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Receive the TCP MSS option and act on it.

This commit is contained in:
whitequark 2017-01-27 03:06:52 +00:00
parent bc1d65ea89
commit d6b7623c37
1 changed files with 43 additions and 3 deletions
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46
src/socket/tcp.rs
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@ -245,6 +245,8 @@ pub struct TcpSocket<'a> {
/// The speculative remote window size.
/// I.e. the actual remote window size minus the count of in-flight octets.
remote_win_len: usize,
/// The maximum number of data octets that the remote side may receive.
remote_mss: usize,
retransmit: Retransmit,
rx_buffer: SocketBuffer<'a>,
tx_buffer: SocketBuffer<'a>,
@ -271,6 +273,7 @@ impl<'a> TcpSocket<'a> {
remote_last_seq: TcpSeqNumber(0),
remote_last_ack: TcpSeqNumber(0),
remote_win_len: 0,
remote_mss: 536,
retransmit: Retransmit::new(),
tx_buffer: tx_buffer.into(),
rx_buffer: rx_buffer.into(),
@ -688,7 +691,8 @@ impl<'a> TcpSocket<'a> {
// SYN packets in the LISTEN state change it to SYN-RECEIVED.
(State::Listen, TcpRepr {
src_port, dst_port, control: TcpControl::Syn, seq_number, ack_number: None, ..
src_port, dst_port, control: TcpControl::Syn, seq_number, ack_number: None,
max_seg_size, ..
}) => {
net_trace!("[{}]{}: received SYN",
self.debug_id, self.local_endpoint);
@ -698,6 +702,9 @@ impl<'a> TcpSocket<'a> {
self.local_seq_no = TcpSeqNumber(-seq_number.0);
self.remote_last_seq = self.local_seq_no + 1;
self.remote_seq_no = seq_number + 1;
if let Some(max_seg_size) = max_seg_size {
self.remote_mss = max_seg_size as usize
}
self.set_state(State::SynReceived);
self.retransmit.reset();
}
@ -897,8 +904,8 @@ impl<'a> TcpSocket<'a> {
let mut size = self.tx_buffer.len();
// Clamp to remote window length.
if size > self.remote_win_len { size = self.remote_win_len }
// Clamp to MSS. Currently we only support the default MSS value.
if size > 536 { size = 536 }
// Clamp to MSS.
if size > self.remote_mss { size = self.remote_mss }
// Extract data from the buffer. This may return less than what we want,
// in case it's not possible to extract a contiguous slice.
let offset = self.remote_last_seq - self.local_seq_no;
@ -2248,4 +2255,37 @@ mod test {
..RECV_TEMPL
}));
}
#[test]
fn test_maximum_segment_size() {
let mut s = socket_listen();
s.tx_buffer = SocketBuffer::new(vec![0; 32767]);
send!(s, TcpRepr {
control: TcpControl::Syn,
seq_number: REMOTE_SEQ,
ack_number: None,
max_seg_size: Some(1000),
..SEND_TEMPL
});
recv!(s, [TcpRepr {
control: TcpControl::Syn,
seq_number: LOCAL_SEQ,
ack_number: Some(REMOTE_SEQ + 1),
max_seg_size: Some(1480),
..RECV_TEMPL
}]);
send!(s, TcpRepr {
seq_number: REMOTE_SEQ + 1,
ack_number: Some(LOCAL_SEQ + 1),
window_len: 32767,
..SEND_TEMPL
});
s.send_slice(&[0; 1200][..]).unwrap();
recv!(s, [TcpRepr {
seq_number: LOCAL_SEQ + 1,
ack_number: Some(REMOTE_SEQ + 1),
payload: &[0; 1000][..],
..RECV_TEMPL
}])
}
}