netdev - QDisc Implementation: Setting bit rate and getting RTT

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Message-ID: <76defaacd96053915523b4ba91693d5dca3d9158.camel@ucdavis.edu>
Date:   Tue, 03 Jul 2018 16:13:18 -0700
From:   Taran Lynn <tflynn@...avis.edu>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: QDisc Implementation: Setting bit rate and getting RTT

Hello,
I'm new to linux development and am working on creating a qdisc module,
similar to those under net/sched/sch_*.c. Currently I'm stuck on two
things.

1. What's the best way to set the maximum bit rate?
2. How do I determine the RTT for packets?

For (1) I'm currently tracking the number of bits sent, and only sending
packets if they stay within the appropriate rate bound. Is there a better
way to do this? I've looked at net/sched/sch_netem.c, and as far as I can
tell it determines the delay between packets for a given rate and sends
them after that delay has passed. However, when I tried to do this I got
inconsistent rates, so I think I may be missing something.

As for (2) I'm not sure where to start.

Thanks in advance for any advise.