tcp: cc improvements and fixes

[vpp.git] / src / vnet / tcp / tcp_newreno.c

diff --git a/src/vnet/tcp/tcp_newreno.c b/src/vnet/tcp/tcp_newreno.c
index 3525f4e..0f43d21 100644 (file)
--- a/src/vnet/tcp/tcp_newreno.c
+++ b/src/vnet/tcp/tcp_newreno.c
@@ -18,7 +18,6 @@
 void
 newreno_congestion (tcp_connection_t * tc)
 {
-  tc->prev_ssthresh = tc->ssthresh;
   tc->ssthresh = clib_max (tcp_flight_size (tc) / 2, 2 * tc->snd_mss);
 }
 
@@ -37,8 +36,16 @@ newreno_rcv_ack (tcp_connection_t * tc)
     }
   else
     {
-      /* Round up to 1 if needed */
-      tc->cwnd += clib_max ((tc->snd_mss * tc->snd_mss) / tc->cwnd, 1);
+      /* tc->cwnd += clib_max ((tc->snd_mss * tc->snd_mss) / tc->cwnd, 1); */
+      tc->cwnd_acc_bytes += tc->bytes_acked;
+      if (tc->cwnd_acc_bytes >= tc->cwnd)
+       {
+         u32 inc = tc->cwnd_acc_bytes / tc->cwnd;
+         tc->cwnd += inc * tc->snd_mss;
+         tc->cwnd_acc_bytes -= inc * tc->cwnd;
+       }
+      tc->cwnd = clib_min (tc->cwnd,
+                          transport_tx_fifo_size (&tc->connection));
     }
 }
 
@@ -47,13 +54,28 @@ newreno_rcv_cong_ack (tcp_connection_t * tc, tcp_cc_ack_t ack_type)
 {
   if (ack_type == TCP_CC_DUPACK)
     {
-      tc->cwnd += tc->snd_mss;
+      if (!tcp_opts_sack_permitted (tc))
+       tc->cwnd += tc->snd_mss;
     }
   else if (ack_type == TCP_CC_PARTIALACK)
     {
-      tc->cwnd -= tc->bytes_acked;
-      if (tc->bytes_acked > tc->snd_mss)
-       tc->bytes_acked += tc->snd_mss;
+      /* RFC 6582 Sec. 3.2 */
+      if (!tcp_opts_sack_permitted (&tc->rcv_opts))
+       {
+         /* Deflate the congestion window by the amount of new data
+          * acknowledged by the Cumulative Acknowledgment field.
+          * If the partial ACK acknowledges at least one SMSS of new data,
+          * then add back SMSS bytes to the congestion window. This
+          * artificially inflates the congestion window in order to reflect
+          * the additional segment that has left the network. This "partial
+          * window deflation" attempts to ensure that, when fast recovery
+          * eventually ends, approximately ssthresh amount of data will be
+          * outstanding in the network.*/
+         tc->cwnd = (tc->cwnd > tc->bytes_acked + tc->snd_mss) ?
+           tc->cwnd - tc->bytes_acked : tc->snd_mss;
+         if (tc->bytes_acked > tc->snd_mss)
+           tc->cwnd += tc->snd_mss;
+       }
     }
 }