At 15:40 21/10/2004 +0200, Andre Oppermann wrote:
> Maybe I'm missing something, but I get the impression that, considering the > value (six seconds) to which the RTO is initialized, that part that says > > } else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 && > tp->t_softerror) { > tcp_drop(tp, error); > return (struct inpcb *)0; > > will never be executed, as the connection-establishment timer will always > timeout before the evaluated condition becomes true. > > Am I missing something? Or is it that this code is there just in case the > initial RTO is reduced to such a value that, in that case, this code would > kick in before the 75-seconds tconnection-establishment timer?
Yes, tcp_notify() gets called from icmp_input() when ICMP unreachable or related error messages from the network are received. In those cases you don't want to wait the full 75 seconds because the network tells you that a connection cannot be established to that destination. It doesn't do that the first time the network tells us that to avoid too fast reaction on spurious network problems, outages or re-routings.
I'd agree with this idea. However, my point is that, given the initial RTO of 6 seconds, the 75-second timer will always expire before the connection is aborted due to the received ICMP error messages.
That is, either the connection-establishment timer should be set to a larger value, or else fewer retransmissions and fewer ICMP errors should be required to abort a connection.
If you have a copy of Stevens' TCPv2 at hand, there's a diagram on page 828 that shows this. The 75-second timer will expire *before* tx->t_rxtshift > 3.
-- Fernando Gont e-mail: [EMAIL PROTECTED] || [EMAIL PROTECTED]
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