--- /dev/null
+From a31d27fbed5d518734cb60956303eb15089a7634 Mon Sep 17 00:00:00 2001
+From: Nicolas Dichtel <nicolas.dichtel@6wind.com>
+Date: Fri, 12 Nov 2021 08:56:03 +0100
+Subject: tun: fix bonding active backup with arp monitoring
+
+From: Nicolas Dichtel <nicolas.dichtel@6wind.com>
+
+commit a31d27fbed5d518734cb60956303eb15089a7634 upstream.
+
+As stated in the bonding doc, trans_start must be set manually for drivers
+using NETIF_F_LLTX:
+ Drivers that use NETIF_F_LLTX flag must also update
+ netdev_queue->trans_start. If they do not, then the ARP monitor will
+ immediately fail any slaves using that driver, and those slaves will stay
+ down.
+
+Link: https://www.kernel.org/doc/html/v5.15/networking/bonding.html#arp-monitor-operation
+Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/net/tun.c | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+--- a/drivers/net/tun.c
++++ b/drivers/net/tun.c
+@@ -1085,6 +1085,7 @@ static netdev_tx_t tun_net_xmit(struct s
+ {
+ struct tun_struct *tun = netdev_priv(dev);
+ int txq = skb->queue_mapping;
++ struct netdev_queue *queue;
+ struct tun_file *tfile;
+ int len = skb->len;
+
+@@ -1131,6 +1132,10 @@ static netdev_tx_t tun_net_xmit(struct s
+ if (ptr_ring_produce(&tfile->tx_ring, skb))
+ goto drop;
+
++ /* NETIF_F_LLTX requires to do our own update of trans_start */
++ queue = netdev_get_tx_queue(dev, txq);
++ queue->trans_start = jiffies;
++
+ /* Notify and wake up reader process */
+ if (tfile->flags & TUN_FASYNC)
+ kill_fasync(&tfile->fasync, SIGIO, POLL_IN);