Make TCP more RFC 5681 compliant wrt immediate ACKs.
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@ -1094,6 +1094,8 @@ impl<'a> TcpSocket<'a> {
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let payload_len = repr.payload.len();
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if payload_len == 0 { return Ok(None) }
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let assembler_was_empty = self.assembler.is_empty();
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// Try adding payload octets to the assembler.
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match self.assembler.add(payload_offset, payload_len) {
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Ok(()) => {
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@ -1121,17 +1123,24 @@ impl<'a> TcpSocket<'a> {
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self.rx_buffer.enqueue_unallocated(contig_len);
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}
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// Per RFC 5681, we should send an immediate ACK when either:
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// 1) an out-of-order segment is received, or
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// 2) a segment arrives that fills in all or part of a gap in sequence space.
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if self.assembler.is_empty() {
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Ok(None)
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} else {
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// The assembler isn't empty, so there's at least one gap.
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if !self.assembler.is_empty() {
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// Print the ranges recorded in the assembler.
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net_trace!("[{}]{}:{}: assembler: {}",
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self.debug_id, self.local_endpoint, self.remote_endpoint,
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self.assembler);
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}
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// Per RFC 5681, we should send an immediate ACK when either:
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// 1) an out-of-order segment is received, or
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// 2) a segment arrives that fills in all or part of a gap in sequence space.
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if !self.assembler.is_empty() || !assembler_was_empty {
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// Note that we change the transmitter state here.
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// This is fine because smoltcp assumes that it can always transmit zero or one
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// packets for every packet it receives.
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self.remote_last_ack = Some(self.remote_seq_no + self.rx_buffer.len());
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Ok(Some(self.ack_reply(ip_repr, &repr)))
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} else {
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Ok(None)
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}
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}
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@ -3270,13 +3279,12 @@ mod test {
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ack_number: Some(LOCAL_SEQ + 1),
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payload: &b"abcdef"[..],
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..SEND_TEMPL
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});
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recv!(s, [TcpRepr {
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}, Ok(Some(TcpRepr {
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seq_number: LOCAL_SEQ + 1,
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ack_number: Some(REMOTE_SEQ + 1 + 6),
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window_len: 58,
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..RECV_TEMPL
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}]);
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})));
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assert_eq!(s.recv(10), Ok(&b"abcdef"[..]));
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}
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