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Re: curl_schannel.c and realloc()

From: Daniel Stenberg <>
Date: Tue, 19 Jun 2012 22:28:46 +0200 (CEST)

On Tue, 19 Jun 2012, Marc Hoersken wrote:

> thanks! Actually there is one more thing we can discuss. In the current
> implementation the increased buffer sizes are tried to be reduced to the
> initial buffer size after each and every receive operation. On the one hand
> this means that libcurl would free up memory after some high memory usage
> scenario which could be very important for long-term SSL/TLS connections.

I can throw in another thought too. We really should aboid unbounded
enlargements of the buffer as it can possibly lead to a rouge server to try to
exploit this by providing a stream that expands to something ridiculously
large making us allocate huge chunks of memory leading to badness. So there
should probably be a maximum. Also, we should double the buffer space for each
loop, not just expand with bufsize/2 IMHO as that is usually what comes out as
the better algorithm.

Given a ceiling as mentioned above, I think it we should leave the enlarged
buffer allocated to avoid lots of reallocs over the course of a single
transfer. That's what we do for several other buffers we expand in similar

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Received on 2012-06-19