UDP packet has timestamp field

UDP::enqueue_ts is filled in
ReceiverSession::route_packet() right before
the packet gets into jitter buffer queue.

src/internal_modules/roc_packet/target_libuv/roc_packet/udp.h

@@ -37,6 +37,11 @@ struct UDP {
     uv_udp_send_t request;
 
     UDP();
+
+    //! It points to a moment when the packet was transferred to a sink-thread, that
+    //! "consumes" this packet. The reason to have it separate is that this allows
+    //! us to account additional jitter introduced by thread-switch time.
+    core::nanoseconds_t enqueue_ts;
 };
 
 } // namespace packet

src/internal_modules/roc_pipeline/receiver_session.cpp

@@ -246,6 +246,7 @@ audio::IFrameReader& ReceiverSession::frame_reader() {
 status::StatusCode ReceiverSession::route_packet(const packet::PacketPtr& packet) {
     roc_panic_if(!is_valid());
 
+    packet->udp()->enqueue_ts = core::timestamp(core::ClockUnix);
     return packet_router_->write(packet);
 }
 

src/tests/roc_rtp/test_link_meter.cpp

@@ -29,9 +29,10 @@ packet::PacketPtr new_packet(packet::seqnum_t sn) {
     packet::PacketPtr packet = packet_factory.new_packet();
     CHECK(packet);
 
-    packet->add_flags(packet::Packet::FlagRTP);
+    packet->add_flags(packet::Packet::FlagRTP | packet::Packet::FlagUDP);
     packet->rtp()->payload_type = PayloadType_L16_Stereo;
     packet->rtp()->seqnum = sn;
+    packet->udp()->enqueue_ts = 666;
 
     return packet;
 }