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Today's Topics:
1. corrupted DNS entry with connman (Terry Bolinger)
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Date: Wed, 15 Jul 2020 23:32:02 -0000
From: "Terry Bolinger" <[email protected]>
Subject: corrupted DNS entry with connman
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset="utf-8"
We have a product that we are selling that uses the Beaglebone Black SBC with
Debian Jessie as a small network appliance in a residential environment.
Connman is the network manager in this distribution. We are experiencing a very
random issue where occasionally the DNS servers being returned by a network
DHCP server get corrupted. All other configurations are fine - IP address,
gateway, etc. When this happens, the unit still has local network connection
but loses the connection to the Internet (as you would expect). This impacts
the operation of the unit in a very negative manner. We have a user interface
that shows the configuration settings and when the Primary DNS server gets
corrupted, the user interface field normally shows the DNS server as " [ ".
The Secondary DNS server is mostly blank when this happens. Manually changing
the Primary DNS Server to a good nameserver always resolves the issue.
It happens often enough that it's annoying us because of the support calls we
get, but it happens so infrequently that it's very difficult to reproduce. In
fact, I've never seen it on my test units - I've only seen it on units
installed in the field.
In almost all applications, the network appliance is connected directly to the
local network router provided by the ISP or the user. We believe that
something happens from the router that causes this issue (and it could even be
with specific routers - we just don't know). In one particular instance, a
unit had been working for several months just fine, but then there was a power
outage, and after rebooting from the power outage, the Primary DNS was showing
the " [ " and the Secondary DNS was blank, and we had to manually enter a good
nameserver.
Since it's so hard to reproduce, I'm looking at some bandaid approaches using
some scripts. But, before I did that, I thought I'd check to see if connman
might have some options that I could use to resolve the issue. One potentially
available option I was reading about was the use of the nodnsproxy option.
This one might be extremely hard to determine if it has resolved the issue or
not, as it is so hard to reproduce but would be simple to implement, if it were
a potential solution. This would assume that DNS proxy feature in connman was
in conflict with the external DNS server, as I was reading, which might be a
real stretch.
A second option I was looking at was the "FallbackNameservers" option.
However, I don't understand how this works. Does connman do a test to verify
Internet connection or proper DNS operation, and if it fails that test, it
"falls back" to a secondary DNS server and then if that also fails, it falls
back to the "FallbackNameservers"? If this is how this works, this is a
possibility to explore - I would try setting the FallBack servers to available
DNS servers such as the Google nameserver at 8.8.8.8.
By the way, the connman version on my Debian distribution is V1.32. I see that
connman is up to at least 1.37. Is it possible that upgrading connman might
resolve this issue?
I apologize - I'm comfortable with simple networking but I'm by no means a
networking expert and I'm really hoping for a sanctioned option to resolve this
issue.
Any guidance would be appreciated.
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End of connman Digest, Vol 56, Issue 11
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