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Commit ce177ae2 authored by Gerrit Renker's avatar Gerrit Renker
Browse files

dccp ccid-3: Remove redundant 'options_received' struct 



The `options_received' struct is redundant, since it re-duplicates the existing
`p' and `x_recv' fields. This patch removes the sub-struct and migrates the
format conversion operations (cf. below) to ccid3_hc_tx_parse_options().

                     Why the fields are redundant
                     ----------------------------
The Loss Event Rate p and the Receive Rate x_recv are initially 0 when first 
loading CCID-3, as ccid_new() zeroes out the entire ccid3_hc_tx_sock. 

When Loss Event Rate or Receive Rate options are received, they are stored by
ccid3_hc_tx_parse_options() into the fields `ccid3or_loss_event_rate' and
`ccid3or_receive_rate' of the sub-struct `options_received' in ccid3_hc_tx_sock.

After parsing (considering only the established state - dccp_rcv_established()),
the packet is passed on to ccid_hc_tx_packet_recv(). This calls the CCID-3
specific routine ccid3_hc_tx_packet_recv(), which performs the following copy
operations between fields of ccid3_hc_tx_sock:

 * hctx->options_received.ccid3or_receive_rate is copied into hctx->x_recv,
   after scaling it for fixpoint arithmetic, by 2^64;
 * hctx->options_received.ccid3or_loss_event_rate is copied into hctx->p,
   considering the above special cases; in addition, a value of 0 here needs to
   be mapped into p=0 (when no Loss Event Rate option has been received yet).

Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
parent 535c55df

net/dccp/ccids/ccid3.c

+8 −16
Original line number Diff line number Diff line
@@ -370,11 +370,10 @@ static void ccid3_hc_tx_packet_sent(struct sock *sk, int more, 
static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)

{

	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);

	struct ccid3_options_received *opt_recv = &hctx->options_received;

	struct tfrc_tx_hist_entry *acked;

	ktime_t now;

	unsigned long t_nfb;

	u32 pinv, r_sample;

	u32 r_sample;



	/* we are only interested in ACKs */

	if (!(DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_ACK ||
@@ -404,17 +403,6 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) 
	r_sample  = dccp_sample_rtt(sk, ktime_us_delta(now, acked->stamp));

	hctx->rtt = tfrc_ewma(hctx->rtt, r_sample, 9);



	/* Update receive rate in units of 64 * bytes/second */

	hctx->x_recv = opt_recv->ccid3or_receive_rate;

	hctx->x_recv <<= 6;



	/* Update loss event rate (which is scaled by 1e6) */

	pinv = opt_recv->ccid3or_loss_event_rate;

	if (pinv == 0)

		hctx->p = 0;

	else

		hctx->p = tfrc_invert_loss_event_rate(pinv);



	/*

	 * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3

	 */
@@ -487,7 +475,6 @@ static int ccid3_hc_tx_parse_options(struct sock *sk, u8 packet_type, 
				     u8 option, u8 *optval, u8 optlen)

{

	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);

	struct ccid3_options_received *opt_recv = &hctx->options_received;

	__be32 opt_val;



	switch (option) {
@@ -504,11 +491,16 @@ static int ccid3_hc_tx_parse_options(struct sock *sk, u8 packet_type, 
		opt_val = ntohl(get_unaligned((__be32 *)optval));



		if (option == TFRC_OPT_RECEIVE_RATE) {

			opt_recv->ccid3or_receive_rate = opt_val;

			/* Receive Rate is kept in units of 64 bytes/second */

			hctx->x_recv = opt_val;

			hctx->x_recv <<= 6;



			ccid3_pr_debug("%s(%p), RECEIVE_RATE=%u\n",

				       dccp_role(sk), sk, opt_val);

		} else {

			opt_recv->ccid3or_loss_event_rate = opt_val;

			/* Update the fixpoint Loss Event Rate fraction */

			hctx->p = tfrc_invert_loss_event_rate(opt_val);



			ccid3_pr_debug("%s(%p), LOSS_EVENT_RATE=%u\n",

				       dccp_role(sk), sk, opt_val);

		}

net/dccp/ccids/ccid3.h

+0 −7
Original line number Diff line number Diff line
@@ -70,11 +70,6 @@ enum ccid3_options { 
	TFRC_OPT_RECEIVE_RATE	 = 194,

};



struct ccid3_options_received {

	u32 ccid3or_loss_event_rate;

	u32 ccid3or_receive_rate;

};



/* TFRC sender states */

enum ccid3_hc_tx_states {

	TFRC_SSTATE_NO_SENT = 1,
@@ -101,7 +96,6 @@ enum ccid3_hc_tx_states { 
 * @t_ld - Time last doubled during slow start

 * @t_nom - Nominal send time of next packet

 * @hist - Packet history

 * @options_received - Parsed set of retrieved options

 */

struct ccid3_hc_tx_sock {

	u64				x;
@@ -119,7 +113,6 @@ struct ccid3_hc_tx_sock { 
	ktime_t				t_ld;

	ktime_t				t_nom;

	struct tfrc_tx_hist_entry	*hist;

	struct ccid3_options_received	options_received;

};



static inline struct ccid3_hc_tx_sock *ccid3_hc_tx_sk(const struct sock *sk)