diff --git a/src/yggdrasil/ckr.go b/src/yggdrasil/ckr.go
index 8036486..f22840c 100644
--- a/src/yggdrasil/ckr.go
+++ b/src/yggdrasil/ckr.go
@@ -46,22 +46,36 @@ func (c *cryptokey) isEnabled() bool {
 	return c.enabled
 }
 
-func (c *cryptokey) isValidSource(addr address) bool {
-	ip := net.IP(addr[:])
+func (c *cryptokey) isValidSource(addr address, addrlen int) bool {
+	ip := net.IP(addr[:addrlen])
 
-	// Does this match our node's address?
-	if bytes.Equal(addr[:16], c.core.router.addr[:16]) {
-		return true
-	}
+	if addrlen == net.IPv6len {
+		// Does this match our node's address?
+		if bytes.Equal(addr[:16], c.core.router.addr[:16]) {
+			return true
+		}
 
-	// Does this match our node's subnet?
-	if bytes.Equal(addr[:8], c.core.router.subnet[:8]) {
-		return true
+		// Does this match our node's subnet?
+		if bytes.Equal(addr[:8], c.core.router.subnet[:8]) {
+			return true
+		}
 	}
 
 	// Does it match a configured CKR source?
 	if c.isEnabled() {
-		for _, subnet := range c.ipv6sources {
+		// Build our references to the routing sources
+		var routingsources *[]net.IPNet
+
+		// Check if the prefix is IPv4 or IPv6
+		if addrlen == net.IPv6len {
+			routingsources = &c.ipv6sources
+		} else if addrlen == net.IPv4len {
+			routingsources = &c.ipv4sources
+		} else {
+			return false
+		}
+
+		for _, subnet := range *routingsources {
 			if subnet.Contains(ip) {
 				return true
 			}
diff --git a/src/yggdrasil/router.go b/src/yggdrasil/router.go
index cd922a9..0c633ac 100644
--- a/src/yggdrasil/router.go
+++ b/src/yggdrasil/router.go
@@ -127,14 +127,26 @@ func (r *router) sendPacket(bs []byte) {
 	var sourceAddr address
 	var dest address
 	var snet subnet
-	copy(sourceAddr[:], bs[8:])
-	if !r.cryptokey.isValidSource(sourceAddr) {
+	var addrlen int
+	if bs[0]&0xf0 == 0x60 {
+		// IPv6 address
+		addrlen = 16
+		copy(sourceAddr[:addrlen], bs[8:])
+		copy(dest[:addrlen], bs[24:])
+		copy(snet[:addrlen/2], bs[24:])
+	} else if bs[0]&0xf0 == 0x40 {
+		// IPv4 address
+		addrlen = 4
+		copy(sourceAddr[:addrlen], bs[12:])
+		copy(dest[:addrlen], bs[16:])
+	} else {
+		return
+	}
+	if !r.cryptokey.isValidSource(sourceAddr, addrlen) {
 		return
 	}
-	copy(dest[:], bs[24:])
-	copy(snet[:], bs[24:])
 	if !dest.isValid() && !snet.isValid() {
-		if key, err := r.cryptokey.getPublicKeyForAddress(dest, 16); err == nil {
+		if key, err := r.cryptokey.getPublicKeyForAddress(dest, addrlen); err == nil {
 			addr := *address_addrForNodeID(getNodeID(&key))
 			copy(dest[:], addr[:])
 			copy(snet[:], addr[:])
@@ -259,21 +271,33 @@ func (r *router) recvPacket(bs []byte, sinfo *sessionInfo) {
 		util_putBytes(bs)
 		return
 	}
+	var sourceAddr address
 	var dest address
-	copy(dest[:], bs[24:])
-	if !r.cryptokey.isValidSource(dest) {
+	var snet subnet
+	var addrlen int
+	if bs[0]&0xf0 == 0x60 {
+		// IPv6 address
+		addrlen = 16
+		copy(sourceAddr[:addrlen], bs[8:])
+		copy(dest[:addrlen], bs[24:])
+		copy(snet[:addrlen/2], bs[24:])
+	} else if bs[0]&0xf0 == 0x40 {
+		// IPv4 address
+		addrlen = 4
+		copy(sourceAddr[:addrlen], bs[12:])
+		copy(dest[:addrlen], bs[16:])
+	} else {
+		return
+	}
+	if !r.cryptokey.isValidSource(dest, addrlen) {
 		util_putBytes(bs)
 		return
 	}
-	var source address
-	copy(source[:], bs[8:])
-	var snet subnet
-	copy(snet[:], bs[8:])
 	switch {
-	case source.isValid() && source == sinfo.theirAddr:
+	case sourceAddr.isValid() && sourceAddr == sinfo.theirAddr:
 	case snet.isValid() && snet == sinfo.theirSubnet:
 	default:
-		key, err := r.cryptokey.getPublicKeyForAddress(source, 16)
+		key, err := r.cryptokey.getPublicKeyForAddress(sourceAddr, addrlen)
 		if err != nil || key != sinfo.theirPermPub {
 			util_putBytes(bs)
 			return
diff --git a/src/yggdrasil/tun.go b/src/yggdrasil/tun.go
index cbbcdea..ac70398 100644
--- a/src/yggdrasil/tun.go
+++ b/src/yggdrasil/tun.go
@@ -105,7 +105,7 @@ func (tun *tunDevice) read() error {
 			n != 256*int(buf[o+4])+int(buf[o+5])+tun_IPv6_HEADER_LENGTH+o {
 			// Either not an IPv6 packet or not the complete packet for some reason
 			//panic("Should not happen in testing")
-			continue
+			//continue
 		}
 		if buf[o+6] == 58 {
 			// Found an ICMPv6 packet