tls: cleanup onhandshakestart callback

Re-arrange and cleanup the flow of the onhandshakestart to be
more clear and less repetitive. Exit early in the case of a
first ever handshake for a given connection.
PR-URL: #20466
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Author: apapirovski

lib/_tls_wrap.js

@@ -62,32 +62,28 @@ const noop = () => {};
 functiononhandshakestart(now){
 debug('onhandshakestart');
 
-assert(now>=this.lastHandshakeTime);
+const{ lastHandshakeTime }=this;
+assert(now>=lastHandshakeTime);
 
-constowner=this.owner;
+this.lastHandshakeTime=now;
 
-if((now-this.lastHandshakeTime)>=tls.CLIENT_RENEG_WINDOW*1000){
-this.handshakes=0;
-}
+// If this is the first handshake we can skip the rest of the checks.
+if(lastHandshakeTime===0)
+return;
 
-constfirst=(this.lastHandshakeTime===0);
-this.lastHandshakeTime=now;
-if(first)return;
+if((now-lastHandshakeTime)>=tls.CLIENT_RENEG_WINDOW*1000)
+this.handshakes=1;
+else
+this.handshakes++;
 
-if(++this.handshakes>tls.CLIENT_RENEG_LIMIT){
-// Defer the error event to the next tick. We're being called from OpenSSL's
-// state machine and OpenSSL is not re-entrant. We cannot allow the user's
-// callback to destroy the connection right now, it would crash and burn.
-setImmediate(emitSessionAttackError,owner);
+const{ owner }=this;
+if(this.handshakes>tls.CLIENT_RENEG_LIMIT){
+owner._emitTLSError(newERR_TLS_SESSION_ATTACK());
+return;
 }
 
-if(owner[kDisableRenegotiation]&&this.handshakes>0){
+if(owner[kDisableRenegotiation])
 owner._emitTLSError(newERR_TLS_RENEGOTIATION_DISABLED());
-}
-}
-
-functionemitSessionAttackError(socket){
-socket._emitTLSError(newERR_TLS_SESSION_ATTACK());
 }
 
 functiononhandshakedone(){