Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 52515e77 authored by Gerrit Renker's avatar Gerrit Renker Committed by David S. Miller
Browse files

[CCID3]: Nofeedback timer according to rfc3448bis 



This implements the changes to the nofeedback timer handling suggested
in draft rfc3448bis00, section 4.4. In particular, these changes mean:

 * better handling of the lossless case (p == 0)
 * the timestamp for computing t_ld becomes obsolete
 * much more recent document (RFC 3448 is almost 5 years old)
 * concepts in rfc3448bis arose from a real, working implementation
   (cf. sec. 12)

Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-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 d8d1252f

net/dccp/ccids/ccid3.c

+29 −34
Original line number Diff line number Diff line
@@ -131,7 +131,6 @@ static u32 ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock *hctx, ktime_t now) 
 *

 */

static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp)



{

	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);

	__u64 min_rate = 2 * hctx->ccid3hctx_x_recv;
@@ -230,27 +229,27 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data) 
	ccid3_pr_debug("%s(%p, state=%s) - entry \n", dccp_role(sk), sk,

		       ccid3_tx_state_name(hctx->ccid3hctx_state));



	switch (hctx->ccid3hctx_state) {

	case TFRC_SSTATE_NO_FBACK:

		/* RFC 3448, 4.4: Halve send rate directly */

	if (hctx->ccid3hctx_state == TFRC_SSTATE_FBACK)

		ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);

	else if (hctx->ccid3hctx_state != TFRC_SSTATE_NO_FBACK)

		goto out;



	/*

	 * Determine new allowed sending rate X as per draft rfc3448bis-00, 4.4

	 */

	if (hctx->ccid3hctx_t_rto == 0 ||	/* no feedback received yet */

	    hctx->ccid3hctx_p == 0) {



		/* halve send rate directly */

		hctx->ccid3hctx_x = max(hctx->ccid3hctx_x / 2,

					(((__u64)hctx->ccid3hctx_s) << 6) /

								    TFRC_T_MBI);



		ccid3_pr_debug("%s(%p, state=%s), updated tx rate to %u "

			       "bytes/s\n", dccp_role(sk), sk,

			       ccid3_tx_state_name(hctx->ccid3hctx_state),

			       (unsigned)(hctx->ccid3hctx_x >> 6));

		/* The value of R is still undefined and so we can not recompute

		 * the timeout value. Keep initial value as per [RFC 4342, 5]. */

		t_nfb = TFRC_INITIAL_TIMEOUT;

		ccid3_update_send_interval(hctx);

		break;

	case TFRC_SSTATE_FBACK:

	} else {

		/*

		 *  Modify the cached value of X_recv [RFC 3448, 4.4]

		 *  Modify the cached value of X_recv

		 *

		 *  If (p == 0 || X_calc > 2 * X_recv)

		 *  If (X_calc > 2 * X_recv)

		 *    X_recv = max(X_recv / 2, s / (2 * t_mbi));

		 *  Else

		 *    X_recv = X_calc / 4;
@@ -259,32 +258,28 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data) 
		 */

		BUG_ON(hctx->ccid3hctx_p && !hctx->ccid3hctx_x_calc);



		if (hctx->ccid3hctx_p == 0 ||

		    (hctx->ccid3hctx_x_calc > (hctx->ccid3hctx_x_recv >> 5))) {



		if (hctx->ccid3hctx_x_calc > (hctx->ccid3hctx_x_recv >> 5))

			hctx->ccid3hctx_x_recv =

				max(hctx->ccid3hctx_x_recv / 2,

				    (((__u64)hctx->ccid3hctx_s) << 6) /

							      (2 * TFRC_T_MBI));

		} else {

		else {

			hctx->ccid3hctx_x_recv = hctx->ccid3hctx_x_calc;

			hctx->ccid3hctx_x_recv <<= 4;

		}

		/* Now recalculate X [RFC 3448, 4.3, step (4)] */

		ccid3_hc_tx_update_x(sk, NULL);

	}

	ccid3_pr_debug("Reduced X to %llu/64 bytes/sec\n",

			(unsigned long long)hctx->ccid3hctx_x);



	/*

		 * Schedule no feedback timer to expire in

		 * max(t_RTO, 2 * s/X)  =  max(t_RTO, 2 * t_ipi)

	 * Set new timeout for the nofeedback timer.

	 * See comments in packet_recv() regarding the value of t_RTO.

	 */

	if (unlikely(hctx->ccid3hctx_t_rto == 0))	/* no feedback yet */

		t_nfb = TFRC_INITIAL_TIMEOUT;

	else

		t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);

		break;

	case TFRC_SSTATE_NO_SENT:

		DCCP_BUG("%s(%p) - Illegal state NO_SENT", dccp_role(sk), sk);

		/* fall through */

	case TFRC_SSTATE_TERM:

		goto out;

	}



restart_timer:

	sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,