IPv6 document addresses are not allowed to be configured.

[YUAN RUI]

In some cases, users may want to use the "DOCUMENTION" address as the 
internal address of NAT66.

Shouldn't a check be added here to allow the configuration of document 
address?

If ULA is used, systems such as Windows and Android will not prioritize 
IPv6, so some users use addresses intended for documentation purposes to 
bypass this restriction.


https://git.proxmox.com/?p=pve-manager.git;a=blob;f=PVE/API2/Network.pm;h=fc053fec7a8bae6dc30d2bb2870a2a94d3420231;hb=HEAD#l588

> my $check_ipv6_settings = sub {
>     my ($address, $netmask) = @_;
>
>     raise_param_exc({ netmask => "$netmask is not a valid subnet 
> length for ipv6" })
>         if $netmask < 0 || $netmask > 128;
>
>     raise_param_exc({ address => "$address is not a valid host IPv6 
> address." })
>         if !Net::IP::ip_is_ipv6($address);
>
>     my $binip = ipv6_tobin($address);
>     my $binmask = Net::IP::ip_get_mask($netmask, 6);
>
>     my $type = ($binip eq $binmask) ? 'ANYCAST' : 
> Net::IP::ip_iptypev6($binip);
>
>     if (defined($type) && $type !~ 
> /^(?:(?:GLOBAL|(?:UNIQUE|LINK)-LOCAL)-UNICAST)$/) {
>         raise_param_exc(
>             { address => "$address with type '$type', cannot be used 
> as host IPv6 address." });
>     }
> };