From 679866d5ff8d300985018420e5bf027be9016a0f Mon Sep 17 00:00:00 2001
From: Arceliar <Arceliar@users.noreply.github.com>
Date: Mon, 5 Aug 2019 19:11:28 -0500
Subject: [PATCH] have createSession fill the sessionInfo.cancel field, have
 Conn use Conn.session.cancel instead of storing its own cancellation, this
 should prevent any of these things from being both nil and reachable at the
 same time

---
 src/yggdrasil/conn.go    | 13 +++++--------
 src/yggdrasil/dialer.go  |  2 +-
 src/yggdrasil/router.go  |  3 +--
 src/yggdrasil/session.go | 11 ++++++++---
 4 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/src/yggdrasil/conn.go b/src/yggdrasil/conn.go
index 1a05bd83..2452a3d6 100644
--- a/src/yggdrasil/conn.go
+++ b/src/yggdrasil/conn.go
@@ -57,7 +57,6 @@ type Conn struct {
 	core          *Core
 	readDeadline  atomic.Value // time.Time // TODO timer
 	writeDeadline atomic.Value // time.Time // TODO timer
-	cancel        util.Cancellation
 	mutex         sync.RWMutex // protects the below
 	nodeID        *crypto.NodeID
 	nodeMask      *crypto.NodeID
@@ -71,7 +70,6 @@ func newConn(core *Core, nodeID *crypto.NodeID, nodeMask *crypto.NodeID, session
 		nodeID:   nodeID,
 		nodeMask: nodeMask,
 		session:  session,
-		cancel:   util.NewCancellation(),
 	}
 	return &conn
 }
@@ -142,10 +140,10 @@ func (c *Conn) doSearch() {
 func (c *Conn) getDeadlineCancellation(value *atomic.Value) util.Cancellation {
 	if deadline, ok := value.Load().(time.Time); ok {
 		// A deadline is set, so return a Cancellation that uses it
-		return util.CancellationWithDeadline(c.cancel, deadline)
+		return util.CancellationWithDeadline(c.session.cancel, deadline)
 	} else {
 		// No cancellation was set, so return a child cancellation with no timeout
-		return util.CancellationChild(c.cancel)
+		return util.CancellationChild(c.session.cancel)
 	}
 }
 
@@ -241,10 +239,9 @@ func (c *Conn) Close() (err error) {
 	defer c.mutex.Unlock()
 	if c.session != nil {
 		// Close the session, if it hasn't been closed already
-		c.core.router.doAdmin(c.session.close)
-	}
-	if e := c.cancel.Cancel(errors.New("connection closed")); e != nil {
-		err = ConnError{errors.New("close failed, session already closed"), false, false, true, 0}
+		if e := c.session.cancel.Cancel(errors.New("connection closed")); e != nil {
+			err = ConnError{errors.New("close failed, session already closed"), false, false, true, 0}
+		}
 	}
 	return
 }
diff --git a/src/yggdrasil/dialer.go b/src/yggdrasil/dialer.go
index 6ce2e8ac..db5d5a4d 100644
--- a/src/yggdrasil/dialer.go
+++ b/src/yggdrasil/dialer.go
@@ -69,7 +69,7 @@ func (d *Dialer) DialByNodeIDandMask(nodeID, nodeMask *crypto.NodeID) (*Conn, er
 	defer t.Stop()
 	select {
 	case <-conn.session.init:
-		conn.session.startWorkers(conn.cancel)
+		conn.session.startWorkers()
 		return conn, nil
 	case <-t.C:
 		conn.Close()
diff --git a/src/yggdrasil/router.go b/src/yggdrasil/router.go
index 161ae60a..a11f6ae5 100644
--- a/src/yggdrasil/router.go
+++ b/src/yggdrasil/router.go
@@ -161,8 +161,7 @@ func (r *router) handleTraffic(packet []byte) {
 		return
 	}
 	sinfo, isIn := r.core.sessions.getSessionForHandle(&p.Handle)
-	if !isIn || sinfo.cancel == nil {
-		// FIXME make sure sinfo.cancel can never be nil
+	if !isIn {
 		util.PutBytes(p.Payload)
 		return
 	}
diff --git a/src/yggdrasil/session.go b/src/yggdrasil/session.go
index c39f60de..f9c38faa 100644
--- a/src/yggdrasil/session.go
+++ b/src/yggdrasil/session.go
@@ -208,6 +208,7 @@ func (ss *sessions) createSession(theirPermKey *crypto.BoxPubKey) *sessionInfo {
 	sinfo.pingTime = now
 	sinfo.pingSend = now
 	sinfo.init = make(chan struct{})
+	sinfo.cancel = util.NewCancellation()
 	higher := false
 	for idx := range ss.core.boxPub {
 		if ss.core.boxPub[idx] > sinfo.theirPermPub[idx] {
@@ -232,6 +233,11 @@ func (ss *sessions) createSession(theirPermKey *crypto.BoxPubKey) *sessionInfo {
 	sinfo.send = make(chan []byte, 32)
 	ss.sinfos[sinfo.myHandle] = &sinfo
 	ss.byTheirPerm[sinfo.theirPermPub] = &sinfo.myHandle
+	go func() {
+		// Run cleanup when the session is canceled
+		<-sinfo.cancel.Finished()
+		sinfo.core.router.doAdmin(sinfo.close)
+	}()
 	return &sinfo
 }
 
@@ -362,7 +368,7 @@ func (ss *sessions) handlePing(ping *sessionPing) {
 			for i := range conn.nodeMask {
 				conn.nodeMask[i] = 0xFF
 			}
-			conn.session.startWorkers(conn.cancel)
+			conn.session.startWorkers()
 			ss.listener.conn <- conn
 		}
 		ss.listenerMutex.Unlock()
@@ -431,8 +437,7 @@ func (ss *sessions) reset() {
 //////////////////////////// Worker Functions Below ////////////////////////////
 ////////////////////////////////////////////////////////////////////////////////
 
-func (sinfo *sessionInfo) startWorkers(cancel util.Cancellation) {
-	sinfo.cancel = cancel
+func (sinfo *sessionInfo) startWorkers() {
 	go sinfo.recvWorker()
 	go sinfo.sendWorker()
 }