netdev - Re: [PATCH net 5/6] rtnetlink: check DO_SETLINK_NOTIFY correctly in do

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Date:   Sun, 15 Oct 2017 19:17:28 -0600
From:   David Ahern <dsahern@...il.com>
To:     Xin Long <lucien.xin@...il.com>,
        network dev <netdev@...r.kernel.org>
Cc:     davem@...emloft.net, hannes@...essinduktion.org,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>
Subject: Re: [PATCH net 5/6] rtnetlink: check DO_SETLINK_NOTIFY correctly in
 do_setlink

[ cc'ed Nicolas ]

On 10/15/17 4:13 AM, Xin Long wrote:
> The check 'status & DO_SETLINK_NOTIFY' in do_setlink doesn't really
> work after status & DO_SETLINK_MODIFIED, as:
> 
>   DO_SETLINK_MODIFIED 0x1
>   DO_SETLINK_NOTIFY 0x3
> 
> Considering that notifications are suppposed to be sent only when
> status have the flag DO_SETLINK_NOTIFY, the right check would be:
> 
>   (status & DO_SETLINK_NOTIFY) == DO_SETLINK_NOTIFY
> 
> This would avoid lots of duplicated notifications when setting some
> properties of a link.
> 
> Fixes: ba9989069f4e ("rtnl/do_setlink(): notify when a netdev is modified")
> Signed-off-by: Xin Long <lucien.xin@...il.com>
> ---
>  net/core/rtnetlink.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index ab98c1c..3e98fb5 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -2248,7 +2248,7 @@ static int do_setlink(const struct sk_buff *skb,
>  
>  errout:
>  	if (status & DO_SETLINK_MODIFIED) {
> -		if (status & DO_SETLINK_NOTIFY)
> +		if ((status & DO_SETLINK_NOTIFY) == DO_SETLINK_NOTIFY)
>  			netdev_state_change(dev);
>  
>  		if (err < 0)
> 

Good catch.

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