From 28a79def5a11c25806eea5c7d17eb96dc94e52e6 Mon Sep 17 00:00:00 2001
From: zzz <zzz@i2pmail.org>
Date: Wed, 14 Dec 2022 10:51:34 -0500
Subject: [PATCH] NTCP: Fix rare NPE sending termination

reported by drzed
---
 .../i2p/router/transport/ntcp/NTCPConnection.java   | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/router/java/src/net/i2p/router/transport/ntcp/NTCPConnection.java b/router/java/src/net/i2p/router/transport/ntcp/NTCPConnection.java
index 50cd07705..785cec6fc 100644
--- a/router/java/src/net/i2p/router/transport/ntcp/NTCPConnection.java
+++ b/router/java/src/net/i2p/router/transport/ntcp/NTCPConnection.java
@@ -904,11 +904,14 @@ public class NTCPConnection implements Closeable {
         synchronized(_writeLock) {
             if (_sender != null) {
                 sendNTCP2(dataBuf.getData(), blocks);
-                _sender.destroy();
-                // this "plugs" the NTCP2 sender, so sendNTCP2()
-                // won't send any more after the termination.
-                _sender = null;
-                new DelayedCloser();
+                // sendNTCP2() -> wantsWrite() -> pumper.processWrite() -> fail -> close() -> NPE
+                if (_sender != null) {
+                    _sender.destroy();
+                    // this "plugs" the NTCP2 sender, so sendNTCP2()
+                    // won't send any more after the termination.
+                    _sender = null;
+                    new DelayedCloser();
+                }
             }
         }
         releaseReadBuf(dataBuf);