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From Lars Eilebrecht <>
Subject [PATCH] mod_proxy, yet another netscape bug
Date Sun, 02 Aug 1998 00:50:55 GMT

a friend of mine discovered a Navigator/Mozilla bug which
results in broken images in some rare cases.
(I was able to reproduce the bug under Solaris 2.6 with Netscape
 Communicator 4.05.)

If you load a page that contains _direct_ links to images via mod_proxy
and try to load the images you'll maybe receive a broken image (is does
not happen with inline images).

Dependent on the length of the http header and TCP/IP settings/values
(MTU, path-MTU, segment size etc) the first read() of Netscape reads
the header plus the beginning of the body. But it seems that Netscape
expects to see only http headers in his first read(), because
the beginning of the body gets ignored. Therefore Netscape fails to
display the image. Shift-Reloading the image-URL works...

The patch contains a workaround for this bug (added a call to
ap_bflush() in proxy_http.c/proxy_ftp.c right before mod_proxy
starts to send the body). Although the workaround should solve
the problem in most situations it is no 100% workaround, because
it is not guaranteed that one read() is related to exactly a write().
So dependent on the buffering behaviour of the TCP/IP stack (and
the phase of the moon ;-) you still get a broken image in some
very rare situations.
If no one has any objections I'll commit the patch and add a note
to the known_client_problems page.

Lars Eilebrecht                     - Modesty: Being comfortable that others                                will discover your greatness.

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