[SRU,Xenial,Yakkety,Zesty,Artful,1/1] bonding: avoid NETDEV_CHANGEMTU event when unregistering slave

From: WANG Cong <xiyou.wangcong@gmail.com>

BugLink: http://bugs.launchpad.net/bugs/1704102

As Hongjun/Nicolas summarized in their original patch:

"
When a device changes from one netns to another, it's first unregistered,
then the netns reference is updated and the dev is registered in the new
netns. Thus, when a slave moves to another netns, it is first
unregistered. This triggers a NETDEV_UNREGISTER event which is caught by
the bonding driver. The driver calls bond_release(), which calls
dev_set_mtu() and thus triggers NETDEV_CHANGEMTU (the device is still in
the old netns).
"

This is a very special case, because the device is being unregistered
no one should still care about the NETDEV_CHANGEMTU event triggered
at this point, we can avoid broadcasting this event on this path,
and avoid touching inetdev_event()/addrconf_notify() path.

It requires to export __dev_set_mtu() to bonding driver.

Reported-by: Hongjun Li <hongjun.li@6wind.com>
Reported-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Cc: Jay Vosburgh <j.vosburgh@gmail.com>
Cc: Veaceslav Falico <vfalico@gmail.com>
Cc: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit f51048c3e07b68c90b21a77541fc4b208f9244d7)
Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com>
---
 drivers/net/bonding/bond_main.c | 15 +++++++++------
 include/linux/netdevice.h       |  1 +
 net/core/dev.c                  |  3 ++-
 3 files changed, 12 insertions(+), 7 deletions(-)

On 14.07.2017 22:58, Joseph Salisbury wrote:
> From: WANG Cong <xiyou.wangcong@gmail.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1704102
> 
> As Hongjun/Nicolas summarized in their original patch:
> 
> "
> When a device changes from one netns to another, it's first unregistered,
> then the netns reference is updated and the dev is registered in the new
> netns. Thus, when a slave moves to another netns, it is first
> unregistered. This triggers a NETDEV_UNREGISTER event which is caught by
> the bonding driver. The driver calls bond_release(), which calls
> dev_set_mtu() and thus triggers NETDEV_CHANGEMTU (the device is still in
> the old netns).
> "
> 
> This is a very special case, because the device is being unregistered
> no one should still care about the NETDEV_CHANGEMTU event triggered
> at this point, we can avoid broadcasting this event on this path,
> and avoid touching inetdev_event()/addrconf_notify() path.
> 
> It requires to export __dev_set_mtu() to bonding driver.
> 
> Reported-by: Hongjun Li <hongjun.li@6wind.com>
> Reported-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
> Cc: Jay Vosburgh <j.vosburgh@gmail.com>
> Cc: Veaceslav Falico <vfalico@gmail.com>
> Cc: Andy Gospodarek <andy@greyhouse.net>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> (cherry picked from commit f51048c3e07b68c90b21a77541fc4b208f9244d7)
> Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com>

Acked-by: Stefan Bader <stefan.bader@canonical.com>

> ---

Guess! :)

>  drivers/net/bonding/bond_main.c | 15 +++++++++------
>  include/linux/netdevice.h       |  1 +
>  net/core/dev.c                  |  3 ++-
>  3 files changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 34481c9..fd92e89 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -1814,7 +1814,7 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>   */
>  static int __bond_release_one(struct net_device *bond_dev,
>  			      struct net_device *slave_dev,
> -			      bool all)
> +			      bool all, bool unregister)
>  {
>  	struct bonding *bond = netdev_priv(bond_dev);
>  	struct slave *slave, *oldcurrent;
> @@ -1958,7 +1958,10 @@ static int __bond_release_one(struct net_device *bond_dev,
>  		dev_set_mac_address(slave_dev, &addr);
>  	}
>  
> -	dev_set_mtu(slave_dev, slave->original_mtu);
> +	if (unregister)
> +		__dev_set_mtu(slave_dev, slave->original_mtu);
> +	else
> +		dev_set_mtu(slave_dev, slave->original_mtu);
>  
>  	slave_dev->priv_flags &= ~IFF_BONDING;
>  
> @@ -1970,7 +1973,7 @@ static int __bond_release_one(struct net_device *bond_dev,
>  /* A wrapper used because of ndo_del_link */
>  int bond_release(struct net_device *bond_dev, struct net_device *slave_dev)
>  {
> -	return __bond_release_one(bond_dev, slave_dev, false);
> +	return __bond_release_one(bond_dev, slave_dev, false, false);
>  }
>  
>  /* First release a slave and then destroy the bond if no more slaves are left.
> @@ -1982,7 +1985,7 @@ static int  bond_release_and_destroy(struct net_device *bond_dev,
>  	struct bonding *bond = netdev_priv(bond_dev);
>  	int ret;
>  
> -	ret = bond_release(bond_dev, slave_dev);
> +	ret = __bond_release_one(bond_dev, slave_dev, false, true);
>  	if (ret == 0 && !bond_has_slaves(bond)) {
>  		bond_dev->priv_flags |= IFF_DISABLE_NETPOLL;
>  		netdev_info(bond_dev, "Destroying bond %s\n",
> @@ -3032,7 +3035,7 @@ static int bond_slave_netdev_event(unsigned long event,
>  		if (bond_dev->type != ARPHRD_ETHER)
>  			bond_release_and_destroy(bond_dev, slave_dev);
>  		else
> -			bond_release(bond_dev, slave_dev);
> +			__bond_release_one(bond_dev, slave_dev, false, true);
>  		break;
>  	case NETDEV_UP:
>  	case NETDEV_CHANGE:
> @@ -4228,7 +4231,7 @@ static void bond_uninit(struct net_device *bond_dev)
>  
>  	/* Release the bonded slaves */
>  	bond_for_each_slave(bond, slave, iter)
> -		__bond_release_one(bond_dev, slave->dev, true);
> +		__bond_release_one(bond_dev, slave->dev, true, true);
>  	netdev_info(bond_dev, "Released all slaves\n");
>  
>  	arr = rtnl_dereference(bond->slave_arr);
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 97456b25..a8d97f0 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -3269,6 +3269,7 @@ void __dev_notify_flags(struct net_device *, unsigned int old_flags,
>  int dev_change_name(struct net_device *, const char *);
>  int dev_set_alias(struct net_device *, const char *, size_t);
>  int dev_change_net_namespace(struct net_device *, struct net *, const char *);
> +int __dev_set_mtu(struct net_device *, int);
>  int dev_set_mtu(struct net_device *, int);
>  void dev_set_group(struct net_device *, int);
>  int dev_set_mac_address(struct net_device *, struct sockaddr *);
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 9b58753..8804076 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -6535,7 +6535,7 @@ int dev_change_flags(struct net_device *dev, unsigned int flags)
>  }
>  EXPORT_SYMBOL(dev_change_flags);
>  
> -static int __dev_set_mtu(struct net_device *dev, int new_mtu)
> +int __dev_set_mtu(struct net_device *dev, int new_mtu)
>  {
>  	const struct net_device_ops *ops = dev->netdev_ops;
>  
> @@ -6545,6 +6545,7 @@ static int __dev_set_mtu(struct net_device *dev, int new_mtu)
>  	dev->mtu = new_mtu;
>  	return 0;
>  }
> +EXPORT_SYMBOL(__dev_set_mtu);
>  
>  /**
>   *	dev_set_mtu - Change maximum transfer unit
>

On Fri, Jul 14, 2017 at 04:58:52PM -0400, Joseph Salisbury wrote:
> From: WANG Cong <xiyou.wangcong@gmail.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1704102
> 
> As Hongjun/Nicolas summarized in their original patch:
> 
> "
> When a device changes from one netns to another, it's first unregistered,
> then the netns reference is updated and the dev is registered in the new
> netns. Thus, when a slave moves to another netns, it is first
> unregistered. This triggers a NETDEV_UNREGISTER event which is caught by
> the bonding driver. The driver calls bond_release(), which calls
> dev_set_mtu() and thus triggers NETDEV_CHANGEMTU (the device is still in
> the old netns).
> "
> 
> This is a very special case, because the device is being unregistered
> no one should still care about the NETDEV_CHANGEMTU event triggered
> at this point, we can avoid broadcasting this event on this path,
> and avoid touching inetdev_event()/addrconf_notify() path.
> 
> It requires to export __dev_set_mtu() to bonding driver.
> 
> Reported-by: Hongjun Li <hongjun.li@6wind.com>
> Reported-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
> Cc: Jay Vosburgh <j.vosburgh@gmail.com>
> Cc: Veaceslav Falico <vfalico@gmail.com>
> Cc: Andy Gospodarek <andy@greyhouse.net>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> (cherry picked from commit f51048c3e07b68c90b21a77541fc4b208f9244d7)
> Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com>

Acked-by: Seth Forshee <seth.forshee@canonical.com>

Applied to artful/master-next and unstable/master, thanks.