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tcp: don't send data outside the remote window #387

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merged 2 commits into from
Dec 19, 2020
Merged

tcp: don't send data outside the remote window #387

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f1e5568
tcp: don't send data outside the remote window
Dirbaio Dec 18, 2020
bd0d0ae
Merge branch 'master' into tcp-win-fix
whitequark Dec 19, 2020
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43 changes: 14 additions & 29 deletions src/socket/tcp.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -230,8 +230,8 @@ pub struct TcpSocket<'a> {
/// The sending window scaling factor advertised to remotes which support RFC 1323.
/// It is zero if the window <= 64KiB and/or the remote does not support it.
remote_win_shift: u8,
/// The speculative remote window size.
/// I.e. the actual remote window size minus the count of in-flight octets.
/// The remote window size, relative to local_seq_no
/// I.e. we're allowed to send octets until local_seq_no+remote_win_len
remote_win_len: usize,
/// The receive window scaling factor for remotes which support RFC 1323, None if unsupported.
remote_win_scale: Option<u8>,
Expand Down Expand Up @@ -1410,11 +1410,11 @@ impl<'a> TcpSocket<'a> {
_ => control = TcpControl::None
}

if self.remote_win_len > 0 {
self.remote_last_seq < self.local_seq_no + self.tx_buffer.len() + control.len()
} else {
false
}
self.remote_last_seq <
self.local_seq_no + core::cmp::min(
self.remote_win_len,
self.tx_buffer.len()
) + control.len()
}

fn ack_to_transmit(&self) -> bool {
Expand Down Expand Up @@ -1558,7 +1558,8 @@ impl<'a> TcpSocket<'a> {
// Extract as much data as the remote side can receive in this packet
// from the transmit buffer.
let offset = self.remote_last_seq - self.local_seq_no;
let size = cmp::min(cmp::min(self.remote_win_len, self.remote_mss),
let win_limit = self.local_seq_no + self.remote_win_len - self.remote_last_seq;
let size = cmp::min(cmp::min(win_limit, self.remote_mss),
caps.max_transmission_unit - ip_repr.buffer_len() - repr.mss_header_len());
repr.payload = self.tx_buffer.get_allocated(offset, size);
// If we've sent everything we had in the buffer, follow it with the PSH or FIN
Expand Down Expand Up @@ -2755,11 +2756,6 @@ mod test {
ack_number: Some(REMOTE_SEQ + 1),
payload: &data[0..16],
..RECV_TEMPL
}, TcpRepr {
seq_number: LOCAL_SEQ + 1 + 16,
ack_number: Some(REMOTE_SEQ + 1),
payload: &data[16..32],
..RECV_TEMPL
}]);
}

Expand Down Expand Up @@ -3525,7 +3521,7 @@ mod test {
#[test]
fn test_data_retransmit_bursts() {
let mut s = socket_established();
s.remote_win_len = 6;
s.remote_mss = 6;
s.send_slice(b"abcdef012345").unwrap();

recv!(s, time 0, Ok(TcpRepr {
Expand All @@ -3535,15 +3531,13 @@ mod test {
payload: &b"abcdef"[..],
..RECV_TEMPL
}), exact);
s.remote_win_len = 6;
recv!(s, time 0, Ok(TcpRepr {
control: TcpControl::Psh,
seq_number: LOCAL_SEQ + 1 + 6,
ack_number: Some(REMOTE_SEQ + 1),
payload: &b"012345"[..],
..RECV_TEMPL
}), exact);
s.remote_win_len = 6;
recv!(s, time 0, Err(Error::Exhausted));

recv!(s, time 50, Err(Error::Exhausted));
Expand All @@ -3555,15 +3549,13 @@ mod test {
payload: &b"abcdef"[..],
..RECV_TEMPL
}), exact);
s.remote_win_len = 6;
recv!(s, time 150, Ok(TcpRepr {
control: TcpControl::Psh,
seq_number: LOCAL_SEQ + 1 + 6,
ack_number: Some(REMOTE_SEQ + 1),
payload: &b"012345"[..],
..RECV_TEMPL
}), exact);
s.remote_win_len = 6;
recv!(s, time 200, Err(Error::Exhausted));
}

Expand Down Expand Up @@ -3791,12 +3783,12 @@ mod test {
#[test]
fn test_fast_retransmit_after_triple_duplicate_ack() {
let mut s = socket_established();
s.remote_mss = 6;

// Normal ACK of previously recived segment
send!(s, time 0, TcpRepr {
seq_number: REMOTE_SEQ + 1,
ack_number: Some(LOCAL_SEQ + 1),
window_len: 6,
..SEND_TEMPL
});

Expand Down Expand Up @@ -3833,22 +3825,19 @@ mod test {
send!(s, time 1050, TcpRepr {
seq_number: REMOTE_SEQ + 1,
ack_number: Some(LOCAL_SEQ + 1),
window_len: 6,
..SEND_TEMPL
});
// Second duplicate ACK
send!(s, time 1055, TcpRepr {
seq_number: REMOTE_SEQ + 1,
ack_number: Some(LOCAL_SEQ + 1),
window_len: 6,
..SEND_TEMPL
});
// Third duplicate ACK
// Should trigger a fast retransmit of dropped packet
send!(s, time 1060, TcpRepr {
seq_number: REMOTE_SEQ + 1,
ack_number: Some(LOCAL_SEQ + 1),
window_len: 6,
..SEND_TEMPL
});

Expand Down Expand Up @@ -3951,28 +3940,27 @@ mod test {
#[test]
fn test_fast_retransmit_duplicate_detection() {
let mut s = socket_established();
s.remote_mss = 6;

// Normal ACK of previously recived segment
send!(s, time 0, TcpRepr {
seq_number: REMOTE_SEQ + 1,
ack_number: Some(LOCAL_SEQ + 1),
window_len: 6,
..SEND_TEMPL
});

// First duplicate, should not be counted as there is nothing to resend
send!(s, time 0, TcpRepr {
seq_number: REMOTE_SEQ + 1,
ack_number: Some(LOCAL_SEQ + 1),
window_len: 6,
..SEND_TEMPL
});

assert_eq!(s.local_rx_dup_acks, 0,
"duplicate ACK counter is set but wound not transmit data");

// Send a long string of text divided into several packets
// because of previously recieved "window_len"
// because of small remote_mss
s.send_slice(b"xxxxxxyyyyyywwwwwwzzzzzz").unwrap();

// This packet is reordered in network
Expand Down Expand Up @@ -4005,21 +3993,18 @@ mod test {
send!(s, time 1050, TcpRepr {
seq_number: REMOTE_SEQ + 1,
ack_number: Some(LOCAL_SEQ + 1),
window_len: 6,
..SEND_TEMPL
});
// Second duplicate ACK
send!(s, time 1055, TcpRepr {
seq_number: REMOTE_SEQ + 1,
ack_number: Some(LOCAL_SEQ + 1),
window_len: 6,
..SEND_TEMPL
});
// Reordered packet arrives which should reset duplicate ACK count
send!(s, time 1060, TcpRepr {
seq_number: REMOTE_SEQ + 1,
ack_number: Some(LOCAL_SEQ + 1 + (6 * 3)),
window_len: 6,
..SEND_TEMPL
});

Expand Down Expand Up @@ -4174,7 +4159,7 @@ mod test {
#[test]
fn test_psh_transmit() {
let mut s = socket_established();
s.remote_win_len = 6;
s.remote_mss = 6;
s.send_slice(b"abcdef").unwrap();
s.send_slice(b"123456").unwrap();
recv!(s, time 0, Ok(TcpRepr {
Expand Down