GNOME.org
 

Re: why does network manager start activating disconnected ethernet ports?

On Sat, 2018-11-10 at 13:54 -0500, David P. Reed wrote:

Dan - thanks! Yes, the ports were in LOWER_UP, now that I understand
what that means.
 
It is not a Network Manager problem. It was a real screwup on my
part. Sorry to waste your time.


No problem, glad it got figured out!

Dan


For some reason two of the ports were actually cabled to a switch
that was otherwise unused (not connecting anywhere). It was supposed
to be powered off, but it turns out that someone (not me, that I know
of) turned it on.  That brought the links up, but there was no DHCP
server reachable.
 
Again, thanks for the help with my troubleshooting.
 
I do like NM a lot, and appreciate your effort put in to continue
improving and supporting it.
 
David
-----Original Message-----
From: "Dan Williams" <dcbw redhat com>
Sent: Thursday, November 8, 2018 5:35pm
To: "David P. Reed" <dpreed deepplum com>
Cc: networkmanager-list gnome org
Subject: Re: why does network manager start activating disconnected
ethernet ports?



On Thu, 2018-11-08 at 16:16 -0500, David P. Reed wrote:

Hi Dan -
I tried the rpm -e command and it said I don't have that module
installed. I did grep the directories (/var/run/NetworkManager and
/etc/NetworkManager) recursively for the string "carrier" and found
nothing there. So that seems not to be the problem.

It's clear from the journalctl log entries that the two non-
connected 
interfaces are being "auto-activated" over and over by something.
They move from prepare->config->ip-config.
Reason is "none", but I think that's normally what goes on.

One personal theory (that I don't know how to test properly) is
that
the RealTek r8169 driver (which seems to have been demonstrating
problems on Ubuntu in the past few months, on some hardware) is
somehow saying the ports are coming online or are online when they
are not. I'm not sure how NetworkManager gets told about such
transitions, but it might be a problem. I also wonder about chrony
somehow trying to probe the interfaces, triggering them by
accident.


NetworkManager listens to kernel messages from the driver. Run "ip
link show dev <dev name>" which should look similar to this:

2: enp0s31f6: <NO-CARRIER,BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500
qdisc fq_codel state DOWN mode DEFAULT group default qlen 1000
 link/ether aa:bb:cc:dd:ee:ff brd ff:ff:ff:ff:ff:ff

if you see LOWER_UP that means the kernel driver thinks there is a
carrier/link. At that point it's a kernel driver bug if nothing is
plugged into the card's port.

If it doesn't show LOWER_UP, then it's probably some configuration
issue or bug in NM itself.

Dan


Is there a "no-ignore-carrier" option that would be something to
try
for debugging? or some specific logging option that will tell more
about why these ports are "auto-activating"?

I have several other Fedora 28 machines running similar
configurations, but they don't seem to do this. They are different,
in that their Ethernet hardware is different, but the software
setup
is roughly similar.

Anyway, I'd love to figure this out. I can share the journals if
you
want or get other data, but this level of logging doesn't say very
much to me other than what I summarize above.

Thanks.
-----Original Message-----
From: "Dan Williams" <dcbw redhat com>
Sent: Wednesday, November 7, 2018 5:55pm
To: "David P. Reed" <dpreed deepplum com>, networkmanager-list@gnom
e.
org
Subject: Re: why does network manager start activating disconnected
ethernet ports?



On Wed, 2018-11-07 at 16:23 -0500, David P. Reed wrote:

I have a Fedora 28 server in my lab that has multiple network
adapters, but only one of them is cabled to a switch. All the
software is updated to NetworkManager-1.10.12-1.fc28.


Did you install the Fedora 28 "Server" spin, or something like
Workstation? Some of the config options are different for different
variants. That includes installing the "00-server.conf" file into
/etc/NetworkManager/conf.d for Server installs in some cases.

One thing that does is set "ignore-carrier=*" which, as you may
guess,
makes NM ignore the carrier detection of the NIC on all interfaces.
Mostly for servers with static IPs where connectivity shouldn't
change
even if you unplug or trip over the cable.

Try 'rpm -e NetworkManager-config-server' and then restarting NM or
rebooting and see if that fixes it.

Dan


However, when I run journalctl -e I typically see pages and pages
and
pages of DHCPDISCOVER requests on the non-connected ports,
constantly
retrying. The logs fill very, very fast.

I did something yesterday that managed to cause the retrying to
stop,
leaving the unused ports all in the disconnected state (nmcli
device
status said disconnected for each one). I thought, hmm... well
that
problem is now fixed. `journalctl -e` showed everything quiet.

Today, I thought I'd check. When I did `journalctl -e` there were
no
DHCPDISCOVERs issued, and when I did `nmcli device status` the
ports
were all still "disconnected".

But then I did `nmcli con show`. It said the ports were in a
disconnected state.

However at this point I happened to repeat the `journalctl -e`
command, and my goodness - the stream of DHCPDISCOVER requests
timing
out were a sight to amaze, and the network manager kept
transitioning
the state of the ports that had no cables correspondingly, trying
to
get an IP address.

This may be my misunderstanding, but the interface knows whether
the
port is connected to some other port with a cable or if it is
not.
It
seems logical also that merely asking for the connection status
shouldn't "turn on" a lot of useless DHCP discovery on
disconnected
ports.

So am I confused or is this a bug?

Tell me what you need to find it if so.

I'd also like to know how to stop the behavior. I know I could
change
the ports to not be "auto", but I'd really like to be able to
just
plug a cable in and start using the port to talk to some other
system
or switch.
_______________________________________________
networkmanager-list mailing list
networkmanager-list gnome org
https://mail.gnome.org/mailman/listinfo/networkmanager-list
[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]