html - wordpress 3.4.1 muti-sites image has not appear in time on safari sometimes -

i'm running muti-sites wordpress nginx, , test on safari (chrome fine).

a important thing is, image upload administrator.

i found sometime image has not appear immediately, thing network trouble before, found rule today.

the rule is:

1. enter page, image shown.
2. refresh page(command + r), image disappeared.
3. refresh again, image shown.
4. again again, disappeared.
5. loops....

notice: disappeared means that's not apear immediately: loaded page 2 second later, image loaded.

when refresh page, safari send image request server http header http_if_none_match , http_if_modified_since.

because of mutiple site, nginx rewrite request ms-files.php process it. ms-files.php found image has not been modified, it's response 304 no content.

the bug is, ms-files.php has set content-length header before decided response 304, response header going 304 no content , content-length > 0. after that, safari down.

fixed bug add header( 'content-length: 0' ); wp-includes/ms-files.php line 79.

 75 if ( ( $client_last_modified && $client_etag )  76     ? ( ( $client_modified_timestamp >= $modified_timestamp) && ( $client_etag == $etag ) )  77     : ( ( $client_modified_timestamp >= $modified_timestamp) || ( $client_etag == $etag ) )  78     ) {  79     header( 'content-length: 0' );  80     status_header( 304 );  81     exit;  82 }