[HECnet] Intermittent Connection with PyDECnet?

[Thomas DeBellis]

Me too.  My position is that most assuredly isn't what this is.

I will admit that my background does effect some of my opinions here.  I 
was part owner of a company that developed software.  If something broke 
or didn't work, that meant an annoyed user, reduced NPS, escalation from 
the help desk to development and then delays.
You /really/ did not want the user picking up the phone to open a 
trouble ticket.  You wanted them happily using your product to run their 
business.

So I don't feel this is simply 'layers' because it is visible tangible 
value.  It's a simple decision that saves somebody some annoyance or 
possibly throwing up their hands or bothering you. It's just too easy to 
run out of bandwidth for something that is obviously not a heavy lift 
and is trivial to comment should there be any maintenance concerns.

On 3/10/20 5:46 PM, Keith Halewood wrote:
>
> I chose the code change I made simply because I don’t use pcap. I also 
> don’t like layers for layers sake.
>
> *From:*owner-hecnet at Update.UU.SE [mailto:owner-hecnet at Update.UU.SE] 
> *On Behalf Of *David Moylan
> *Sent:* 10 March 2020 21:19
> *To:* hecnet at Update.UU.SE
> *Subject:* RE: [HECnet] Intermittent Connection with PyDECnet?
>
> I’m all for backwards compatibility, however the /dev/net/tun 
> interface has been in linux since the 2.6 days. A quick google shows 
> that people back in 2010 have been using it, and browsing on 
> kernel.org for the oldest archived kernel entry of 2.6.11 shows code 
> examples for /dev/net/tun dated 2005.
>
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/Documentation/networking/tuntap.txt?h=linux-2.6.11.y
>
> I think the starting date for support of /dev/net/tun is earlier than 
> that of the discontinuation of support for /dev/tapx.
>
> Given that the whole goal of pyDECnet is to permit usage of decnet on 
> more modern environments, I think having code that supports back to 
> 2005 is a pretty solid move.
>
> Cheers, Wiz!!
>
> *From:*owner-hecnet at Update.UU.SE <mailto:owner-hecnet at Update.UU.SE> 
> [mailto:owner-hecnet at Update.UU.SE] *On Behalf Of *Thomas DeBellis
> *Sent:* Wednesday, 11 March 2020 2:08 AM
> *To:* hecnet at Update.UU.SE <mailto:hecnet at Update.UU.SE>
> *Subject:* Re: [HECnet] Intermittent Connection with PyDECnet?
>
> Since you may be running both on newer and older kernels, does it make 
> sense to test for which tunnel type interface exists and simply use that?
>
> You don't even need to test versions, but rather try /dev/net/tun and 
> if it works, use that or if it fails, use /dev/tapx.
>
> I'm a big fan of dynamic configuration, also known in the trade as 
> 'auto magic' or 'automatic nice things'.
>
>     ------------------------------------------------------------------------
>
>     On 3/10/20 9:40 AM, Paul Koning wrote:
>
>     Thanks, sorry for leaving that dangling.  I'll test that and merge
>     it into my code.
>
>     paul
>
>         ------------------------------------------------------------------------
>
>         On Mar 10, 2020, at 4:28 AM, Keith Halewood
>         <Keith.Halewood at pitbulluk.org>
>         <mailto:Keith.Halewood at pitbulluk.org> wrote:
>
>         Hi,
>
>         These are the changes:
>
>         In  Ethernet.py:
>
>            class _TapEth (_Ethernet):
>
>                def open (self):
>
>                    fd = os.open('/dev/net/tun', os.O_RDWR | os.O_NONBLOCK)
>
>                    ifr = struct.pack('16sH', self.dev.encode('utf-8'),
>         IFF_TAP | IFF_NO_PI)
>
>                    ioctl(fd, TUNSETIFF, ifr)
>
>                    self.tap = fd
>
>                    self.sellist = ( fd, )
>
>                    # Turn the interface on -- needed only on Mac OS
>
>         With the definitions of those constants up near the top:
>
>         TUNSETIFF = 0x400454ca
>
>         TUNSETOWNER = TUNSETIFF + 2
>
>         IFF_TUN = 0x0001
>
>         IFF_TAP = 0x0002
>
>         IFF_NO_PI = 0x1000
>
>         Keith
>
>         ------------------------------------------------------------------------
>
>         From: owner-hecnet at Update.UU.SE
>         <mailto:owner-hecnet at Update.UU.SE>
>         [mailto:owner-hecnet at Update.UU.SE] On Behalf Of David Moylan
>
>         Sent: 10 March 2020 07:46
>
>         To: hecnet at Update.UU.SE <mailto:hecnet at Update.UU.SE>
>
>         Subject: RE: [HECnet] Intermittent Connection with PyDECnet?
>
>         Robert Armstrong said on Tuesday, 10 March 2020 4:17 AM
>
>             FWIW, the "tap:" option in pyDECnet never worked for me. 
>             I use pcap
>
>         to
>
>             access tap devices -
>
>                 circuit TAP-0 Ethernet pcap:tap0 --single-address --cost=2
>
>             works for me with Ubuntu 18.04...
>
>         When I first went to play with pyDECnet under Ubuntu 18, I
>         also discovered issues with the tap adapter. Fundamentally the
>         issue comes down to newer kernels (such as in Ubuntu 18) that
>         use a /dev/net/tun interface to communicate instead of /dev/tapx
>
>         I heard on the list that Keith Halewood had modified Paul's
>         code to work with the newer interface standard, so I reached
>         out to him and he provided me with the changes. It's only a
>         few lines of code that need modification.
>
>         I believe Keith has provided Paul with the changes. I'd love
>         to see them become mainstream in pyDECnet, as at the moment if
>         I pull down a new build, I have to make the modifications by
>         hand again.
>
>         With the code changes, tap works a dream for me.
>
>         circuit tap-1022 Ethernet tap:tap1022 --random-address
>
>         cheers, Wiz!!
>
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