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