From 3eb4083cb3d18dfb57eadc467dabd6d280a05d14 Mon Sep 17 00:00:00 2001
From: zzz <zzz@i2pmail.org>
Date: Thu, 15 Dec 2022 14:50:38 -0500
Subject: [PATCH] SSU2: Fix retransmission of session confirmed

Was setting packet length to number of packets.
Add check and log in UDPSender
Add notes where length is checked
---
 .../src/net/i2p/router/transport/udp/PacketHandler.java     | 3 +--
 .../java/src/net/i2p/router/transport/udp/PeerState2.java   | 6 ++++--
 router/java/src/net/i2p/router/transport/udp/UDPSender.java | 2 ++
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/router/java/src/net/i2p/router/transport/udp/PacketHandler.java b/router/java/src/net/i2p/router/transport/udp/PacketHandler.java
index 7cfb8b4a4..c7c87930b 100644
--- a/router/java/src/net/i2p/router/transport/udp/PacketHandler.java
+++ b/router/java/src/net/i2p/router/transport/udp/PacketHandler.java
@@ -946,8 +946,7 @@ class PacketHandler {
                 // Session Confirmed or retransmitted Session Request or Token Request
                 header = SSU2Header.trialDecryptShortHeader(packet, k1, k2);
                 if (header == null) {
-                    // too short, perhaps SSU 1/2 confusion?
-                    // Java 0.9.55 short destroy bug?
+                    // Java I2P thru 0.9.56 retransmits session confirmed with 1-2 byte packets
                     if (_log.shouldWarn())
                         _log.warn("Session Confirmed too short len: " +
                                   + packet.getPacket().getLength() + " on " + state);
diff --git a/router/java/src/net/i2p/router/transport/udp/PeerState2.java b/router/java/src/net/i2p/router/transport/udp/PeerState2.java
index 89a20ceca..fab15c08a 100644
--- a/router/java/src/net/i2p/router/transport/udp/PeerState2.java
+++ b/router/java/src/net/i2p/router/transport/udp/PeerState2.java
@@ -407,7 +407,9 @@ public class PeerState2 extends PeerState implements SSU2Payload.PayloadCallback
         try {
             SSU2Header.Header header = SSU2Header.trialDecryptShortHeader(packet, _rcvHeaderEncryptKey1, _rcvHeaderEncryptKey2);
             if (header == null) {
-                if (_log.shouldWarn())
+                // Java I2P thru 0.9.55 would send 35-39 byte ping packets
+                // Java I2P thru 0.9.56 retransmits session confirmed with 1-2 byte packets
+                if (len > 2 && len < 35 && _log.shouldWarn())
                     _log.warn("Inbound packet too short " + len + " on " + this);
                 return;
             }
@@ -1024,7 +1026,7 @@ public class PeerState2 extends PeerState implements SSU2Payload.PayloadCallback
             byte data[] = pkt.getData();
             int off = pkt.getOffset();
             System.arraycopy(_sessConfForReTX[i], 0, data, off, _sessConfForReTX[i].length);
-            pkt.setLength(_sessConfForReTX.length);
+            pkt.setLength(_sessConfForReTX[i].length);
             pkt.setAddress(addr);
             pkt.setPort(_remotePort);
             packet.setMessageType(PacketBuilder2.TYPE_CONF);
diff --git a/router/java/src/net/i2p/router/transport/udp/UDPSender.java b/router/java/src/net/i2p/router/transport/udp/UDPSender.java
index 3a164a467..87283721d 100644
--- a/router/java/src/net/i2p/router/transport/udp/UDPSender.java
+++ b/router/java/src/net/i2p/router/transport/udp/UDPSender.java
@@ -196,6 +196,8 @@ class UDPSender {
             _log.error("Dropping large UDP packet " + psz + " bytes: " + packet, new Exception());
             return;
         }
+        if (psz > 0 && psz < SSU2Util.MIN_DATA_LEN && _log.shouldWarn())
+            _log.warn("Small UDP packet " + psz + " bytes: " + packet, new Exception());
         if (_dummy) {
             // testing
             // back to the cache