# HG changeset patch
# User Roman Arutyunyan <arut@nginx.com>
# Date 1612460387 -10800
# Node ID 88c9c868a7c965ca8e48d88e86f514c854828ee9
# Parent  0b3d70fbba99b58c8287a0c9c94c167e4128ff21
QUIC: disabled non-immediate ACKs for Initial and Handshake.

As per quic-transport-33:

   An endpoint MUST acknowledge all ack-eliciting Initial and Handshake
   packets immediately

If a packet carrying Initial or Handshake ACK was lost, a non-immediate ACK
should not be sent later.  Instead, client is expected to send a new packet
to acknowledge.

Sending non-immediate ACKs for Initial packets can cause the client to
generate an inflated RTT sample.

diff --git a/src/event/quic/ngx_event_quic.c b/src/event/quic/ngx_event_quic.c
--- a/src/event/quic/ngx_event_quic.c
+++ b/src/event/quic/ngx_event_quic.c
@@ -5527,8 +5527,11 @@ ngx_quic_resend_frames(ngx_connection_t 
         switch (f->type) {
         case NGX_QUIC_FT_ACK:
         case NGX_QUIC_FT_ACK_ECN:
-            /* force generation of most recent acknowledgment */
-            ctx->send_ack = NGX_QUIC_MAX_ACK_GAP;
+            if (ctx->level == ssl_encryption_application) {
+                /* force generation of most recent acknowledgment */
+                ctx->send_ack = NGX_QUIC_MAX_ACK_GAP;
+            }
+
             ngx_quic_free_frame(c, f);
             break;