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Commit b4d4f7c7 authored by Gerrit Renker's avatar Gerrit Renker Committed by David S. Miller
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[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: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: default avatarIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8109616e

include/linux/dccp.h

+14 −2
Original line number Diff line number Diff line
@@ -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;

net/dccp/minisocks.c

+13 −8
Original line number Diff line number Diff line
@@ -121,6 +121,8 @@ struct sock *dccp_create_openreq_child(struct sock *sk, 
		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))
@@ -303,9 +305,12 @@ EXPORT_SYMBOL_GPL(dccp_reqsk_send_ack); 


void dccp_reqsk_init(struct request_sock *req, struct sk_buff *skb)

{

	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);

net/dccp/options.c

+36 −20
Original line number Diff line number Diff line
@@ -166,16 +166,27 @@ int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq, 
		case DCCPO_TIMESTAMP:

			if (len != 4)

				goto out_invalid_option;



			/*

			 * RFC 4340 13.1: "The precise time corresponding to

			 * Timestamp Value zero is not specified". We use

			 * zero to indicate absence of a meaningful timestamp.

			 */

			opt_val = get_unaligned((__be32 *)value);

			opt_recv->dccpor_timestamp = ntohl(opt_val);



			/* FIXME: if dreq != NULL, don't store this on listening socket */

			dp->dccps_timestamp_echo = opt_recv->dccpor_timestamp;

			dp->dccps_timestamp_time = ktime_get_real();

			if (unlikely(opt_val == 0)) {

				DCCP_WARN("Timestamp with zero value\n");

				break;

			}



			if (dreq != NULL) {

				dreq->dreq_timestamp_echo = ntohl(opt_val);

				dreq->dreq_timestamp_time = dccp_timestamp();

			} else {

				opt_recv->dccpor_timestamp =

					dp->dccps_timestamp_echo = ntohl(opt_val);

				dp->dccps_timestamp_time = dccp_timestamp();

			}

			dccp_pr_debug("%s rx opt: TIMESTAMP=%u, ackno=%llu\n",

				      dccp_role(sk), opt_recv->dccpor_timestamp,

				      dccp_role(sk), ntohl(opt_val),

				      (unsigned long long)

				      DCCP_SKB_CB(skb)->dccpd_ack_seq);

			break;
@@ -393,16 +404,24 @@ int dccp_insert_option_timestamp(struct sock *sk, struct sk_buff *skb) 


EXPORT_SYMBOL_GPL(dccp_insert_option_timestamp);



static int dccp_insert_option_timestamp_echo(struct sock *sk,

static int dccp_insert_option_timestamp_echo(struct dccp_sock *dp,

					     struct dccp_request_sock *dreq,

					     struct sk_buff *skb)

{

	struct dccp_sock *dp = dccp_sk(sk);

	__be32 tstamp_echo;

	int len, elapsed_time_len;

	unsigned char *to;

	const suseconds_t delta = ktime_us_delta(ktime_get_real(),

						 dp->dccps_timestamp_time);

	u32 elapsed_time = delta / 10;

	u32 elapsed_time, elapsed_time_len, len;



	if (dreq != NULL) {

		elapsed_time = dccp_timestamp() - dreq->dreq_timestamp_time;

		tstamp_echo  = htonl(dreq->dreq_timestamp_echo);

		dreq->dreq_timestamp_echo = 0;

	} else {

		elapsed_time = dccp_timestamp() - dp->dccps_timestamp_time;

		tstamp_echo  = htonl(dp->dccps_timestamp_echo);

		dp->dccps_timestamp_echo = 0;

	}



	elapsed_time_len = dccp_elapsed_time_len(elapsed_time);

	len = 6 + elapsed_time_len;
@@ -415,7 +434,6 @@ static int dccp_insert_option_timestamp_echo(struct sock *sk, 
	*to++ = DCCPO_TIMESTAMP_ECHO;

	*to++ = len;



	tstamp_echo = htonl(dp->dccps_timestamp_echo);

	memcpy(to, &tstamp_echo, 4);

	to += 4;
@@ -427,8 +445,6 @@ static int dccp_insert_option_timestamp_echo(struct sock *sk, 
		memcpy(to, &var32, 4);

	}



	dp->dccps_timestamp_echo = 0;

	dp->dccps_timestamp_time = ktime_set(0, 0);

	return 0;

}
@@ -537,10 +553,6 @@ int dccp_insert_options(struct sock *sk, struct sk_buff *skb) 
		    dccp_ackvec_pending(dp->dccps_hc_rx_ackvec) &&

		    dccp_insert_option_ackvec(sk, skb))

			return -1;



		if (dp->dccps_timestamp_echo != 0 &&

		    dccp_insert_option_timestamp_echo(sk, skb))

			return -1;

	}



	if (dp->dccps_hc_rx_insert_options) {
@@ -564,6 +576,10 @@ int dccp_insert_options(struct sock *sk, struct sk_buff *skb) 
	    dccp_insert_option_timestamp(sk, skb))

		return -1;



	if (dp->dccps_timestamp_echo != 0 &&

	    dccp_insert_option_timestamp_echo(dp, NULL, skb))

		return -1;



	/* XXX: insert other options when appropriate */



	if (DCCP_SKB_CB(skb)->dccpd_opt_len != 0) {