tcp: delivery rate estimator

Type: feature

First cut implementation with limited testing. The feature is not
enabled by default and the expectation is that cc algorithms will enable
it on demand.

Change-Id: I92b70cb4dabcff0e9ccd1d725952c4880af394da
Signed-off-by: Florin Coras <fcoras@cisco.com>

1 files changed, 20 insertions, 1 deletions

diff --git a/src/vnet/tcp/tcp_output.c b/src/vnet/tcp/tcp_output.c
index 1adac95731f..d3c4ca4a314 100644
--- a/src/vnet/tcp/tcp_output.c
+++ b/src/vnet/tcp/tcp_output.c
@@ -422,6 +422,9 @@ tcp_update_burst_snd_vars (tcp_connection_t * tc)
 		     &tc->snd_opts);
 
   tcp_update_rcv_wnd (tc);
+
+  if (tc->flags & TCP_CONN_RATE_SAMPLE)
+    tc->flags |= TCP_CONN_TRACK_BURST;
 }
 
 void
@@ -1129,8 +1132,17 @@ u32
 tcp_session_push_header (transport_connection_t * tconn, vlib_buffer_t * b)
 {
   tcp_connection_t *tc = (tcp_connection_t *) tconn;
+
+  if (tc->flags & TCP_CONN_TRACK_BURST)
+    {
+      tcp_bt_check_app_limited (tc);
+      tcp_bt_track_tx (tc);
+      tc->flags &= ~TCP_CONN_TRACK_BURST;
+    }
+
   tcp_push_hdr_i (tc, b, tc->snd_nxt, /* compute opts */ 0, /* burst */ 1,
 		  /* update_snd_nxt */ 1);
+
   tc->snd_una_max = seq_max (tc->snd_nxt, tc->snd_una_max);
   tcp_validate_txf_size (tc, tc->snd_una_max - tc->snd_una);
   /* If not tracking an ACK, start tracking */
@@ -1418,7 +1430,11 @@ tcp_prepare_retransmit_segment (tcp_worker_ctx_t * wrk,
     return 0;
 
   if (tcp_in_fastrecovery (tc))
-    tc->snd_rxt_bytes += n_bytes;
+    {
+      tc->snd_rxt_bytes += n_bytes;
+      if (tc->flags & TCP_CONN_RATE_SAMPLE)
+	tcp_bt_track_rxt (tc, start, start + n_bytes);
+    }
 
 done:
   TCP_EVT_DBG (TCP_EVT_CC_RTX, tc, offset, n_bytes);
@@ -1540,6 +1556,9 @@ tcp_timer_retransmit_handler_i (u32 index, u8 is_syn)
       else
 	scoreboard_clear (&tc->sack_sb);
 
+      if (tc->flags & TCP_CONN_RATE_SAMPLE)
+	tcp_bt_flush_samples (tc);
+
       /* If we've sent beyond snd_congestion, update it */
       tc->snd_congestion = seq_max (tc->snd_nxt, tc->snd_congestion);