On 10/9/07, Gerrit Renker <gerrit@xxxxxxxxxxxxxx> wrote:
> This is a reworked patch, using the suggested static allocation, with the following differences
> * made the field names consistent between request_sock and dccp_sock;
> * since the time between receiving a Timestamp and sending the Timestamp Echo is not huge, it makes
> sense to use dccp_timestamp() instead of ktime; which also halved the size of the field;
> * whitespace adapted to make assignments toe in line;
> * added a warning when 0-valued timestamps arrive, since we use this to test whether one was present.
>
> I have tested this for functioning in two different environments.
>
> ----------------------------------> Patch v2 <------------------------------------------------------------
> [DCCP]: Handle timestamps on Request/Response exchange separately
>
> In DCCP, timestamps can occur on packets anytime, CCID3 uses a timestamp(/echo) on the Request/Response
> exchange. This patch addresses the following situation:
> * timestamps are recorded on the listening socket;
> * Responses are sent from dccp_request_sockets;
> * suppose two connections reach the listening socket with very small time in between:
> * the first timestamp value gets overwritten by the second connection request.
>
> This is not really good, so this patch separates timestamps into
> * those which are received by the server during the initial handshake (on dccp_request_sock);
> * those which are received by the client or the client after connection establishment.
>
> As before, a timestamp of 0 is regarded as indicating that no (meaningful) timestamp has been
> received (in addition, a warning message is printed if hosts send 0-valued timestamps).
>
> The timestamp-echoing now works as follows:
> * when a timestamp is present on the initial Request, it is placed into dreq, due to the
> call to dccp_parse_options in dccp_v{4,6}_conn_request;
> * when a timestamp is present on the Ack leading from RESPOND => OPEN, it is copied over
> from the request_sock into the child cocket in dccp_create_openreq_child;
> * timestamps received on an (established) dccp_sock are treated as before.
>
> Since Elapsed Time is measured in hundredths of milliseconds (13.2), the new dccp_timestamp()
> function is used, as it is expected that the time between receiving the timestamp and
> sending the timestamp echo will be very small against the wrap-around time. As a byproduct,
> this allows smaller timestamping-time fields.
>
> Furthermore, inserting the Timestamp Echo option has been taken out of the block starting with
> '!dccp_packet_without_ack()', since Timestamp Echo can be carried on any packet (5.8 and 13.3).
>
> Signed-off-by: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
Acked-by: Ian McDonald <ian.mcdonald@xxxxxxxxxxx>
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