[Bug 1929122] [NEW] networkd crashes when advertising blackhole route thru BGP

[Matija Vižintin]

Public bug reported:

lsb_release -rd
Description:	Ubuntu 20.04.2 LTS
Release:	20.04

apt-cache policy systemd
systemd:
  Installed: 245.4-4ubuntu3.6

[Impact]
Networkd crashes when a blackhole route (route aggregation is installed as a blackhole route) is advertised via FRR.

[Fix]
networkd should not crash

[Test case]
Bug was reported to systemd (not accepted because systemd version too old) where a test case is described: https://github.com/systemd/systemd/issues/19648 Lower in the comment you can find the full debug log from networkd.

Here you can see the core dump:
https://drive.google.com/file/d/1tCKiOSnGkLbx3w9du5_NNepkOQZC_hx7/view?usp=sharing

For convenience I also packed the relevant parts of the prod env in a
vagrant box showing the issue: vagrant init matijavizintin/networkd-
debug

After some more testing i noticed that immediately after the route is
being advertised, networkd detects the change and crashes with
"Assertion 'ifindex' failed at src/network/networkd-link.c:757, function
link_get(). Aborting."

Steps how it happens:
1. networkd is running
2. frr is started without advertising the aggregated address
3. add aggregated address and reload frr
4. blackhole route is installed and networkd crashes with the error above

** Affects: systemd (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: systemd systemd-networkd

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https://bugs.launchpad.net/bugs/1929122

Title:
  networkd crashes when advertising blackhole route thru BGP

Status in systemd package in Ubuntu:
  New

Bug description:
  lsb_release -rd
  Description:	Ubuntu 20.04.2 LTS
  Release:	20.04

  apt-cache policy systemd
  systemd:
    Installed: 245.4-4ubuntu3.6

  [Impact]
  Networkd crashes when a blackhole route (route aggregation is installed as a blackhole route) is advertised via FRR.

  [Fix]
  networkd should not crash

  [Test case]
  Bug was reported to systemd (not accepted because systemd version too old) where a test case is described: https://github.com/systemd/systemd/issues/19648 Lower in the comment you can find the full debug log from networkd.

  Here you can see the core dump:
  https://drive.google.com/file/d/1tCKiOSnGkLbx3w9du5_NNepkOQZC_hx7/view?usp=sharing

  For convenience I also packed the relevant parts of the prod env in a
  vagrant box showing the issue: vagrant init matijavizintin/networkd-
  debug

  After some more testing i noticed that immediately after the route is
  being advertised, networkd detects the change and crashes with
  "Assertion 'ifindex' failed at src/network/networkd-link.c:757,
  function link_get(). Aborting."

  Steps how it happens:
  1. networkd is running
  2. frr is started without advertising the aggregated address
  3. add aggregated address and reload frr
  4. blackhole route is installed and networkd crashes with the error above

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