From 1c59338f01c89b9bdd823602f2ee1c861d1579e8 Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Thu, 15 Feb 2018 13:38:54 +0000
Subject: [PATCH] Fix checksums and packet buffers, sends ICMPv6 Packet Too Big
 messages successfully now

---
 src/yggdrasil/icmpv6.go | 42 ++++++++++++++++++++---------------------
 src/yggdrasil/router.go |  5 +----
 2 files changed, 21 insertions(+), 26 deletions(-)

diff --git a/src/yggdrasil/icmpv6.go b/src/yggdrasil/icmpv6.go
index 85a6bbb..da62111 100644
--- a/src/yggdrasil/icmpv6.go
+++ b/src/yggdrasil/icmpv6.go
@@ -8,6 +8,7 @@ import "net"
 import "golang.org/x/net/ipv6"
 import "golang.org/x/net/icmp"
 import "encoding/binary"
+import "errors"
 
 type macAddress [6]byte
 
@@ -130,14 +131,11 @@ func (i *icmpv6) parse_packet_tun(datain []byte) ([]byte, error) {
 			if err == nil {
 				// Create our ICMPv6 response
 				responsePacket, err := i.create_icmpv6_tun(ipv6Header.Src, ipv6.ICMPTypeNeighborAdvertisement, 0,
-					&icmp.DefaultMessageBody{ Data: response })
+					&icmp.DefaultMessageBody{Data: response})
 				if err != nil {
 					return nil, err
 				}
 
-				// Fix the checksum because I don't even know why, net/icmp is stupid
-				responsePacket[17] ^= 0x4
-
 				// Send it back
 				return responsePacket, nil
 			} else {
@@ -146,7 +144,7 @@ func (i *icmpv6) parse_packet_tun(datain []byte) ([]byte, error) {
 		}
 	}
 
-	return nil, nil
+	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) {
@@ -157,7 +155,7 @@ func (i *icmpv6) create_icmpv6_tap(dstmac macAddress, dst net.IP, mtype ipv6.ICM
 	}
 
 	// Create the response buffer
-	dataout := make([]byte, ETHER+ipv6.HeaderLen+mbody.Len(0))
+	dataout := make([]byte, ETHER+len(ipv6packet))
 
 	// Populate the response ethernet headers
 	copy(dataout[:6], dstmac[:6])
@@ -170,16 +168,6 @@ func (i *icmpv6) create_icmpv6_tap(dstmac macAddress, dst net.IP, mtype ipv6.ICM
 }
 
 func (i *icmpv6) create_icmpv6_tun(dst net.IP, mtype ipv6.ICMPType, mcode int, mbody icmp.MessageBody) ([]byte, error) {
-	// Create the IPv6 header
-	ipv6Header := ipv6.Header{
-		Version:    ipv6.Version,
-		NextHeader: 58,
-		PayloadLen: mbody.Len(0),
-		HopLimit:   255,
-		Src:        i.mylladdr,
-		Dst:        dst,
-	}
-
 	// Create the ICMPv6 message
 	icmpMessage := icmp.Message{
 		Type: mtype,
@@ -187,14 +175,24 @@ func (i *icmpv6) create_icmpv6_tun(dst net.IP, mtype ipv6.ICMPType, mcode int, m
 		Body: mbody,
 	}
 
-	// Convert the IPv6 header into []byte
-	ipv6HeaderBuf, err := ipv6Header_Marshal(&ipv6Header)
+	// Convert the ICMPv6 message into []byte
+	icmpMessageBuf, err := icmpMessage.Marshal(icmp.IPv6PseudoHeader(i.mylladdr, dst))
 	if err != nil {
 		return nil, err
 	}
 
-	// Convert the ICMPv6 message into []byte
-	icmpMessageBuf, err := icmpMessage.Marshal(icmp.IPv6PseudoHeader(ipv6Header.Dst, ipv6Header.Src))
+	// Create the IPv6 header
+	ipv6Header := ipv6.Header{
+		Version:    ipv6.Version,
+		NextHeader: 58,
+		PayloadLen: len(icmpMessageBuf),
+		HopLimit:   255,
+		Src:        i.mylladdr,
+		Dst:        dst,
+	}
+
+	// Convert the IPv6 header into []byte
+	ipv6HeaderBuf, err := ipv6Header_Marshal(&ipv6Header)
 	if err != nil {
 		return nil, err
 	}
@@ -211,11 +209,11 @@ func (i *icmpv6) create_icmpv6_tun(dst net.IP, mtype ipv6.ICMPType, mcode int, m
 func (i *icmpv6) handle_ndp(in []byte) ([]byte, error) {
 	// Ignore NDP requests for anything outside of fd00::/8
 	if in[8] != 0xFD {
-		return nil, nil
+		return nil, errors.New("Not an NDP for fd00::/8")
 	}
 
 	// Create our NDP message body response
-	body := make([]byte, 32)
+	body := make([]byte, 28)
 	binary.BigEndian.PutUint32(body[:4], uint32(0x20000000))
 	copy(body[4:20], in[8:24]) // Target address
 	body[20] = uint8(2)
diff --git a/src/yggdrasil/router.go b/src/yggdrasil/router.go
index abd51c4..8ca5d2b 100644
--- a/src/yggdrasil/router.go
+++ b/src/yggdrasil/router.go
@@ -149,8 +149,6 @@ func (r *router) sendPacket(bs []byte) {
 	default:
 		// Generate an ICMPv6 Packet Too Big for packets larger than session MTU
 		if len(bs) > int(sinfo.getMTU()) {
-			sinfo.core.log.Printf("Packet length %d exceeds session MTU %d", len(bs), sinfo.getMTU())
-
 			// Get the size of the oversized payload, up to a max of 900 bytes
 			window := 900
 			if int(sinfo.getMTU()) < window {
@@ -159,14 +157,13 @@ func (r *router) sendPacket(bs []byte) {
 
 			// Create the Packet Too Big response
 			ptb := &icmp.PacketTooBig{
-				MTU: int(sinfo.getMTU()),
+				MTU:  int(sinfo.getMTU()),
 				Data: bs[:window],
 			}
 
 			// Create the ICMPv6 response from it
 			icmpv6Buf, err := r.core.tun.icmpv6.create_icmpv6_tun(bs[8:24], ipv6.ICMPTypePacketTooBig, 0, ptb)
 			if err == nil {
-				sinfo.core.log.Printf("Sending ICMPv6 Message Too Big")
 				r.recv <- icmpv6Buf
 			}