From 0a7291e90fa058cc1a7b9ee49bf38271676ed29a Mon Sep 17 00:00:00 2001
From: KokaKiwi <kokakiwi+tor@kokakiwi.net>
Date: Sat, 9 Aug 2025 14:11:54 +0200
Subject: [PATCH] client,proxy: add a media channel

---
 client/lib/util.go     | 11 ++++++++++
 client/lib/webrtc.go   | 46 ++++++++++++++++++++++++++++++++++++++++++
 proxy/lib/snowflake.go | 13 ++++++++++++
 3 files changed, 70 insertions(+)

diff --git a/client/lib/util.go b/client/lib/util.go
index 536fa17..6dbbf2f 100644
--- a/client/lib/util.go
+++ b/client/lib/util.go
@@ -1,7 +1,9 @@
 package snowflake_client
 
 import (
+	"crypto/rand"
 	"log"
+	"math/big"
 	"time"
 )
 
@@ -69,3 +71,12 @@ func (b *bytesSyncLogger) addOutbound(amount int64) {
 func (b *bytesSyncLogger) addInbound(amount int64) {
 	b.inboundChan <- amount
 }
+
+func randomInt(min, max int) int {
+	nBig, err := rand.Int(rand.Reader, big.NewInt(int64(max-min)))
+	if err != nil {
+		panic(err)
+	}
+
+	return int(nBig.Int64()) + min
+}
diff --git a/client/lib/webrtc.go b/client/lib/webrtc.go
index 397ba85..3c12a43 100644
--- a/client/lib/webrtc.go
+++ b/client/lib/webrtc.go
@@ -15,6 +15,7 @@ import (
 	"github.com/pion/transport/v3"
 	"github.com/pion/transport/v3/stdnet"
 	"github.com/pion/webrtc/v4"
+	"github.com/pion/webrtc/v4/pkg/media"
 
 	"gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/v2/common/event"
 	"gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/v2/common/proxy"
@@ -296,6 +297,7 @@ func (c *WebRTCPeer) preparePeerConnection(
 		log.Printf("NewPeerConnection ERROR: %s", err)
 		return err
 	}
+
 	ordered := true
 	dataChannelOptions := &webrtc.DataChannelInit{
 		Ordered: &ordered,
@@ -340,6 +342,8 @@ func (c *WebRTCPeer) preparePeerConnection(
 	c.open = make(chan struct{})
 	log.Println("WebRTC: DataChannel created")
 
+	c.openMediaTrack()
+
 	offer, err := c.pc.CreateOffer(nil)
 	// TODO: Potentially timeout and retry if ICE isn't working.
 	if err != nil {
@@ -365,6 +369,48 @@ func (c *WebRTCPeer) preparePeerConnection(
 	return nil
 }
 
+func (c *WebRTCPeer) openMediaTrack() {
+	videoTrack, err := webrtc.NewTrackLocalStaticSample(
+		webrtc.RTPCodecCapability{MimeType: webrtc.MimeTypeAV1}, "video", "pion",
+	)
+	if err != nil {
+		log.Printf("webrtc.NewTrackLocalStaticSample ERROR: %s", err)
+		return
+	}
+
+	rtpSender, err := c.pc.AddTrack(videoTrack)
+	if err != nil {
+		log.Printf("webrtc.AddTrack ERROR: %s", err)
+		return
+	}
+
+	go func() {
+		rtcpBuf := make([]byte, 1500)
+		for {
+			if _, _, rtcpErr := rtpSender.Read(rtcpBuf); rtcpErr != nil {
+				return
+			}
+		}
+	}()
+
+	go func() {
+		ticker := time.NewTicker(time.Second)
+		defer ticker.Stop()
+
+		for ; true; <-ticker.C {
+			bufSize := randomInt(1000, 2500)
+			buf := make([]byte, bufSize)
+
+			err := videoTrack.WriteSample(media.Sample{Data: buf, Duration: time.Second})
+			if err != nil {
+				log.Printf("webrtc.WriteSample ERROR: %s", err)
+			}
+		}
+	}()
+
+	log.Println("WebRTC: Media track opened")
+}
+
 // cleanup closes all channels and transports
 func (c *WebRTCPeer) cleanup() {
 	// Close this side of the SOCKS pipe.
diff --git a/proxy/lib/snowflake.go b/proxy/lib/snowflake.go
index bcdfbda..4d6881c 100644
--- a/proxy/lib/snowflake.go
+++ b/proxy/lib/snowflake.go
@@ -451,6 +451,19 @@ func (sf *SnowflakeProxy) makePeerConnectionFromOffer(
 		return nil, fmt.Errorf("accept: NewPeerConnection: %s", err)
 	}
 
+	pc.OnTrack(func(remote *webrtc.TrackRemote, receiver *webrtc.RTPReceiver) {
+		log.Printf("Track has started streamId(%s) id(%s) rid(%s) \n", remote.StreamID(), remote.ID(), remote.RID())
+
+		for {
+			rtcpBuf := make([]byte, 1500)
+			for {
+				if _, _, err := receiver.Read(rtcpBuf); err != nil {
+					return
+				}
+			}
+		}
+	})
+
 	pc.OnDataChannel(func(dc *webrtc.DataChannel) {
 		log.Printf("New Data Channel %s-%d\n", dc.Label(), dc.ID())
 		close(dataChan)