nft: complete reject support

nft: complete reject support

This patch allows to use the reject action in rules. For example:

  nft add rule filter input udp dport 22 reject

In this rule, we assume that the reason is network unreachable. Also
we can specify the reason with the option "with" and the reason. For example:

  nft add rule filter input tcp dport 22 reject with icmp type host-unreachable

In the bridge tables and inet tables, we can use this action too. For example:

  nft add rule inet filter input reject with icmp type host-unreachable

In this rule above, this generates a meta nfproto dependency to match
ipv4 traffic because we use a icmpv4 reason to reject.

If the reason is not specified, we infer it from the context.

Moreover, we have the new icmpx datatype. You can use this datatype for
the bridge and the inet tables to simplify your ruleset. For example:

  nft add rule inet filter input reject with icmpx type host-unreachable

We have four icmpx reason and the mapping is:

ICMPX reason            |       ICMPv6          |      ICMPv4
                        |                       |
admin-prohibited        | admin-prohibited      | admin-prohibited
port-unreachable        | port-unreachable      | port-unreachable
no-route                | no-route              | net-unreachable
host-unreachable        | addr-unreachable      | host-unreachable

Signed-off-by: Alvaro Neira Ayuso <alvaroneay@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>