Potential Bug: Gzipping preventing HTTP range requests

Sat Jun 25 08:22:21 MSD 2011

On Fri, Jun 24, 2011 at 07:04:04PM -0400, Ensiferous wrote:
> Yeah it's a weird situation. As a user I would probably expect that the
> range applied to the actual content served, before it was compressed. So
> that if I request 100 bytes when everything is transferred and
> decompressed I have 100 bytes worth of content.

A "Content-Length" header of a gzipped response corresponds to length
of the gzipped data. I'm not sure if this specified in RFC, but this
is de facto behaviour. So since range is associated with the
"Content-Length" header it should work with already gzipped body,
so Apache 2.3.8 does it right:

---------
$ nc httpd.apache.org 80
GET / HTTP/1.0
Host: httpd.apache.org
Range: bytes=10-151
Accept-Encoding: gzip

HTTP/1.1 206 Partial Content
Date: Sat, 25 Jun 2011 04:17:51 GMT
Server: Apache/2.3.8 (Unix) mod_ssl/2.3.8 OpenSSL/1.0.0c
Last-Modified: Sun, 22 May 2011 17:04:34 GMT
ETag: "b96c29-247b-4a3e0595b4c80-gzip"
Accept-Ranges: bytes
Vary: Accept-Encoding
Content-Encoding: gzip
Content-Range: bytes 10-151/2631
Content-Length: 142
Connection: close
Content-Type: text/html

?Zms?:??_  [ ...  gzipped data ]

---------
$ nc httpd.apache.org 80
GET / HTTP/1.0
Host: httpd.apache.org
Range: bytes=10-20, 30-50
Accept-Encoding: gzip

HTTP/1.1 206 Partial Content
Date: Sat, 25 Jun 2011 04:19:14 GMT
Server: Apache/2.3.8 (Unix) mod_ssl/2.3.8 OpenSSL/1.0.0c
Last-Modified: Sun, 22 May 2011 17:04:34 GMT
ETag: "b96c29-247b-4a3e0595b4c80-gzip"
Accept-Ranges: bytes
Vary: Accept-Encoding
Content-Encoding: gzip
Content-Length: 226
Connection: close
Content-Type: multipart/byteranges; boundary=4a6819ef865b815212

--4a6819ef865b815212
Content-type: text/html
Content-range: bytes 10-20/2631

?Zms?:??_?
--4a6819ef865b815212
Content-type: text/html
Content-range: bytes 30-50/2631

oo	????;yas?SF?Vc[
--4a6819ef865b815212--
--------

However, curl does not understand it:

--------
$ curl -r 10-151 httpd.apache.org/
html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
               "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
 <head>
$ curl -r 10-151 --compressed httpd.apache.org/
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
               "http://www.w3.org/TR/
--------

Note also that it's impossible to ungzip a response part if you have not
preceding parts from the very start.

-- 
Igor Sysoev