[Bug 1775131] Re: Ubuntu 18.04 networking issue (connection drops after approx. 15 minutes)

[Julian Andres Klode]

Anyhow, none of this is a bug I nthe dispatcher, and I don't know what
else, so I'm going to reassign it to the kernel - if there are broken
ARP tables and whatnot, what else could it be.

** Package changed: networkd-dispatcher (Ubuntu) => linux (Ubuntu)

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Title:
  Ubuntu 18.04 networking issue (connection drops after approx. 15
  minutes)

Status in linux package in Ubuntu:
  Confirmed

Bug description:
  I'm currently troubleshooting some network issues on Ubuntu 18.04 LTS Bionic. After checking a few logs I noticed that the networkd-dispatcher is generating errors. I'm unsure if this is a bug but I'd like to report it over here just to be sure:
   
  ```
  Jun 04 18:14:21 [servername] systemd-networkd-wait-online[2079]: managing: br2
  Jun 04 18:14:22 [servername] networkd-dispatcher[1890]: WARNING:Unknown index 7 seen, reloading interface list
  Jun 04 18:14:23 [servername] networkd-dispatcher[1890]: WARNING:Unknown index 8 seen, reloading interface list
  Jun 04 18:14:23 [servername] networkd-dispatcher[1890]: ERROR:Unknown interface index 8 seen even after reload
  Jun 04 18:14:23 [servername] networkd-dispatcher[1890]: WARNING:Unknown index 8 seen, reloading interface list
  Jun 04 18:14:23 [servername] networkd-dispatcher[1890]: ERROR:Unknown interface index 8 seen even after reload
  ```

  These issues occur consistently on several servers. The problem is
  that I lose the connection  specifically towards the internet after
  approx. 15 minutes. Internal facing interfaces (same hardware and
  driver) seem to behave differently and remain properly connected to
  the internal network. These network-dispatcher errors seem to occur
  simultanously when the connection on the external interface
  permanently drops.

  The physical network links still appears to be online when the
  connection is lost.

  I'm still also able to ping the default gateway from my provider to
  access the Internet. But all IP addresses beyond this gateway on the
  Internet seem to be unreachable.

  I have disabled TCP offloading and firewalls to eliminate any influences. But that didn't work.
  The ARP table shows that my gateway is a STALE record after the connection drops. So it seems related to the ARP-table or something likewise.

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