Re: IPv6 ranges

[David Fifield <david () bamsoftware com>]

On Wed, Jun 22, 2011 at 05:16:32PM -0700, David Fifield wrote:
> Weilin,
>
> I think that we must implement IPv6 ranges before doing multicast host
> discovery. The reason for this is that I think it only makes sense to
> use multicast when dealing with a whole network.
>
> Currently Nmap's model is to parse the command-line host specifications,
> return one host at a time (see TargetGroup::get_next_host), and then
> feed those (4096 at a time) into ping scan. We need to change that, so
> that we can feed an entire block like fe80::/64 into ping scan when
> appropriate, without enumerating 2^64 addresses.
>
> The addrset code does not yet support iteration over members. We need to
> make it do that, but it must be capable of returning entire blocks when
> asked. For example, given the address specifications
>       ::1 fe80::/64 1:2:3::4:5:6 scanmev6.nmap.org/112
> the iteration would return the single host ::1, the network fe80::/64,
> the single host 1:2:3::4:5:6, and the network
> 2600:3c01::f03c:91ff:fe93:cd19/112. The next higher level would see:
>       * ::1 as a localhost address (and not ping it),
>       * fe80::/64 as a local network (and do multicast ping on it),
>       * 1:2:3::4:5:6 as a single IP address (and do unicast ping on it), and
>       * 2600:3c01::f03c:91ff:fe93:cd19/112 as a remote network (which it
>         would then further iterate into 256 unicast hosts).

These are my recommendations for what Nmap should do when asked to scan
large and small, local and remote networks, over unicast and multicast.

                                          multicast        unicast
                                 default  requested      requested
                           ---------------------------------------
Small IPv6 local network       multicast  multicast        unicast
Large IPv6 local network       multicast  multicast  error/warning
Small IPv6 remote network        unicast      error        unicast
Large IPv6 remote network  error/warning      error  error/warning

David Fifield
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