[nginx] Range filter: fixed duplicate last buffers.

[Maxim Dounin]

details:   https://hg.nginx.org/nginx/rev/c30a20e06c21
branches:  
changeset: 7508:c30a20e06c21
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Mon May 13 22:44:49 2019 +0300
description:
Range filter: fixed duplicate last buffers.

In ngx_http_range_singlepart_body() special buffers where passed
unmodified, including ones after the end of the range.  As such,
if the last buffer of a response was sent separately as a special
buffer, two buffers with b->last_buf set were present in the response.

In particular, this might result in a duplicate final chunk when using
chunked transfer encoding (normally range filter and chunked transfer
encoding are not used together, but this may happen if there are trailers
in the response).  This also likely to cause problems in HTTP/2.

Fix is to skip all special buffers after we've sent the last part of
the range requested.  These special buffers are not meaningful anyway,
since we set b->last_buf in the buffer with the last part of the range,
and everything is expected to be flushed due to it.

Additionally, ngx_http_next_body_filter() is now called even
if no buffers are to be passed to it.  This ensures that various
write events are properly propagated through the filter chain.  In
particular, this fixes test failures observed with the above change
and aio enabled.

diffstat:

 src/http/modules/ngx_http_range_filter_module.c |  8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diffs (25 lines):

diff --git a/src/http/modules/ngx_http_range_filter_module.c b/src/http/modules/ngx_http_range_filter_module.c
--- a/src/http/modules/ngx_http_range_filter_module.c
+++ b/src/http/modules/ngx_http_range_filter_module.c
@@ -723,6 +723,10 @@ ngx_http_range_singlepart_body(ngx_http_
 
         if (ngx_buf_special(buf)) {
 
+            if (range->end <= start) {
+                continue;
+            }
+
             tl = ngx_alloc_chain_link(r->pool);
             if (tl == NULL) {
                 return NGX_ERROR;
@@ -802,10 +806,6 @@ ngx_http_range_singlepart_body(ngx_http_
         ll = &tl->next;
     }
 
-    if (out == NULL) {
-        return NGX_OK;
-    }
-
     rc = ngx_http_next_body_filter(r, out);
 
     while (out) {