Provide support for ipv6

Signed-off-by: Manuel Buil <mbuil@suse.com>

entry

@@ -3,13 +3,21 @@ set -e -x
 
 trap exit TERM INT
 
-if [ `cat /proc/sys/net/ipv4/ip_forward` != 1 ]; then
-    exit 1
+if echo ${DEST_IP} | grep -Eq ":" 
+then
+    if [ `cat /proc/sys/net/ipv6/conf/all/forwarding` != 1 ]; then
+        exit 1
+    fi
+    ip6tables -t nat -I PREROUTING ! -s ${DEST_IP}/128 -p ${DEST_PROTO} --dport ${SRC_PORT} -j DNAT --to ${DEST_IP}:${DEST_PORT}
+    ip6tables -t nat -I POSTROUTING -d ${DEST_IP}/128 -p ${DEST_PROTO} -j MASQUERADE
+else
+    if [ `cat /proc/sys/net/ipv4/ip_forward` != 1 ]; then
+        exit 1
+    fi
+    iptables -t nat -I PREROUTING ! -s ${DEST_IP}/32 -p ${DEST_PROTO} --dport ${SRC_PORT} -j DNAT --to ${DEST_IP}:${DEST_PORT}
+    iptables -t nat -I POSTROUTING -d ${DEST_IP}/32 -p ${DEST_PROTO} -j MASQUERADE
 fi
 
-iptables -t nat -I PREROUTING ! -s ${DEST_IP}/32 -p ${DEST_PROTO} --dport ${SRC_PORT} -j DNAT --to ${DEST_IP}:${DEST_PORT}
-iptables -t nat -I POSTROUTING -d ${DEST_IP}/32 -p ${DEST_PROTO} -j MASQUERADE
-
 if [ ! -e /pause ]; then
     mkfifo /pause
 fi

package/Dockerfile

@@ -1,4 +1,4 @@
 FROM alpine:3.12
-RUN apk add -U --no-cache iptables
+RUN apk add -U --no-cache iptables ip6tables
 COPY entry /usr/bin/
 CMD ["entry"]

package/Dockerfile.arm

@@ -1,5 +1,5 @@
 # Alpine has a different image for arm https://github.com/docker-library/repo-info/blob/master/repos/alpine/remote/3.12.8.md
 FROM alpine@sha256:a296b4c6f6ee2b88f095b61e95c7ef4f51ba25598835b4978c9256d8c8ace48a
-RUN apk add -U --no-cache iptables
+RUN apk add -U --no-cache iptables ip6tables
 COPY entry /usr/bin/
 CMD ["entry"]