diff options
-rw-r--r-- | net/dccp/ccids/lib/packet_history.c | 83 |
1 files changed, 24 insertions, 59 deletions
diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c index e2e250aa5c8..5c4ded1cf42 100644 --- a/net/dccp/ccids/lib/packet_history.c +++ b/net/dccp/ccids/lib/packet_history.c @@ -428,31 +428,16 @@ int tfrc_rx_hist_init(struct tfrc_rx_hist *h, struct sock *sk) EXPORT_SYMBOL_GPL(tfrc_rx_hist_init); /** - * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against - */ -static inline struct tfrc_rx_hist_entry * - tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h) -{ - return h->ring[0]; -} - -/** - * tfrc_rx_hist_rtt_prev_s: previously suitable (wrt rtt_last_s) RTT-sampling entry - */ -static inline struct tfrc_rx_hist_entry * - tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h) -{ - return h->ring[h->rtt_sample_prev]; -} - -/** * tfrc_rx_hist_sample_rtt - Sample RTT from timestamp / CCVal - * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able - * to compute a sample with given data - calling function should check this. + * Based on ideas presented in RFC 4342, 8.1. This function expects that no loss + * is pending and uses the following history entries (via rtt_sample_prev): + * - h->ring[0] contains the most recent history entry prior to @skb; + * - h->ring[1] is an unused `dummy' entry when the current difference is 0; */ void tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb) { - u32 sample = 0, delta_v; + struct tfrc_rx_hist_entry *last = h->ring[0]; + u32 sample, delta_v; /* * When not to sample: @@ -466,47 +451,27 @@ void tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb) tfrc_rx_hist_loss_pending(h)) return; - delta_v = SUB16(dccp_hdr(skb)->dccph_ccval, - tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval); - - if (delta_v < 1 || delta_v > 4) { /* unsuitable CCVal delta */ - if (h->rtt_sample_prev == 2) { /* previous candidate stored */ - sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval, - tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval); - if (sample) - sample = 4 / sample * - ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp, - tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp); - else /* - * FIXME: This condition is in principle not - * possible but occurs when CCID is used for - * two-way data traffic. I have tried to trace - * it, but the cause does not seem to be here. - */ - DCCP_BUG("please report to dccp@vger.kernel.org" - " => prev = %u, last = %u", - tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval, - tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval); - } else if (delta_v < 1) { - h->rtt_sample_prev = 1; - goto keep_ref_for_next_time; - } - - } else if (delta_v == 4) /* optimal match */ - sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp)); - else { /* suboptimal match */ - h->rtt_sample_prev = 2; - goto keep_ref_for_next_time; - } + h->rtt_sample_prev = 0; /* reset previous candidate */ - if (unlikely(sample > DCCP_SANE_RTT_MAX)) { - DCCP_WARN("RTT sample %u too large, using max\n", sample); - sample = DCCP_SANE_RTT_MAX; + delta_v = SUB16(dccp_hdr(skb)->dccph_ccval, last->tfrchrx_ccval); + if (delta_v == 0) { /* less than RTT/4 difference */ + h->rtt_sample_prev = 1; + return; } + sample = dccp_sane_rtt(ktime_to_us(net_timedelta(last->tfrchrx_tstamp))); - h->rtt_sample_prev = 0; /* use current entry as next reference */ -keep_ref_for_next_time: + if (delta_v <= 4) /* between RTT/4 and RTT */ + sample *= 4 / delta_v; + else if (!(sample < h->rtt_estimate && sample > h->rtt_estimate/2)) + /* + * Optimisation: CCVal difference is greater than 1 RTT, yet the + * sample is less than the local RTT estimate; which means that + * the RTT estimate is too high. + * To avoid noise, it is not done if the sample is below RTT/2. + */ + return; - h->rtt_estimate = tfrc_ewma(h->rtt_estimate, sample, 9); + /* Use a lower weight than usual to increase responsiveness */ + h->rtt_estimate = tfrc_ewma(h->rtt_estimate, sample, 5); } EXPORT_SYMBOL_GPL(tfrc_rx_hist_sample_rtt); |