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tcp: do not scale window in SYN packets.

This commit is contained in:
Dario Nieuwenhuis 2021-06-17 06:22:30 +02:00
parent 4045dee3f9
commit 9101e039d5
1 changed files with 15 additions and 5 deletions
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20
src/socket/tcp.rs
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@ -1515,7 +1515,11 @@ impl<'a> TcpSocket<'a> {
// RFC 1323: The window field (SEG.WND) in the header of every incoming segment, with the
// exception of SYN segments, is left-shifted by Snd.Wind.Scale bits before updating SND.WND.
self.remote_win_len = (repr.window_len as usize) << (self.remote_win_scale.unwrap_or(0) as usize);
let scale = match repr.control {
TcpControl::Syn => 0,
_ => self.remote_win_scale.unwrap_or(0),
};
self.remote_win_len = (repr.window_len as usize) << (scale as usize);
if ack_len > 0 {
// Dequeue acknowledged octets.
@ -1746,7 +1750,7 @@ impl<'a> TcpSocket<'a> {
fn window_to_update(&self) -> bool {
match self.state {
State::SynSent | State::SynReceived | State::Established | State::FinWait1 | State::FinWait2 =>
(self.rx_buffer.window() >> self.remote_win_shift) as u16 > self.remote_last_win,
self.scaled_window() > self.remote_last_win,
_ => false,
}
}
@ -1858,6 +1862,8 @@ impl<'a> TcpSocket<'a> {
// We transmit a SYN|ACK in the SYN-RECEIVED state.
State::SynSent | State::SynReceived => {
repr.control = TcpControl::Syn;
// window len must NOT be scaled in SYNs.
repr.window_len = self.rx_buffer.window().min((1<<16)-1) as u16;
if self.state == State::SynSent {
repr.ack_number = None;
repr.window_scale = Some(self.remote_win_shift);
@ -2503,7 +2509,7 @@ mod test {
ack_number: Some(REMOTE_SEQ + 1),
max_seg_size: Some(BASE_MSS),
window_scale: Some(*shift_amt),
window_len: cmp::min(*buffer_size >> *shift_amt, 65535) as u16,
window_len: cmp::min(*buffer_size, 65535) as u16,
..RECV_TEMPL
}]);
}
@ -2932,7 +2938,7 @@ mod test {
ack_number: None,
max_seg_size: Some(BASE_MSS),
window_scale: Some(*shift_amt),
window_len: cmp::min(*buffer_size >> *shift_amt, 65535) as u16,
window_len: cmp::min(*buffer_size, 65535) as u16,
sack_permitted: true,
..RECV_TEMPL
}]);
@ -2947,7 +2953,8 @@ mod test {
seq_number: LOCAL_SEQ,
ack_number: None,
max_seg_size: Some(BASE_MSS),
window_len: 32768,
// scaling does NOT apply to the window value in SYN packets
window_len: 65535,
window_scale: Some(5),
sack_permitted: true,
..RECV_TEMPL
@ -2965,6 +2972,7 @@ mod test {
assert_eq!(s.state, State::Established);
assert_eq!(s.remote_win_shift, 0);
assert_eq!(s.remote_win_scale, None);
assert_eq!(s.remote_win_len, 42);
}
#[test]
@ -2990,6 +2998,8 @@ mod test {
});
assert_eq!(s.state, State::Established);
assert_eq!(s.remote_win_scale, Some(7));
// scaling does NOT apply to the window value in SYN packets
assert_eq!(s.remote_win_len, 42);
}
// =========================================================================================//