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_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -4183,7 +4183,12 @@ ngx_http_upstream_copy_allow_ranges(ngx_
     if (r->cached) {
         r->allow_ranges = 1;
         return NGX_OK;
-
+    }
+
+    if (r->upstream->cacheable) {
+        r->allow_ranges = 1;
+        r->single_range = 1;
+        return NGX_OK;
     }
 
 #endif