FAILED: patch "[PATCH] batman-adv: tt: ignore ROAM flag of received ADD changes" failed to apply to 6.1-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 6.1-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-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x c5d68abe6e7f1dbd132a602cb696fe1fff0389eb
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261109201522-failed-6.1-c5d68abe6e7f@kernel.org' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Thanks,
Sasha

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

From c5d68abe6e7f1dbd132a602cb696fe1fff0389eb Mon Sep 17 00:00:00 2001
From: Sven Eckelmann <sven@narfation.org>
Date: Wed, 7 Oct 2026 13:03:29 +0200
Subject: [PATCH] batman-adv: tt: ignore ROAM flag of received ADD changes

A received TT change (OGM diff or full table response) with the ROAM flag
but without DEL is handled by batadv_tt_global_add() like a ROAMING_ADV:

* a newly created global entry gets BATADV_TT_CLIENT_ROAM and is
  therefore excluded from the global CRC. The sender has it in its local
  CRC and the receiver has to request the full table again
* batadv_tt_global_purge_local() removes the local entry of the
  receiver. The receiver's own client is considered as roamed to the sender
  and frames for it are rerouted

The ROAM flag only has a meaning together with DEL. Drop it on reception to
keep it from populating the global table with a temporary ROAMING entry
which is not part of the CRC - and therefore causing a CRC mismatch.

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 | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 0df51523dcf0c..247cce95c09f4 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -3941,21 +3941,30 @@ static void _batadv_tt_update_changes(struct batadv_priv *bat_priv,
 				      u16 tt_num_changes, u8 ttvn)
 {
 	int roams;
+	u8 flags;
 	int i;
 
 	for (i = 0; i < tt_num_changes; i++) {
-		if ((tt_change + i)->flags & BATADV_TT_CLIENT_DEL) {
-			roams = (tt_change + i)->flags & BATADV_TT_CLIENT_ROAM;
+		flags = (tt_change + i)->flags;
+
+		if (flags & BATADV_TT_CLIENT_DEL) {
+			roams = flags & BATADV_TT_CLIENT_ROAM;
 			batadv_tt_global_del(bat_priv, orig_node,
 					     (tt_change + i)->addr,
 					     ntohs((tt_change + i)->vid),
 					     "tt removed by changes",
 					     roams);
 		} else {
+			/* an announced client cannot have roamed away from
+			 * orig_node. Only a ROAMING_ADV is allowed to add a
+			 * global entry with the ROAM flag
+			 */
+			flags &= ~BATADV_TT_CLIENT_ROAM;
+
 			if (!batadv_tt_global_add(bat_priv, orig_node,
 						  (tt_change + i)->addr,
 						  ntohs((tt_change + i)->vid),
-						  (tt_change + i)->flags, ttvn))
+						  flags, ttvn))
 				/* In case of problem while storing a
 				 * global_entry, we stop the updating
 				 * procedure without committing the
-- 
2.53.0