Math operations on graphs

Hello all. It would be very useful if math operations can be supported on dashboards for adding or subtraction in the same graph from multiple sources. I comment this because in our network we provide internet services and one of the principal monitoring graph is the total Caching + ISP traffic, currently we are using Billing graphs to show it and a separate engine to get octet rates from DB to calculate the rest of numbers for our KPIs.


I think I have a related (or basically the same?) request.
Adding interfaces to the same graph is well supported. But subtracting is not, as far as I know.

I want to calculate the amount of untunneled traffic on an interface.
E.g. on interface eth0 I have one (or more) tunnels passing through, but also some traffic that is NOT part of a tunnel.
It would be great to have a graph with something like

eth0 in: 300 Mbit/s
tunnel1 in: 200 Mbit/s
native in: 100 Mbit/s

eth0 out: 400 Mbit/s
tunnel1 out: 250 Mbit/s
native out: 150 Mbit/s

I imagine a setting similar to multiport_bits_separate but where the first port ID is considere the “total”, and the other ports are subtracted from that total to end up with “native”.