ngx_event_quic.c.diff

--- ngx_event_quic.c	2024-05-28 15:28:07.000000000 +0200
+++ ngx_event_quic.c	2025-02-04 23:33:38.990662931 +0100
@@ -308,8 +308,13 @@
     qc->streams.client_max_streams_uni = qc->tp.initial_max_streams_uni;
     qc->streams.client_max_streams_bidi = qc->tp.initial_max_streams_bidi;
 
-    qc->congestion.window = ngx_min(10 * qc->tp.max_udp_payload_size,
-                                    ngx_max(2 * qc->tp.max_udp_payload_size,
+    // qc->tp.max_udp_payload_size is set via a constant in ngx_quic_init_transport_params() to 65527 which is wrong.
+    // It is not set by inspecting the peer's transport parameters, i think this happens at a later time in ngx_quic_apply_transport_params(),
+    // but there the initial congestion window is not recalculated and can't be since the peer's transport parameters are not available at that time.
+    // So for a fix for this experiment, the max_udp_payload_size is set to 1200 for only the calculation of the initial congestion window.
+    const int PATCHED_MAX_UDP_PAYLOAD_SIZE = 1200;
+    qc->congestion.window = ngx_min(10 * PATCHED_MAX_UDP_PAYLOAD_SIZE,
+                                    ngx_max(2 * PATCHED_MAX_UDP_PAYLOAD_SIZE,
                                             14720));
     qc->congestion.ssthresh = (size_t) -1;
     qc->congestion.recovery_start = ngx_current_msec;