On 6/14/19 7:25 AM, Eric Dumazet wrote:
> On Fri, Jun 14, 2019 at 7:04 AM maowenan <maowe...@huawei.com> 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.
>>
>> tcp_conn_request->tcp_v4_init_seq->secure_tcp_seq->seq_scale
>> 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 ?
>
Oh well, maybe I should not have answered before my breakfast/coffee.
What I meant to say is that we do not want to fix this problem by working around
the issue you noticed (which leads to RST packets)
