X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;f=src%2Fvnet%2Ftcp%2Ftcp_newreno.c;h=c66250e41eaf33e1e558b20a4a41f37da68a8bb1;hb=93992a9048cb6e5dcd22de5091e72de778122627;hp=3525f4e5918663b752c6dbf3e2ed06bd555bae80;hpb=583dc8d3e23a780c85ebe48ea59f0338aad4df17;p=vpp.git

diff --git a/src/vnet/tcp/tcp_newreno.c b/src/vnet/tcp/tcp_newreno.c
index 3525f4e5918..c66250e41ea 100644
--- a/src/vnet/tcp/tcp_newreno.c
+++ b/src/vnet/tcp/tcp_newreno.c
@@ -51,9 +51,23 @@ newreno_rcv_cong_ack (tcp_connection_t * tc, tcp_cc_ack_t ack_type)
     }
   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->cwnd - tc->bytes_acked : 0;
+	  if (tc->bytes_acked > tc->snd_mss)
+	    tc->cwnd += tc->snd_mss;
+	}
     }
 }