Make net.fibs growable

[melifaro]

Summary

Allow to dynamically grow the amount of fibs in each vnet.

This change alters current behaviour: currently, if one defines ROUTETABLES > 1 in the kernel config, each vnet will be created with the number of fibs defined in the kernel config. This change sets default number of fibs in the vnet to be always 1.

Dynamic net.fibs is not compatible with net.add_addr_allfibs. The plan is to deprecate the latter and make the net.add_addr_allfibs=0 default behaviour.

Next steps:

• Update rt_numfibs to V_rt_numfibs (60 occasions).
• Add interface fib handler, similar to vnet fib handler
• Deprecate net.add_addr_allfibs

Test Plan

8:53 [0] m@current s sysctl net.fibs=2
net.fibs: 1 -> 2
8:54 [0] m@current setfib 1 netstat -rn
Routing tables (fib: 1)
8:54 [0] m@current s ifconfig vlan2 create vlan 2 vlandev em0 fib 1
8:54 [0] m@current
8:54 [0] m@current s ifconfig vlan2
vlan2: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
	options=4000003<RXCSUM,TXCSUM,NOMAP>
	ether 00:0c:29:4b:db:9c
	groups: vlan
	vlan: 2 vlanpcp: 0 parent interface: em0
	fib: 1
	media: Ethernet autoselect (1000baseT <full-duplex>)
	status: active
	nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
8:54 [0] m@current s ifconfig vlan2 inet 1.2.3.4/29
8:54 [0] m@current s ifconfig vlan2 inet6 2a02:6b8::1/120
8:54 [0] m@current setfib 1 netstat -rn
Routing tables (fib: 1)

Internet:
Destination        Gateway            Flags     Netif Expire
1.2.3.0/29         link#5             U         vlan2
1.2.3.4            link#4             UHS         lo0

Internet6:
Destination                       Gateway                       Flags     Netif Expire
2a02:6b8::/120                    link#5                        U         vlan2
2a02:6b8::1                       link#4                        UHS         lo0
fe80::%vlan2/64                   link#5                        U         vlan2
fe80::20c:29ff:fe4b:db9c%vlan2    link#4                        UHS         lo0

[melifaro]

Update diff to address comments and fix vnet behaviour.

[melifaro]

Update functions parameters.

[melifaro]

I intend to commit this on Friday, Aug 21 unless there are any objections.

[glebius]

sys/net/route/route_tables.c

182

Unlikely we will ever allocate a huge number of fibs on a 32bit machine, but just to be safer makes sense to use mallocarray() here.