Route Metric at Kernel Level

Hello,

I've been trying for a while now, to readout the Routing-Metric from a given socket at kernel level. So far, I've always set the routing-table metric by hand using the ifmetric command.
When I tried reading out the struct sock->sk_dst_cache->metrics values, I always got a Metric value which was 0. I thought I was reading out the wrong value, until I discovered, that the metric values, that I put into the standard routing table are not copied into the kernel routing cache which I was reading out. Now I am wondering if it is supposed to be like that, and if so, why it was implemented that way.

Also, since I need to read out the Metric value from the Routing Table, I am in need of some help. Maybe just a push into the right direction. I've been looking at the fib_frontend.c and the other fib_* files which, as I understand, implement the routing tables. Unfortunately they don't seem to export their functions for my Kernel-Module, so I am unable to use those. Is there an entrypoint from where I am able to use the functions given in the fib_* files, or are they strictly closed off from the rest of the Kernel?

Thank you for any help!

Greetings

Tim