From 781cd7571f8ba92fe9ab1834b30b457efb338cdc Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Sun, 21 Apr 2019 12:00:31 +0100
Subject: [PATCH] Fix race on tun conns, but still deadlocks if more than one
 connection is opened

---
 cmd/yggdrasil/main.go |  1 -
 src/tuntap/tun.go     | 23 ++++++++++++++++++-----
 src/yggdrasil/conn.go |  2 --
 3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/cmd/yggdrasil/main.go b/cmd/yggdrasil/main.go
index f3d933c..9634983 100644
--- a/cmd/yggdrasil/main.go
+++ b/cmd/yggdrasil/main.go
@@ -265,7 +265,6 @@ func main() {
 	// Start the TUN/TAP interface
 	if listener, err := n.core.ConnListen(); err == nil {
 		if dialer, err := n.core.ConnDialer(); err == nil {
-			logger.Println("Got listener", listener, "and dialer", dialer)
 			n.tuntap.Init(state, logger, listener, dialer)
 			if err := n.tuntap.Start(); err != nil {
 				logger.Errorln("An error occurred starting TUN/TAP:", err)
diff --git a/src/tuntap/tun.go b/src/tuntap/tun.go
index 9e46124..acdcf3a 100644
--- a/src/tuntap/tun.go
+++ b/src/tuntap/tun.go
@@ -30,7 +30,6 @@ type TunAdapter struct {
 	config      *config.NodeState
 	log         *log.Logger
 	reconfigure chan chan error
-	conns       map[crypto.NodeID]*yggdrasil.Conn
 	listener    *yggdrasil.Listener
 	dialer      *yggdrasil.Dialer
 	addr        address.Address
@@ -39,6 +38,7 @@ type TunAdapter struct {
 	mtu         int
 	iface       *water.Interface
 	mutex       sync.RWMutex // Protects the below
+	conns       map[crypto.NodeID]*yggdrasil.Conn
 	isOpen      bool
 }
 
@@ -173,13 +173,24 @@ func (tun *TunAdapter) handler() error {
 			tun.log.Errorln("TUN/TAP error accepting connection:", err)
 			return err
 		}
-		tun.log.Println("Accepted connection from", conn.RemoteAddr())
 		go tun.connReader(conn)
 	}
 }
 
 func (tun *TunAdapter) connReader(conn *yggdrasil.Conn) error {
-	tun.conns[conn.RemoteAddr()] = conn
+	remoteNodeID := conn.RemoteAddr()
+	tun.mutex.Lock()
+	if _, isIn := tun.conns[remoteNodeID]; isIn {
+		tun.mutex.Unlock()
+		return errors.New("duplicate connection")
+	}
+	tun.conns[remoteNodeID] = conn
+	tun.mutex.Unlock()
+	defer func() {
+		tun.mutex.Lock()
+		delete(tun.conns, remoteNodeID)
+		tun.mutex.Unlock()
+	}()
 	b := make([]byte, 65535)
 	for {
 		n, err := conn.Read(b)
@@ -242,8 +253,9 @@ func (tun *TunAdapter) ifaceReader() error {
 		}
 		dstNodeID, dstNodeIDMask = dstAddr.GetNodeIDandMask()
 		// Do we have an active connection for this node ID?
+		tun.mutex.Lock()
 		if conn, isIn := tun.conns[*dstNodeID]; isIn {
-			tun.log.Println("Got", &conn)
+			tun.mutex.Unlock()
 			w, err := conn.Write(bs)
 			if err != nil {
 				tun.log.Println("Unable to write to remote:", err)
@@ -253,11 +265,12 @@ func (tun *TunAdapter) ifaceReader() error {
 				continue
 			}
 		} else {
-			tun.log.Println("Opening connection for", *dstNodeID)
 			if conn, err := tun.dialer.DialByNodeIDandMask(dstNodeID, dstNodeIDMask); err == nil {
 				tun.conns[*dstNodeID] = &conn
+				tun.mutex.Unlock()
 				go tun.connReader(&conn)
 			} else {
+				tun.mutex.Unlock()
 				tun.log.Println("Error dialing:", err)
 			}
 		}
diff --git a/src/yggdrasil/conn.go b/src/yggdrasil/conn.go
index daba298..ed9eb6c 100644
--- a/src/yggdrasil/conn.go
+++ b/src/yggdrasil/conn.go
@@ -2,7 +2,6 @@ package yggdrasil
 
 import (
 	"errors"
-	"fmt"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -124,7 +123,6 @@ func (c *Conn) Write(b []byte) (bytesWritten int, err error) {
 		return 0, errors.New("session is closed")
 	}
 	if c.session == nil {
-		fmt.Println("No session found, starting search for", &c)
 		c.core.router.doAdmin(func() {
 			c.startSearch()
 		})