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From Nick Holloway <Nick.Hollo...@pyrites.org.uk>
Subject mod_proxy/7383: Apache as non-caching proxy doesn't abort transfer when client aborts
Date Fri, 09 Mar 2001 15:58:22 GMT

>Number:         7383
>Category:       mod_proxy
>Synopsis:       Apache as non-caching proxy doesn't abort transfer when client aborts
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    apache
>State:          open
>Class:          sw-bug
>Submitter-Id:   apache
>Arrival-Date:   Fri Mar 09 08:00:01 PST 2001
>Originator:     Nick.Holloway@pyrites.org.uk
>Release:        1.3.19
Linux 2.2.18, Debian stable
If Apache is configured as a non-caching proxy, then when the client disconnects
the proxy will continue to read the content, despite there being no need for it.

If the URL referenced is a streaming image, then there will be no termination
of this process.  This has the effect of tying up bandwith (of both the proxy
and the server) and preventing dial-on-demand links from disconnecting.

Although I have actually experienced this with Apache 1.3.9, I am reporting
this against 1.3.19 as I see that the source of 1.3.19 is unchanged and will
have the same problem.
Apache is configured as a non-caching proxy as follows (note no CacheRoot):
    ProxyRequests on
    CacheForceCompletion 100

Now access a URL containing a streaming image, such as:

After page has loaded close the browser (I've used Netscape 4.76).

Trace the system calls on the apache process handling the proxy request -- you
will see that it just performs endless "read()" syscalls.  This will continue
until Apache is stopped.
In proxy_util.c, when the client aborts the connection, the decision to
continue is made on line 599 based on the cache completion setting, and the
amount of data seen so far.

However, this code is protected by the "if" on line 594, which means that it
is never executed if the proxied contents are not also being cached.

I suggest putting "ok = 0;" between lines 593, and 594 so that the default
action is to abort the transfer.  If the content is being cached, and has
sufficient has transferred, then "ok" will be set to continue as before.
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