[OpenAFS-devel] fileserver -> client NAT ping

[Jeffrey Altman]

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On 8/14/2013 2:09 PM, Andrew Deason wrote:
> During the release-team meeting today, we talked a little about
> <http://gerrit.openafs.org/#change,9420>. That change was proposed by m=
e
> to turn on the "NAT ping" in the opposite direction in addition to what=

> we do now; fileservers ping clients, with the goal of improving
> communication in NAT environments when the clients don't do NAT ping.
>=20
> jaltman mentioned that this may not help, since many NATs don't care if=

> you ping them only in one direction. We're going to try and get some
> testing on a real site, but I also had an alternative idea. That made m=
e
> think if we could get bidirectional traffic out of such clients, to kee=
p
> the port mapping alive. Of course, we can send an rx version query, but=

> sending that to every client connected to a fileserver generates
> nontrivial traffic, and loads every client.

The reference is RFC 4787.   The requirement is that NAT mapping refresh
direction MUST have a "NAT Outbound refresh behavior" of "True" BUT MAY
have a "NAT Inbound refresh behavior" of "True".

In my experience the vast majority of NATs (and firewalls) do not
maintain mappings for inbound UDP packets.

> So can we send it to only NAT clients? We can't detect NATed clients
> with perfect accuracy, but I think we can make a guess, with little
> chance for false positives, since we have the alleged local IPs for the=

> client from TellMeAboutYourself.

Given that the TellMeAboutYourself addresses cannot be trusted and there
are still many file servers out in the wild that do trust them and block
try to send packets to them, I want the clients to stop sending
addresses entirely.

I believe that end users that are having trouble with NATs should
upgrade their clients.

Jeffrey Altman



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