[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@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>

1 files changed, 13 insertions, 8 deletions

diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index b1d5da6..027d181 100644
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -117,11 +117,13 @@ struct sock *dccp_create_openreq_child(struct sock *sk,
 		struct dccp_sock *newdp = dccp_sk(newsk);
 		struct dccp_minisock *newdmsk = dccp_msk(newsk);
 
-		newdp->dccps_role	   = DCCP_ROLE_SERVER;
-		newdp->dccps_hc_rx_ackvec  = NULL;
-		newdp->dccps_service_list  = NULL;
-		newdp->dccps_service	   = dreq->dreq_service;
-		newicsk->icsk_rto	   = DCCP_TIMEOUT_INIT;
+		newdp->dccps_role	    = DCCP_ROLE_SERVER;
+		newdp->dccps_hc_rx_ackvec   = NULL;
+		newdp->dccps_service_list   = NULL;
+		newdp->dccps_service	    = dreq->dreq_service;
+		newdp->dccps_timestamp_echo = dreq->dreq_timestamp_echo;
+		newdp->dccps_timestamp_time = dreq->dreq_timestamp_time;
+		newicsk->icsk_rto	    = DCCP_TIMEOUT_INIT;
 
 		if (dccp_feat_clone(sk, newsk))
 			goto out_free;
@@ -303,9 +305,12 @@ EXPORT_SYMBOL_GPL(dccp_reqsk_send_ack);
 
 void dccp_reqsk_init(struct request_sock *req, struct sk_buff *skb)
 {
-	inet_rsk(req)->rmt_port = dccp_hdr(skb)->dccph_sport;
-	inet_rsk(req)->acked	= 0;
-	req->rcv_wnd		= sysctl_dccp_feat_sequence_window;
+	struct dccp_request_sock *dreq = dccp_rsk(req);
+
+	inet_rsk(req)->rmt_port	  = dccp_hdr(skb)->dccph_sport;
+	inet_rsk(req)->acked	  = 0;
+	req->rcv_wnd		  = sysctl_dccp_feat_sequence_window;
+	dreq->dreq_timestamp_echo = 0;
 }
 
 EXPORT_SYMBOL_GPL(dccp_reqsk_init);