Some HTTP clients only receive first 4k

Mykel Mykel at mWare.ca
Mon May 23 14:14:17 PDT 2005


Scott Stevenson wrote:

> This is a follow-up to a post back in February.
> <http://www.monkey.org/freebsd/archive/freebsd-questions/200502/ 
> msg03071.html>
>
>
> Summary: Certain HTTP clients only receive partial file contents. The  
> majority of visitors have no problems, but those that do seem to  
> experience it 100% of the time.
>
> After looking into this further, I've discovered some interesting  
> data points:
>
>
> 1. Affected clients consistently receive only the first 4096 bytes  of 
> .html and .css files. After that, they encounter a single garbage  
> character (looks like a memory stomp), and then nothing.
>
> 2. At least two of the sites hosted on the machine are affected.
>
> 3. The issue can be reproduced via the W3 validator:
>
> <http://validator.w3.org/check?uri=http%3A%2F%2Fcocoadevcentral.com% 
> 2Farticles%2F000085-test.html&charset=%28detect+automatically% 
> 29&doctype=%28detect+automatically%29&ss=1>
>
> The bottom of this page shows the first 4k that was successfully  
> fetched. It stops right in the middle of a tag. The same thing  
> happens with this css file:
>
> <http://jigsaw.w3.org/css-validator/validator?uri=http%3A%2F% 
> 2Fcocoadevcentral.com%2Fcss% 
> 2Fcocoadevcentral-20050401.css&usermedium=all>
>
>
> 4. At least in the case of the validator, the requests don't show up  
> in Apache's access or error logs! This is consistently reproducible.
>
> 5. For some reason, clients consistently only get to byte 3883 (or  
> perhaps 3884) in .php files, and then get the garbage character.
>
>
> These same sites were previously running on the same network with the  
> same version of apache. I've done hours of googling and also searched  
> the freebsd-questions mailing list archives. I've gone out of my way  
> to keep the installation as vanilla as possible. The system  
> configuration is essentially:
>
> FreeBSD 5.3-Release
> Apache 2.0.50
> PHP 5.0.2 

Perhaps there's an MTU problem along the way? Can you ping/traceroute 
all the way between endpoints? Some people idiotically block all ICMP, 
when they probably just want to filter ICMP ECHO... (idijjits... ping 
ain't the biggest of your problems)

It comes to packet sizes on the various links.

Myke



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