ptp: add ipv6 support

* Wait for addresses to leave tentative state before setting routes
* Enable forwarding correctly
* Set up masquerading according to the active protocol

pkg/ip/ipforward.go

@@ -16,6 +16,8 @@ package ip
 
 import (
 	"io/ioutil"
+
+	"github.com/containernetworking/cni/pkg/types/current"
 )
 
 func EnableIP4Forward() error {
@@ -26,6 +28,28 @@ func EnableIP6Forward() error {
 	return echo1("/proc/sys/net/ipv6/conf/all/forwarding")
 }
 
+// EnableForward will enable forwarding for all configured
+// address families
+func EnableForward(ips []*current.IPConfig) error {
+	v4 := false
+	v6 := false
+
+	for _, ip := range ips {
+		if ip.Version == "4" && !v4 {
+			if err := EnableIP4Forward(); err != nil {
+				return err
+			}
+			v4 = true
+		} else if ip.Version == "6" && !v6 {
+			if err := EnableIP6Forward(); err != nil {
+				return err
+			}
+			v6 = true
+		}
+	}
+	return nil
+}
+
 func echo1(f string) error {
 	return ioutil.WriteFile(f, []byte("1"), 0644)
 }