Diffusion FreeBSD src repository 6d8fdfa9d5e7

Rework IP encapsulation handling code.
6d8fdfa9d5e7
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Description

Rework IP encapsulation handling code.

Currently it has several disadvantages:

it uses single mutex to protect internal structures. It is used by data- and control- path, thus there are no parallelism at all.
it uses single list to keep encap handlers for both INET and INET6 families.
struct encaptab keeps unneeded information (src, dst, masks, protosw), that isn't used by code in the source tree.
matches are prioritized and when many tunneling interfaces are registered, encapcheck handler of each interface is invoked for each packet. The search takes O(n) for n interfaces. All this work is done with exclusive lock held.

What this patch includes:

the datapath is converted to be lockless using epoch(9) KPI.
struct encaptab now linked using CK_LIST.
all unused fields removed from struct encaptab. Several new fields addedr: min_length is the minimum packet length, that encapsulation handler expects to see; exact_match is maximum number of bits, that can return an encapsulation handler, when it wants to consume a packet.
IPv6 and IPv4 handlers are stored in separate lists;
added new "encap_lookup_t" method, that will be used later. It is targeted to speedup lookup of needed interface, when gif(4)/gre(4) have many interfaces.
the need to use protosw structure is eliminated. The only pr_input method was used from this structure, so I don't see the need to keep using it.
encap_input_t method changed to avoid using mbuf tags to store softc pointer. Now it is passed directly trough encap_input_t method. encap_getarg() funtions is removed.
all sockaddr structures and code that uses them removed. We don't have any code in the tree that uses them. All consumers use encap_attach_func() method, that relies on invoking of encapcheck() to determine the needed handler.
introduced struct encap_config, it contains parameters of encap handler that is going to be registered by encap_attach() function.
encap handlers are stored in lists ordered by exact_match value, thus handlers that need more bits to match will be checked first, and if encapcheck method returns exact_match value, the search will be stopped.
all current consumers changed to use new KPI.