[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: Gerrit Renker <gerrit@erg.abdn.ac.uk> Signed-off-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>
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@ -131,12 +131,11 @@ static u32 ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock *hctx, ktime_t now)
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*
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*/
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static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp)
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{
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struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
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__u64 min_rate = 2 * hctx->ccid3hctx_x_recv;
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const __u64 old_x = hctx->ccid3hctx_x;
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ktime_t now = stamp? *stamp : ktime_get_real();
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ktime_t now = stamp ? *stamp : ktime_get_real();
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/*
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* Handle IDLE periods: do not reduce below RFC3390 initial sending rate
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@ -230,27 +229,27 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
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ccid3_pr_debug("%s(%p, state=%s) - entry \n", dccp_role(sk), sk,
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ccid3_tx_state_name(hctx->ccid3hctx_state));
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switch (hctx->ccid3hctx_state) {
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case TFRC_SSTATE_NO_FBACK:
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/* RFC 3448, 4.4: Halve send rate directly */
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if (hctx->ccid3hctx_state == TFRC_SSTATE_FBACK)
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ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
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else if (hctx->ccid3hctx_state != TFRC_SSTATE_NO_FBACK)
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goto out;
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/*
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* Determine new allowed sending rate X as per draft rfc3448bis-00, 4.4
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*/
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if (hctx->ccid3hctx_t_rto == 0 || /* no feedback received yet */
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hctx->ccid3hctx_p == 0) {
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/* halve send rate directly */
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hctx->ccid3hctx_x = max(hctx->ccid3hctx_x / 2,
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(((__u64)hctx->ccid3hctx_s) << 6) /
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TFRC_T_MBI);
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ccid3_pr_debug("%s(%p, state=%s), updated tx rate to %u "
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"bytes/s\n", dccp_role(sk), sk,
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ccid3_tx_state_name(hctx->ccid3hctx_state),
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(unsigned)(hctx->ccid3hctx_x >> 6));
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/* The value of R is still undefined and so we can not recompute
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* the timeout value. Keep initial value as per [RFC 4342, 5]. */
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t_nfb = TFRC_INITIAL_TIMEOUT;
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ccid3_update_send_interval(hctx);
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break;
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case TFRC_SSTATE_FBACK:
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} else {
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/*
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* Modify the cached value of X_recv [RFC 3448, 4.4]
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* Modify the cached value of X_recv
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*
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* If (p == 0 || X_calc > 2 * X_recv)
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* If (X_calc > 2 * X_recv)
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* X_recv = max(X_recv / 2, s / (2 * t_mbi));
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* Else
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* X_recv = X_calc / 4;
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@ -259,32 +258,28 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
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*/
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BUG_ON(hctx->ccid3hctx_p && !hctx->ccid3hctx_x_calc);
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if (hctx->ccid3hctx_p == 0 ||
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(hctx->ccid3hctx_x_calc > (hctx->ccid3hctx_x_recv >> 5))) {
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if (hctx->ccid3hctx_x_calc > (hctx->ccid3hctx_x_recv >> 5))
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hctx->ccid3hctx_x_recv =
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max(hctx->ccid3hctx_x_recv / 2,
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(((__u64)hctx->ccid3hctx_s) << 6) /
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(2 * TFRC_T_MBI));
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} else {
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else {
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hctx->ccid3hctx_x_recv = hctx->ccid3hctx_x_calc;
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hctx->ccid3hctx_x_recv <<= 4;
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}
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/* Now recalculate X [RFC 3448, 4.3, step (4)] */
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ccid3_hc_tx_update_x(sk, NULL);
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/*
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* Schedule no feedback timer to expire in
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* max(t_RTO, 2 * s/X) = max(t_RTO, 2 * t_ipi)
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* See comments in packet_recv() regarding the value of t_RTO.
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*/
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t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);
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break;
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case TFRC_SSTATE_NO_SENT:
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DCCP_BUG("%s(%p) - Illegal state NO_SENT", dccp_role(sk), sk);
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/* fall through */
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case TFRC_SSTATE_TERM:
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goto out;
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}
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ccid3_pr_debug("Reduced X to %llu/64 bytes/sec\n",
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(unsigned long long)hctx->ccid3hctx_x);
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/*
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* Set new timeout for the nofeedback timer.
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* See comments in packet_recv() regarding the value of t_RTO.
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*/
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if (unlikely(hctx->ccid3hctx_t_rto == 0)) /* no feedback yet */
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t_nfb = TFRC_INITIAL_TIMEOUT;
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else
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t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);
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restart_timer:
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sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
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