[HECnet] Third Release of Route20 User Mode DECnet Router

[Johnny Billquist]

While I don't think we ever figured out what was changing ports, it is a 
well known behavior of NAT routers that the can change the source port 
of UDP packets. It is often possible to configure things in such a way 
that it don't happen, but you need to know where it happens first, 
before that can be done.

I actually have had, for many years, a solution in the bridge to work 
around this, if ever needed because it is outside of the control of 
either party. I thought I had mentioned it, but maybe I haven't.
The character '*' before a hostname means that the entry will accept 
packets from any port from the remote machine, and packets sent back 
will be sent to the same port packets are coming in on.

But it's a noticeable decrease of security that I'm not too happy about, 
so I tend to try and make people figure out how to configure their NAT 
first.

   Johnny

On 2020-10-11 22:39, Thomas DeBellis wrote:
> That reminds me of something else.  I had been using Johnny's bridge for 
> a number of months, when all of the sudden, I got some decidedly odd 
> behavior.
> 
> While my router was dutifully forwarding the correct port to the right 
> machine, by the time the bridge got a hold of the port, the port had 
> gotten overwritten by ... somebody ...  Bob and I spent some trying to 
> figure out what was going on; the typical stuff, reboot this, re-power 
> that, what has changed? (absolutely nothing!!)
> 
> I couldn't figure it out and after 'a while' became very annoyed (not 
> that it takes much).  I modified the bridge to have a different prefix 
> character ('$') in the bridge stanza.  This causes the bridge to stomp 
> the correct port in, always.  There is some extra logic to count packets 
> where the port had to be overwritten and display it, Etc.
> 
> So that all worked.  And to look at the counts, sometimes an override is 
> necessary and then there are the other times.  Lately, it hasn't, viz:
> 
>     0: purgatorio 0.0.0.0:0 (Rx: 977(1107) Tx: 558 Fw: 419 (Drop rx:
>     688)) Active: 1 Throttle: 0(015)
>     1: legato aa.bb.cc.dd:_4711_[Ov: 0, Nov: 560, Lst: 0 (Rx: 558(560)
>     Tx: 419 Fw: 558 (Drop rx: 2)) Active: 1 Throttle: 0(167)
> 
> I doubt anybody else has ever had this, but if you do, then speak up.  
> Meanwhile, I'll get my changes back to Johnny.
> 
>> ------------------------------------------------------------------------
>>
>> This reminds me - I had ROUT20 on Hecnet for months - first on Linux 
>> then on FreeBSD - worked great with Bob Armstrong at the other end. I 
>> took it off due to reasons I do not remember fully - but was probably 
>> when Bob discovered something when we were trying DDCMP ... maybe Bob 
>> or Paul remembers more?
>>
>>
>> To be honest, I have never actually looked at PyDECnet! But I should 
>> again acknowledge that you have provided me with invaluable help and 
>> insight.
>> ---
>> Supratim Sanyal, W1XMT
>> 39.19151 N, 77.23432 W
>> QCOCAL::SANYAL via HECnet
>>
>>> ------------------------------------------------------------------------
>>> On 10/10/20 4:50 PM, Paul Koning wrote:
>>>
>>> I'll have to look at your work, have not done that in a long time.
>>>
>>> My 2 cents worth: we're aiming at different things.  I set out to build a full DECnet implementation in Python, with emphasis on supporting all the parts of the architecture in a very straightforward way.  Efficiency was very much a secondary consideration.  As it happens, the performance is not bad, adequate for a lot of purposes.
>>>
>>> A C based implement such as you did is somewhat harder to write, but much more efficient.  For anyone who is running on a slow machine, or under heavy load, your work is likely to be the right answer.  Also, of course, if you want to run on a machine where Python is not available or not efficient.
>>>
>>> 	paul
>>>> ------------------------------------------------------------------------
>>>> On Oct 10, 2020, at 5:11 AM, Rob Jarratt<robert.jarratt at ntlworld.com>  wrote:
>>>>
>>>> Hello Everyone,
>>>>   
>>>> As some of you may be aware, I have been writing my own DECnet router. Since the last formal release a few years ago I have added a few things, the details are herehttps://github.com/rjarratt/Route20. These were all on the Dev branch, which I know a few people have tried. I have been running the Dev branch for a long time myself, so I am sure it is stable. All I have done really is make the current Dev branch “official” by merging it to the master branch.
>>>>   
>>>> I know Paul has been much more active than me lately on this front, so I am probably a bit behind, but if anyone would like to take a look that would be great.
>>>
>>>

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol