Range filter: single_range flag in request. If set, it means that response body is going to be in more than one buffer, hence only range requests with a single range should be honored. The flag is now used by mp4 and cacheable upstream responses, thus allowing range requests of mp4 files with start/end, as well as range processing on a first request to a not-yet-cached files with proxy_cache. Notably this makes it possible to play mp4 files (with proxy_cache, or with mp4 module) on iOS devices, as byte-range support is required by Apple.

--- a/src/http/ngx_http_request.h
+++ b/src/http/ngx_http_request.h
@@ -528,6 +528,7 @@ struct ngx_http_request_s {
     unsigned                          filter_need_in_memory:1;
     unsigned                          filter_need_temporary:1;
     unsigned                          allow_ranges:1;
+    unsigned                          single_range:1;
 
 #if (NGX_STAT_STUB)
     unsigned                          stat_reading:1;