tcp: use sacks for timer based recovery

Type: feature

If available, reuse sack scoreboard in timer triggered retransmit to
minimize spurious retransmits.

Additional changes/refactoring:
- limited transmit updates
- add sacked rxt count to scoreboard
- prr pacing of fast retransmits
- startup pacing updates
- changed loss window to flight + mss

Change-Id: I057de6a9d6401698bd1031d5cf5cfbb62f2bdf61
Signed-off-by: Florin Coras <fcoras@cisco.com>
(cherry picked from commit 36ebcfffbc7ab0e83b4bb8dfaec16bf16cafb954)

1 files changed, 2 insertions, 6 deletions

diff --git a/src/vnet/tcp/tcp_cubic.c b/src/vnet/tcp/tcp_cubic.c
index aa318961533..17f7932ea2e 100644
--- a/src/vnet/tcp/tcp_cubic.c
+++ b/src/vnet/tcp/tcp_cubic.c
@@ -103,10 +103,7 @@ cubic_congestion (tcp_connection_t * tc)
 
   cd->w_max = w_max;
   tc->ssthresh = clib_max (tc->cwnd * beta_cubic, 2 * tc->snd_mss);
-
   tc->cwnd = tc->ssthresh;
-  if (!tcp_opts_sack_permitted (&tc->rcv_opts))
-    tc->cwnd += 3 * tc->snd_mss;
 }
 
 static void
@@ -114,11 +111,10 @@ cubic_loss (tcp_connection_t * tc)
 {
   cubic_data_t *cd = (cubic_data_t *) tcp_cc_data (tc);
 
-  tc->ssthresh = clib_max (tc->cwnd * beta_cubic, 2 * tc->snd_mss);
   tc->cwnd = tcp_loss_wnd (tc);
   cd->t_start = cubic_time (tc->c_thread_index);
   cd->K = 0;
-  cd->w_max = 0;
+  cd->w_max = tc->cwnd / tc->snd_mss;
 }
 
 static void
@@ -159,7 +155,7 @@ cubic_rcv_ack (tcp_connection_t * tc, tcp_rate_sample_t * rs)
 
   if (tcp_in_slowstart (tc))
     {
-      tc->cwnd += clib_min (tc->snd_mss, tc->bytes_acked);
+      tc->cwnd += tc->bytes_acked;
       return;
     }