From e1982a1abafda2e1e541dc6d6516d4087c0e5bd8 Mon Sep 17 00:00:00 2001
From: Sergey Kandaurov <pluknet@nginx.com>
Date: Wed, 21 Oct 2020 12:03:23 +0100
Subject: [PATCH] QUIC: teach how to compute only the length of created QUIC
 headers.

It will be used for precise expansion of UDP datagram payload.
---
 src/event/ngx_event_quic_transport.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/event/ngx_event_quic_transport.c b/src/event/ngx_event_quic_transport.c
index cea69ab7a..93b3bae78 100644
--- a/src/event/ngx_event_quic_transport.c
+++ b/src/event/ngx_event_quic_transport.c
@@ -420,6 +420,12 @@ ngx_quic_create_long_header(ngx_quic_header_t *pkt, u_char *out,
 {
     u_char  *p, *start;
 
+    if (out == NULL) {
+        return 5 + 2 + pkt->dcid.len + pkt->scid.len
+               + ngx_quic_varint_len(pkt_len + pkt->num_len) + pkt->num_len
+               + (pkt->level == ssl_encryption_initial ? 1 : 0);
+    }
+
     p = start = out;
 
     *p++ = pkt->flags;
@@ -465,6 +471,10 @@ ngx_quic_create_short_header(ngx_quic_header_t *pkt, u_char *out,
 {
     u_char  *p, *start;
 
+    if (out == NULL) {
+        return 1 + pkt->dcid.len + pkt->num_len;
+    }
+
     p = start = out;
 
     *p++ = pkt->flags;