From 5e90d67bdee2966fe3257458c2bfeb549533b5f5 Mon Sep 17 00:00:00 2001
From: David Smith <David.Smith@cern.ch>
Date: Fri, 24 Feb 2023 11:27:35 +0100
Subject: [PATCH] [XrdCl] Check for closed connection between handling of read
 and write events

---
 src/XrdCl/XrdClAsyncSocketHandler.cc | 17 +++++++++++++++++
 src/XrdCl/XrdClAsyncSocketHandler.hh |  2 ++
 2 files changed, 19 insertions(+)

diff --git a/src/XrdCl/XrdClAsyncSocketHandler.cc b/src/XrdCl/XrdClAsyncSocketHandler.cc
index c416cebb367..a028bb1cd4e 100644
--- a/src/XrdCl/XrdClAsyncSocketHandler.cc
+++ b/src/XrdCl/XrdClAsyncSocketHandler.cc
@@ -46,6 +46,7 @@ namespace XrdCl
     pStreamName( ToStreamName( url, subStreamNum ) ),
     pSocket( new Socket() ),
     pHandShakeDone( false ),
+    pCloseCount( 0 ),
     pConnectionStarted( 0 ),
     pConnectionTimeout( 0 ),
     pHSWaitStarted( 0 ),
@@ -190,6 +191,7 @@ namespace XrdCl
 
     pPoller->RemoveSocket( pSocket );
     pSocket->Close();
+    pCloseCount++;
     return XRootDStatus();
   }
 
@@ -213,6 +215,12 @@ namespace XrdCl
     //--------------------------------------------------------------------------
     type = pSocket->MapEvent( type );
 
+    //--------------------------------------------------------------------------
+    // In case we'll be handling both read and write events be prepared to
+    // detect a close between the handling of each.
+    //--------------------------------------------------------------------------
+    const uint32_t closeCount = pCloseCount;
+
     //--------------------------------------------------------------------------
     // Read event
     //--------------------------------------------------------------------------
@@ -241,6 +249,15 @@ namespace XrdCl
         OnTimeoutWhileHandshaking();
     }
 
+    //--------------------------------------------------------------------------
+    // We check to see if any of the read event handlers above may have caused
+    // us to be closed. If so, we may have been re-opened, added to another
+    // poller and now be concurrently handling requests for another connection.
+    // Discontinue processing if a close is detected.
+    //--------------------------------------------------------------------------
+    if( closeCount != pCloseCount )
+      return;
+
     //--------------------------------------------------------------------------
     // Write event
     //--------------------------------------------------------------------------
diff --git a/src/XrdCl/XrdClAsyncSocketHandler.hh b/src/XrdCl/XrdClAsyncSocketHandler.hh
index f696e754af9..91c31f46cf3 100644
--- a/src/XrdCl/XrdClAsyncSocketHandler.hh
+++ b/src/XrdCl/XrdClAsyncSocketHandler.hh
@@ -30,6 +30,7 @@
 #include "XrdCl/XrdClAsyncHSReader.hh"
 #include "XrdCl/XrdClAsyncMsgWriter.hh"
 #include "XrdCl/XrdClAsyncHSWriter.hh"
+#include "XrdSys/XrdSysRAtomic.hh"
 
 namespace XrdCl
 {
@@ -264,6 +265,7 @@ namespace XrdCl
       std::unique_ptr<HandShakeData> pHandShakeData;
       bool                           pHandShakeDone;
       uint16_t                       pTimeoutResolution;
+      RAtomic_uint32_t               pCloseCount;
       time_t                         pConnectionStarted;
       time_t                         pConnectionTimeout;
       time_t                         pLastActivity;