On Wed, 2012-08-22 at 12:00 +0200, Eric Dumazet wrote:
> On Wed, 2012-08-22 at 11:29 +0200, Alex Bergmann wrote:
>
> > Actual 6 SYN frames are sent. The initial one and 5 retries.
> >
>
> first one had a t0 + 0 delay. How can it count ???
>
> > The kernel is waiting another 32 seconds for a SYN+ACK and then gives
> > the ETIMEDOUT back to userspace.
> >
> > Do you mean that we have to send another SYN packet after the 3 minutes?
> >
>
> First SYN is not a retransmit
>
> R2 = time_of_last_SYN - time_of_initial_SYN (t0) = 31
>
> If you read RFC it states :
>
> "In particular, R2 for a SYN segment MUST
> be set large enough to provide retransmission of the segment
> for at least 3 minutes."
>
>
> That means that the last _retransmit_ MUST happen after 180 seconds.
>
> And not :
>
> Send all the restransmits at t0 + 1, then wait 180 seconds before giving
> connect() a timeout indication.
>
>
Therefore, the minimal connect() timeout should be : 180 + 100 seconds
(allowing 100 seconds for the SYNACKs sent in answer of the very last
retransmit to come back)
(100 seconds is the R2 for non SYN frames)
RFC quote : The value of R2 SHOULD
correspond to at least 100 seconds.
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