[Bug 1940635] Re: systemd-networkd failing to acquire a DHCP6 lease from dnsmasq on armhf

[Simon Chopin]

Can somebody confirm my assumptions on the architecture of the test ?

First, it sets up a veth with router_eth42 at one end and test_eth42 at
the other (the itf names might be different ?). dnsmasq is bound against
router_eth42 which is configured manually via iproute with both IPv4 and
IPv6 addresses.

networkd is in charge of configuring test_eth42. In this specific case,
it is expected that it sends a DHCPv6 request via test_eth42, and that
we get an answer from dnsmasq with an lease to an address between
2600::10 and 2600::20.

When running tcpdump on test_eth42, I can only see some ICMPv6 router
solicitations (from both ends of the tunnel), with no router
advertisement as answer. This bit is expected AFAIK. However, I do not
see any other traffic, crucially, no DHCPv6 traffic at all.

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Title:
  systemd-networkd failing to acquire a DHCP6 lease from dnsmasq on
  armhf

Status in glibc package in Ubuntu:
  New
Status in netplan.io package in Ubuntu:
  New
Status in systemd package in Ubuntu:
  New

Bug description:
  systemd-networkd is failing to acquire a DCHP6 lease from dnsmasq on
  armhf since glibc 2.34-0ubuntu1, failing systemd (tests-name=networkd-
  test.py) and netplan.io (test-name=ethernets) tests on armhf.

  Reproducer:
  * Setup an armhf container, e.g. via:
  autopkgtest systemd --test-name=networkd-test.py --shell -U --apt-pocket=proposed=src:systemd,src:glibc -s -- lxd autopkgtest/ubuntu/impish/armhf
  * It will fail and drop you into the shell
  * cd test/ && apt install python3-nose
  * nosetests3 -v -s -m "test_.*_dhcp_ip6" networkd-test.py

  
  This is unrelated to the recent dnsmasq changes (LP: #1894619), as that would fail on all architectures, not just armhf.

  It still passes inside an amd64 LXD container, so it is also not related to armhf being tested inside a container. But it shows the difference between armhf vs amd64 container, that on armhf we're missing the DHCPSOLICIT (and therefore DHCPREPLY) messages, as can be seen from the dnsmasq log:
  dnsmasq-dhcp[]: DHCPSOLICIT(router_eth42) 00:02:00:00:ab:11:57:1e:20:2f:9e:56:5f:34 
  dnsmasq-dhcp[]: DHCPREPLY(router_eth42) 2600::1f 00:02:00:00:ab:11:57:1e:20:2f:9e:56:5f:34 autopkgtest-lxd-rtypaf

  The issue is most probably the same that causes the currently failing
  netplan.io/ethernets autopkgtest on armhf, if tested against glibc
  2.34-0ubuntu1.

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