netdev - Re: [net-next v3] bridge: trigger RTM_NEWLINK when interface is modified by bridge ioctl

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Date:   Thu, 21 Sep 2017 10:43:35 -0600
From:   David Ahern <dsahern@...il.com>
To:     Vincent Bernat <vincent@...nat.im>,
        Stephen Hemminger <stephen@...workplumber.org>,
        David Miller <davem@...emloft.net>,
        bridge@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [net-next v3] bridge: trigger RTM_NEWLINK when interface is
 modified by bridge ioctl

On 9/21/17 4:05 AM, Vincent Bernat wrote:
> Currently, there is a difference in netlink events received when an
> interface is modified through bridge ioctl() or through netlink. This
> patch generates additional events when an interface is added to or
> removed from a bridge via ioctl().
> 
> When adding then removing an interface from a bridge with netlink, we
> get:
> 
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue master bridge0 state UNKNOWN group default
>     link/ether 9e:da:60:ee:cf:c8 brd ff:ff:ff:ff:ff:ff
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 master bridge0 state UNKNOWN
>     link/ether 9e:da:60:ee:cf:c8
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 master bridge0 state UNKNOWN
>     link/ether 9e:da:60:ee:cf:c8
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 master bridge0 state UNKNOWN
>     link/ether 9e:da:60:ee:cf:c8
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 master bridge0 state UNKNOWN
>     link/ether 9e:da:60:ee:cf:c8
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue master bridge0 state UNKNOWN group default
>     link/ether 9e:da:60:ee:cf:c8 brd ff:ff:ff:ff:ff:ff
> 
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue master bridge0 state UNKNOWN group default
>     link/ether 9e:da:60:ee:cf:c8 brd ff:ff:ff:ff:ff:ff
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 master bridge0 state UNKNOWN
>     link/ether 9e:da:60:ee:cf:c8
> Deleted 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 master bridge0 state UNKNOWN
>     link/ether 9e:da:60:ee:cf:c8
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
>     link/ether 9e:da:60:ee:cf:c8 brd ff:ff:ff:ff:ff:ff
> 
> When using ioctl():
> 
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue master bridge0 state UNKNOWN group default
>     link/ether 9e:da:60:ee:cf:c8 brd ff:ff:ff:ff:ff:ff
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 master bridge0 state UNKNOWN
>     link/ether 9e:da:60:ee:cf:c8
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 master bridge0 state UNKNOWN
>     link/ether 9e:da:60:ee:cf:c8
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 master bridge0 state UNKNOWN
>     link/ether 9e:da:60:ee:cf:c8
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue master bridge0 state UNKNOWN group default
>     link/ether 9e:da:60:ee:cf:c8 brd ff:ff:ff:ff:ff:ff
> 
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue master bridge0 state UNKNOWN group default
>     link/ether 9e:da:60:ee:cf:c8 brd ff:ff:ff:ff:ff:ff
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 master bridge0 state UNKNOWN
>     link/ether 9e:da:60:ee:cf:c8
> Deleted 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 master bridge0 state UNKNOWN
>     link/ether 9e:da:60:ee:cf:c8
> 5: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
>     link/ether 9e:da:60:ee:cf:c8 brd ff:ff:ff:ff:ff:ff
> 
> Without this patch, the last netlink notification is not sent.
> 
> Signed-off-by: Vincent Bernat <vincent@...nat.im>
> ---
>  net/bridge/br_ioctl.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/bridge/br_ioctl.c b/net/bridge/br_ioctl.c
> index 7970f8540cbb..66cd98772051 100644
> --- a/net/bridge/br_ioctl.c
> +++ b/net/bridge/br_ioctl.c
> @@ -102,6 +102,9 @@ static int add_del_if(struct net_bridge *br, int ifindex, int isadd)
>  	else
>  		ret = br_del_if(br, dev);
>  
> +	if (!ret)
> +		rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_MASTER, GFP_KERNEL);
> +
>  	return ret;
>  }
>  
> 

Agreed that this is needed for userspace to know about the master change
when done through ioctl. The bridge code is emitting a lot of what
appears to be redundant messages for both paths (netlink and ioctl).

Reviewed-by: David Ahern <dsahern@...il.com>