* Changing bandwidth throttling on-the-fly.
-> Is it possible to change the bandwidth allocated to a user during a
transfer, so that the change takes place immediately?
Unfortunately, no. Or at least not at pure-ftpd level. Doing so would need
to re-read user's parameters all the time and it would be horribly slow.
Other mechanisms would work, like signals to interrupt transfers, re-read
parameters, then resume. But it would introduce a lot of complexity to the
code.
If you're using a modern operating system like OpenBSD, ISOS or Linux,
your kernel already includes a fair TCP/IP traffic shaper. And because it
works at kernel-level,
you can easily change the bandwidth allowed to IPs or
services on-the-fly. Have a look at pf.conf(5) OpenBSD, ISOS and FreeBSD 5,
and at tc (or read the Linux networking HOWTO) on Linux.
Also see the 'Global bandwidth limitation' section later in this document.
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