ipv4: Update fib_select_default to handle nexthop objects
A user reported [0] hitting the WARN_ON in fib_info_nh:
[ 8633.839816] ------------[ cut here ]------------
[ 8633.839819] WARNING: CPU: 0 PID: 1719 at include/net/nexthop.h:251 fib_select_path+0x303/0x381
...
[ 8633.839846] RIP: 0010:fib_select_path+0x303/0x381
...
[ 8633.839848] RSP: 0018:
ffffb04d407f7d00 EFLAGS:
00010286
[ 8633.839850] RAX:
0000000000000000 RBX:
ffff9460b9897ee8 RCX:
00000000000000fe
[ 8633.839851] RDX:
0000000000000000 RSI:
00000000ffffffff RDI:
0000000000000000
[ 8633.839852] RBP:
ffff946076049850 R08:
0000000059263a83 R09:
ffff9460840e4000
[ 8633.839853] R10:
0000000000000014 R11:
0000000000000000 R12:
ffffb04d407f7dc0
[ 8633.839854] R13:
ffffffffa4ce3240 R14:
0000000000000000 R15:
ffff9460b7681f60
[ 8633.839857] FS:
00007fcac2e02700(0000) GS:
ffff9460bdc00000(0000) knlGS:
0000000000000000
[ 8633.839858] CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
[ 8633.839859] CR2:
00007f27beb77e28 CR3:
0000000077734000 CR4:
00000000000006f0
[ 8633.839867] Call Trace:
[ 8633.839871] ip_route_output_key_hash_rcu+0x421/0x890
[ 8633.839873] ip_route_output_key_hash+0x5e/0x80
[ 8633.839876] ip_route_output_flow+0x1a/0x50
[ 8633.839878] __ip4_datagram_connect+0x154/0x310
[ 8633.839880] ip4_datagram_connect+0x28/0x40
[ 8633.839882] __sys_connect+0xd6/0x100
...
The WARN_ON is triggered in fib_select_default which is invoked when
there are multiple default routes. Update the function to use
fib_info_nhc and convert the nexthop checks to use fib_nh_common.
Add test case that covers the affected code path.
[0] https://github.com/FRRouting/frr/issues/6089
Fixes: 493ced1ac47c ("ipv4: Allow routes to use nexthop objects")
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>