Re: New "tc qdisc" options



On Mon, Oct 05, 2020 at 06:35:19AM -0400, Dave Collier-Brown via networkmanager-list wrote:
I see code in

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/blob/master/libnm-core/nm-setting-tc-config.c

which implements setting tc qdisc, and a brief mention in

https://developer.gnome.org/NetworkManager/stable/

However the man pages do not mention tc.

Can you provide a hint on setting, for example, /tc qdisc replace dev
enp0s25 root cake bandwidth 20mbit/ in network manager?
"cake" is currently not supported. Until that is added, the intended
solution is to use a dispatcher script. See `man NetworkManager`.

Alas, that's the first place I looked (:-()

Cake doesn't need to be supported in network manager, as I can work
around it's lack with fq_codel.

However, I do need to discover the location and notation interpreted by
nm-setting-tc-config.c

1) can you help me with that?

To configure fq_codel, you can use nmcli in this way:

 $ nmcli connection modify $myconnection tc.qdiscs \
         "root fq_codel limit 2000 target 3000 interval 40000"
 
 $ nmcli connection up $myconnection
 
 $ tc qdisc show dev $mydev
 qdisc fq_codel 8003: root refcnt 2 limit 2000p flows 1024 quantum 1514 target 3.0ms interval 40.0ms 
memory_limit 32Mb ecn


2) is adding (the name of) the cake qdisc on your backlog?

Currently NM doesn't support configuring CAKE parameters. IOW, if you
set "root cake bandwidth 100Mbit", you will see in the tc output that
cake was set but with default parameters.

Yes, I think it will be useful to have CAKE support in NM, but I can't
say when it will be implemented. Of course, patches are always
welcome; if anybody is interested in contributing it, please have a
look at the work that was done to support SFQ:

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/commit/b22b4f9101b1cbfde49b65d9e2107e4ae0d817c0

Beniamino

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