* Note that although the original article, srtt and rttvar are scaled
* to minimize round-off errors, here we don't. Instead, we rely on
* better precision time measurements.
- *
- * TODO support us rtt resolution
*/
static void
tcp_estimate_rtt (tcp_connection_t * tc, u32 mrtt)
}
}
+static inline void
+tcp_estimate_rtt_us (tcp_connection_t * tc, f64 mrtt)
+{
+ tc->mrtt_us = tc->mrtt_us + (mrtt - tc->mrtt_us) * 0.125;
+}
+
/**
- * Update RTT estimate and RTO timer
+ * Update rtt estimate
+ *
+ * We have potentially three sources of rtt measurements:
*
- * Measure RTT: We have two sources of RTT measurements: TSOPT and ACK
- * timing. Middle boxes are known to fiddle with TCP options so we
- * should give higher priority to ACK timing.
+ * TSOPT difference between current and echoed timestamp. It has ms
+ * precision and can be computed per ack
+ * ACK timing one sequence number is tracked per rtt with us (micro second)
+ * precision.
+ * rate sample if enabled, all outstanding bytes are tracked with us
+ * precision. Every ack and sack are a rtt sample
*
- * This should be called only if previously sent bytes have been acked.
+ * Middle boxes are known to fiddle with TCP options so we give higher
+ * priority to ACK timing.
*
- * return 1 if valid rtt 0 otherwise
+ * For now, rate sample rtts are only used under congestion.
*/
static int
tcp_update_rtt (tcp_connection_t * tc, tcp_rate_sample_t * rs, u32 ack)
if (tcp_in_cong_recovery (tc))
{
/* Accept rtt estimates for samples that have not been retransmitted */
- if ((tc->cfg_flags & TCP_CFG_F_RATE_SAMPLE)
- && !(rs->flags & TCP_BTS_IS_RXT))
- {
- mrtt = rs->rtt_time * THZ;
- goto estimate_rtt;
- }
- goto done;
+ if (!(tc->cfg_flags & TCP_CFG_F_RATE_SAMPLE)
+ || (rs->flags & TCP_BTS_IS_RXT))
+ goto done;
+ if (rs->rtt_time)
+ tcp_estimate_rtt_us (tc, rs->rtt_time);
+ mrtt = rs->rtt_time * THZ;
+ goto estimate_rtt;
}
if (tc->rtt_ts && seq_geq (ack, tc->rtt_seq))
{
f64 sample = tcp_time_now_us (tc->c_thread_index) - tc->rtt_ts;
- tc->mrtt_us = tc->mrtt_us + (sample - tc->mrtt_us) * 0.125;
+ tcp_estimate_rtt_us (tc, sample);
mrtt = clib_max ((u32) (sample * THZ), 1);
/* Allow measuring of a new RTT */
tc->rtt_ts = 0;
if (tc->cfg_flags & TCP_CFG_F_RATE_SAMPLE)
tcp_bt_sample_delivery_rate (tc, &rs);
- if (tc->bytes_acked)
+ if (tc->bytes_acked + tc->sack_sb.last_sacked_bytes)
{
- tcp_program_dequeue (wrk, tc);
tcp_update_rtt (tc, &rs, vnet_buffer (b)->tcp.ack_number);
+ if (tc->bytes_acked)
+ tcp_program_dequeue (wrk, tc);
}
TCP_EVT (TCP_EVT_ACK_RCVD, tc);
return TCP_ERROR_ENQUEUED_OOO;
}
-/**
- * Check if ACK could be delayed. If ack can be delayed, it should return
- * true for a full frame. If we're always acking return 0.
- */
-always_inline int
-tcp_can_delack (tcp_connection_t * tc)
-{
- /* Send ack if ... */
- if (TCP_ALWAYS_ACK
- /* just sent a rcv wnd 0
- || (tc->flags & TCP_CONN_SENT_RCV_WND0) != 0 */
- /* constrained to send ack */
- || (tc->flags & TCP_CONN_SNDACK) != 0
- /* we're almost out of tx wnd */
- || tcp_available_cc_snd_space (tc) < 4 * tc->snd_mss)
- return 0;
-
- return 1;
-}
-
static int
tcp_buffer_discard_bytes (vlib_buffer_t * b, u32 n_bytes_to_drop)
{
/* In order data, enqueue. Fifo figures out by itself if any out-of-order
* segments can be enqueued after fifo tail offset changes. */
error = tcp_session_enqueue_data (tc, b, n_data_bytes);
- if (tcp_can_delack (tc))
- {
- if (!tcp_timer_is_active (tc, TCP_TIMER_DELACK))
- tcp_timer_set (&wrk->timer_wheel, tc, TCP_TIMER_DELACK,
- tcp_cfg.delack_time);
- goto done;
- }
-
tcp_program_ack (tc);
done:
child->tx_fifo_size = transport_tx_fifo_size (&child->connection);
- tcp_send_synack (child);
-
+ /* This initializes elog track, must be done before synack */
TCP_EVT (TCP_EVT_SYN_RCVD, child, 1);
+ tcp_send_synack (child);
+
done:
if (PREDICT_FALSE (b->flags & VLIB_BUFFER_IS_TRACED))