So, structute 'socket' include structute 'inpcb', structure 'inpcb' include structute 'rtentry', and rtentry contain data about routes.
If we execute 'man rtentry', we'll see, what for get acces to info about routes, we must use function 'rtalloc' (#include <net/route.h>),
but when I did:
>gcc getroute.cpp -o getroute, when got message:
implicit declaration of function `int rtalloc(...)'
and when I did:
>cp getroute.cpp getroute.c
>cc getroute.c -o getroute, when got message:
/tmp/ccD1UzcN.o: In function `main':
/tmp/ccD1UzcN.o(.text+0xe): undefined reference to `rtalloc'