fix(networking): align SSU2 and tunnel policy with Java I2P

Implement byte congestion control, adaptive MTU, Java-style transport bids, and randomized profile-driven tunnel selection. Preserve queued SSU2 sends across window pressure and make ACK and release concurrency alias-safe.

Author: lemon-mint

networking/internal/router/ssu2_introduction.go

@@ -219,16 +219,16 @@ func (m *SSU2Manager) forwardRelayStore(job ssu2RelayStoreJob) {
 	store, err := m.cachedSSU2RouterInfoStore(job.aliceInfo, m.now())
 	if err == nil {
 		job.charlie.frameMu.Lock()
-		err = forEachSSU2I2NPFragment(job.charlie.frame[:], store, ssu2SessionPacketSize(job.charlie), func(fragment []byte, last bool) error {
-			return m.sendData(job.charlie, fragment, last)
+		err = forEachSSU2I2NPFragment(job.charlie.frame[:], store, ssu2SessionPacketSize(job.charlie), func(fragment []byte, _ bool) error {
+			return m.sendData(job.charlie, fragment)
 		})
 		job.charlie.frameMu.Unlock()
 	}
 	if err == nil {
 		var intro []byte
 		intro, err = ssu2.MarshalRelayIntroBlock(nil, ssu2.RelayIntro{AliceHash: [32]byte(job.alice.peer), Request: job.request})
 		if err == nil {
-			err = m.sendSessionData(job.charlie, intro, true)
+			err = m.sendSessionData(job.charlie, intro, false)
 		}
 
 	}
@@ -318,7 +318,7 @@ func (m *SSU2Manager) processRelayIntro(bob *ssu2TransportSession, intro ssu2.Re
 		return response, true
 	}
 	block, err := ssu2.MarshalRelayResponseBlock(nil, response)
-	if err != nil || m.sendSessionData(bob, block, true) != nil {
+	if err != nil || m.sendSessionData(bob, block, false) != nil {
 		return response, true
 	}
 	m.sendHolePunch(aliceAddress, intro.Request.Endpoint, response)
@@ -380,7 +380,7 @@ func (m *SSU2Manager) forwardRelayResponse(from *ssu2TransportSession, response
 	}
 	payload, err := ssu2.MarshalBlock(nil, ssu2.BlockRelayResponse, data)
 	if err == nil {
-		_ = m.sendSessionData(forward.alice, payload, true)
+		_ = m.sendSessionData(forward.alice, payload, false)
 	}
 }
 
@@ -444,7 +444,7 @@ func (m *SSU2Manager) sendRelayResponse(session *ssu2TransportSession, bobHash f
 	}
 	payload, err := ssu2.MarshalRelayResponseBlock(nil, response)
 	if err == nil {
-		_ = m.sendSessionData(session, payload, true)
+		_ = m.sendSessionData(session, payload, false)
 	}
 }