>Number: 1710 >Category: os-irix >Synopsis: Some image files get corrupted during transfer >Confidential: no >Severity: non-critical >Priority: medium >Responsible: apache >State: open >Class: sw-bug >Submitter-Id: apache >Arrival-Date: Tue Jan 20 21:30:00 PST 1998 >Last-Modified: >Originator: [EMAIL PROTECTED] >Organization: apache >Release: 1.2.5 >Environment: Silicon Graphics Indy IRIX shelob 6.2 03131015 IP22 gcc version 2.7.2.2 Also used standard IRIX cc with same results >Description: We have noticed some particular GIF and JPEG files seem to get corrupted when dowloading or viewing them. That is, the files downloaded are exactly the same size but the contents are slightly different, when a checksum value is computed.
This may not be immediately obvious when viewing the images, but in the section below on how to repeat the problem, I show how you can easily test this out. Note that this only happens for SOME images. Other images (gif or jpeg) download perfectly every time. Also, some images that are very similar in size to problem images also download perfectly. It's almost as if the content of the image is to blame. I doubt this is a problem with the way the apache web server is configured because I tested this out on a Sun Sparc (Solaris 2.6, Apache 1.2.5) and the problem images from our Irix web server downloaded perfectly under Solaris. That Solaris web server is set up essentially identically to the Irix one we are having trouble with. >How-To-Repeat: Repeatedly visit: http://www.cs.monash.edu.au/test1.gif and http://www.cs.monash.edu.au/test1.jpg Repeated downloads of those images should result in files of differing content. The easiest way is to run from the unix shell something like this: # while true # do # wget http://www.cs.monash.edu.au/test1.jpg # wget http://www.cs.monash.edu.au/test1.gif # done Control-C out of that after up to 50 downloads. Then compare the checksums since the files are the same size. # cksum test1.gif* # cksum test1.jpg* A lot should be very different. Make sure you don't use a proxy server with wget. Also check exactly where the differences lie in the files. # cmp test1.jpg test1.jpg.1 # cmp test1.jpg.1 test1.jpg.2 ...etc The differences all seem to occur at the same point. >Fix: >Audit-Trail: >Unformatted: [In order for any reply to be added to the PR database, ] [you need to include <[EMAIL PROTECTED]> in the Cc line ] [and leave the subject line UNCHANGED. This is not done] [automatically because of the potential for mail loops. ]
