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[DCCP]: Handle timestamps on Request/Response exchange separately

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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@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gerrit Renker 2007-12-13 12:37:19 -02:00 • committed by David S. Miller
parent 8109616e2e
commit b4d4f7c70f
3 changed files with 63 additions and 30 deletions
Download patch file Download diff file Expand all files Collapse all files

16
include/linux/dccp.h
View file

@ -407,11 +407,23 @@ struct dccp_opt_pend {
extern void dccp_minisock_init(struct dccp_minisock *dmsk);
/**
* struct dccp_request_sock - represent DCCP-specific connection request
* @dreq_inet_rsk: structure inherited from
* @dreq_iss: initial sequence number sent on the Response (RFC 4340, 7.1)
* @dreq_isr: initial sequence number received on the Request
* @dreq_service: service code present on the Request (there is just one)
* The following two fields are analogous to the ones in dccp_sock:
* @dreq_timestamp_echo: last received timestamp to echo (13.1)
* @dreq_timestamp_echo: the time of receiving the last @dreq_timestamp_echo
*/
struct dccp_request_sock {
struct inet_request_sock dreq_inet_rsk;
__u64 dreq_iss;
__u64 dreq_isr;
__be32 dreq_service;
__u32 dreq_timestamp_echo;
__u32 dreq_timestamp_time;
};
static inline struct dccp_request_sock *dccp_rsk(const struct request_sock *req)
@ -477,8 +489,8 @@ struct dccp_ackvec;
* @dccps_gar - greatest valid ack number received on a non-Sync; initialized to %dccps_iss
* @dccps_service - first (passive sock) or unique (active sock) service code
* @dccps_service_list - second .. last service code on passive socket
* @dccps_timestamp_time - time of latest TIMESTAMP option
* @dccps_timestamp_echo - latest timestamp received on a TIMESTAMP option
* @dccps_timestamp_time - time of receiving latest @dccps_timestamp_echo
* @dccps_l_ack_ratio - feature-local Ack Ratio
* @dccps_r_ack_ratio - feature-remote Ack Ratio
* @dccps_pcslen - sender partial checksum coverage (via sockopt)
@ -514,8 +526,8 @@ struct dccp_sock {
__u64 dccps_gar;
__be32 dccps_service;
struct dccp_service_list *dccps_service_list;
ktime_t dccps_timestamp_time;
__u32 dccps_timestamp_echo;
__u32 dccps_timestamp_time;
__u16 dccps_l_ack_ratio;
__u16 dccps_r_ack_ratio;
__u16 dccps_pcslen;