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tcp: reply with RST to invalid ACKs in SynReceived state. 

This mirrors the Linux behavior, and helps cleanup desynced state.
master
Dario Nieuwenhuis 2021-10-06 02:25:11 +02:00
parent 3a2cdc8680
commit 1f25a986c7
1 changed files with 23 additions and 5 deletions
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28
src/socket/tcp.rs
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@ -1364,6 +1364,18 @@ impl<'a> TcpSocket<'a> {
self.abort();
return Err(Error::Dropped);
}
// ACK in the SYN-RECEIVED state must have the exact ACK number, or we RST it.
(State::SynReceived, _, Some(ack_number)) => {
if ack_number != self.local_seq_no + 1 {
net_debug!(
"{}:{}:{}: unacceptable ACK in response to SYN|ACK",
self.meta.handle,
self.local_endpoint,
self.remote_endpoint
);
return Ok(Some(Self::rst_reply(ip_repr, repr)));
}
}
// Every acknowledgement must be for transmitted but unacknowledged data.
(_, _, Some(ack_number)) => {
let unacknowledged = self.tx_buffer.len() + control_len;
@ -3040,7 +3052,13 @@ mod test {
ack_number: Some(LOCAL_SEQ), // wrong
..SEND_TEMPL
},
Err(Error::Dropped)
Ok(Some(TcpRepr {
control: TcpControl::Rst,
seq_number: LOCAL_SEQ,
ack_number: None,
window_len: 0,
..RECV_TEMPL
}))
);
assert_eq!(s.state, State::SynReceived);
}
@ -3065,11 +3083,11 @@ mod test {
ack_number: Some(LOCAL_SEQ + 2), // wrong
..SEND_TEMPL
},
// TODO is this correct? probably not
Ok(Some(TcpRepr {
control: TcpControl::None,
seq_number: LOCAL_SEQ + 1,
ack_number: Some(REMOTE_SEQ + 1),
control: TcpControl::Rst,
seq_number: LOCAL_SEQ + 2,
ack_number: None,
window_len: 0,
..RECV_TEMPL
}))
);