v4.19.13 snapshot.
diff --git a/net/batman-adv/bitarray.c b/net/batman-adv/bitarray.c
new file mode 100644
index 0000000..a296a4d
--- /dev/null
+++ b/net/batman-adv/bitarray.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2006-2018 B.A.T.M.A.N. contributors:
+ *
+ * Simon Wunderlich, Marek Lindner
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "bitarray.h"
+#include "main.h"
+
+#include <linux/bitmap.h>
+
+#include "log.h"
+
+/* shift the packet array by n places. */
+static void batadv_bitmap_shift_left(unsigned long *seq_bits, s32 n)
+{
+ if (n <= 0 || n >= BATADV_TQ_LOCAL_WINDOW_SIZE)
+ return;
+
+ bitmap_shift_left(seq_bits, seq_bits, n, BATADV_TQ_LOCAL_WINDOW_SIZE);
+}
+
+/**
+ * batadv_bit_get_packet() - receive and process one packet within the sequence
+ * number window
+ * @priv: the bat priv with all the soft interface information
+ * @seq_bits: pointer to the sequence number receive packet
+ * @seq_num_diff: difference between the current/received sequence number and
+ * the last sequence number
+ * @set_mark: whether this packet should be marked in seq_bits
+ *
+ * Return: true if the window was moved (either new or very old),
+ * false if the window was not moved/shifted.
+ */
+bool batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
+ s32 seq_num_diff, int set_mark)
+{
+ struct batadv_priv *bat_priv = priv;
+
+ /* sequence number is slightly older. We already got a sequence number
+ * higher than this one, so we just mark it.
+ */
+ if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) {
+ if (set_mark)
+ batadv_set_bit(seq_bits, -seq_num_diff);
+ return false;
+ }
+
+ /* sequence number is slightly newer, so we shift the window and
+ * set the mark if required
+ */
+ if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) {
+ batadv_bitmap_shift_left(seq_bits, seq_num_diff);
+
+ if (set_mark)
+ batadv_set_bit(seq_bits, 0);
+ return true;
+ }
+
+ /* sequence number is much newer, probably missed a lot of packets */
+ if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE &&
+ seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) {
+ batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
+ "We missed a lot of packets (%i) !\n",
+ seq_num_diff - 1);
+ bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
+ if (set_mark)
+ batadv_set_bit(seq_bits, 0);
+ return true;
+ }
+
+ /* received a much older packet. The other host either restarted
+ * or the old packet got delayed somewhere in the network. The
+ * packet should be dropped without calling this function if the
+ * seqno window is protected.
+ *
+ * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE
+ * or
+ * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE
+ */
+ batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
+ "Other host probably restarted!\n");
+
+ bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
+ if (set_mark)
+ batadv_set_bit(seq_bits, 0);
+
+ return true;
+}