NETLINK_FIB_LOOKUP and NETLINK_ROUTE

[Kevin Wilson]

Hi,
Why do we need NETLINK_FIB_LOOKUP ?
I see that NETLINK_FIB_LOOKUP is used in a libnl util named nl-fib-lookup,
and that NETLINK_FIB_LOOKUP is also used in lib/fib_lookup/lookup.c.

Is there anything in which NETLINK_FIB_LOOKUP is better than using RTM_GETROUTE?

With NETLINK_FIB_LOOKUP, we call nl_fib_input() which eventually calls
fib_table_lookup().

In the kernel we have these two registrations:
rtnl_register(PF_INET, RTM_GETROUTE, inet_rtm_getroute, NULL, NULL);
rtnl_register(PF_INET, RTM_GETROUTE, NULL, inet_dump_fib, NULL);
The first is for doit action and the second is for dumpit action.

inet_rtm_getroute() finds routing entry by ip_route_input()/ip_route_output(),
which eventually calls also fib_table_lookup().

I saw here:
http://lists.openwall.net/netdev/2009/05/25/33
...	
...
"This was added when fib_trie was introduced and in this case we're comparing
 NETLINK_FIB_LOOKUP result with a userland program doing longest prefix match
 on the same routing table.
...

iproute normally dumps the table, it doesn't look up a particular route
 as done via the RX softirq."

But
Indeed, "ip route" calls inet_dump_fib()
But,
"ip route get" calls inet_rtm_getroute(), which as said above, performs
also a fib lookup.
Example:
ip route get 192.168.1.100
192.168.1.100 dev p2p1  src 192.168.1.10
    cache

Maybe using NETLINK_FIB_LOOKUP should be replaced with lookup with RTM_GETROUTE
of NETLINK_ROUTE?
I don't see anything in which NETLINK_FIB_LOOKUP is better than
using RTM_GETROUTE.

regards,
Kevin