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changeset 8963:5acd0d89d8c2 quic

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QUIC: fixed handling stream input buffers. Previously, ngx_quic_write_chain() treated each input buffer as a memory buffer, which is not always the case. Special buffers were not skipped, which is especially important when hitting the input byte limit. The issue manifested itself with ngx_quic_write_chain() returning a non-empty chain consisting of a special last_buf buffer when called from QUIC stream send_chain(). In order for this to happen, input byte limit should be equal to the chain length, and the input chain should end with an empty last_buf buffer. An easy way to achieve this is the following: location /empty { return 200; } When this non-empty chain was returned from send_chain(), it signalled to the caller that input was blocked, while in fact it wasn't. This prevented HTTP request from finalization, which prevented QUIC from sending STREAM FIN to the client. The QUIC stream was then reset after a timeout. Now special buffers are skipped and send_chain() returns NULL in the case above, which signals to the caller a successful operation. Also, original byte limit is now passed to ngx_quic_write_chain() from send_chain() instead of actual chain length to make sure it's never zero.
author Roman Arutyunyan <arut@nginx.com>
date Thu, 13 Jan 2022 11:23:53 +0300
parents 47f45a98f892
children ad67fcc30567
files src/event/quic/ngx_event_quic_frames.c src/event/quic/ngx_event_quic_streams.c
diffstat 2 files changed, 12 insertions(+), 6 deletions(-) [+]
line wrap: on
line diff
--- a/src/event/quic/ngx_event_quic_frames.c
+++ b/src/event/quic/ngx_event_quic_frames.c
@@ -527,7 +527,17 @@ ngx_quic_write_chain(ngx_connection_t *c
             continue;
         }
 
-        for (p = b->pos + offset; p != b->last && in && limit; /* void */ ) {
+        for (p = b->pos + offset; p != b->last && in; /* void */ ) {
+
+            if (!ngx_buf_in_memory(in->buf) || in->buf->pos == in->buf->last) {
+                in = in->next;
+                continue;
+            }
+
+            if (limit == 0) {
+                break;
+            }
+
             n = ngx_min(b->last - p, in->buf->last - in->buf->pos);
             n = ngx_min(n, limit);
 
@@ -539,10 +549,6 @@ ngx_quic_write_chain(ngx_connection_t *c
             in->buf->pos += n;
             offset += n;
             limit -= n;
-
-            if (in->buf->pos == in->buf->last) {
-                in = in->next;
-            }
         }
 
         if (b->sync && p == b->last) {
--- a/src/event/quic/ngx_event_quic_streams.c
+++ b/src/event/quic/ngx_event_quic_streams.c
@@ -861,7 +861,7 @@ ngx_quic_stream_send_chain(ngx_connectio
         }
     }
 
-    in = ngx_quic_write_chain(pc, &qs->out, in, n, 0);
+    in = ngx_quic_write_chain(pc, &qs->out, in, limit, 0);
     if (in == NGX_CHAIN_ERROR) {
         return NGX_CHAIN_ERROR;
     }