netdev - Re: [PATCH net-next 1/1] Allow 0.0.0.0/8 as a valid address range

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Message-Id: <20190626.132003.50827799670386389.davem@davemloft.net>
Date:   Wed, 26 Jun 2019 13:20:03 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dave.taht@...il.com
Cc:     netdev@...r.kernel.org, gnu@...d.com
Subject: Re: [PATCH net-next 1/1] Allow 0.0.0.0/8 as a valid address range

From: Dave Taht <dave.taht@...il.com>
Date: Sat, 22 Jun 2019 10:07:34 -0700

> The longstanding prohibition against using 0.0.0.0/8 dates back
> to two issues with the early internet.
> 
> There was an interoperability problem with BSD 4.2 in 1984, fixed in
> BSD 4.3 in 1986. BSD 4.2 has long since been retired. 
> 
> Secondly, addresses of the form 0.x.y.z were initially defined only as
> a source address in an ICMP datagram, indicating "node number x.y.z on
> this IPv4 network", by nodes that know their address on their local
> network, but do not yet know their network prefix, in RFC0792 (page
> 19).  This usage of 0.x.y.z was later repealed in RFC1122 (section
> 3.2.2.7), because the original ICMP-based mechanism for learning the
> network prefix was unworkable on many networks such as Ethernet (which
> have longer addresses that would not fit into the 24 "node number"
> bits).  Modern networks use reverse ARP (RFC0903) or BOOTP (RFC0951)
> or DHCP (RFC2131) to find their full 32-bit address and CIDR netmask
> (and other parameters such as default gateways). 0.x.y.z has had
> 16,777,215 addresses in 0.0.0.0/8 space left unused and reserved for
> future use, since 1989.
> 
> This patch allows for these 16m new IPv4 addresses to appear within
> a box or on the wire. Layer 2 switches don't care.
> 
> 0.0.0.0/32 is still prohibited, of course.
> 
> Signed-off-by: Dave Taht <dave.taht@...il.com>
> Signed-off-by: John Gilmore <gnu@...d.com>
> Acked-by: Toke Høiland-Jørgensen <toke@...hat.com>

Applied, thanks for following up on this.