X-Git-Url: https://code.octet-stream.net/m17rt/blobdiff_plain/e67ea96c8a3d7c23ba29c6ed91ddb451927176a1..253c89360003ac72c4f7078c03af973c58a1b129:/m17core/src/tnc.rs

diff --git a/m17core/src/tnc.rs b/m17core/src/tnc.rs
index a6af088..7851948 100644
--- a/m17core/src/tnc.rs
+++ b/m17core/src/tnc.rs
@@ -1,38 +1,741 @@
-use crate::protocol::Frame;
+use crate::address::{Address, Callsign};
+use crate::kiss::{KissBuffer, KissFrame, PORT_PACKET_BASIC, PORT_PACKET_FULL, PORT_STREAM};
+use crate::modem::ModulatorFrame;
+use crate::protocol::{
+    Frame, LichCollection, LsfFrame, Mode, PacketFrame, PacketFrameCounter, StreamFrame,
+};
 
 /// Handles the KISS protocol and frame management for `SoftModulator` and `SoftDemodulator`.
 ///
 /// These components work alongside each other. User is responsible for chaining them together
 /// or doing something else with the data.
-pub struct SoftTnc {}
+pub struct SoftTnc {
+    /// Handle framing of KISS commands from the host, which may arrive in arbitrary binary blobs.
+    kiss_buffer: KissBuffer,
+
+    /// Kiss message that needs to be sent to the host.
+    outgoing_kiss: Option<OutgoingKiss>,
+
+    /// Current RX or TX function of the TNC.
+    state: State,
+
+    /// Latest state of data carrier detect from demodulator - controls whether we can go to TX
+    dcd: bool,
+
+    /// Current monotonic time, counted in samples
+    now: u64,
+
+    // TODO: use a static ring buffer crate of some sort?
+    /// Circular buffer of packets enqueued for transmission
+    packet_queue: [PendingPacket; 4],
+
+    /// Next slot to fill
+    packet_next: usize,
+
+    /// Current packet index, which is either partly transmitted or not transmitted at all.
+    packet_curr: usize,
+
+    /// If true, packet_next == packet_curr implies full queue. packet_next is invalid.
+    /// If false, it implies empty queue.
+    packet_full: bool,
+
+    /// The LSF for a stream we are going to start transmitting.
+    ///
+    /// This serves as a general indicator that we want to tx a stream.
+    stream_pending_lsf: Option<LsfFrame>,
+
+    /// Circular buffer of stream data enqueued for transmission.
+    ///
+    /// When the queue empties out, we hope that the last one has the end-of-stream flag set.
+    /// Otherwise a buffer underrun has occurred.
+    ///
+    /// Overruns are less troublesome - we can drop frames and receiving stations should cope.
+    stream_queue: [StreamFrame; 8],
+
+    /// Next slot to fill
+    stream_next: usize,
+
+    /// Current unsent stream frame index
+    stream_curr: usize,
+
+    /// True if stream_next == stream_curr because the queue is full. stream_next is invalid.
+    stream_full: bool,
+
+    /// Should PTT be on right now? Polled by external
+    ptt: bool,
+}
 
 impl SoftTnc {
+    pub fn new() -> Self {
+        Self {
+            kiss_buffer: KissBuffer::new(),
+            outgoing_kiss: None,
+            state: State::Idle,
+            dcd: false,
+            now: 0,
+            packet_queue: Default::default(),
+            packet_next: 0,
+            packet_curr: 0,
+            packet_full: false,
+            stream_pending_lsf: None,
+            stream_queue: Default::default(),
+            stream_next: 0,
+            stream_curr: 0,
+            stream_full: false,
+            ptt: false,
+        }
+    }
+
     /// Process an individual `Frame` that has been decoded by the modem.
-    pub fn handle_frame(&mut self, _frame: Frame) -> Result<(), SoftTncError> {
-        Ok(())
+    pub fn handle_frame(&mut self, frame: Frame) {
+        match frame {
+            Frame::Lsf(lsf) => {
+                // A new LSF implies a clean slate.
+                // If we were partway through decoding something else then we missed it.
+                match lsf.mode() {
+                    Mode::Packet => {
+                        self.state = State::RxPacket(RxPacketState {
+                            lsf,
+                            packet: [0u8; 825],
+                            count: 0,
+                        })
+                    }
+                    Mode::Stream => {
+                        let kiss = KissFrame::new_stream_setup(&lsf.0).unwrap();
+                        self.kiss_to_host(kiss);
+                        self.state = State::RxStream(RxStreamState { lsf, index: 0 });
+                    }
+                }
+            }
+            Frame::Packet(packet) => {
+                match &mut self.state {
+                    State::RxPacket(ref mut rx) => {
+                        match packet.counter {
+                            PacketFrameCounter::Frame { index } => {
+                                if index == rx.count && index < 32 {
+                                    let start = 25 * index;
+                                    rx.packet[start..(start + 25)].copy_from_slice(&packet.payload);
+                                    rx.count += 1;
+                                } else {
+                                    // unexpected order - something has gone wrong
+                                    self.state = State::Idle;
+                                }
+                            }
+                            PacketFrameCounter::FinalFrame { payload_len } => {
+                                let start = 25 * rx.count;
+                                let end = start + payload_len;
+                                rx.packet[start..(start + payload_len)]
+                                    .copy_from_slice(&packet.payload);
+                                // TODO: compatible packets should be sent on port 0 too
+                                let kiss =
+                                    KissFrame::new_full_packet(&rx.lsf.0, &rx.packet[0..end])
+                                        .unwrap();
+                                self.kiss_to_host(kiss);
+                                self.state = State::Idle;
+                            }
+                        }
+                    }
+                    _ => {
+                        // Invalid transition
+                        self.state = State::Idle;
+                    }
+                }
+            }
+            Frame::Stream(stream) => {
+                match &mut self.state {
+                    State::RxStream(ref mut rx) => {
+                        // TODO: consider wraparound from 0x7fff
+                        if stream.frame_number < rx.index {
+                            let mut lich = LichCollection::new();
+                            lich.set_segment(stream.lich_idx, stream.lich_part);
+                            self.state = State::RxAcquiringStream(RxAcquiringStreamState { lich });
+                        } else {
+                            rx.index = stream.frame_number + 1;
+                            let kiss = KissFrame::new_stream_data(&stream).unwrap();
+                            self.kiss_to_host(kiss);
+                            // TODO: end stream if LICH updates indicate non-META part has changed
+                            // (this implies a new station)
+                            if stream.end_of_stream {
+                                self.state = State::Idle;
+                            }
+                        }
+                    }
+                    State::RxAcquiringStream(ref mut rx) => {
+                        rx.lich.set_segment(stream.lich_idx, stream.lich_part);
+                        if let Some(maybe_lsf) = rx.lich.try_assemble() {
+                            let lsf = LsfFrame(maybe_lsf);
+                            // LICH can change mid-transmission so wait until the CRC is correct
+                            // to ensure (to high probability) we haven't done a "torn read"
+                            if lsf.check_crc() == 0 {
+                                let kiss = KissFrame::new_stream_setup(&lsf.0).unwrap();
+                                self.kiss_to_host(kiss);
+                                // TODO: avoid discarding the first data payload here
+                                // need a queue depth of 2 for outgoing kiss
+                                self.state = State::RxStream(RxStreamState {
+                                    lsf,
+                                    index: stream.frame_number + 1,
+                                });
+                            }
+                        }
+                    }
+                    _ => {
+                        // If coming from another state, we have missed something.
+                        // Never mind, let's start tracking LICH.
+                        let mut lich = LichCollection::new();
+                        lich.set_segment(stream.lich_idx, stream.lich_part);
+                        self.state = State::RxAcquiringStream(RxAcquiringStreamState { lich })
+                    }
+                }
+            }
+        }
     }
 
-    ///
-    pub fn advance_samples(&mut self, _samples: u64) {}
+    pub fn set_data_carrier_detect(&mut self, dcd: bool) {
+        self.dcd = dcd;
+    }
 
-    pub fn set_data_carrier_detect(&mut self, _dcd: bool) {}
+    pub fn set_now(&mut self, now_samples: u64) {
+        self.now = now_samples;
+        match self.state {
+            State::TxEndingAtTime(time) => {
+                if now_samples >= time {
+                    self.ptt = false;
+                    self.state = State::Idle;
+                }
+            }
+            _ => (),
+        }
+    }
+
+    pub fn ptt(&self) -> bool {
+        self.ptt
+    }
 
-    pub fn read_tx_frame(&mut self) -> Result<Option<Frame>, SoftTncError> {
-        // yes we want to deal with Frames here
-        // it's important to establish successful decode that SoftDemodulator is aware of the frame innards
-        Ok(None)
+    pub fn set_tx_end_time(&mut self, in_samples: usize) {
+        log::debug!("tnc has been told that tx will complete in {in_samples} samples");
+        match self.state {
+            State::TxEnding => {
+                self.state = State::TxEndingAtTime(self.now + in_samples as u64);
+            }
+            _ => (),
+        }
     }
 
-    pub fn read_kiss(&mut self, _buf: &mut [u8]) -> Result<usize, SoftTncError> {
-        Ok(0)
+    pub fn read_tx_frame(&mut self) -> Option<ModulatorFrame> {
+        match self.state {
+            State::Idle | State::RxAcquiringStream(_) | State::RxStream(_) | State::RxPacket(_) => {
+                // We will let CSMA decide whether to actually go ahead.
+                // That's not implemented yet, so let's just check DCD.
+                let channel_free = !self.dcd;
+                let stream_wants_to_tx = self.stream_pending_lsf.is_some();
+                let packet_wants_to_tx = self.packet_full || (self.packet_next != self.packet_curr);
+                if channel_free && stream_wants_to_tx {
+                    self.state = State::TxStream;
+                } else if channel_free && packet_wants_to_tx {
+                    self.state = State::TxPacket;
+                } else {
+                    return None;
+                }
+                self.ptt = true;
+                // TODO: true txdelay
+                Some(ModulatorFrame::Preamble { tx_delay: 0 })
+            }
+            State::TxStream => {
+                if !self.stream_full && self.stream_next == self.stream_curr {
+                    return None;
+                }
+                if let Some(lsf) = self.stream_pending_lsf.take() {
+                    return Some(ModulatorFrame::Lsf(lsf));
+                }
+                let frame = self.stream_queue[self.stream_curr].clone();
+                if self.stream_full {
+                    self.stream_full = false;
+                }
+                self.stream_curr = (self.stream_curr + 1) % 8;
+                if frame.end_of_stream {
+                    self.state = State::TxStreamSentEndOfStream;
+                }
+                Some(ModulatorFrame::Stream(frame))
+            }
+            State::TxStreamSentEndOfStream => {
+                self.state = State::TxEnding;
+                Some(ModulatorFrame::EndOfTransmission)
+            }
+            State::TxPacket => {
+                if !self.packet_full && self.packet_next == self.packet_curr {
+                    return None;
+                }
+                while self.packet_next != self.packet_curr {
+                    match self.packet_queue[self.packet_curr].next_frame() {
+                        Some(frame) => {
+                            return Some(frame);
+                        }
+                        None => {
+                            self.packet_curr = (self.packet_curr + 1) % 4;
+                        }
+                    }
+                }
+                self.state = State::TxEnding;
+                Some(ModulatorFrame::EndOfTransmission)
+            }
+            State::TxEnding | State::TxEndingAtTime(_) => {
+                // Once we have signalled EOT we withold any new frames until
+                // the channel fully clears and we are ready to TX again
+                None
+            }
+        }
+    }
+
+    /// Read KISS message to be sent to host.
+    ///
+    /// After each frame input, this should be consumed in a loop until length 0 is returned.
+    /// This component will never block. Upstream interface can provide blocking `read()` if desired.
+    pub fn read_kiss(&mut self, target_buf: &mut [u8]) -> usize {
+        match self.outgoing_kiss.as_mut() {
+            Some(outgoing) => {
+                let n = (outgoing.kiss_frame.len - outgoing.sent).min(target_buf.len());
+                target_buf[0..n]
+                    .copy_from_slice(&outgoing.kiss_frame.data[outgoing.sent..(outgoing.sent + n)]);
+                outgoing.sent += n;
+                if outgoing.sent == outgoing.kiss_frame.len {
+                    self.outgoing_kiss = None;
+                }
+                n
+            }
+            None => 0,
+        }
     }
 
-    pub fn write_kiss(&mut self, _buf: &[u8]) -> Result<usize, SoftTncError> {
-        Ok(0)
+    /// Host sends in some KISS data.
+    pub fn write_kiss(&mut self, buf: &[u8]) -> usize {
+        let target_buf = self.kiss_buffer.buf_remaining();
+        let n = buf.len().min(target_buf.len());
+        target_buf[0..n].copy_from_slice(&buf[0..n]);
+        self.kiss_buffer.did_write(n);
+        while let Some(kiss_frame) = self.kiss_buffer.next_frame() {
+            let Ok(port) = kiss_frame.port() else {
+                continue;
+            };
+            if port == PORT_PACKET_BASIC {
+                if self.packet_full {
+                    continue;
+                }
+                let mut pending = PendingPacket::new();
+                pending.app_data[0] = 0x00; // RAW
+                let Ok(mut len) = kiss_frame.decode_payload(&mut pending.app_data[1..]) else {
+                    continue;
+                };
+                len += 1; // for RAW prefix
+                let packet_crc = crate::crc::m17_crc(&pending.app_data[0..len]);
+                pending.app_data[len..len + 2].copy_from_slice(&packet_crc.to_be_bytes());
+                pending.app_data_len = len + 2;
+                pending.lsf = Some(LsfFrame::new_packet(
+                    &Address::Callsign(Callsign(b"M17RT-PKT".clone())),
+                    &Address::Broadcast,
+                ));
+                self.packet_queue[self.packet_next] = pending;
+                self.packet_next = (self.packet_next + 1) % 4;
+                if self.packet_next == self.packet_curr {
+                    self.packet_full = true;
+                }
+            } else if port == PORT_PACKET_FULL {
+                if self.packet_full {
+                    continue;
+                }
+                let mut pending = PendingPacket::new();
+                let mut payload = [0u8; 855];
+                let Ok(len) = kiss_frame.decode_payload(&mut payload) else {
+                    continue;
+                };
+                if len < 33 {
+                    continue;
+                }
+                let mut lsf = LsfFrame([0u8; 30]);
+                lsf.0.copy_from_slice(&payload[0..30]);
+                if lsf.check_crc() != 0 {
+                    continue;
+                }
+                pending.lsf = Some(lsf);
+                let app_data_len = len - 30;
+                pending.app_data[0..app_data_len].copy_from_slice(&payload[30..]);
+                pending.app_data_len = app_data_len;
+                self.packet_queue[self.packet_next] = pending;
+                self.packet_next = (self.packet_next + 1) % 4;
+                if self.packet_next == self.packet_curr {
+                    self.packet_full = true;
+                }
+            } else if port == PORT_STREAM {
+                let mut payload = [0u8; 30];
+                let Ok(len) = kiss_frame.decode_payload(&mut payload) else {
+                    continue;
+                };
+                if len < 26 {
+                    log::debug!("payload len too short");
+                    continue;
+                }
+                if len == 30 {
+                    let lsf = LsfFrame(payload);
+                    if lsf.check_crc() != 0 {
+                        continue;
+                    }
+                    self.stream_pending_lsf = Some(lsf);
+                } else {
+                    if self.stream_full {
+                        log::debug!("stream full");
+                        continue;
+                    }
+                    let frame_num_part = u16::from_be_bytes([payload[6], payload[7]]);
+                    self.stream_queue[self.stream_next] = StreamFrame {
+                        lich_idx: payload[5] >> 5,
+                        lich_part: payload[0..5].try_into().unwrap(),
+                        frame_number: frame_num_part & 0x7fff,
+                        end_of_stream: frame_num_part & 0x8000 > 0,
+                        stream_data: payload[8..24].try_into().unwrap(),
+                    };
+                    self.stream_next = (self.stream_next + 1) % 8;
+                    if self.stream_next == self.stream_curr {
+                        self.stream_full = true;
+                    }
+                }
+            }
+        }
+        n
+    }
+
+    fn kiss_to_host(&mut self, kiss_frame: KissFrame) {
+        self.outgoing_kiss = Some(OutgoingKiss {
+            kiss_frame,
+            sent: 0,
+        });
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, PartialEq, Eq, Clone)]
 pub enum SoftTncError {
     General(&'static str),
+    InvalidState,
+}
+
+struct OutgoingKiss {
+    kiss_frame: KissFrame,
+    sent: usize,
+}
+
+enum State {
+    /// Nothing happening. We may have TX data queued but we won't act on it until CSMA opens up.
+    Idle,
+
+    /// We received some stream data but missed the leading LSF so we are trying to assemble from LICH.
+    RxAcquiringStream(RxAcquiringStreamState),
+
+    /// We have acquired an identified stream transmission and are sending data payloads to the host.
+    RxStream(RxStreamState),
+
+    /// We are receiving a packet. All is well so far, and there is more data to come before we tell the host.
+    RxPacket(RxPacketState),
+
+    /// PTT is on and this is a stream-type transmission. New data may be added.
+    TxStream,
+
+    /// We have delivered the last frame in the current stream
+    TxStreamSentEndOfStream,
+
+    /// PTT is on and this is a packet-type transmission. New packets may be enqueued.
+    TxPacket,
+
+    /// We gave modulator an EndOfTransmission. PTT is still on, waiting for modulator to advise end time.
+    TxEnding,
+
+    /// Ending transmission, PTT remains on, but we know the timestamp at which we should disengage it.
+    TxEndingAtTime(u64),
+}
+
+struct RxAcquiringStreamState {
+    /// Partial assembly of LSF by accumulating LICH fields.
+    lich: LichCollection,
+}
+
+struct RxStreamState {
+    /// Track identifying information for this transmission so we can tell if it changes.
+    lsf: LsfFrame,
+
+    /// Expected next frame number. Allowed to skip values on RX, but not go backwards.
+    index: u16,
+}
+
+struct RxPacketState {
+    /// Initial LSF
+    lsf: LsfFrame,
+
+    /// Accumulation of packet data that we have received so far.
+    packet: [u8; 825],
+
+    /// Number of payload frames we have received. If we are stably in the RxPacket state,
+    /// this will be between 0 and 32 inclusive.
+    count: usize,
+}
+
+struct PendingPacket {
+    lsf: Option<LsfFrame>,
+
+    app_data: [u8; 825],
+    app_data_len: usize,
+    app_data_transmitted: usize,
+}
+
+impl PendingPacket {
+    fn new() -> Self {
+        Self {
+            lsf: None,
+            app_data: [0u8; 825],
+            app_data_len: 0,
+            app_data_transmitted: 0,
+        }
+    }
+
+    /// Returns next frame, not including preamble or EOT.
+    ///
+    /// False means all data frames have been sent.
+    fn next_frame(&mut self) -> Option<ModulatorFrame> {
+        if let Some(lsf) = self.lsf.take() {
+            return Some(ModulatorFrame::Lsf(lsf));
+        }
+        if self.app_data_len == self.app_data_transmitted {
+            return None;
+        }
+        let remaining = self.app_data_len - self.app_data_transmitted;
+        let (counter, data_len) = if remaining <= 25 {
+            (
+                PacketFrameCounter::FinalFrame {
+                    payload_len: remaining,
+                },
+                remaining,
+            )
+        } else {
+            (
+                PacketFrameCounter::Frame {
+                    index: self.app_data_transmitted / 25,
+                },
+                25,
+            )
+        };
+        let mut payload = [0u8; 25];
+        payload.copy_from_slice(
+            &self.app_data[self.app_data_transmitted..(self.app_data_transmitted + data_len)],
+        );
+        self.app_data_transmitted += data_len;
+        Some(ModulatorFrame::Packet(PacketFrame { payload, counter }))
+    }
+}
+
+impl Default for PendingPacket {
+    fn default() -> Self {
+        Self {
+            lsf: None,
+            app_data: [0u8; 825],
+            app_data_len: 0,
+            app_data_transmitted: 0,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::kiss::{KissCommand, PORT_STREAM};
+    use crate::protocol::StreamFrame;
+
+    // TODO: finish all handle_frame tests as below
+    // this will be much more straightforward when we have a way to create LSFs programatically
+
+    // receiving a single-frame packet
+
+    // receiving a multi-frame packet
+
+    // part of one packet and then another
+
+    #[test]
+    fn tnc_receive_stream() {
+        let lsf = LsfFrame([
+            255, 255, 255, 255, 255, 255, 0, 0, 0, 159, 221, 81, 5, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 131, 53,
+        ]);
+        let stream1 = StreamFrame {
+            lich_idx: 0,
+            lich_part: [255, 255, 255, 255, 255],
+            frame_number: 0,
+            end_of_stream: false,
+            stream_data: [
+                128, 0, 119, 115, 220, 252, 41, 235, 8, 0, 116, 195, 94, 244, 45, 75,
+            ],
+        };
+        let stream2 = StreamFrame {
+            lich_idx: 1,
+            lich_part: [255, 0, 0, 0, 159],
+            frame_number: 1,
+            end_of_stream: true,
+            stream_data: [
+                17, 0, 94, 82, 216, 135, 181, 15, 30, 0, 125, 195, 152, 183, 41, 57,
+            ],
+        };
+        let mut tnc = SoftTnc::new();
+        let mut kiss = KissFrame::new_empty();
+        assert_eq!(tnc.read_kiss(&mut kiss.data), 0);
+
+        tnc.handle_frame(Frame::Lsf(lsf));
+        kiss.len = tnc.read_kiss(&mut kiss.data);
+        assert_eq!(kiss.command().unwrap(), KissCommand::DataFrame);
+        assert_eq!(kiss.port().unwrap(), PORT_STREAM);
+
+        let mut payload_buf = [0u8; 2048];
+        let n = kiss.decode_payload(&mut payload_buf).unwrap();
+        assert_eq!(n, 30);
+
+        tnc.handle_frame(Frame::Stream(stream1));
+        kiss.len = tnc.read_kiss(&mut kiss.data);
+        assert_eq!(kiss.command().unwrap(), KissCommand::DataFrame);
+        assert_eq!(kiss.port().unwrap(), PORT_STREAM);
+
+        let n = kiss.decode_payload(&mut payload_buf).unwrap();
+        assert_eq!(n, 26);
+
+        tnc.handle_frame(Frame::Stream(stream2));
+        kiss.len = tnc.read_kiss(&mut kiss.data);
+        assert_eq!(kiss.command().unwrap(), KissCommand::DataFrame);
+        assert_eq!(kiss.port().unwrap(), PORT_STREAM);
+
+        let n = kiss.decode_payload(&mut payload_buf).unwrap();
+        assert_eq!(n, 26);
+    }
+
+    #[test]
+    fn tnc_acquire_stream() {
+        let frames = [
+            StreamFrame {
+                lich_idx: 0,
+                lich_part: [255, 255, 255, 255, 255],
+                frame_number: 0,
+                end_of_stream: false,
+                stream_data: [
+                    128, 0, 119, 115, 220, 252, 41, 235, 8, 0, 116, 195, 94, 244, 45, 75,
+                ],
+            },
+            StreamFrame {
+                lich_idx: 1,
+                lich_part: [255, 0, 0, 0, 159],
+                frame_number: 1,
+                end_of_stream: false,
+                stream_data: [
+                    17, 0, 94, 82, 216, 135, 181, 15, 30, 0, 125, 195, 152, 183, 41, 57,
+                ],
+            },
+            StreamFrame {
+                lich_idx: 2,
+                lich_part: [221, 81, 5, 5, 0],
+                frame_number: 2,
+                end_of_stream: false,
+                stream_data: [
+                    17, 128, 93, 74, 154, 167, 169, 11, 20, 0, 116, 91, 158, 220, 45, 111,
+                ],
+            },
+            StreamFrame {
+                lich_idx: 3,
+                lich_part: [0, 0, 0, 0, 0],
+                frame_number: 3,
+                end_of_stream: false,
+                stream_data: [
+                    15, 128, 114, 83, 218, 252, 59, 111, 31, 128, 116, 91, 84, 231, 45, 105,
+                ],
+            },
+            StreamFrame {
+                lich_idx: 4,
+                lich_part: [0, 0, 0, 0, 0],
+                frame_number: 4,
+                end_of_stream: false,
+                stream_data: [
+                    9, 128, 119, 115, 220, 220, 57, 15, 48, 128, 124, 83, 158, 236, 181, 91,
+                ],
+            },
+            StreamFrame {
+                lich_idx: 5,
+                lich_part: [0, 0, 0, 131, 53],
+                frame_number: 5,
+                end_of_stream: false,
+                stream_data: [
+                    52, 0, 116, 90, 152, 167, 225, 216, 32, 0, 116, 83, 156, 212, 33, 216,
+                ],
+            },
+        ];
+
+        let mut tnc = SoftTnc::new();
+        let mut kiss = KissFrame::new_empty();
+        for f in frames {
+            tnc.handle_frame(Frame::Stream(f));
+        }
+        kiss.len = tnc.read_kiss(&mut kiss.data);
+        let mut payload_buf = [0u8; 2048];
+        let n = kiss.decode_payload(&mut payload_buf).unwrap();
+        assert_eq!(n, 30);
+        assert_eq!(
+            &payload_buf[0..30],
+            [
+                255, 255, 255, 255, 255, 255, 0, 0, 0, 159, 221, 81, 5, 5, 0, 0, 0, 0, 0, 0, 0, 0,
+                0, 0, 0, 0, 0, 0, 131, 53,
+            ]
+        );
+    }
+
+    #[test]
+    fn tnc_handle_skipped_stream_frame() {
+        let lsf = LsfFrame([
+            255, 255, 255, 255, 255, 255, 0, 0, 0, 159, 221, 81, 5, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 131, 53,
+        ]);
+        let stream1 = StreamFrame {
+            lich_idx: 0,
+            lich_part: [255, 255, 255, 255, 255],
+            frame_number: 0,
+            end_of_stream: false,
+            stream_data: [
+                128, 0, 119, 115, 220, 252, 41, 235, 8, 0, 116, 195, 94, 244, 45, 75,
+            ],
+        };
+        let stream3 = StreamFrame {
+            lich_idx: 2,
+            lich_part: [221, 81, 5, 5, 0],
+            frame_number: 2,
+            end_of_stream: false,
+            stream_data: [
+                17, 128, 93, 74, 154, 167, 169, 11, 20, 0, 116, 91, 158, 220, 45, 111,
+            ],
+        };
+        let mut tnc = SoftTnc::new();
+        let mut kiss = KissFrame::new_empty();
+        assert_eq!(tnc.read_kiss(&mut kiss.data), 0);
+
+        tnc.handle_frame(Frame::Lsf(lsf));
+        kiss.len = tnc.read_kiss(&mut kiss.data);
+        assert_eq!(kiss.command().unwrap(), KissCommand::DataFrame);
+        assert_eq!(kiss.port().unwrap(), PORT_STREAM);
+
+        let mut payload_buf = [0u8; 2048];
+        let n = kiss.decode_payload(&mut payload_buf).unwrap();
+        assert_eq!(n, 30);
+
+        tnc.handle_frame(Frame::Stream(stream1));
+        kiss.len = tnc.read_kiss(&mut kiss.data);
+        assert_eq!(kiss.command().unwrap(), KissCommand::DataFrame);
+        assert_eq!(kiss.port().unwrap(), PORT_STREAM);
+
+        let n = kiss.decode_payload(&mut payload_buf).unwrap();
+        assert_eq!(n, 26);
+
+        tnc.handle_frame(Frame::Stream(stream3));
+        kiss.len = tnc.read_kiss(&mut kiss.data);
+        assert_eq!(kiss.command().unwrap(), KissCommand::DataFrame);
+        assert_eq!(kiss.port().unwrap(), PORT_STREAM);
+
+        let n = kiss.decode_payload(&mut payload_buf).unwrap();
+        assert_eq!(n, 26);
+    }
 }