Implement TCP data transmission.
parent
0bf822c77e
commit
0e20ea9205
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@ -46,7 +46,8 @@ The UDP protocol is supported over IPv4.
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The TCP protocol is supported over IPv4.
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* TCP header checksum is supported.
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* TCP options are **not** supported.
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* TCP options are **not** supported. In particular, the MSS of the remote endpoint
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is hardcoded at the default value, 536.
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* Reassembly of out-of-order segments is **not** supported.
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Installation
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@ -90,6 +90,7 @@ impl<'a> SocketBuffer<'a> {
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self.length -= size;
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}
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#[allow(dead_code)] // only used in tests
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fn dequeue(&mut self, size: usize) -> &[u8] {
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let (read_at, size) = self.clamp_reader(size);
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self.read_at = (self.read_at + size) % self.storage.len();
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@ -422,54 +423,75 @@ impl<'a> TcpSocket<'a> {
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/// See [Socket::dispatch](enum.Socket.html#method.dispatch).
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pub fn dispatch<F, R>(&mut self, emit: &mut F) -> Result<R, Error>
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where F: FnMut(&IpRepr, &IpPayload) -> Result<R, Error> {
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let mut repr = TcpRepr {
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src_port: self.local_endpoint.port,
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dst_port: self.remote_endpoint.port,
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control: TcpControl::None,
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seq_number: 0,
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ack_number: None,
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window_len: self.rx_buffer.window() as u16,
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payload: &[]
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};
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// FIXME: process
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match self.state {
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State::Closed |
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State::Listen => {
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return Err(Error::Exhausted)
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}
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State::SynReceived => {
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if !self.retransmit.check() { return Err(Error::Exhausted) }
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repr.control = TcpControl::Syn;
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repr.seq_number = self.local_seq_no;
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repr.ack_number = Some(self.remote_seq_no);
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net_trace!("tcp:{}:{}: SYN|ACK sent",
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self.local_endpoint, self.remote_endpoint);
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self.remote_last_ack = self.remote_seq_no;
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}
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State::Established => {
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let ack_number = self.remote_seq_no + self.rx_buffer.len() as i32;
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if self.remote_last_ack == ack_number { return Err(Error::Exhausted) }
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repr.seq_number = self.local_seq_no;
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repr.ack_number = Some(ack_number);
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net_trace!("tcp:{}:{}: ACK sent",
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self.local_endpoint, self.remote_endpoint);
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self.remote_last_ack = ack_number;
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}
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_ => unreachable!()
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}
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let ip_repr = IpRepr::Unspecified {
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src_addr: self.local_endpoint.addr,
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dst_addr: self.remote_endpoint.addr,
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protocol: IpProtocol::Tcp,
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};
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let mut repr = TcpRepr {
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src_port: self.local_endpoint.port,
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dst_port: self.remote_endpoint.port,
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control: TcpControl::None,
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seq_number: self.local_seq_no,
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ack_number: None,
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window_len: self.rx_buffer.window() as u16,
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payload: &[]
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};
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let ack_number = self.remote_seq_no + self.rx_buffer.len() as i32;
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match self.state {
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State::Closed | State::Listen => return Err(Error::Exhausted),
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State::SynReceived => {
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if !self.retransmit.check() { return Err(Error::Exhausted) }
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repr.control = TcpControl::Syn;
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net_trace!("tcp:{}:{}: sending SYN|ACK",
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self.local_endpoint, self.remote_endpoint);
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self.remote_last_ack = self.remote_seq_no;
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}
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State::Established => {
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if self.tx_buffer.len() > 0 && self.remote_win_len > 0 {
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if !self.retransmit.check() { return Err(Error::Exhausted) }
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// We can send something, so let's do that.
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let mut size = self.remote_win_len;
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// Clamp to MSS. Currently we only support the default MSS value.
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if size > 536 { size = 536 }
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// Extract data from the buffer. This may return less than what we want,
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// in case it's not possible to extract a contiguous slice.
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let data = self.tx_buffer.peek(size);
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net_trace!("tcp:{}:{}: sending {} octets",
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self.local_endpoint, self.remote_endpoint, data.len());
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repr.payload = data;
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} else if self.remote_last_ack != ack_number {
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// We don't have anything to send, or can't because the remote end does not
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// have any space to accept it, but we haven't yet acknowledged everything
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// we have received. So, do it.
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net_trace!("tcp:{}:{}: sending ACK",
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self.local_endpoint, self.remote_endpoint);
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} else {
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// We don't have anything to send and we've already acknowledged everything.
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return Err(Error::Exhausted)
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}
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}
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_ => unreachable!()
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}
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match self.state {
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// We don't have anything to acknowledge yet.
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State::Closed | State::Listen | State::SynSent => (),
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// Acknowledge all data we have received, since it is all in order.
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_ => {
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self.remote_last_ack = ack_number;
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repr.ack_number = Some(ack_number);
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}
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}
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emit(&ip_repr, &repr)
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}
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}
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@ -749,11 +771,12 @@ mod test {
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s.remote_endpoint = REMOTE_END;
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s.local_seq_no = LOCAL_SEQ + 1;
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s.remote_seq_no = REMOTE_SEQ + 1;
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s.remote_win_len = 128;
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s
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}
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#[test]
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fn test_established_data() {
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fn test_established_receive() {
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let mut s = socket_established();
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send!(s, [TcpRepr {
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seq_number: REMOTE_SEQ + 1,
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@ -770,6 +793,25 @@ mod test {
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assert_eq!(s.rx_buffer.dequeue(6), &b"abcdef"[..]);
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}
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#[test]
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fn test_established_send() {
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let mut s = socket_established();
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s.tx_buffer.enqueue_slice(b"abcdef");
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recv!(s, [TcpRepr {
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seq_number: LOCAL_SEQ + 1,
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ack_number: Some(REMOTE_SEQ + 1),
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payload: &b"abcdef"[..],
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..RECV_TEMPL
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}]);
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assert_eq!(s.tx_buffer.len(), 6);
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send!(s, [TcpRepr {
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seq_number: REMOTE_SEQ + 1,
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ack_number: Some(LOCAL_SEQ + 1 + 6),
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..SEND_TEMPL
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}]);
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assert_eq!(s.tx_buffer.len(), 0);
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}
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#[test]
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fn test_established_no_ack() {
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let mut s = socket_established();
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