dccp tfrc: Perform early loss detection
This enables the TFRC code to begin loss detection (as soon as the module is loaded), using the latest updates from rfc3448bis-06, 6.3.1: * when the first data packet(s) are lost or marked, set * X_target = s/(2*R) => f(p) = s/(R * X_target) = 2, * corresponding to a loss rate of ~ 20.64%. The handle_loss() function is now called right at the begin of rx_packet_recv() and thus no longer protected against duplicates: hence a call to rx_duplicate() has been added. Such a call makes sense now, as the previous patch initialises the first entry with a sequence number of GSR. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
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@ -577,6 +577,28 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk,
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hcrx->p_inverse = ~0U; /* see RFC 4342, 8.5 */
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break;
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case CCID3_FBACK_PARAM_CHANGE:
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if (unlikely(hcrx->state == TFRC_RSTATE_NO_DATA)) {
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/*
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* rfc3448bis-06, 6.3.1: First packet(s) lost or marked
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* FIXME: in rfc3448bis the receiver returns X_recv=0
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* here as it normally would in the first feedback packet.
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* However this is not possible yet, since the code still
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* uses RFC 3448, i.e.
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* If (p > 0)
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* Calculate X_calc using the TCP throughput equation.
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* X = max(min(X_calc, 2*X_recv), s/t_mbi);
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* would bring X down to s/t_mbi. That is why we return
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* X_recv according to rfc3448bis-06 for the moment.
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*/
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u32 rtt = hcrx->rtt ? : DCCP_FALLBACK_RTT, s = hcrx->s;
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if (s == 0) {
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DCCP_WARN("No sample for s, using fallback\n");
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s = TCP_MIN_RCVMSS;
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}
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hcrx->x_recv = scaled_div32(s, 2 * rtt);
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break;
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}
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/*
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* When parameters change (new loss or p > p_prev), we do not
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* have a reliable estimate for R_m of [RFC 3448, 6.2] and so
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@ -650,6 +672,14 @@ static u32 ccid3_first_li(struct sock *sk)
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u32 x_recv, p, delta;
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u64 fval;
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/*
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* rfc3448bis-06, 6.3.1: First data packet(s) are marked or lost. Set p
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* to give the equivalent of X_target = s/(2*R). Thus fval = 2 and so p
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* is about 20.64%. This yields an interval length of 4.84 (rounded up).
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*/
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if (unlikely(hcrx->state == TFRC_RSTATE_NO_DATA))
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return 5;
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if (hcrx->rtt == 0) {
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DCCP_WARN("No RTT estimate available, using fallback RTT\n");
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hcrx->rtt = DCCP_FALLBACK_RTT;
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@ -683,6 +713,15 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
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const u64 ndp = dccp_sk(sk)->dccps_options_received.dccpor_ndp;
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const bool is_data_packet = dccp_data_packet(skb);
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/*
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* Perform loss detection and handle pending losses
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*/
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if (tfrc_rx_handle_loss(&hcrx->hist, &hcrx->li_hist,
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skb, ndp, ccid3_first_li, sk)) {
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do_feedback = CCID3_FBACK_PARAM_CHANGE;
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goto done_receiving;
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}
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if (unlikely(hcrx->state == TFRC_RSTATE_NO_DATA)) {
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if (is_data_packet) {
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const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
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@ -710,15 +749,6 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
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hcrx->bytes_recv += payload;
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}
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/*
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* Perform loss detection and handle pending losses
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*/
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if (tfrc_rx_handle_loss(&hcrx->hist, &hcrx->li_hist,
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skb, ndp, ccid3_first_li, sk)) {
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do_feedback = CCID3_FBACK_PARAM_CHANGE;
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goto done_receiving;
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}
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if (tfrc_rx_hist_loss_pending(&hcrx->hist))
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return; /* done receiving */
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@ -335,6 +335,9 @@ int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
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{
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int is_new_loss = 0;
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if (tfrc_rx_hist_duplicate(h, skb))
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return 0;
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if (h->loss_count == 0) {
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__do_track_loss(h, skb, ndp);
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} else if (h->loss_count == 1) {
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