> [PATCH] tcp: allow timestamps even if SYN packet has tsval=0
>
> Some systems send SYN packets with apparently wrong RFC1323 timestamp
> option values [timestamp tsval=0 tsecr=0].
> It might be for security reasons (
http://www.secuobs.com/plugs/25220.shtml )
>
> Linux TCP stack ignores this option and sends back a SYN+ACK packet
> without timestamp option, thus many TCP flows cannot use timestamps
> and lose some benefit of RFC1323.
>
> Other operating systems seem to not care about initial tsval value, and let
> tcp flows to negotiate timestamp option.
>
> Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>