[ih] The history of "This" 0.0.0.0/8 network?

[Grant Taylor]

On 02/12/2019 11:23 AM, Dave Taht wrote:
> I loved that book. It needs a sequel. Multiple sequels.

Agreed!!!

> One tidbit from that book I'd love to track down - it said paul buran 
> wrote 11?13? 14? - can't remember- *books* about packet processing, 
> and yet these have vanished from the internet. Whenever I struggle on 
> something - like the whol bufferbloat thing - I fantasize that scribbled 
> in the margin of book 13 was the answer to my problem.

Hum.

I'll have to look for that in context when I next re-read the book and 
then start researching things.  }:-)

> What we see nowadays is 0.0.0.0/32 is used for useful stuff. 0.0.0.0/8, 
> by history and by extension (including the 4.2 BSD broadcast gaff), 
> is unused.
> 
> However, 0.0.0.1 - 0.255.255.254 *does work* as a real address with a 
> very simple patch to linux.

~chuckle~

Why do I now want to use this as something akin to 169.254/16 link-local 
IP addresses.  }:-)

> Boom. arp works, address assignement via dhcp works, it works as an 
> address on everything patched.

:-)

> So trying to find the cases where that address range wouldn't work is 
> on my mind. Clearly 0.0.0.0/32 is special, but...

0.0.0.0/32 is special.  But that doesn't directly translate to the 
zeroth address in a subnet.

I don't recall at the moment where 0.0.0.0/32 is used as a /destination/ 
address.  I'm sure there is something, but I don't recall it at the moment.

> The zeroth address is another long standing problem. Since cidr, and 
> 4.2BSD's retirement, zeroth should be a usable address.

The best I've found is that the zeroth address / subnet can be 
misconstrued when addressing the (sub)network.

Does 192.168.0.0 sans netmask address the 192.168.0.0/16 network, or the 
192.168.0.0/24 sub-network, or one of the 14 other sub-networks?

As I think about it, I guess the broadcast (all ones host) address could 
suffer from the same problem.  But the broadcast address is already 
special and unused by hosts.

> Explicit checks in the OS.

Sorry, I was asking about what the reasoning was for them to be special, 
not the code used to enforce / protect their special nature.

Asked another way, what is the reasoning behind the zeroth (all zeros 
host) address special and in need of protection to prevent it's use by 
normal hosts?

> Good question. But the issue died with BSD 4.2

Indeed.

I had (what I think is) another one come to mind last night.

What, if any, security / specialness do people still ascribe to ports 
below 1024?

If it's a throwback to thinking that it requires root on a host to be 
able to source traffic from ports below 1024....  Well, I don't trust 
the remote host across the Internet at all.  So, I don't personally 
ascribe any security to the port number.  But I don't know if I'm 
strange in that.

I personally (in my current naive state of mind) would like to see 
daemons daemons source traffic from any of the other 65,535 ports 
excluding than the destination port as a possible source port.

Aside:  Why is port 0 special?  }:-)



-- 
Grant. . . .
unix || die