From d20ed95f8bf3d98d31dbbab8b00bb4c1a4a140f3 Mon Sep 17 00:00:00 2001 From: Gerrit Renker Date: Thu, 4 Sep 2008 07:30:19 +0200 Subject: 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 --- net/dccp/ccids/ccid3.c | 48 ++++++++++++++++++++++++++++++------- net/dccp/ccids/lib/packet_history.c | 3 +++ 2 files changed, 42 insertions(+), 9 deletions(-) (limited to 'net/dccp') diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c index 36f4992f3c3..0a7c22598d6 100644 --- a/net/dccp/ccids/ccid3.c +++ b/net/dccp/ccids/ccid3.c @@ -577,6 +577,28 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk, hcrx->p_inverse = ~0U; /* see RFC 4342, 8.5 */ break; case CCID3_FBACK_PARAM_CHANGE: + if (unlikely(hcrx->state == TFRC_RSTATE_NO_DATA)) { + /* + * rfc3448bis-06, 6.3.1: First packet(s) lost or marked + * FIXME: in rfc3448bis the receiver returns X_recv=0 + * here as it normally would in the first feedback packet. + * However this is not possible yet, since the code still + * uses RFC 3448, i.e. + * If (p > 0) + * Calculate X_calc using the TCP throughput equation. + * X = max(min(X_calc, 2*X_recv), s/t_mbi); + * would bring X down to s/t_mbi. That is why we return + * X_recv according to rfc3448bis-06 for the moment. + */ + u32 rtt = hcrx->rtt ? : DCCP_FALLBACK_RTT, s = hcrx->s; + + if (s == 0) { + DCCP_WARN("No sample for s, using fallback\n"); + s = TCP_MIN_RCVMSS; + } + hcrx->x_recv = scaled_div32(s, 2 * rtt); + break; + } /* * When parameters change (new loss or p > p_prev), we do not * have a reliable estimate for R_m of [RFC 3448, 6.2] and so @@ -650,6 +672,14 @@ static u32 ccid3_first_li(struct sock *sk) u32 x_recv, p, delta; u64 fval; + /* + * rfc3448bis-06, 6.3.1: First data packet(s) are marked or lost. Set p + * to give the equivalent of X_target = s/(2*R). Thus fval = 2 and so p + * is about 20.64%. This yields an interval length of 4.84 (rounded up). + */ + if (unlikely(hcrx->state == TFRC_RSTATE_NO_DATA)) + return 5; + if (hcrx->rtt == 0) { DCCP_WARN("No RTT estimate available, using fallback RTT\n"); hcrx->rtt = DCCP_FALLBACK_RTT; @@ -683,6 +713,15 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb) const u64 ndp = dccp_sk(sk)->dccps_options_received.dccpor_ndp; const bool is_data_packet = dccp_data_packet(skb); + /* + * Perform loss detection and handle pending losses + */ + if (tfrc_rx_handle_loss(&hcrx->hist, &hcrx->li_hist, + skb, ndp, ccid3_first_li, sk)) { + do_feedback = CCID3_FBACK_PARAM_CHANGE; + goto done_receiving; + } + if (unlikely(hcrx->state == TFRC_RSTATE_NO_DATA)) { if (is_data_packet) { const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4; @@ -710,15 +749,6 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb) hcrx->bytes_recv += payload; } - /* - * Perform loss detection and handle pending losses - */ - if (tfrc_rx_handle_loss(&hcrx->hist, &hcrx->li_hist, - skb, ndp, ccid3_first_li, sk)) { - do_feedback = CCID3_FBACK_PARAM_CHANGE; - goto done_receiving; - } - if (tfrc_rx_hist_loss_pending(&hcrx->hist)) return; /* done receiving */ diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c index 5b4e1cf8439..8db34225c00 100644 --- a/net/dccp/ccids/lib/packet_history.c +++ b/net/dccp/ccids/lib/packet_history.c @@ -335,6 +335,9 @@ int tfrc_rx_handle_loss(struct tfrc_rx_hist *h, { int is_new_loss = 0; + if (tfrc_rx_hist_duplicate(h, skb)) + return 0; + if (h->loss_count == 0) { __do_track_loss(h, skb, ndp); } else if (h->loss_count == 1) { -- cgit v1.2.3