[nginx] QUIC: fixed congesion control in GSO mode.

[Roman Arutyunyan]

details:   https://hg.nginx.org/nginx/rev/e9a003d40485
branches:  
changeset: 9140:e9a003d40485
user:      Roman Arutyunyan <arut at nginx.com>
date:      Thu Jul 27 13:35:42 2023 +0400
description:
QUIC: fixed congesion control in GSO mode.

In non-GSO mode, a datagram is sent if congestion window is not exceeded by the
time of send.  The window could be exceeded by a small amount after the send.
In GSO mode, congestion window was checked in a similar way, but for all
concatenated datagrams as a whole.  This could result in exceeding congestion
window by a lot.  Now congestion window is checked for every datagram in GSO
mode as well.

diffstat:

 src/event/quic/ngx_event_quic_output.c |  2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diffs (12 lines):

diff -r d7dec2970161 -r e9a003d40485 src/event/quic/ngx_event_quic_output.c
--- a/src/event/quic/ngx_event_quic_output.c	Thu Aug 10 20:11:29 2023 +0400
+++ b/src/event/quic/ngx_event_quic_output.c	Thu Jul 27 13:35:42 2023 +0400
@@ -358,7 +358,7 @@ ngx_quic_create_segments(ngx_connection_
 
         len = ngx_min(segsize, (size_t) (end - p));
 
-        if (len && cg->in_flight < cg->window) {
+        if (len && cg->in_flight + (p - dst) < cg->window) {
 
             n = ngx_quic_output_packet(c, ctx, p, len, len);
             if (n == NGX_ERROR) {