From: Chas Williams <3chas3@gmail.com>
Date: Sat, 2 Jun 2018 17:49:53 -0400
Subject: Allow ethtool to change tun link settings
Patch-mainline: v4.18-rc1
Git-commit: 4e24f2dd516ed85fc8fd568ceae589ad0a07b7d5
References: bsc#1109837

Let user space set whatever it would like to advertise for the
tun interface.  Preserve the existing defaults.

Signed-off-by: Chas Williams <3chas3@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/tun.c |   27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -80,6 +80,9 @@
 
 #include <linux/uaccess.h>
 
+static void tun_default_link_ksettings(struct net_device *dev,
+				       struct ethtool_link_ksettings *cmd);
+
 /* Uncomment to enable debugging */
 /* #define TUN_DEBUG 1 */
 
@@ -241,6 +244,7 @@ struct tun_struct {
 	struct bpf_prog __rcu *xdp_prog;
 	struct tun_prog __rcu *steering_prog;
 	struct tun_prog __rcu *filter_prog;
+	struct ethtool_link_ksettings link_ksettings;
 };
 
 struct veth {
@@ -2292,6 +2296,7 @@ static void tun_setup(struct net_device
 
 	tun->owner = INVALID_UID;
 	tun->group = INVALID_GID;
+	tun_default_link_ksettings(dev, &tun->link_ksettings);
 
 	dev->ethtool_ops = &tun_ethtool_ops;
 	dev->needs_free_netdev = true;
@@ -3316,8 +3321,8 @@ static struct miscdevice tun_miscdev = {
 
 /* ethtool interface */
 
-static int tun_get_link_ksettings(struct net_device *dev,
-				  struct ethtool_link_ksettings *cmd)
+static void tun_default_link_ksettings(struct net_device *dev,
+				       struct ethtool_link_ksettings *cmd)
 {
 	ethtool_link_ksettings_zero_link_mode(cmd, supported);
 	ethtool_link_ksettings_zero_link_mode(cmd, advertising);
@@ -3326,6 +3331,23 @@ static int tun_get_link_ksettings(struct
 	cmd->base.port		= PORT_TP;
 	cmd->base.phy_address	= 0;
 	cmd->base.autoneg	= AUTONEG_DISABLE;
+}
+
+static int tun_get_link_ksettings(struct net_device *dev,
+				  struct ethtool_link_ksettings *cmd)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	memcpy(cmd, &tun->link_ksettings, sizeof(*cmd));
+	return 0;
+}
+
+static int tun_set_link_ksettings(struct net_device *dev,
+				  const struct ethtool_link_ksettings *cmd)
+{
+	struct tun_struct *tun = netdev_priv(dev);
+
+	memcpy(&tun->link_ksettings, cmd, sizeof(*cmd));
 	return 0;
 }
 
@@ -3396,6 +3418,7 @@ static const struct ethtool_ops tun_etht
 	.get_coalesce   = tun_get_coalesce,
 	.set_coalesce   = tun_set_coalesce,
 	.get_link_ksettings = tun_get_link_ksettings,
+	.set_link_ksettings = tun_set_link_ksettings,
 };
 
 static int tun_queue_resize(struct tun_struct *tun)