From 8752b8d0ae3606d3f75809f94b9711790fa997df Mon Sep 17 00:00:00 2001
From: zzz <zzz@i2pmail.org>
Date: Wed, 26 Aug 2026 12:08:29 -0400
Subject: [PATCH] I2CP: Add new discardMessage() to session API

to avoid decompression overhead on messages with no match
in the demuxer.

Log hexdump of discarded message if enabled
---
 core/java/src/net/i2p/client/I2PSession.java  |  8 ++++++++
 .../client/impl/I2PSessionDemultiplexer.java  | 19 +++++++++++--------
 .../net/i2p/client/impl/I2PSessionImpl.java   | 10 ++++++++++
 3 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/core/java/src/net/i2p/client/I2PSession.java b/core/java/src/net/i2p/client/I2PSession.java
index b9fa72807..850752bf1 100644
--- a/core/java/src/net/i2p/client/I2PSession.java
+++ b/core/java/src/net/i2p/client/I2PSession.java
@@ -229,6 +229,14 @@ public interface I2PSession {
      */
     public byte[] receiveMessage(int msgId) throws I2PSessionException;
 
+    /**
+     * Throw away the received message, we don't want it.
+     * Use instead of receiveMessage() to avoid gunzip overhead.
+     *
+     * @since 0.9.71
+     */
+    public void discardMessage(int msgId);
+
     /** Instruct the router that the message received was abusive (including how
      * abusive on a 1-100 scale) in the hopes the router can do something to
      * minimize receiving abusive messages like that in the future.
diff --git a/core/java/src/net/i2p/client/impl/I2PSessionDemultiplexer.java b/core/java/src/net/i2p/client/impl/I2PSessionDemultiplexer.java
index 6480733e1..72b8d9c65 100644
--- a/core/java/src/net/i2p/client/impl/I2PSessionDemultiplexer.java
+++ b/core/java/src/net/i2p/client/impl/I2PSessionDemultiplexer.java
@@ -46,17 +46,20 @@ public class I2PSessionDemultiplexer implements I2PSessionMuxedListener {
             l.messageAvailable(session, msgId, size, proto, fromport, toport);
         } else {
             // no listener, throw it out
-            if (_listeners.isEmpty()) {
-                if (_log.shouldLog(Log.WARN))
+            if (_log.shouldWarn()) {
+                if (_listeners.isEmpty()) {
                     _log.warn("No listeners for incoming message");
-            } else {
-                if (_log.shouldLog(Log.WARN))
-                    _log.warn("No listener found for proto: " + proto + " port: " + toport + " msg id: " + msgId +
+                } else {
+                    _log.warn("No listener found for proto: " + proto + " fromport: " + fromport + " toport: " + toport + " msg id: " + msgId +
                            " from pool of " + _listeners.size() + " listeners");
+                }
+                try {
+                    byte[] msg = session.receiveMessage(msgId);
+                    _log.warn("Message:\n" + net.i2p.util.HexDump.dump(msg));
+                } catch (I2PSessionException ise) {}
+            } else {
+                session.discardMessage(msgId);
             }
-            try {
-                session.receiveMessage(msgId);
-            } catch (I2PSessionException ise) {}
         }
     }
 
diff --git a/core/java/src/net/i2p/client/impl/I2PSessionImpl.java b/core/java/src/net/i2p/client/impl/I2PSessionImpl.java
index 44123f7c2..6dfd60e3f 100644
--- a/core/java/src/net/i2p/client/impl/I2PSessionImpl.java
+++ b/core/java/src/net/i2p/client/impl/I2PSessionImpl.java
@@ -912,6 +912,16 @@ public abstract class I2PSessionImpl implements I2PSession, I2CPMessageReader.I2
         return msg.getPayload().getUnencryptedData();
     }
 
+    /**
+     * Throw away the received message, we don't want it.
+     * Use instead of receiveMessage() to avoid gunzip overhead.
+     *
+     * @since 0.9.71
+     */
+    public void discardMessage(int msgId) {
+        _availableMessages.remove(Long.valueOf(msgId));
+    }
+
     /**
      * Report abuse with regards to the given messageId
      */