From 815f2a28220801f11c4ee9af9fa566051dec09dc Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Mon, 10 May 2021 23:09:59 +0100
Subject: [PATCH] Respond with ICMPv6 Packet Too Big over network

---
 cmd/yggdrasil/main.go |  3 ++-
 src/tuntap/icmpv6.go  |  7 -------
 src/tuntap/iface.go   | 14 ++++++++++++++
 src/tuntap/tun.go     | 15 ---------------
 4 files changed, 16 insertions(+), 23 deletions(-)

diff --git a/cmd/yggdrasil/main.go b/cmd/yggdrasil/main.go
index e409f4ab..f3158250 100644
--- a/cmd/yggdrasil/main.go
+++ b/cmd/yggdrasil/main.go
@@ -295,7 +295,7 @@ func main() {
 	}
 	n.multicast.SetupAdminHandlers(n.admin.(*admin.AdminSocket))
 	// Start the TUN/TAP interface
-	n.tuntap.Init(&n.core, n.state, logger, tuntap.TunOptions{})
+	n.tuntap.Init(&n.core, n.state, logger, nil)
 	if err := n.tuntap.Start(); err != nil {
 		logger.Errorln("An error occurred starting TUN/TAP:", err)
 	}
@@ -325,6 +325,7 @@ func main() {
 	c := make(chan os.Signal, 1)
 	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
 	// Capture the service being stopped on Windows.
+	<-c
 	minwinsvc.SetOnExit(n.shutdown)
 	n.shutdown()
 }
diff --git a/src/tuntap/icmpv6.go b/src/tuntap/icmpv6.go
index 67c10e54..59d07af3 100644
--- a/src/tuntap/icmpv6.go
+++ b/src/tuntap/icmpv6.go
@@ -40,13 +40,6 @@ func ipv6Header_Marshal(h *ipv6.Header) ([]byte, error) {
 	return b, nil
 }
 
-// Initialises the ICMPv6 module by assigning our link-local IPv6 address and
-// our MAC address. ICMPv6 messages will always appear to originate from these
-// addresses.
-func (i *ICMPv6) Init(t *TunAdapter) {
-	i.tun = t
-}
-
 // Creates an ICMPv6 packet based on the given icmp.MessageBody and other
 // parameters, complete with IP headers only, which can be written directly to
 // a TUN adapter, or called directly by the CreateICMPv6L2 function when
diff --git a/src/tuntap/iface.go b/src/tuntap/iface.go
index c7222266..30eaf32a 100644
--- a/src/tuntap/iface.go
+++ b/src/tuntap/iface.go
@@ -4,6 +4,9 @@ import (
 	"crypto/ed25519"
 
 	"github.com/yggdrasil-network/yggdrasil-go/src/address"
+	"golang.org/x/net/icmp"
+	"golang.org/x/net/ipv6"
+
 	//"github.com/yggdrasil-network/yggdrasil-go/src/crypto"
 	//"github.com/yggdrasil-network/yggdrasil-go/src/yggdrasil"
 
@@ -70,6 +73,17 @@ func (tun *TunAdapter) write() {
 		if len(bs) < 40 {
 			continue
 		}
+		tun.log.Println(len(bs), tun.MTU())
+		if len(bs) > int(tun.MTU()) {
+			ptb := &icmp.PacketTooBig{
+				MTU:  int(tun.mtu),
+				Data: bs[:40],
+			}
+			if packet, err := CreateICMPv6(bs[8:24], bs[24:40], ipv6.ICMPTypePacketTooBig, 0, ptb); err == nil {
+				_, _ = tun.core.WriteTo(packet, from)
+			}
+			continue
+		}
 		var srcAddr, dstAddr address.Address
 		var srcSubnet, dstSubnet address.Subnet
 		copy(srcAddr[:], bs[8:])
diff --git a/src/tuntap/tun.go b/src/tuntap/tun.go
index 1618506a..8c8cbf19 100644
--- a/src/tuntap/tun.go
+++ b/src/tuntap/tun.go
@@ -29,8 +29,6 @@ import (
 
 type MTU = types.MTU
 
-const tun_IPv6_HEADER_LENGTH = 40
-
 // TunAdapter represents a running TUN interface and extends the
 // yggdrasil.Adapter type. In order to use the TUN adapter with Yggdrasil, you
 // should pass this object to the yggdrasil.SetRouterAdapter() function before
@@ -43,7 +41,6 @@ type TunAdapter struct {
 	addr        address.Address
 	subnet      address.Subnet
 	ckr         cryptokey
-	icmpv6      ICMPv6
 	mtu         MTU
 	iface       tun.Device
 	phony.Inbox // Currently only used for _handlePacket from the reader, TODO: all the stuff that currently needs a mutex below
@@ -51,11 +48,6 @@ type TunAdapter struct {
 	isOpen bool
 }
 
-type TunOptions struct {
-	//Listener *yggdrasil.Listener
-	//Dialer   *yggdrasil.Dialer
-}
-
 // Gets the maximum supported MTU for the platform based on the defaults in
 // defaults.GetDefaults().
 func getSupportedMTU(mtu MTU) MTU {
@@ -105,12 +97,6 @@ func MaximumMTU() MTU {
 // Init initialises the TUN module. You must have acquired a Listener from
 // the Yggdrasil core before this point and it must not be in use elsewhere.
 func (tun *TunAdapter) Init(core *yggdrasil.Core, config *config.NodeState, log *log.Logger, options interface{}) error {
-	/* TODO
-	tunoptions, ok := options.(TunOptions)
-	if !ok {
-		return fmt.Errorf("invalid options supplied to TunAdapter module")
-	}
-	*/
 	tun.core = core
 	tun.store.init(tun)
 	tun.config = config
@@ -118,7 +104,6 @@ func (tun *TunAdapter) Init(core *yggdrasil.Core, config *config.NodeState, log
 	if err := tun.core.SetOutOfBandHandler(tun.oobHandler); err != nil {
 		return fmt.Errorf("tun.core.SetOutOfBandHander: %w", err)
 	}
-
 	return nil
 }