[Feature-Request] ipv6_connection_totall metrics support

[Psigh]

hello, i want to draw a pannel in grafana to monitor connection usage by time, however only ipv4 connetions can shown by mktxp_ipv6_connections_total, on my router ipv6 usually even more connctions than ipv4, please add this feature if possible

[ABHIRAMSHIBU]

This PR #313 may fix this.