From: Paul Marks <pmarks@google.com>
To: David Miller <davem@davemloft.net>
Cc: dave.taht@gmail.com, netdev@vger.kernel.org, gnu@toad.com
Subject: Re: [PATCH net-next 1/1] Allow 0.0.0.0/8 as a valid address range
Date: Sat, 13 Jul 2019 20:57:50 -0700 [thread overview]
Message-ID: <CAHaKRv+Fnrxd=jD6itFXBGrLKA-kphxhUQhvd9ngN1dDNhd4nQ@mail.gmail.com> (raw)
In-Reply-To: <20190626.132003.50827799670386389.davem@davemloft.net>
On Wed, Jun 26, 2019 at 1:20 PM David Miller <davem@davemloft.net> wrote:
>
> From: Dave Taht <dave.taht@gmail.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 This usage of 0.x.y.z was later repealed in RFC1122 (section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@gmail.com>
> > Signed-off-by: John Gilmore <gnu@toad.com>
> > Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
>
> Applied, thanks for following up on this.
This breaks an undocumented feature of Linux:
$ telnet 0.0.0.1 22
Trying 0.0.0.1...
telnet: Unable to connect to remote host: Invalid argument
It's sometimes useful to put 0.x.x.x in command-line flags,
/etc/hosts, or other config files, because it forces connect() to fail
immediately, instead of sending packets and waiting for a timeout.
Given that this has been user-visible for decades, is it a good idea
to pull out the rug?
prev parent reply other threads:[~2019-07-14 3:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-22 17:07 [net-next 0/1] Allow 0.0.0.0/8 as a valid address range Dave Taht
2019-06-22 17:07 ` [PATCH net-next 1/1] " Dave Taht
2019-06-26 20:20 ` David Miller
2019-07-14 3:57 ` Paul Marks [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAHaKRv+Fnrxd=jD6itFXBGrLKA-kphxhUQhvd9ngN1dDNhd4nQ@mail.gmail.com' \
--to=pmarks@google.com \
--cc=dave.taht@gmail.com \
--cc=davem@davemloft.net \
--cc=gnu@toad.com \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).