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Fix the TCP SEQ acceptability check. 

It has nothing to do with the last ACK transmitted.
This commit is contained in:
whitequark 2017-08-30 21:10:23 +00:00
parent c2bc20e9bf
commit 41ceeea9ac
1 changed files with 16 additions and 13 deletions
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29
src/socket/tcp.rs
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@ -830,30 +830,33 @@ impl<'a> TcpSocket<'a> {
}
}
match (self.state, repr) {
match self.state {
// In LISTEN and SYN-SENT states, we have not yet synchronized with the remote end.
(State::Listen, _) => (),
(State::SynSent, _) => (),
State::Listen => (),
State::SynSent => (),
// In all other states, segments must occupy a valid portion of the receive window.
(_, &TcpRepr { seq_number, .. }) => {
_ => {
let mut send_challenge_ack = false;
let window_start = self.remote_last_ack;
let window_end = window_start + self.rx_buffer.capacity();
if seq_number < window_start || seq_number > window_end {
net_debug!("[{}]{}:{}: SEQ not in receive window ({} not in {}..{}), \
will send challenge ACK",
let window_start = self.remote_seq_no;
let window_end = window_start + self.rx_buffer.capacity();
let segment_start = repr.seq_number;
let segment_end = segment_start + repr.segment_len();
if !((window_start <= segment_start && segment_start <= window_end) ||
(window_start <= segment_end && segment_end <= window_end)) {
net_debug!("[{}]{}:{}: segment not in receive window \
({}..{} not intersecting {}..{}), will send challenge ACK",
self.debug_id, self.local_endpoint, self.remote_endpoint,
seq_number, window_start, window_end);
segment_start, segment_end, window_start, window_end);
send_challenge_ack = true;
}
// For now, do not actually try to reassemble out-of-order segments.
if seq_number != self.remote_last_ack {
net_debug!("[{}]{}:{}: out-of-order SEQ ({} not in ..{}), \
if segment_start != window_start + self.rx_buffer.len() {
net_debug!("[{}]{}:{}: out-of-order SEQ ({} not equal to {}), \
will send challenge ACK",
self.debug_id, self.local_endpoint, self.remote_endpoint,
seq_number, self.remote_last_ack);
segment_start, window_start + self.rx_buffer.len());
// Some segments between what we have last received and this segment
// went missing. Send a duplicate ACK; RFC 793 does not specify the behavior
// required when receiving a duplicate ACK, but in practice (see RFC 1122