SSU2: Fix packets exceeding MTU by up to 3 bytes

history.txt

@@ -1,6 +1,9 @@
 2022-08-25 zzz
  * Router: Fix deadlock via rebuildRouterAddress() and UDPTransport
- * SSU2: Implement path challenge and connection migration
+ * SSU2:
+   - Implement path challenge and connection migration
+   - Fix packets exceeding MTU by up to 3 bytes
+   - Immediately fail session request containing zero token
 
 2022-08-23 zzz
  * Router: Add deadlocks to event log

router/java/src/net/i2p/router/RouterVersion.java

@@ -18,7 +18,7 @@ public class RouterVersion {
     /** deprecated */
     public final static String ID = "Git";
     public final static String VERSION = CoreVersion.VERSION;
-    public final static long BUILD = 1;
+    public final static long BUILD = 2;
 
     /** for example "-test" */
     public final static String EXTRA = "";

router/java/src/net/i2p/router/transport/udp/OutboundMessageFragments.java

@@ -463,8 +463,11 @@ class OutboundMessageFragments {
             if (_log.shouldDebug())
                 _log.debug("Building packet for " + next + " to " + peer);
             int curTotalDataSize = state.fragmentSize(next.num);
-            if (next.num > 0 && peer.getVersion() > 1)
-                curTotalDataSize += SSU2Util.DATA_FOLLOWON_EXTRA_SIZE;
+            if (peer.getVersion() > 1) {
+                curTotalDataSize += SSU2Util.FIRST_FRAGMENT_HEADER_SIZE;
+                if (next.num > 0)
+                    curTotalDataSize += SSU2Util.DATA_FOLLOWON_EXTRA_SIZE;
+            }
             // now stuff in more fragments if they fit
             if (i +1 < toSend.size()) {
                 int maxAvail;