Re: [PATCH net v2] tcp: avoid creating multiple req socks with the same tuples
From: Eric Dumazet
Date: Fri Jun 14 2019 - 10:30:22 EST
On Fri, Jun 14, 2019 at 7:04 AM maowenan <maowenan@xxxxxxxxxx> wrote:
> I agree that this is a special case.
> I propose one point about the sequence of synack, if two synack with two different
> sequence since the time elapse 64ns, this issue disappear.
> static u32 seq_scale(u32 seq)
> * As close as possible to RFC 793, which
> * suggests using a 250 kHz clock.
> * Further reading shows this assumes 2 Mb/s networks.
> * For 10 Mb/s Ethernet, a 1 MHz clock is appropriate.
> * For 10 Gb/s Ethernet, a 1 GHz clock should be ok, but
> * we also need to limit the resolution so that the u32 seq
> * overlaps less than one time per MSL (2 minutes).
> * Choosing a clock of 64 ns period is OK. (period of 274 s)
> return seq + (ktime_get_real_ns() >> 6);
> So if the long delay larger than 64ns, the seq is difference.
The core issue has nothing to do with syncookies.
Are you sure you really understand this stack ?