From bf0413a0c49d7a42c0ea067ecb822c55425a9a22 Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Sat, 10 Mar 2018 22:31:36 +0000
Subject: [PATCH] Modify ICMPv6 source address for "Packet Too Big" messages to
 a routable address so that it correctly routes to nodes in an yggdrasil /64
 subnet

---
 src/yggdrasil/icmpv6.go | 14 ++++++++------
 src/yggdrasil/router.go |  4 +++-
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/src/yggdrasil/icmpv6.go b/src/yggdrasil/icmpv6.go
index da62111a..96c5218f 100644
--- a/src/yggdrasil/icmpv6.go
+++ b/src/yggdrasil/icmpv6.go
@@ -130,7 +130,9 @@ func (i *icmpv6) parse_packet_tun(datain []byte) ([]byte, error) {
 			response, err := i.handle_ndp(datain[ipv6.HeaderLen:])
 			if err == nil {
 				// Create our ICMPv6 response
-				responsePacket, err := i.create_icmpv6_tun(ipv6Header.Src, ipv6.ICMPTypeNeighborAdvertisement, 0,
+				responsePacket, err := i.create_icmpv6_tun(
+					ipv6Header.Src, i.mylladdr,
+					ipv6.ICMPTypeNeighborAdvertisement, 0,
 					&icmp.DefaultMessageBody{Data: response})
 				if err != nil {
 					return nil, err
@@ -147,9 +149,9 @@ func (i *icmpv6) parse_packet_tun(datain []byte) ([]byte, error) {
 	return nil, errors.New("ICMPv6 type not matched")
 }
 
-func (i *icmpv6) create_icmpv6_tap(dstmac macAddress, dst net.IP, mtype ipv6.ICMPType, mcode int, mbody icmp.MessageBody) ([]byte, error) {
+func (i *icmpv6) create_icmpv6_tap(dstmac macAddress, dst net.IP, src net.IP, mtype ipv6.ICMPType, mcode int, mbody icmp.MessageBody) ([]byte, error) {
 	// Pass through to create_icmpv6_tun
-	ipv6packet, err := i.create_icmpv6_tun(dst, mtype, mcode, mbody)
+	ipv6packet, err := i.create_icmpv6_tun(dst, src, mtype, mcode, mbody)
 	if err != nil {
 		return nil, err
 	}
@@ -167,7 +169,7 @@ func (i *icmpv6) create_icmpv6_tap(dstmac macAddress, dst net.IP, mtype ipv6.ICM
 	return dataout, nil
 }
 
-func (i *icmpv6) create_icmpv6_tun(dst net.IP, mtype ipv6.ICMPType, mcode int, mbody icmp.MessageBody) ([]byte, error) {
+func (i *icmpv6) create_icmpv6_tun(dst net.IP, src net.IP, mtype ipv6.ICMPType, mcode int, mbody icmp.MessageBody) ([]byte, error) {
 	// Create the ICMPv6 message
 	icmpMessage := icmp.Message{
 		Type: mtype,
@@ -176,7 +178,7 @@ func (i *icmpv6) create_icmpv6_tun(dst net.IP, mtype ipv6.ICMPType, mcode int, m
 	}
 
 	// Convert the ICMPv6 message into []byte
-	icmpMessageBuf, err := icmpMessage.Marshal(icmp.IPv6PseudoHeader(i.mylladdr, dst))
+	icmpMessageBuf, err := icmpMessage.Marshal(icmp.IPv6PseudoHeader(src, dst))
 	if err != nil {
 		return nil, err
 	}
@@ -187,7 +189,7 @@ func (i *icmpv6) create_icmpv6_tun(dst net.IP, mtype ipv6.ICMPType, mcode int, m
 		NextHeader: 58,
 		PayloadLen: len(icmpMessageBuf),
 		HopLimit:   255,
-		Src:        i.mylladdr,
+		Src:        src,
 		Dst:        dst,
 	}
 
diff --git a/src/yggdrasil/router.go b/src/yggdrasil/router.go
index 5028b493..9d4a5cbe 100644
--- a/src/yggdrasil/router.go
+++ b/src/yggdrasil/router.go
@@ -163,7 +163,9 @@ func (r *router) sendPacket(bs []byte) {
 			}
 
 			// Create the ICMPv6 response from it
-			icmpv6Buf, err := r.core.tun.icmpv6.create_icmpv6_tun(bs[8:24], ipv6.ICMPTypePacketTooBig, 0, ptb)
+			icmpv6Buf, err := r.core.tun.icmpv6.create_icmpv6_tun(
+				bs[8:24], bs[24:40],
+				ipv6.ICMPTypePacketTooBig, 0, ptb)
 			if err == nil {
 				r.recv <- icmpv6Buf
 			}