netdev - "[RFC PATCH net-next 1/2] Allow 225/8-231/8 as unicast"

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Date:   Fri, 13 Sep 2019 19:16:42 +1000
From:   Mark Smith <markzzzsmith@...il.com>
To:     dave.taht@...il.com, netdev@...r.kernel.org
Subject: "[RFC PATCH net-next 1/2] Allow 225/8-231/8 as unicast"

Hi,

(Not subscribed to the mailing list)

I've just noticed this patch.

I don't think it should be applied, as 225/8 through 231/8 falls
within the IANA designated Class D multicast address range.
(https://www.iana.org/assignments/ipv4-address-space/ipv4-address-space.xhtml)

Using this address range as unicast addresses would mean that ICMP
messages would need to be able to use them as a source address.

However, Internet Standard number 3, RFC 1122, "Requirements for
Internet Hosts -- Communication Layers", prohibits using addresses
from within the multicast address range from being used as source
addresses:

"       An ICMP error message MUST NOT be sent as the result of
         receiving:

         *    an ICMP error message, or

         *    a datagram destined to an IP broadcast or IP multicast
              address, or

         *    a datagram sent as a link-layer broadcast, or

         *    a non-initial fragment, or

         *    a datagram whose source address does not define a single
              host -- e.g., a zero address, a loopback address, a
              broadcast address, a multicast address, or a Class E
              address."

Please note, IPv6 has and is being widely adopted. Trying to extend
use of IPv4 should be considered an unnecessary, in particular when it
violates Internet Standards.

There are more than 75 000 IPv6 routes in the Internet route table.
Nearly 18 000 BGP Autonomous Systems are announcing at least one IPv6
prefix.

 http://www.cidr-report.org/v6/as2.0/#General_Status

A number of countries have exceeded 50% IPv6 capability and preference
according to APNIC.

https://stats.labs.apnic.net/ipv6

Globally, Google are receiving more than 25% of their traffic via IPv6:

https://www.google.com/intl/en/ipv6/statistics.html

Regards,
Mark.