[nginx] Range filter: allowed ranges on empty files (ticket #1031).

[Maxim Dounin]

details:   http://hg.nginx.org/nginx/rev/aeaac3ccee4f
branches:  
changeset: 7043:aeaac3ccee4f
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Tue Jun 27 00:53:46 2017 +0300
description:
Range filter: allowed ranges on empty files (ticket #1031).

As per RFC 2616 / RFC 7233, any range request to an empty file
is expected to result in 416 Range Not Satisfiable response, as
there cannot be a "byte-range-spec whose first-byte-pos is less
than the current length of the entity-body".  On the other hand,
this makes use of byte-range requests inconvenient in some cases,
as reported for the slice module here:

http://mailman.nginx.org/pipermail/nginx-devel/2017-June/010177.html

This commit changes range filter to instead return 200 if the file
is empty and the range requested starts at 0.

diffstat:

 src/http/modules/ngx_http_range_filter_module.c |  3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diffs (13 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
@@ -382,6 +382,9 @@ ngx_http_range_parse(ngx_http_request_t 
             if (ranges-- == 0) {
                 return NGX_DECLINED;
             }
+
+        } else if (start == 0) {
+            return NGX_DECLINED;
         }
 
         if (*p++ != ',') {