rusty_cotp/
service.rs

1use std::collections::VecDeque;
2
3use bytes::BytesMut;
4use rusty_tpkt::{ProtocolInformation, TpktConnection, TpktReader, TpktWriter};
5
6use crate::{
7    CotpConnectionParameters, api::{CotpConnection, CotpError, CotpProtocolInformation, CotpReader, CotpResponder, CotpWriter}, packet::{
8        connection_confirm::ConnectionConfirm,
9        connection_request::ConnectionRequest,
10        data_transfer::DataTransfer,
11        parameters::{ConnectionClass, CotpParameter, TpduSize},
12        payload::TransportProtocolDataUnit,
13    }, parser::packet::TransportProtocolDataUnitParser, serialiser::packet::serialise
14};
15
16/// A COTP connection provides a packet based data exchange mechanism.
17/// 
18/// Initiator connections may be initiated via this struct. To act as a responder, the acceptor class should be used.
19pub struct RustyCotpConnection<R: TpktReader, W: TpktWriter> {
20    reader: R,
21    writer: W,
22
23    max_payload_size: usize,
24    parser: TransportProtocolDataUnitParser,
25    connection_options: CotpConnectionParameters,
26    protocol_infomation_list: Vec<Box<dyn ProtocolInformation>>,
27}
28
29impl<R: TpktReader, W: TpktWriter> RustyCotpConnection<R, W> {
30    /// Initiates a connection to a responder COTP service.
31    pub async fn initiate(connection: impl TpktConnection, options: CotpProtocolInformation, connection_options: CotpConnectionParameters) -> Result<RustyCotpConnection<impl TpktReader, impl TpktWriter>, CotpError> {
32        // FIXME WARN Log the differences between remote and local parameters.
33        let mut protocol_infomation_list = connection.get_protocol_infomation_list().clone();
34        let local_calling_tsap = options.calling_tsap_id().cloned();
35
36        let source_reference: u16 = options.initiator_reference();
37        let parser = TransportProtocolDataUnitParser::new();
38        let (mut reader, mut writer) = connection.split().await?;
39
40        send_connection_request(&mut writer, source_reference, options).await?;
41        let connection_confirm = receive_connection_confirm(&mut reader, &parser).await?;
42        let (_, max_payload_size) = calculate_remote_size_payload(connection_confirm.parameters()).await?;
43
44        let remote_called_tsap = connection_confirm.parameters().iter().filter_map(|x| if let CotpParameter::CalledTsap(tsap) = x { Some(tsap.clone()) } else { None }).last();
45        protocol_infomation_list.push(Box::new(CotpProtocolInformation::new(source_reference, connection_confirm.destination_reference(), local_calling_tsap, remote_called_tsap)));
46
47        Ok(RustyCotpConnection::new(reader, writer, max_payload_size, protocol_infomation_list, connection_options).await)
48    }
49
50    async fn new(reader: R, writer: W, max_payload_size: usize, protocol_infomation_list: Vec<Box<dyn ProtocolInformation>>, connection_options: CotpConnectionParameters) -> RustyCotpConnection<R, W> {
51        RustyCotpConnection { reader, writer, max_payload_size, parser: TransportProtocolDataUnitParser::new(), protocol_infomation_list, connection_options }
52    }
53}
54
55impl<R: TpktReader, W: TpktWriter> CotpConnection for RustyCotpConnection<R, W> {
56    fn get_protocol_infomation_list(&self) -> &Vec<Box<dyn rusty_tpkt::ProtocolInformation>> {
57        &self.protocol_infomation_list
58    }
59
60    async fn split(self) -> Result<(impl CotpReader, impl CotpWriter), CotpError> {
61        let reader = self.reader;
62        let writer = self.writer;
63        Ok((RustyCotpReader::new(reader, self.parser, self.connection_options), RustyCotpWriter::new(writer, self.max_payload_size)))
64    }
65}
66
67/// Creates a responder that consumes the underlying TPKT service to negotiate a COTP connection.
68pub struct RustyCotpAcceptor<R: TpktReader, W: TpktWriter> {
69    reader: R,
70    writer: W,
71    initiator_reference: u16,
72    max_payload_size: usize,
73    max_payload_indicator: TpduSize,
74    called_tsap_id: Option<Vec<u8>>,
75    calling_tsap_id: Option<Vec<u8>>,
76    connection_options: CotpConnectionParameters,
77    lower_layer_protocol_options_list: Vec<Box<dyn ProtocolInformation>>,
78}
79
80impl<R: TpktReader, W: TpktWriter> RustyCotpAcceptor<R, W> {
81    /// Creates an acceptor.
82    /// 
83    /// This is a single use component used to upgrade an underlying TPKT connection to a COTP connection.
84    /// The TPKT connection should be a server, but this is not enforced.
85    pub async fn new(tpkt_connection: impl TpktConnection, connection_options: CotpConnectionParameters) -> Result<(RustyCotpAcceptor<impl TpktReader, impl TpktWriter>, CotpProtocolInformation), CotpError> {
86        let parser = TransportProtocolDataUnitParser::new();
87        let lower_layer_protocol_options_list = tpkt_connection.get_protocol_infomation_list().clone();
88        let (mut reader, writer) = tpkt_connection.split().await?;
89
90        let connection_request = receive_connection_request(&mut reader, &parser).await?;
91        let (max_payload_indicator, max_payload_size) = calculate_remote_size_payload(connection_request.parameters()).await?;
92        verify_class_compatibility(&connection_request).await?;
93
94        let mut calling_tsap_id = None;
95        let mut called_tsap_id = None;
96        for parameter in connection_request.parameters() {
97            match parameter {
98                CotpParameter::CallingTsap(tsap_id) => calling_tsap_id = Some(tsap_id.clone()),
99                CotpParameter::CalledTsap(tsap_id) => called_tsap_id = Some(tsap_id.clone()),
100                _ => (),
101            }
102        }
103
104        Ok((
105            RustyCotpAcceptor {
106                reader,
107                writer,
108                max_payload_size,
109                connection_options,
110                max_payload_indicator,
111                called_tsap_id: called_tsap_id.clone(),
112                calling_tsap_id: calling_tsap_id.clone(),
113                initiator_reference: connection_request.source_reference(),
114                lower_layer_protocol_options_list,
115            },
116            CotpProtocolInformation::new(connection_request.source_reference(), 0, calling_tsap_id, called_tsap_id),
117        ))
118    }
119}
120
121impl<R: TpktReader, W: TpktWriter> CotpResponder for RustyCotpAcceptor<R, W> {
122    async fn accept(mut self, options: CotpProtocolInformation) -> Result<impl CotpConnection, CotpError> {
123        send_connection_confirm(&mut self.writer, options.responder_reference(), self.initiator_reference, self.max_payload_indicator, self.calling_tsap_id, self.called_tsap_id).await?;
124        Ok(RustyCotpConnection::new(self.reader, self.writer, self.max_payload_size, self.lower_layer_protocol_options_list, self.connection_options).await)
125    }
126}
127
128// Used to receive data to a remote a COTP host.
129pub struct RustyCotpReader<R: TpktReader> {
130    reader: R,
131    parser: TransportProtocolDataUnitParser,
132    connection_options: CotpConnectionParameters,
133
134    data_buffer: BytesMut,
135}
136
137impl<R: TpktReader> RustyCotpReader<R> {
138    fn new(reader: R, parser: TransportProtocolDataUnitParser, connection_options: CotpConnectionParameters,
139) -> Self {
140        Self { reader, parser, data_buffer: BytesMut::new(), connection_options }
141    }
142}
143
144impl<R: TpktReader> CotpReader for RustyCotpReader<R> {
145    async fn recv(&mut self) -> Result<Option<Vec<u8>>, CotpError> {
146        loop {
147            let raw_data = match self.reader.recv().await? {
148                None => return Ok(None),
149                Some(raw_data) => raw_data,
150            };
151            let data_transfer = match self.parser.parse(raw_data.as_slice())? {
152                // Choosing the standards based option of reporting the TPDU error locally but not sending an error.
153                TransportProtocolDataUnit::ER(tpdu_error) => return Err(CotpError::ProtocolError(format!("Received an error from the remote host: {:?}", tpdu_error.reason()).into())),
154                TransportProtocolDataUnit::CR(_) => return Err(CotpError::ProtocolError("Received a Connection Request when expecting data.".into())),
155                TransportProtocolDataUnit::CC(_) => return Err(CotpError::ProtocolError("Received a Connection Config when expecting data.".into())),
156                TransportProtocolDataUnit::DR(_) => return Ok(None),
157                TransportProtocolDataUnit::DT(data_transfer) => data_transfer,
158            };
159
160            // Not performing strict checking of source and destination reference:
161            // - This is running over a TCP stream.
162            // - This package supports Class 0 only, which is a single COTP association per TCP stream. References look like the are used in Class 1-4.
163
164            self.data_buffer.extend_from_slice(data_transfer.user_data());
165            if self.data_buffer.len() > self.connection_options.max_reassembled_payload_size {
166                let reassembled_size = self.data_buffer.len();
167                let max_reassembled_size = self.connection_options.max_reassembled_payload_size;
168                self.data_buffer.clear();
169                return Err(CotpError::ProtocolError(format!("Reassembled payload size {reassembled_size} exceeds maximum payload size {max_reassembled_size}")))
170            }
171            if data_transfer.end_of_transmission() {
172                let data = self.data_buffer.to_vec();
173                self.data_buffer.clear();
174                return Ok(Some(data));
175            }
176        }
177    }
178}
179
180// Used to send data to a remote a COTP host.
181pub struct RustyCotpWriter<W: TpktWriter> {
182    writer: W,
183    max_payload_size: usize,
184    chunks: VecDeque<Vec<u8>>,
185}
186
187impl<W: TpktWriter> RustyCotpWriter<W> {
188    fn new(writer: W, max_payload_size: usize) -> Self {
189        Self { writer, max_payload_size, chunks: VecDeque::new() }
190    }
191}
192
193impl<W: TpktWriter> CotpWriter for RustyCotpWriter<W> {
194    async fn send(&mut self, input: &mut VecDeque<Vec<u8>>) -> Result<(), CotpError> {
195        const HEADER_LENGTH: usize = 3;
196
197        while let Some(data_item) = input.pop_front() {
198            let chunks = data_item.as_slice().chunks(self.max_payload_size - HEADER_LENGTH);
199            let chunk_count = chunks.len();
200            for (chunk_index, chunk_data) in chunks.enumerate() {
201                let end_of_transmission = chunk_index + 1 >= chunk_count;
202                let tpdu = DataTransfer::new(end_of_transmission, chunk_data);
203                let tpdu_data = serialise(&TransportProtocolDataUnit::DT(tpdu))?;
204                self.chunks.push_back(tpdu_data);
205            }
206        }
207
208        while !self.chunks.is_empty() {
209            self.writer.send(&mut self.chunks).await?;
210        }
211
212        // Perform one more to ensure lower levels are also flushed even if this layer is complete.
213        self.writer.send(&mut self.chunks).await?;
214        Ok(())
215    }
216}
217
218async fn verify_class_compatibility(connection_request: &ConnectionRequest) -> Result<(), CotpError> {
219    let empty_set = Vec::new();
220    let class_parameters = connection_request
221        .parameters()
222        .iter()
223        .filter_map(|p| match p {
224            CotpParameter::AlternativeClassParameter(x) => Some(x),
225            _ => None,
226        })
227        .last()
228        .unwrap_or(&empty_set);
229
230    // Verify we can downgrade to Class 0
231    match connection_request.preferred_class() {
232        ConnectionClass::Class0 => (),
233        ConnectionClass::Class1 => (),
234        ConnectionClass::Class2 if class_parameters.contains(&&ConnectionClass::Class0) => (),
235        ConnectionClass::Class3 if class_parameters.contains(&&ConnectionClass::Class0) => (),
236        ConnectionClass::Class3 if class_parameters.contains(&&ConnectionClass::Class1) => (),
237        ConnectionClass::Class4 if class_parameters.contains(&&ConnectionClass::Class0) => (),
238        ConnectionClass::Class4 if class_parameters.contains(&&ConnectionClass::Class1) => (),
239        _ => {
240            return Err(CotpError::ProtocolError(format!("Cannot downgrade connection request to Class 0 {:?} - {:?}", connection_request.preferred_class(), class_parameters)));
241        }
242    };
243    Ok(())
244}
245
246async fn receive_connection_request(reader: &mut impl TpktReader, parser: &TransportProtocolDataUnitParser) -> Result<ConnectionRequest, CotpError> {
247    let data = match reader.recv().await {
248        Ok(Some(x)) => x,
249        Ok(None) => return Err(CotpError::ProtocolError("The connection was closed before the COTP handshake was complete.".into())),
250        Err(e) => return Err(e.into()),
251    };
252    return Ok(match parser.parse(data.as_slice())? {
253        TransportProtocolDataUnit::CR(x) => x,
254        TransportProtocolDataUnit::CC(_) => return Err(CotpError::ProtocolError("Expected connection request on handshake but got a connextion confirm".into())),
255        TransportProtocolDataUnit::DR(_) => return Err(CotpError::ProtocolError("Expected connection request on handshake but got a disconnect reqeust".into())),
256        TransportProtocolDataUnit::DT(_) => return Err(CotpError::ProtocolError("Expected connection request on handshake but got a data transfer".into())),
257        TransportProtocolDataUnit::ER(_) => return Err(CotpError::ProtocolError("Expected connection request on handshake but got a error response".into())),
258    });
259}
260
261async fn calculate_remote_size_payload(parameters: &[CotpParameter]) -> Result<(TpduSize, usize), CotpError> {
262    let parameter: &TpduSize = parameters
263        .iter()
264        .filter_map(|p| match p {
265            CotpParameter::TpduLengthParameter(x) => Some(x),
266            _ => None,
267        })
268        .last()
269        .unwrap_or(&TpduSize::Size128);
270
271    Ok(match parameter {
272        TpduSize::Size8192 => return Err(CotpError::ProtocolError("The remote side selected an 8192 bytes COTP payload but Class 0 support a maximum for 2048 bytes.".into())),
273        TpduSize::Size4096 => return Err(CotpError::ProtocolError("The remote side selected an 4096 bytes COTP payload but Class 0 support a maximum for 2048 bytes.".into())),
274        TpduSize::Unknown(x) => return Err(CotpError::ProtocolError(format!("The requested TPDU size is unknown {:?}.", x).into())),
275        TpduSize::Size128 => (TpduSize::Size128, 128),
276        TpduSize::Size256 => (TpduSize::Size256, 256),
277        TpduSize::Size512 => (TpduSize::Size512, 512),
278        TpduSize::Size1024 => (TpduSize::Size1024, 1024),
279        TpduSize::Size2048 => (TpduSize::Size2048, 2048),
280    })
281}
282
283async fn send_connection_confirm<W: TpktWriter>(writer: &mut W, source_reference: u16, destination_reference: u16, size: TpduSize, calling_tsap_id: Option<Vec<u8>>, called_tsap_id: Option<Vec<u8>>) -> Result<(), CotpError> {
284    let mut parameters = vec![CotpParameter::TpduLengthParameter(size)];
285    if let Some(tsap_id) = calling_tsap_id {
286        parameters.push(CotpParameter::CallingTsap(tsap_id));
287    }
288    if let Some(tsap_id) = called_tsap_id {
289        parameters.push(CotpParameter::CalledTsap(tsap_id));
290    }
291
292    let payload = serialise(&TransportProtocolDataUnit::CC(ConnectionConfirm::new(0, source_reference, destination_reference, ConnectionClass::Class0, vec![], parameters, &[])))?;
293    Ok(writer.send(&mut VecDeque::from_iter(vec![payload].into_iter())).await?)
294}
295
296async fn send_connection_request(writer: &mut impl TpktWriter, source_reference: u16, options: CotpProtocolInformation) -> Result<(), CotpError> {
297    let mut parameters = vec![CotpParameter::TpduLengthParameter(TpduSize::Size2048)];
298    if let Some(calling_tsap) = options.calling_tsap_id() {
299        parameters.push(CotpParameter::CallingTsap(calling_tsap.clone()));
300    }
301    if let Some(called_tsap) = options.called_tsap_id() {
302        parameters.push(CotpParameter::CalledTsap(called_tsap.clone()));
303    }
304
305    let payload = serialise(&TransportProtocolDataUnit::CR(ConnectionRequest::new(source_reference, 0, ConnectionClass::Class0, vec![], parameters, &[])))?;
306    Ok(writer.send(&mut VecDeque::from_iter(vec![payload].into_iter())).await?)
307}
308
309async fn receive_connection_confirm(reader: &mut impl TpktReader, parser: &TransportProtocolDataUnitParser) -> Result<ConnectionConfirm, CotpError> {
310    let data = match reader.recv().await {
311        Ok(Some(x)) => x,
312        Ok(None) => return Err(CotpError::ProtocolError("The connection was closed before the COTP handshake was complete.".into())),
313        Err(e) => return Err(e.into()),
314    };
315    return Ok(match parser.parse(data.as_slice())? {
316        TransportProtocolDataUnit::CC(x) if x.preferred_class() != &ConnectionClass::Class0 => return Err(CotpError::ProtocolError("Remote failed to select COTP Class 0.".into())),
317        TransportProtocolDataUnit::CC(x) => x,
318        TransportProtocolDataUnit::CR(_) => return Err(CotpError::ProtocolError("Expected connection confirmed on handshake but got a connection request".into())),
319        TransportProtocolDataUnit::DR(_) => return Err(CotpError::ProtocolError("Expected connection confirmed on handshake but got a disconnect reqeust".into())),
320        TransportProtocolDataUnit::DT(_) => return Err(CotpError::ProtocolError("Expected connection confirmed on handshake but got a data transfer".into())),
321        TransportProtocolDataUnit::ER(_) => return Err(CotpError::ProtocolError("Expected connection confirmed on handshake but got a error response".into())),
322    });
323}
rusty_cotp/service.rs

rusty_cotp/
service.rs
