Re: traffic statistics by network connection

[Thomas Haller <thaller redhat com>]

On Tue, 2021-07-20 at 16:26 -0400, David H Durgee via networkmanager-
list wrote:
> How can I get traffic statistics by network connection?  Is there a
> way 
> to retrieve this using nmcli?  Is there another tool that will do so?
>
> I have looked around and the tools I see work at the interface level,
> not at the connection level.
>
> I am using nmcli 1.22.18 as distributed with linux mint 20.1 x64
> here.

Ui,

a "connection" is a profile, that is a bunch of settings for
configuring a network interface. Basically, see the lower-case keys in
`nmcli connection show "$PROFILE". A profile has no traffic statstics,
nor would it make sense.

Well, that's not entirely correct and I guess it might make some sense
to collect statistics associated with a profile. NM associates
additional information to prfiles with "connection.timestamp" and
"wifi.seen-bssids" properties and there are also the lease files under
/var/lib/NetworkManager. But these are exceptions, usually a profile is
just the settings that the user configured. In particular traffic
statistics are not tracked or associated with connection profiles in
NetworkManager (yet).



On D-Bus,

  $ busctl -j call org.freedesktop.NetworkManager /org/freedesktop org.freedesktop.DBus.ObjectManager 
GetManagedObjects

you see the "org.freedesktop.NetworkManager.Device.Statistics"
interface (which is per-interface). That exposes the RX/TX bytes. That
is basically the same as kernel reports via netlink API. However, the
values are stale unless you RefreshRateMs to a positive value (which
causes NM to periodically poll the statistics from kernel).


There is no further magic with
"org.freedesktop.NetworkManager.Device.Statistics". You could just as
well read the information via netlink.

These statistics are ad-hoc, and will be lost after reboot (or when the
interface dispears). I guess you could build an interesting tool for
that. I am not aware that one exists. However, the API was added by
Ubuntu developers, and presumably the do have a use for it and a tool. 


best,
Thomas