move ICMP PacketTooBig sending into core

src/core/api.go

@@ -231,6 +231,18 @@ func (c *Core) MaxMTU() uint64 {
 	return c.store.maxSessionMTU()
 }
 
+// SetMTU can only safely be called after Init and before Start.
+func (c *Core) SetMTU(mtu uint64) {
+	if mtu < 1280 {
+		mtu = 1280
+	}
+	c.store.mtu = mtu
+}
+
+func (c *Core) MTU() uint64 {
+	return c.store.mtu
+}
+
 // Implement io.ReadWriteCloser
 
 func (c *Core) Read(p []byte) (n int, err error) {

src/core/keystore.go

@@ -7,6 +7,9 @@ import (
 	"sync"
 	"time"
 
+	"golang.org/x/net/icmp"
+	"golang.org/x/net/ipv6"
+
 	iwt "github.com/Arceliar/ironwood/types"
 
 	"github.com/yggdrasil-network/yggdrasil-go/src/address"
@@ -26,6 +29,7 @@ type keyStore struct {
 	addrBuffer   map[address.Address]*buffer
 	subnetToInfo map[address.Subnet]*keyInfo
 	subnetBuffer map[address.Subnet]*buffer
+	mtu          uint64
 }
 
 type keyInfo struct {
@@ -53,6 +57,7 @@ func (k *keyStore) init(core *Core) {
 	k.addrBuffer = make(map[address.Address]*buffer)
 	k.subnetToInfo = make(map[address.Subnet]*keyInfo)
 	k.subnetBuffer = make(map[address.Subnet]*buffer)
+	k.mtu = 1280 // Default to something safe, expect user to set this
 }
 
 func (k *keyStore) sendToAddress(addr address.Address, bs []byte) {
@@ -238,18 +243,19 @@ func (k *keyStore) readPC(p []byte) (int, error) {
 		if len(bs) < 40 {
 			continue
 		}
-		/* TODO? ICMP packet too big, for now tuntap sends this when needed
-		  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
-		  }
-		*/
+		if len(bs) > int(k.mtu) {
+			// Using bs would make it leak off the stack, so copy to buf
+			buf := make([]byte, 40)
+			copy(buf, bs)
+			ptb := &icmp.PacketTooBig{
+				MTU:  int(k.mtu),
+				Data: buf[:40],
+			}
+			if packet, err := CreateICMPv6(buf[8:24], buf[24:40], ipv6.ICMPTypePacketTooBig, 0, ptb); err == nil {
+				_, _ = k.writePC(packet)
+			}
+			continue
+		}
 		var srcAddr, dstAddr address.Address
 		var srcSubnet, dstSubnet address.Subnet
 		copy(srcAddr[:], bs[8:])

src/tuntap/icmpv6.go

@@ -1,80 +0,0 @@
-package tuntap
-
-// The ICMPv6 module implements functions to easily create ICMPv6
-// packets. These functions, when mixed with the built-in Go IPv6
-// and ICMP libraries, can be used to send control messages back
-// to the host. Examples include:
-// - NDP messages, when running in TAP mode
-// - Packet Too Big messages, when packets exceed the session MTU
-// - Destination Unreachable messages, when a session prohibits
-//   incoming traffic
-
-import (
-	"encoding/binary"
-	"net"
-
-	"golang.org/x/net/icmp"
-	"golang.org/x/net/ipv6"
-)
-
-type ICMPv6 struct{}
-
-// Marshal returns the binary encoding of h.
-func ipv6Header_Marshal(h *ipv6.Header) ([]byte, error) {
-	b := make([]byte, 40)
-	b[0] |= byte(h.Version) << 4
-	b[0] |= byte(h.TrafficClass) >> 4
-	b[1] |= byte(h.TrafficClass) << 4
-	b[1] |= byte(h.FlowLabel >> 16)
-	b[2] = byte(h.FlowLabel >> 8)
-	b[3] = byte(h.FlowLabel)
-	binary.BigEndian.PutUint16(b[4:6], uint16(h.PayloadLen))
-	b[6] = byte(h.NextHeader)
-	b[7] = byte(h.HopLimit)
-	copy(b[8:24], h.Src)
-	copy(b[24:40], h.Dst)
-	return b, nil
-}
-
-// 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
-// generating a message for TAP adapters.
-func CreateICMPv6(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,
-		Code: mcode,
-		Body: mbody,
-	}
-
-	// Convert the ICMPv6 message into []byte
-	icmpMessageBuf, err := icmpMessage.Marshal(icmp.IPv6PseudoHeader(src, dst))
-	if err != nil {
-		return nil, err
-	}
-
-	// Create the IPv6 header
-	ipv6Header := ipv6.Header{
-		Version:    ipv6.Version,
-		NextHeader: 58,
-		PayloadLen: len(icmpMessageBuf),
-		HopLimit:   255,
-		Src:        src,
-		Dst:        dst,
-	}
-
-	// Convert the IPv6 header into []byte
-	ipv6HeaderBuf, err := ipv6Header_Marshal(&ipv6Header)
-	if err != nil {
-		return nil, err
-	}
-
-	// Construct the packet
-	responsePacket := make([]byte, ipv6.HeaderLen+ipv6Header.PayloadLen)
-	copy(responsePacket[:ipv6.HeaderLen], ipv6HeaderBuf)
-	copy(responsePacket[ipv6.HeaderLen:], icmpMessageBuf)
-
-	// Send it back
-	return responsePacket, nil
-}

src/tuntap/iface.go

@@ -1,10 +1,5 @@
 package tuntap
 
-import (
-	"golang.org/x/net/icmp"
-	"golang.org/x/net/ipv6"
-)
-
 const TUN_OFFSET_BYTES = 4
 
 func (tun *TunAdapter) read() {
@@ -37,15 +32,8 @@ func (tun *TunAdapter) write() {
 			tun.log.Errorln("Exiting tun writer due to core read error:", err)
 			return
 		}
-		if n > 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.Write(packet)
-			}
-			continue
+		if !tun.isEnabled {
+			continue // Nothing to do, the tun isn't enabled
 		}
 		bs = buf[:TUN_OFFSET_BYTES+n]
 		if _, err = tun.iface.Write(bs, TUN_OFFSET_BYTES); err != nil {

src/tuntap/tun.go

@@ -139,6 +139,7 @@ func (tun *TunAdapter) _start() error {
 	if tun.MTU() != mtu {
 		tun.log.Warnf("Warning: Interface MTU %d automatically adjusted to %d (supported range is 1280-%d)", tun.config.IfMTU, tun.MTU(), MaximumMTU())
 	}
+	tun.core.SetMTU(tun.MTU())
 	tun.isOpen = true
 	tun.isEnabled = true
 	go tun.read()