FAILED: patch "[PATCH] batman-adv: tt: send ROAM_ADV on each roamed back client" failed to apply to 5.15-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x aff4d5d10f2dcb4a9b604e27414dafa1d51b6406
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261109202030-failed-5.15-aff4d5d10f2d@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From aff4d5d10f2dcb4a9b604e27414dafa1d51b6406 Mon Sep 17 00:00:00 2001
From: Sven Eckelmann <sven@narfation.org>
Date: Thu, 8 Oct 2026 12:00:27 +0200
Subject: [PATCH] batman-adv: tt: send ROAM_ADV on each roamed back client

When a ROAMING_ADV is received for an announced local client,
batadv_roam_tvlv_unicast_handler_v1() creates a global entry with the
BATADV_TT_CLIENT_ROAM flag set.

If the client sends a frame again before the next TTVN commit,
batadv_tt_local_add_roam() is expected to announce this return via a
ROAM_ADV frame. But this doesn't happen because the global entry (created
by the first ROAMING_ADV) carries BATADV_TT_CLIENT_ROAM until the new
originator announces the client.

Let batadv_tt_local_add_roam() always handle a roamed back client -
independent of the ROAM flag of the global entry:

* trigger sending of the ROAM_ADV frame(s)
* remove the (with the roaming) associated global entry

Cc: stable@vger.kernel.org
Fixes: 068ee6e204e1 ("batman-adv: roaming handling mechanism redesign")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 net/batman-adv/translation-table.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index e13c2828da475..0df51523dcf0c 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -819,14 +819,21 @@ static void batadv_tt_local_add_roam(struct batadv_priv *bat_priv,
 	if (!tt_global)
 		return;
 
-	/* Check whether it is a roaming, but don't do anything if the roaming
-	 * process has already been handled
+	/* Handle newly roamed client - but not roamed back client.
+	 *
+	 * A client which roamed back must always be reclaimed from the
+	 * originator(s) which sent the ROAMING_ADV. The global entry created by
+	 * this ROAMING_ADV might still carry BATADV_TT_CLIENT_ROAM because the
+	 * new originator did not yet announce the client.
 	 */
-	scoped_guard(spinlock_bh, &tt_global->common.flags_lock) {
-		if (tt_global->common.flags & BATADV_TT_CLIENT_ROAM)
-			return;
+	if (!roamed_back) {
+		scoped_guard(spinlock_bh, &tt_global->common.flags_lock) {
+			/* Check whether it is a roaming, but don't do anything
+			 * if the roaming process has already been handled.
+			 */
+			if (tt_global->common.flags & BATADV_TT_CLIENT_ROAM)
+				return;
 
-		if (!roamed_back) {
 			/* The global entry has to be marked as ROAMING and has to be
 			 * kept for consistency purpose.
 			 *
-- 
2.53.0