package/network/config/gre/Makefile
@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=gre
 PKG_VERSION:=1
-PKG_RELEASE:=3
+PKG_RELEASE:=4
 PKG_LICENSE:=GPL-2.0
 
 include $(INCLUDE_DIR)/package.mk
@@ -32,7 +32,7 @@ endef
 define Package/grev4
 $(call Package/gre/Default)
   TITLE:=Generic Routing Encapsulation (IPv4) config support
-  DEPENDS:=@(PACKAGE_gre) +kmod-gre
+  DEPENDS:=@(PACKAGE_gre) +kmod-gre +resolveip
 endef
 
 define Package/grev4/description
@@ -42,7 +42,7 @@ endef
 define Package/grev6
 $(call Package/gre/Default)
   TITLE:=Generic Routing Encapsulation (IPv6) config support
-  DEPENDS:=@(PACKAGE_gre) @IPV6 +kmod-gre6
+  DEPENDS:=@(PACKAGE_gre) @IPV6 +kmod-gre6 +resolveip
 endef
 
 define Package/grev6/description
diff --git a/package/network/config/gre/files/gre.sh b/package/network/config/gre/files/gre.sh
index cab52d3..3f472c4 100755
--- a/package/network/config/gre/files/gre.sh
+++ b/package/network/config/gre/files/gre.sh
@@ -44,16 +44,29 @@ gre_generic_setup() {
 gre_setup() {
 	local cfg="$1"
 	local mode="$2"
+	local remoteip
 
 	local ipaddr peeraddr
 	json_get_vars df ipaddr peeraddr tunlink
 
 	[ -z "$peeraddr" ] && {
-		proto_notify_error "$cfg" "MISSING_ADDRESS"
+		proto_notify_error "$cfg" "MISSING_PEER_ADDRESS"
 		proto_block_restart "$cfg"
 		exit
 	}
 
+	remoteip=$(resolveip -t 10 -4 "$peeraddr")
+
+	if [ -z "$remoteip" ]; then
+		proto_notify_error "$cfg" "PEER_RESOLVE_FAIL"
+		exit
+	fi
+
+	for ip in $remoteip; do
+		peeraddr=$ip
+		break
+	done
+
 	( proto_add_host_dependency "$cfg" "$peeraddr" "$tunlink" )
 
 	[ -z "$ipaddr" ] && {
@@ -101,16 +114,29 @@ proto_gretap_setup() {
 grev6_setup() {
 	local cfg="$1"
 	local mode="$2"
+	local remoteip6
 
 	local ip6addr peer6addr weakif
 	json_get_vars ip6addr peer6addr tunlink weakif
 
 	[ -z "$peer6addr" ] && {
-		proto_notify_error "$cfg" "MISSING_ADDRESS"
+		proto_notify_error "$cfg" "MISSING_PEER_ADDRESS"
 		proto_block_restart "$cfg"
 		exit
 	}
 
+	remoteip6=$(resolveip -t 10 -6 "$peer6addr")
+
+	if [ -z "$remoteip6" ]; then
+		proto_notify_error "$cfg" "PEER_RESOLVE_FAIL"
+		exit
+	fi
+
+	for ip6 in $remoteip6; do
+		peer6addr=$ip6
+		break
+	done
+
 	( proto_add_host_dependency "$cfg" "$peer6addr" "$tunlink" )
 
 	[ -z "$ip6addr" ] && {