Bug 4766

Summary: httpd fails to honor byte range requests if the range begins with 0
Product: Busybox Reporter: Rob Walker <rwalker>
Component: NetworkingAssignee: unassigned
Status: RESOLVED FIXED    
Severity: normal CC: busybox-cvs
Priority: P5    
Version: 1.19.x   
Target Milestone: ---   
Hardware: All   
OS: All   
Host: Target:
Build:
Attachments: change byte range test to use a separate boolean

Description Rob Walker 2012-02-17 19:45:35 UTC 
Httpd fails to honor byte range requests if the range begins with 0.

Whether to return a byte range is predicated on the value of range_start (treated as a boolean).  If range start is 0, httpd treats the request as if it were for the entire file.

Range: bytes=0-1 of a 100 byte file returns 100 bytes.
Comment 1 Rob Walker 2012-02-17 19:47:19 UTC 
Created attachment 4046 [details]
change byte range test to use a separate boolean
Comment 2 Rob Walker 2012-02-18 05:51:59 UTC 
I don't know how sensitive BusyBox is to a word vs. a byte vs. a bit for data.  Negative values of range_start could also be used as a positive boolean, instead of the smallint range_req I've proposed.

To summarize:
if a range is requested and the Range: header is reasonable, set range_start to requested value | ~MAX_INT (sets high bit)

range_start == 0 => no byte range requested or served
range_start != 0 => serve a byte range starting from (range_start ^ ~MAX_INT)

I don't know if BusyBox httpd has been tested or is expected to work with > 2GB files, though.
Comment 3 Bernhard Reutner-Fischer 2012-02-18 10:57:20 UTC 
(In reply to comment #2)
> I don't know how sensitive BusyBox is to a word vs. a byte vs. a bit for data. 

You can check the size increase with
$ scripts/bloat-o-meter busybox_unstripped.unpatched busybox_unstripped
(cp busybox_unstripped busybox_unstripped.unpatched for a pristine build, then apply your patch and rebuild).

> Negative values of range_start could also be used as a positive boolean,
> instead of the smallint range_req I've proposed.
> 
> To summarize:
> if a range is requested and the Range: header is reasonable, set range_start to
> requested value | ~MAX_INT (sets high bit)
> 
> range_start == 0 => no byte range requested or served
> range_start != 0 => serve a byte range starting from (range_start ^ ~MAX_INT)
> 
> I don't know if BusyBox httpd has been tested or is expected to work with > 2GB
> files, though.

The httpd works fine with files > 2GB, yes.
Comment 4 Denys Vlasenko 2012-02-19 16:15:59 UTC 
I propose to change "range_start != 0" condition for range_start >= 0 everywhere, and set range_start = -1 when range is off.