rusty_cotp/
service.rs

1use std::collections::VecDeque;
2
3use bytes::BytesMut;
4use rusty_tpkt::{TpktConnection, TpktReader, TpktRecvResult, TpktWriter};
5
6use crate::{
7    CotpAcceptInformation,
8    api::{CotpConnectInformation, CotpConnection, CotpError, CotpReader, CotpRecvResult, CotpResponder, CotpWriter},
9    packet::{
10        connection_confirm::ConnectionConfirm,
11        connection_request::ConnectionRequest,
12        data_transfer::DataTransfer,
13        parameters::{ConnectionClass, CotpParameter, TpduSize},
14        payload::TransportProtocolDataUnit,
15    },
16    parser::packet::TransportProtocolDataUnitParser,
17    serialiser::packet::serialise,
18};
19
20pub struct TcpCotpConnection<R: TpktReader, W: TpktWriter> {
21    reader: R,
22    writer: W,
23
24    max_payload_size: usize,
25    parser: TransportProtocolDataUnitParser,
26}
27
28impl<R: TpktReader, W: TpktWriter> TcpCotpConnection<R, W> {
29    pub async fn initiate(connection: impl TpktConnection, options: CotpConnectInformation) -> Result<TcpCotpConnection<impl TpktReader, impl TpktWriter>, CotpError> {
30        let source_reference: u16 = options.initiator_reference;
31        let parser = TransportProtocolDataUnitParser::new();
32        let (mut reader, mut writer) = connection.split().await?;
33
34        send_connection_request(&mut writer, source_reference, options).await?;
35        let connection_confirm = receive_connection_confirm(&mut reader, &parser).await?;
36        let (_, max_payload_size) = calculate_remote_size_payload(connection_confirm.parameters()).await?;
37
38        Ok(TcpCotpConnection::new(reader, writer, max_payload_size).await)
39    }
40
41    async fn new(reader: R, writer: W, max_payload_size: usize) -> TcpCotpConnection<R, W> {
42        TcpCotpConnection { reader, writer, max_payload_size, parser: TransportProtocolDataUnitParser::new() }
43    }
44}
45
46impl<R: TpktReader, W: TpktWriter> CotpConnection for TcpCotpConnection<R, W> {
47    async fn split(self) -> Result<(impl CotpReader, impl CotpWriter), CotpError> {
48        let reader = self.reader;
49        let writer = self.writer;
50        Ok((TcpCotpReader::new(reader, self.parser), TcpCotpWriter::new(writer, self.max_payload_size)))
51    }
52}
53
54pub struct TcpCotpAcceptor<R: TpktReader, W: TpktWriter> {
55    reader: R,
56    writer: W,
57    initiator_reference: u16,
58    max_payload_size: usize,
59    max_payload_indicator: TpduSize,
60    called_tsap_id: Option<Vec<u8>>,
61    calling_tsap_id: Option<Vec<u8>>,
62}
63
64impl<R: TpktReader, W: TpktWriter> TcpCotpAcceptor<R, W> {
65    pub async fn new(tpkt_connection: impl TpktConnection) -> Result<(TcpCotpAcceptor<impl TpktReader, impl TpktWriter>, CotpConnectInformation), CotpError> {
66        let parser = TransportProtocolDataUnitParser::new();
67        let (mut reader, writer) = tpkt_connection.split().await?;
68
69        let connection_request = receive_connection_request(&mut reader, &parser).await?;
70        let (max_payload_indicator, max_payload_size) = calculate_remote_size_payload(connection_request.parameters()).await?;
71        verify_class_compatibility(&connection_request).await?;
72
73        let mut calling_tsap_id = None;
74        let mut called_tsap_id = None;
75        for parameter in connection_request.parameters() {
76            match parameter {
77                CotpParameter::CallingTsap(tsap_id) => calling_tsap_id = Some(tsap_id.clone()),
78                CotpParameter::CalledTsap(tsap_id) => called_tsap_id = Some(tsap_id.clone()),
79                _ => (),
80            }
81        }
82
83        Ok((
84            TcpCotpAcceptor { reader, writer, max_payload_size, max_payload_indicator, called_tsap_id: called_tsap_id.clone(), calling_tsap_id: calling_tsap_id.clone(), initiator_reference: connection_request.source_reference() },
85            CotpConnectInformation { calling_tsap_id, called_tsap_id, initiator_reference: connection_request.source_reference() },
86        ))
87    }
88}
89
90impl<R: TpktReader, W: TpktWriter> CotpResponder for TcpCotpAcceptor<R, W> {
91    async fn accept(mut self, options: CotpAcceptInformation) -> Result<impl CotpConnection, CotpError> {
92        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?;
93        Ok(TcpCotpConnection::new(self.reader, self.writer, self.max_payload_size).await)
94    }
95}
96
97pub struct TcpCotpReader<R: TpktReader> {
98    // Not caring about the size of the payload we receive.
99    reader: R,
100    parser: TransportProtocolDataUnitParser,
101
102    data_buffer: BytesMut,
103}
104
105impl<R: TpktReader> TcpCotpReader<R> {
106    pub fn new(reader: R, parser: TransportProtocolDataUnitParser) -> Self {
107        Self { reader, parser, data_buffer: BytesMut::new() }
108    }
109}
110
111impl<R: TpktReader> CotpReader for TcpCotpReader<R> {
112    async fn recv(&mut self) -> Result<CotpRecvResult, CotpError> {
113        loop {
114            // I don't really care to check max size. It is 2025.
115            let raw_data = match self.reader.recv().await? {
116                TpktRecvResult::Closed => return Ok(CotpRecvResult::Closed),
117                TpktRecvResult::Data(raw_data) => raw_data,
118            };
119            let data_transfer = match self.parser.parse(raw_data.as_slice())? {
120                // Choosing the standards based option of reporting the TPDU error locally but not sending an error.
121                TransportProtocolDataUnit::ER(tpdu_error) => return Err(CotpError::ProtocolError(format!("Received an error from the remote host: {:?}", tpdu_error.reason()).into())),
122                TransportProtocolDataUnit::CR(_) => return Err(CotpError::ProtocolError("Received a Connection Request when expecting data.".into())),
123                TransportProtocolDataUnit::CC(_) => return Err(CotpError::ProtocolError("Received a Connection Config when expecting data.".into())),
124                TransportProtocolDataUnit::DR(_) => return Ok(CotpRecvResult::Closed),
125                TransportProtocolDataUnit::DT(data_transfer) => data_transfer,
126            };
127            // I do not really care about the source and destination reference here. It is over a TCP stream. I'd rather keep it relaxed and avoid interop issues.
128
129            self.data_buffer.extend_from_slice(data_transfer.user_data());
130            if data_transfer.end_of_transmission() {
131                let data = self.data_buffer.to_vec();
132                self.data_buffer.clear();
133                return Ok(CotpRecvResult::Data(data));
134            }
135        }
136    }
137}
138
139pub struct TcpCotpWriter<W: TpktWriter> {
140    writer: W,
141    max_payload_size: usize,
142    chunks: VecDeque<Vec<u8>>,
143}
144
145impl<W: TpktWriter> TcpCotpWriter<W> {
146    pub fn new(writer: W, max_payload_size: usize) -> Self {
147        Self { writer, max_payload_size, chunks: VecDeque::new() }
148    }
149}
150
151impl<W: TpktWriter> CotpWriter for TcpCotpWriter<W> {
152    async fn send(&mut self, input: &mut VecDeque<Vec<u8>>) -> Result<(), CotpError> {
153        const HEADER_LENGTH: usize = 3;
154
155        while let Some(data_item) = input.pop_front() {
156            let chunks = data_item.as_slice().chunks(self.max_payload_size - HEADER_LENGTH);
157            let chunk_count = chunks.len();
158            for (chunk_index, chunk_data) in chunks.enumerate() {
159                let end_of_transmission = chunk_index + 1 >= chunk_count;
160                let tpdu = DataTransfer::new(end_of_transmission, chunk_data);
161                let tpdu_data = serialise(&TransportProtocolDataUnit::DT(tpdu))?;
162                self.chunks.push_back(tpdu_data);
163            }
164        }
165
166        while !self.chunks.is_empty() {
167            self.writer.send(&mut self.chunks).await?;
168        }
169
170        // Perform one more to ensure lower levels are also flushed even if this layer is complete.
171        self.writer.send(&mut self.chunks).await?;
172        Ok(())
173    }
174}
175
176async fn verify_class_compatibility(connection_request: &ConnectionRequest) -> Result<(), CotpError> {
177    let empty_set = Vec::new();
178    let class_parameters = connection_request
179        .parameters()
180        .iter()
181        .filter_map(|p| match p {
182            CotpParameter::AlternativeClassParameter(x) => Some(x),
183            _ => None,
184        })
185        .last()
186        .unwrap_or(&empty_set);
187
188    // Verify we can downgrade to Class 0
189    match connection_request.preferred_class() {
190        ConnectionClass::Class0 => (),
191        ConnectionClass::Class1 => (),
192        ConnectionClass::Class2 if class_parameters.contains(&&ConnectionClass::Class0) => (),
193        ConnectionClass::Class3 if class_parameters.contains(&&ConnectionClass::Class0) => (),
194        ConnectionClass::Class3 if class_parameters.contains(&&ConnectionClass::Class1) => (),
195        ConnectionClass::Class4 if class_parameters.contains(&&ConnectionClass::Class0) => (),
196        ConnectionClass::Class4 if class_parameters.contains(&&ConnectionClass::Class1) => (),
197        _ => {
198            return Err(CotpError::ProtocolError(format!("Cannot downgrade connection request to Class 0 {:?} - {:?}", connection_request.preferred_class(), class_parameters)));
199        }
200    };
201    Ok(())
202}
203
204async fn receive_connection_request(reader: &mut impl TpktReader, parser: &TransportProtocolDataUnitParser) -> Result<ConnectionRequest, CotpError> {
205    let data = match reader.recv().await {
206        Ok(TpktRecvResult::Data(x)) => x,
207        Ok(TpktRecvResult::Closed) => return Err(CotpError::ProtocolError("The connection was closed before the COTP handshake was complete.".into())),
208        Err(e) => return Err(e.into()),
209    };
210    return Ok(match parser.parse(data.as_slice())? {
211        TransportProtocolDataUnit::CR(x) => x,
212        TransportProtocolDataUnit::CC(_) => return Err(CotpError::ProtocolError("Expected connection request on handshake but got a connextion confirm".into())),
213        TransportProtocolDataUnit::DR(_) => return Err(CotpError::ProtocolError("Expected connection request on handshake but got a disconnect reqeust".into())),
214        TransportProtocolDataUnit::DT(_) => return Err(CotpError::ProtocolError("Expected connection request on handshake but got a data transfer".into())),
215        TransportProtocolDataUnit::ER(_) => return Err(CotpError::ProtocolError("Expected connection request on handshake but got a error response".into())),
216    });
217}
218
219async fn calculate_remote_size_payload(parameters: &[CotpParameter]) -> Result<(TpduSize, usize), CotpError> {
220    let parameter: &TpduSize = parameters
221        .iter()
222        .filter_map(|p| match p {
223            CotpParameter::TpduLengthParameter(x) => Some(x),
224            _ => None,
225        })
226        .last()
227        .unwrap_or(&TpduSize::Size128);
228
229    Ok(match parameter {
230        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())),
231        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())),
232        TpduSize::Unknown(x) => return Err(CotpError::ProtocolError(format!("The requested TPDU size is unknown {:?}.", x).into())),
233        TpduSize::Size128 => (TpduSize::Size128, 128),
234        TpduSize::Size256 => (TpduSize::Size256, 256),
235        TpduSize::Size512 => (TpduSize::Size512, 512),
236        TpduSize::Size1024 => (TpduSize::Size1024, 1024),
237        TpduSize::Size2048 => (TpduSize::Size2048, 2048),
238    })
239}
240
241async 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> {
242    let mut parameters = vec![CotpParameter::TpduLengthParameter(size)];
243    if let Some(tsap_id) = calling_tsap_id {
244        parameters.push(CotpParameter::CallingTsap(tsap_id));
245    }
246    if let Some(tsap_id) = called_tsap_id {
247        parameters.push(CotpParameter::CalledTsap(tsap_id));
248    }
249
250    let payload = serialise(&TransportProtocolDataUnit::CC(ConnectionConfirm::new(0, source_reference, destination_reference, ConnectionClass::Class0, vec![], parameters, &[])))?;
251    Ok(writer.send(&mut VecDeque::from_iter(vec![payload].into_iter())).await?)
252}
253
254async fn send_connection_request(writer: &mut impl TpktWriter, source_reference: u16, options: CotpConnectInformation) -> Result<(), CotpError> {
255    let mut parameters = vec![CotpParameter::TpduLengthParameter(TpduSize::Size2048)];
256    if let Some(calling_tsap) = options.calling_tsap_id {
257        parameters.push(CotpParameter::CallingTsap(calling_tsap));
258    }
259    if let Some(called_tsap) = options.called_tsap_id {
260        parameters.push(CotpParameter::CalledTsap(called_tsap));
261    }
262
263    let payload = serialise(&TransportProtocolDataUnit::CR(ConnectionRequest::new(source_reference, 0, ConnectionClass::Class0, vec![], parameters, &[])))?;
264    Ok(writer.send(&mut VecDeque::from_iter(vec![payload].into_iter())).await?)
265}
266
267async fn receive_connection_confirm(reader: &mut impl TpktReader, parser: &TransportProtocolDataUnitParser) -> Result<ConnectionConfirm, CotpError> {
268    let data = match reader.recv().await {
269        Ok(TpktRecvResult::Data(x)) => x,
270        Ok(TpktRecvResult::Closed) => return Err(CotpError::ProtocolError("The connection was closed before the COTP handshake was complete.".into())),
271        Err(e) => return Err(e.into()),
272    };
273    return Ok(match parser.parse(data.as_slice())? {
274        TransportProtocolDataUnit::CC(x) if x.preferred_class() != &ConnectionClass::Class0 => return Err(CotpError::ProtocolError("Remote failed to select COTP Class 0.".into())),
275        TransportProtocolDataUnit::CC(x) => x,
276        TransportProtocolDataUnit::CR(_) => return Err(CotpError::ProtocolError("Expected connection confirmed on handshake but got a connection request".into())),
277        TransportProtocolDataUnit::DR(_) => return Err(CotpError::ProtocolError("Expected connection confirmed on handshake but got a disconnect reqeust".into())),
278        TransportProtocolDataUnit::DT(_) => return Err(CotpError::ProtocolError("Expected connection confirmed on handshake but got a data transfer".into())),
279        TransportProtocolDataUnit::ER(_) => return Err(CotpError::ProtocolError("Expected connection confirmed on handshake but got a error response".into())),
280    });
281}
rusty_cotp/service.rs

rusty_cotp/
service.rs
