On Wed, Aug 22, 2012 at 3:03 AM, Eric Dumazet <eric.duma...@gmail.com> wrote: > 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.
I agree if you take RFC1122 literally the last retransmission must happen no less than 3 minutes from the 1st SYN... Oh actually it'd be 3 minutes plus initRTO because the 3 minutes applies only to "retransmission" as in "R2 for a SYN segment MUST be set large enough to provide retransmission of the segment for at least 3 minutes.: But IMHO 6 retries providing 1+2+4+8+16+32 = 63 secs retransmission plus 64 secs wait time totaling 127 secs is really plenty enough. You have a good point on SYN-ACK. Jerry > > > > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
