Re: [PATCH] net: Support filtering interfaces on no master

[David Ahern <dsahern@gmail.com>]

On 8/8/21 7:28 AM, Lahav Schlesinger wrote:
> Currently there's support for filtering neighbours/links for interfaces
> which have a specific master device (using the IFLA_MASTER/NDA_MASTER
> attributes).
> 
> This patch adds support for filtering interfaces/neighbours dump for
> interfaces that *don't* have a master.
> 
> I have a patch for iproute2 ready for adding this support in userspace.
> 
> Signed-off-by: Lahav Schlesinger <lschlesinger@drivenets.com>
> Cc: David Ahern <dsahern@kernel.org>
> Cc: David S. Miller <davem@davemloft.net>
> Cc: Jakub Kicinski <kuba@kernel.org>
> ---
>  net/core/neighbour.c | 7 +++++++
>  net/core/rtnetlink.c | 7 +++++++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index 53e85c70c6e5..1b1e0ca70650 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c
> @@ -2533,6 +2533,13 @@ static bool neigh_master_filtered(struct net_device *dev, int master_idx)
>  		return false;
>  
>  	master = dev ? netdev_master_upper_dev_get(dev) : NULL;
> +
> +	/* 0 is already used to denote NDA_MASTER wasn't passed, therefore need another
> +	 * invalid value for ifindex to denote "no master".
> +	 */
> +	if (master_idx == -1)
> +                return (bool)master;

return !!master;

same below

> +
>  	if (!master || master->ifindex != master_idx)
>  		return true;
>  
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index f6af3e74fc44..8ccc314744d4 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -1970,6 +1970,13 @@ static bool link_master_filtered(struct net_device *dev, int master_idx)
>  		return false;
>  
>  	master = netdev_master_upper_dev_get(dev);
> +
> +	/* 0 is already used to denote IFLA_MASTER wasn't passed, therefore need
> +	 * another invalid value for ifindex to denote "no master".
> +	 */
> +	if (master_idx == -1)
> +                return (bool)master;
> +
>  	if (!master || master->ifindex != master_idx)
>  		return true;
>  
>