Re: [OE-core] [scarthgap][PATCHv2] systemd: backport networkd route readiness fix from upstream

["Yoann Congal" <yoann.congal@smile.fr>]

Hello,

On Fri Oct 9, 2026 at 12:28 PM CEST, Akash Hadke via lists.openembedded.org wrote:
> From: Akash Hadke <Akash.Hadke@bmwtechworks.in>
>
> Backport upstream systemd PR #41000 to v255.22 to fix route handling
> in systemd-networkd when routes are configured on links that are not
> yet up.
>
> In 255.21, networkd only checks link readiness when configuring
> explicit nexthops. Routes using an implicit nexthop can therefore
> be processed while the bound link is still down, which breaks setups
> using ConfigureWithoutCarrier= and BindCarrier=. One visible symptom
> is that static multicast routes are not installed until much later,
> or are missed entirely, even though the address configuration succeeds.
>
> The upstream fix makes the readiness checks consistent by introducing
> a common link_is_up() helper, limiting gateway readiness checks to
> nexthops that are actually bound to a link, and moving the
> "link must be up" check into the shared gateway readiness path so both
> explicit and implicit nexthops follow the same logic. Upstream also
> adds a regression test for issue #40106.
>
> This backport is needed to keep route configuration reliable on
> carrier-dependent interfaces in our 255.22-based systemd.
>
> Ref: https://github.com/systemd/systemd/pull/41000
> https://github.com/systemd/systemd/issues/40106
>
> Tested:
> - Built core-image-minimal with INIT_MANAGER = "systemd" on qemux86-64.
> - Verified functional test case in QEMU:
>   * Setup dummy parent (carrier off) and VLAN child with BindCarrier=.
>   * Verified multicast route remains deferred while carrier is down.
>   * Verified multicast route installs immediately upon carrier up.
>   * Verified clean route recovery across carrier toggles.
>
> Signed-off-by: Akash Hadke <UpStream_IP-AH@bmwtechworks.in>
> Signed-off-by: Akash Hadke <Akash.Hadke@bmwtechworks.in>
> ---
>  ...introduce-link_is_up-helper-function.patch | 167 ++++++++++++++++++
>  ...-gateway-is-ready-only-when-the-next.patch |  74 ++++++++
>  ...und-to-a-link-requires-the-link-is-u.patch |  59 +++++++
>  ...etwork-add-test-case-for-issue-40106.patch | 120 +++++++++++++
>  meta/recipes-core/systemd/systemd_255.22.bb   |   4 +
>  5 files changed, 424 insertions(+)
>  create mode 100644 meta/recipes-core/systemd/systemd/0023-network-introduce-link_is_up-helper-function.patch
>  create mode 100644 meta/recipes-core/systemd/systemd/0024-network-check-if-gateway-is-ready-only-when-the-next.patch
>  create mode 100644 meta/recipes-core/systemd/systemd/0025-network-route-bound-to-a-link-requires-the-link-is-u.patch
>  create mode 100644 meta/recipes-core/systemd/systemd/0026-test-network-add-test-case-for-issue-40106.patch
>
> diff --git a/meta/recipes-core/systemd/systemd/0023-network-introduce-link_is_up-helper-function.patch b/meta/recipes-core/systemd/systemd/0023-network-introduce-link_is_up-helper-function.patch
> new file mode 100644
> index 0000000000..45f2733b50
> --- /dev/null
> +++ b/meta/recipes-core/systemd/systemd/0023-network-introduce-link_is_up-helper-function.patch
> @@ -0,0 +1,167 @@
> +From ec4f646759d6625bbafcd4ce67224fb63b99a96c Mon Sep 17 00:00:00 2001
> +From: Yu Watanabe <watanabe.yu+github@gmail.com>
> +Date: Mon, 9 Mar 2026 10:57:06 +0900
> +Subject: [PATCH] network: introduce link_is_up() helper function
> +
> +Upstream-Status: Backport [https://github.com/systemd/systemd/pull/41000/commits/ec4f646759d6625bbafcd4ce67224fb63b99a96c]
> +Comment: Patch is refreshed based on the 255.22 codebase
> +Did not pick changes from the below files as it is not matches to our code base.
> +src/network/netdev/bond.c
> +src/network/networkd-route.c
> +
> +Signed-off-by: Akash Hadke <Akash.Hadke@bmwtechworks.in>
> +---
> + src/network/networkd-link.c    | 21 +++++++++++----------
> + src/network/networkd-link.h    |  1 +
> + src/network/networkd-nexthop.c |  2 +-
> + src/network/networkd-setlink.c |  9 ++++-----
> + 4 files changed, 17 insertions(+), 16 deletions(-)

After some thoughts, this patch looks too intrusive "just" to add the
link_is_up() function that is just a flag check.
I know I usually ask to use upstream as much as possible but here, I
think it make sense to port the relevant code without the link_is_up()
function addition (and keep the inlined flag check).

Note: it matters less now but I prefer plain /commit/ URLs instead of the
one from the pull request:
https://github.com/systemd/systemd/commit/ec4f646759d6625bbafcd4ce67224fb63b99a96c

Thanks!
-- 
Yoann Congal
Smile ECS