From 5a41fd5ee7af8d39106d5fc5de7f2d17d7356b30 Mon Sep 17 00:00:00 2001
From: Florin Coras <fcoras@cisco.com>
Date: Mon, 19 Apr 2021 10:17:26 -0700
Subject: [PATCH] tcp: req app deq notification on fifo full

If fifo full, default to requesting an app deq notification and forcing
an ack (window update) if zero rcv window sent is still active.

Type: improvement

Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: Iade7e1722503da149c62c465c472edbb0a5599f7
---
 src/vnet/session/session.h |  7 +++++++
 src/vnet/tcp/tcp.c         | 22 ++++++++++++++++++++++
 src/vnet/tcp/tcp_output.c  |  5 ++++-
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/src/vnet/session/session.h b/src/vnet/session/session.h
index 44cbaebf4ab..8b591339edb 100644
--- a/src/vnet/session/session.h
+++ b/src/vnet/session/session.h
@@ -574,6 +574,13 @@ transport_rx_fifo_has_ooo_data (transport_connection_t * tc)
   return svm_fifo_has_ooo_data (s->rx_fifo);
 }
 
+always_inline void
+transport_rx_fifo_req_deq_ntf (transport_connection_t *tc)
+{
+  session_t *s = session_get (tc->s_index, tc->thread_index);
+  svm_fifo_add_want_deq_ntf (s->rx_fifo, SVM_FIFO_WANT_DEQ_NOTIF);
+}
+
 always_inline clib_time_type_t
 transport_time_now (u32 thread_index)
 {
diff --git a/src/vnet/tcp/tcp.c b/src/vnet/tcp/tcp.c
index e447fac00b5..a6c1e216c20 100644
--- a/src/vnet/tcp/tcp.c
+++ b/src/vnet/tcp/tcp.c
@@ -1272,6 +1272,27 @@ tcp_session_flush_data (transport_connection_t * tconn)
   tc->psh_seq = tc->snd_una + transport_max_tx_dequeue (tconn) - 1;
 }
 
+static int
+tcp_session_app_rx_evt (transport_connection_t *conn)
+{
+  tcp_connection_t *tc = (tcp_connection_t *) conn;
+  u32 min_free, lo = 4 << 10, hi = 128 << 10;
+
+  if (!(tc->flags & TCP_CONN_ZERO_RWND_SENT))
+    return 0;
+
+  min_free = clib_clamp (transport_rx_fifo_size (conn) >> 3, lo, hi);
+  if (transport_max_rx_enqueue (conn) < min_free)
+    {
+      transport_rx_fifo_req_deq_ntf (conn);
+      return 0;
+    }
+
+  tcp_send_ack (tc);
+
+  return 0;
+}
+
 /* *INDENT-OFF* */
 const static transport_proto_vft_t tcp_proto = {
   .enable = vnet_tcp_enable_disable,
@@ -1291,6 +1312,7 @@ const static transport_proto_vft_t tcp_proto = {
   .update_time = tcp_update_time,
   .flush_data = tcp_session_flush_data,
   .custom_tx = tcp_session_custom_tx,
+  .app_rx_evt = tcp_session_app_rx_evt,
   .format_connection = format_tcp_session,
   .format_listener = format_tcp_listener_session,
   .format_half_open = format_tcp_half_open_session,
diff --git a/src/vnet/tcp/tcp_output.c b/src/vnet/tcp/tcp_output.c
index 928e8249eb1..dac50b5bf40 100644
--- a/src/vnet/tcp/tcp_output.c
+++ b/src/vnet/tcp/tcp_output.c
@@ -463,7 +463,10 @@ tcp_make_ack_i (tcp_connection_t * tc, vlib_buffer_t * b, tcp_state_t state,
   vnet_buffer (b)->tcp.connection_index = tc->c_c_index;
 
   if (wnd == 0)
-    tcp_zero_rwnd_sent_on (tc);
+    {
+      transport_rx_fifo_req_deq_ntf (&tc->connection);
+      tcp_zero_rwnd_sent_on (tc);
+    }
   else
     tcp_zero_rwnd_sent_off (tc);
 }
-- 
2.16.6