From 055025fa3b6d42d61ee99d8b6d26a0bf93444e85 Mon Sep 17 00:00:00 2001
From: Roman Arutyunyan <arut@nginx.com>
Date: Mon, 14 Feb 2022 14:51:10 +0300
Subject: [PATCH] QUIC: trim input chain in ngx_quic_buffer_write().

This allows to eliminate explicit trimming when handling input STREAM frame.
As a result, ngx_quic_trim_chain() is eliminated as well.
---
 src/event/quic/ngx_event_quic_frames.c  | 36 +++++++++++--------------
 src/event/quic/ngx_event_quic_frames.h  |  1 -
 src/event/quic/ngx_event_quic_streams.c |  5 ----
 3 files changed, 16 insertions(+), 26 deletions(-)

diff --git a/src/event/quic/ngx_event_quic_frames.c b/src/event/quic/ngx_event_quic_frames.c
index b89072ea2..4a39141eb 100644
--- a/src/event/quic/ngx_event_quic_frames.c
+++ b/src/event/quic/ngx_event_quic_frames.c
@@ -258,26 +258,6 @@ ngx_quic_free_frame(ngx_connection_t *c, ngx_quic_frame_t *frame)
 }
 
 
-void
-ngx_quic_trim_chain(ngx_chain_t *in, size_t size)
-{
-    size_t      n;
-    ngx_buf_t  *b;
-
-    while (in && size > 0) {
-        b = in->buf;
-        n = ngx_min((size_t) (b->last - b->pos), size);
-
-        b->pos += n;
-        size -= n;
-
-        if (b->pos == b->last) {
-            in = in->next;
-        }
-    }
-}
-
-
 void
 ngx_quic_free_chain(ngx_connection_t *c, ngx_chain_t *in)
 {
@@ -551,6 +531,22 @@ ngx_quic_write_buffer(ngx_connection_t *c, ngx_quic_buffer_t *qb,
     chain = &qb->chain;
 
     while (in && limit) {
+
+        if (offset < base) {
+            n = ngx_min((uint64_t) (in->buf->last - in->buf->pos),
+                        ngx_min(base - offset, limit));
+
+            in->buf->pos += n;
+            offset += n;
+            limit -= n;
+
+            if (in->buf->pos == in->buf->last) {
+                in = in->next;
+            }
+
+            continue;
+        }
+
         cl = *chain;
 
         if (cl == NULL) {
diff --git a/src/event/quic/ngx_event_quic_frames.h b/src/event/quic/ngx_event_quic_frames.h
index 853e36ca1..48cb22e91 100644
--- a/src/event/quic/ngx_event_quic_frames.h
+++ b/src/event/quic/ngx_event_quic_frames.h
@@ -26,7 +26,6 @@ ngx_int_t ngx_quic_split_frame(ngx_connection_t *c, ngx_quic_frame_t *f,
 ngx_chain_t *ngx_quic_alloc_chain(ngx_connection_t *c);
 ngx_chain_t *ngx_quic_copy_buf(ngx_connection_t *c, u_char *data,
     size_t len);
-void ngx_quic_trim_chain(ngx_chain_t *in, size_t size);
 void ngx_quic_free_chain(ngx_connection_t *c, ngx_chain_t *in);
 
 ngx_chain_t *ngx_quic_read_buffer(ngx_connection_t *c, ngx_quic_buffer_t *qb,
diff --git a/src/event/quic/ngx_event_quic_streams.c b/src/event/quic/ngx_event_quic_streams.c
index 1906bc695..78650b04f 100644
--- a/src/event/quic/ngx_event_quic_streams.c
+++ b/src/event/quic/ngx_event_quic_streams.c
@@ -1115,11 +1115,6 @@ ngx_quic_handle_stream_frame(ngx_connection_t *c, ngx_quic_header_t *pkt,
         return NGX_OK;
     }
 
-    if (f->offset < qs->recv_offset) {
-        ngx_quic_trim_chain(frame->data, qs->recv_offset - f->offset);
-        f->offset = qs->recv_offset;
-    }
-
     if (f->fin) {
         if (qs->recv_final_size != (uint64_t) -1 && qs->recv_final_size != last)
         {