peer_connection: Make sure all packets are read through interceptor

Instead of reading first packet when probing simulcast directly from RTP
stream, rather let SRTP session accept() fn return the RTP header for
the first packet. This makes us able to configure interceptor and let
all packets travel through the regular path.

Fixes #391

srtp/src/session/mod.rs

@@ -28,7 +28,7 @@ const DEFAULT_SESSION_SRTCP_REPLAY_PROTECTION_WINDOW: usize = 64;
 pub struct Session {
     local_context: Arc<Mutex<Context>>,
     streams_map: Arc<Mutex<HashMap<u32, Arc<Stream>>>>,
-    new_stream_rx: Arc<Mutex<mpsc::Receiver<Arc<Stream>>>>,
+    new_stream_rx: Arc<Mutex<mpsc::Receiver<(Arc<Stream>, Option<rtp::header::Header>)>>>,
     close_stream_tx: mpsc::Sender<u32>,
     close_session_tx: mpsc::Sender<()>,
     pub(crate) udp_tx: Arc<dyn Conn + Send + Sync>,
@@ -128,7 +128,7 @@ impl Session {
         buf: &mut [u8],
         streams_map: &Arc<Mutex<HashMap<u32, Arc<Stream>>>>,
         close_stream_tx: &mpsc::Sender<u32>,
-        new_stream_tx: &mut mpsc::Sender<Arc<Stream>>,
+        new_stream_tx: &mut mpsc::Sender<(Arc<Stream>, Option<rtp::header::Header>)>,
         remote_context: &mut Context,
         is_rtp: bool,
     ) -> Result<()> {
@@ -144,24 +144,28 @@ impl Session {
         };
 
         let mut buf = &decrypted[..];
-        let ssrcs = if is_rtp {
-            vec![rtp::header::Header::unmarshal(&mut buf)?.ssrc]
+        let (ssrcs, header) = if is_rtp {
+            let header = rtp::header::Header::unmarshal(&mut buf)?;
+            (vec![header.ssrc], Some(header))
         } else {
             let pkts = rtcp::packet::unmarshal(&mut buf)?;
-            destination_ssrc(&pkts)
+            (destination_ssrc(&pkts), None)
         };
 
         for ssrc in ssrcs {
             let (stream, is_new) =
                 Session::get_or_create_stream(streams_map, close_stream_tx.clone(), is_rtp, ssrc)
                     .await;
+
             if is_new {
                 log::trace!(
                     "srtp session got new {} stream {}",
                     if is_rtp { "rtp" } else { "rtcp" },
                     ssrc
                 );
-                new_stream_tx.send(Arc::clone(&stream)).await?;
+                new_stream_tx
+                    .send((Arc::clone(&stream), header.clone()))
+                    .await?;
             }
 
             match stream.buffer.write(&decrypted).await {
@@ -210,14 +214,13 @@ impl Session {
     }
 
     /// accept returns a stream to handle RTCP for a single SSRC
-    pub async fn accept(&self) -> Result<Arc<Stream>> {
+    pub async fn accept(&self) -> Result<(Arc<Stream>, Option<rtp::header::Header>)> {
         let mut new_stream_rx = self.new_stream_rx.lock().await;
-        let result = new_stream_rx.recv().await;
-        if let Some(stream) = result {
-            Ok(stream)
-        } else {
-            Err(Error::SessionSrtpAlreadyClosed)
-        }
+
+        new_stream_rx
+            .recv()
+            .await
+            .ok_or(Error::SessionSrtpAlreadyClosed)
     }
 
     pub async fn close(&self) -> Result<()> {

srtp/src/session/session_rtcp_test.rs

@@ -84,7 +84,7 @@ async fn test_session_srtcp_accept() -> Result<()> {
     let test_payload = rtcp_packet.marshal()?;
     sa.write_rtcp(&rtcp_packet).await?;
 
-    let read_stream = sb.accept().await?;
+    let (read_stream, _) = sb.accept().await?;
     let ssrc = read_stream.get_ssrc();
     assert_eq!(
         ssrc, TEST_SSRC,

srtp/src/session/session_rtp_test.rs

@@ -86,19 +86,22 @@ async fn test_session_srtp_accept() -> Result<()> {
 
     let packet = rtp::packet::Packet {
         header: rtp::header::Header {
+            version: 2,
             ssrc: TEST_SSRC,
+            payload_type: 96,
             ..Default::default()
         },
         payload: test_payload.clone(),
     };
     sa.write_rtp(&packet).await?;
 
-    let read_stream = sb.accept().await?;
+    let (read_stream, header) = sb.accept().await?;
     let ssrc = read_stream.get_ssrc();
     assert_eq!(
         ssrc, TEST_SSRC,
         "SSRC mismatch during accept exp({TEST_SSRC}) actual({ssrc})"
     );
+    assert_eq!(header, Some(packet.header));
 
     read_stream.read(&mut read_buffer).await?;
 

webrtc/src/peer_connection/mod.rs

@@ -81,8 +81,7 @@ use crate::rtp_transceiver::rtp_receiver::RTCRtpReceiver;
 use crate::rtp_transceiver::rtp_sender::RTCRtpSender;
 use crate::rtp_transceiver::rtp_transceiver_direction::RTCRtpTransceiverDirection;
 use crate::rtp_transceiver::{
-    find_by_mid, handle_unknown_rtp_packet, satisfy_type_and_direction, RTCRtpTransceiver,
-    RTCRtpTransceiverInit, SSRC,
+    find_by_mid, satisfy_type_and_direction, RTCRtpTransceiver, RTCRtpTransceiverInit, SSRC,
 };
 use crate::sctp_transport::sctp_transport_capabilities::SCTPTransportCapabilities;
 use crate::sctp_transport::sctp_transport_state::RTCSctpTransportState;

webrtc/src/peer_connection/peer_connection_internal.rs

@@ -2,7 +2,7 @@ use std::collections::VecDeque;
 use std::sync::Weak;
 
 use super::*;
-use crate::rtp_transceiver::create_stream_info;
+use crate::rtp_transceiver::{create_stream_info, PayloadType};
 use crate::stats::stats_collector::StatsCollector;
 use crate::stats::{
     InboundRTPStats, OutboundRTPStats, RTCStatsType, RemoteInboundRTPStats, RemoteOutboundRTPStats,
@@ -15,7 +15,6 @@ use arc_swap::ArcSwapOption;
 use portable_atomic::AtomicIsize;
 use smol_str::SmolStr;
 use tokio::time::Instant;
-use util::Unmarshal;
 
 pub(crate) struct PeerConnectionInternal {
     /// a value containing the last known greater mid value
@@ -309,8 +308,12 @@ impl PeerConnectionInternal {
                     }
                 };
 
-                let stream = match srtp_session.accept().await {
-                    Ok(stream) => stream,
+                let (stream, header) = match srtp_session.accept().await {
+                    Ok((stream, Some(header))) => (stream, header),
+                    Ok((_, None)) => {
+                        log::error!("Accepting RTP session, without RTP header?");
+                        return;
+                    }
                     Err(err) => {
                         log::warn!("Failed to accept RTP {}", err);
                         return;
@@ -338,16 +341,16 @@ impl PeerConnectionInternal {
                     let pci = Arc::clone(&pci);
                     tokio::spawn(async move {
                         let ssrc = stream.get_ssrc();
-
                         dtls_transport
                             .store_simulcast_stream(ssrc, Arc::clone(&stream))
                             .await;
 
-                        if let Err(err) = pci.handle_incoming_ssrc(stream, ssrc).await {
+                        if let Err(err) = pci
+                            .handle_incoming_rtp_stream(stream, header.payload_type)
+                            .await
+                        {
                             log::warn!(
-                                "Incoming unhandled RTP ssrc({}), on_track will not be fired. {}",
-                                ssrc,
-                                err
+                                "Incoming unhandled RTP ssrc({ssrc}), on_track will not be fired. {err}"
                             );
                         }
 
@@ -370,17 +373,18 @@ impl PeerConnectionInternal {
                         }
                     };
 
-                    let stream = match srtcp_session.accept().await {
-                        Ok(stream) => stream,
+                    match srtcp_session.accept().await {
+                        Ok((stream, _)) => {
+                            let ssrc = stream.get_ssrc();
+                            log::warn!(
+                                "Incoming unhandled RTCP ssrc({ssrc}), on_track will not be fired"
+                            );
+                        }
                         Err(err) => {
-                            log::warn!("Failed to accept RTCP {}", err);
+                            log::warn!("Failed to accept RTCP {err}");
                             return;
                         }
                     };
-                    log::warn!(
-                        "Incoming unhandled RTCP ssrc({}), on_track will not be fired",
-                        stream.get_ssrc()
-                    );
                 }
             });
         }
@@ -1002,18 +1006,18 @@ impl PeerConnectionInternal {
         Ok(true)
     }
 
-    async fn handle_incoming_ssrc(
+    async fn handle_incoming_rtp_stream(
         self: &Arc<Self>,
         rtp_stream: Arc<Stream>,
-        ssrc: SSRC,
+        payload_type: PayloadType,
     ) -> Result<()> {
+        let ssrc = rtp_stream.get_ssrc();
         let parsed = match self.remote_description().await.and_then(|rd| rd.parsed) {
             Some(r) => r,
             None => return Err(Error::ErrPeerConnRemoteDescriptionNil),
         };
         // If the remote SDP was only one media section the ssrc doesn't have to be explicitly declared
-        let handled = self.handle_undeclared_ssrc(ssrc, &parsed).await?;
-        if handled {
+        if self.handle_undeclared_ssrc(ssrc, &parsed).await? {
             return Ok(());
         }
 
@@ -1046,26 +1050,6 @@ impl PeerConnectionInternal {
             })
             .await;
 
-        // Packets that we read as part of simulcast probing that we need to make available
-        // if we do find a track later.
-        let mut buffered_packets: VecDeque<(rtp::packet::Packet, Attributes)> = VecDeque::default();
-
-        let mut buf = vec![0u8; self.setting_engine.get_receive_mtu()];
-        let n = rtp_stream.read(&mut buf).await?;
-        let mut b = &buf[..n];
-
-        let (mut mid, mut rid, mut rsid, payload_type) = handle_unknown_rtp_packet(
-            b,
-            mid_extension_id as u8,
-            sid_extension_id as u8,
-            rsid_extension_id as u8,
-        )?;
-
-        let packet = rtp::packet::Packet::unmarshal(&mut b).unwrap();
-
-        // TODO: Can we have attributes on the first packets?
-        buffered_packets.push_back((packet, Attributes::new()));
-
         let params = self
             .media_engine
             .get_rtp_parameters_by_payload_type(payload_type)
@@ -1089,21 +1073,24 @@ impl PeerConnectionInternal {
             .streams_for_ssrc(ssrc, &stream_info, &icpr)
             .await?;
 
-        let a = Attributes::new();
+        // Packets that we read as part of simulcast probing that we need to make available
+        // if we do find a track later.
+        let mut buffered_packets: VecDeque<(rtp::packet::Packet, Attributes)> = VecDeque::default();
+        let mut buf = vec![0u8; self.setting_engine.get_receive_mtu()];
+
         for _ in 0..=SIMULCAST_PROBE_COUNT {
+            let (pkt, a) = rtp_interceptor
+                .read(&mut buf, &stream_info.attributes)
+                .await?;
+            let (mid, rid, rsid) = get_stream_mid_rid(
+                &pkt.header,
+                mid_extension_id as u8,
+                sid_extension_id as u8,
+                rsid_extension_id as u8,
+            )?;
+            buffered_packets.push_back((pkt, a.clone()));
+
             if mid.is_empty() || (rid.is_empty() && rsid.is_empty()) {
-                let (pkt, _) = rtp_interceptor.read(&mut buf, &a).await?;
-                let (m, r, rs, _) = handle_unknown_rtp_packet(
-                    &buf[..n],
-                    mid_extension_id as u8,
-                    sid_extension_id as u8,
-                    rsid_extension_id as u8,
-                )?;
-                mid = m;
-                rid = r;
-                rsid = rs;
-
-                buffered_packets.push_back((pkt, a.clone()));
                 continue;
             }
 
@@ -1544,3 +1531,34 @@ fn capitalize(s: &str) -> String {
 
     result
 }
+
+fn get_stream_mid_rid(
+    header: &rtp::header::Header,
+    mid_extension_id: u8,
+    sid_extension_id: u8,
+    rsid_extension_id: u8,
+) -> Result<(String, String, String)> {
+    if !header.extension {
+        return Ok((String::new(), String::new(), String::new()));
+    }
+
+    let mid = if let Some(payload) = header.get_extension(mid_extension_id) {
+        String::from_utf8(payload.to_vec())?
+    } else {
+        String::new()
+    };
+
+    let rid = if let Some(payload) = header.get_extension(sid_extension_id) {
+        String::from_utf8(payload.to_vec())?
+    } else {
+        String::new()
+    };
+
+    let srid = if let Some(payload) = header.get_extension(rsid_extension_id) {
+        String::from_utf8(payload.to_vec())?
+    } else {
+        String::new()
+    };
+
+    Ok((mid, rid, srid))
+}

webrtc/src/rtp_transceiver/mod.rs

@@ -14,7 +14,6 @@ use portable_atomic::{AtomicBool, AtomicU8};
 use serde::{Deserialize, Serialize};
 use smol_str::SmolStr;
 use tokio::sync::{Mutex, OnceCell};
-use util::Unmarshal;
 
 use crate::api::media_engine::MediaEngine;
 use crate::error::{Error, Result};
@@ -523,41 +522,3 @@ pub(crate) async fn satisfy_type_and_direction(
 
     None
 }
-
-/// handle_unknown_rtp_packet consumes a single RTP Packet and returns information that is helpful
-/// for demuxing and handling an unknown SSRC (usually for Simulcast)
-pub(crate) fn handle_unknown_rtp_packet(
-    buf: &[u8],
-    mid_extension_id: u8,
-    sid_extension_id: u8,
-    rsid_extension_id: u8,
-) -> Result<(String, String, String, PayloadType)> {
-    let mut reader = buf;
-    let rp = rtp::packet::Packet::unmarshal(&mut reader)?;
-
-    if !rp.header.extension {
-        return Ok((String::new(), String::new(), String::new(), 0));
-    }
-
-    let payload_type = rp.header.payload_type;
-
-    let mid = if let Some(payload) = rp.header.get_extension(mid_extension_id) {
-        String::from_utf8(payload.to_vec())?
-    } else {
-        String::new()
-    };
-
-    let rid = if let Some(payload) = rp.header.get_extension(sid_extension_id) {
-        String::from_utf8(payload.to_vec())?
-    } else {
-        String::new()
-    };
-
-    let srid = if let Some(payload) = rp.header.get_extension(rsid_extension_id) {
-        String::from_utf8(payload.to_vec())?
-    } else {
-        String::new()
-    };
-
-    Ok((mid, rid, srid, payload_type))
-}