On Wed, 2012-08-22 at 10:48 +0200, Alex Bergmann wrote: > On 08/22/2012 10:06 AM, Eric Dumazet wrote: > >> Prior to 9ad7c049 the timeout was defined with 189secs. Now we have only > >> a timeout of 63secs. > >> > >> ((2 << 5) - 1) * 3 secs = 189 secs > >> ((2 << 5) - 1) * 1 secs = 63 secs > > > > Strange maths ... here I have : > > > > (1+2+4+8+16) * 3 = 93 secs > > vs > > (1+2+4+8+16) * 1 = 31 secs > > > > So even before said commit, we were not rfc1122 compliant. > > > > Using 7 retries would give 127 seconds, still not rfc compliant. > > You're missing the timeout after the 5th SYN packet was sent. This > would result in another 32 seconds (96 seconds). > > The timeout is calculated here: > > net/ipv4/tcp_timer.c(146:150) > > if (boundary <= linear_backoff_thresh) > timeout = ((2 << boundary) - 1) * rto_base; > else > timeout = ((2 << linear_backoff_thresh) - 1) * rto_base + > (boundary - linear_backoff_thresh) * TCP_RTO_MAX;
Thats the code yes but you miss the fact that last occurence of the timer doesnt send a frame on the _network_ R2 is derived from the last frame sent. Fact that the connect() is a bit long to return to user space is not relevant. We could block the task for 2 hours and still be non RFC compliant. Actual 5 frames are sent, so the effective global timeout is the one I quoted. 1 + 2 + 4 + 8 + 16 and its 31 Just do a tcpdump and you can see it. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
