linux-kernel - Re: [PATCH net-next] net: netlink: remove netlink_broadcast

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Date:   Wed, 26 May 2021 11:28:09 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     menglong8.dong@...il.com, kuba@...nel.org
Cc:     davem@...emloft.net, mkubecek@...e.cz, dsahern@...nel.org,
        zhudi21@...wei.com, johannes.berg@...el.com,
        marcelo.leitner@...il.com, dong.menglong@....com.cn,
        ast@...nel.org, yhs@...com, rdunlap@...radead.org,
        yangyingliang@...wei.com, 0x7f454c46@...il.com,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net: netlink: remove netlink_broadcast_filtered

On 09/03/2021 16:18, menglong8.dong@...il.com wrote:
> From: Menglong Dong <dong.menglong@....com.cn>
> 
> It seems that 'netlink_broadcast_filtered()' is not used anywhere
> besides 'netlink_broadcast()'. In order to reduce function calls,
> just remove it.
> 
> Signed-off-by: Menglong Dong <dong.menglong@....com.cn>

I was trying to figure out if the function could be useful to filter out
some netlink messages when sending them to userspace.

Still looking for examples :/

On the other side, this function was put there as part of the network
namespace infrastructure. Even there is no user, it may be needed.

> ---
>  include/linux/netlink.h  |  4 ----
>  net/netlink/af_netlink.c | 22 ++--------------------
>  2 files changed, 2 insertions(+), 24 deletions(-)
> 
> diff --git a/include/linux/netlink.h b/include/linux/netlink.h
> index 0bcf98098c5a..277f33e64bb3 100644
> --- a/include/linux/netlink.h
> +++ b/include/linux/netlink.h
> @@ -160,10 +160,6 @@ bool netlink_strict_get_check(struct sk_buff *skb);
>  int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
>  int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
>  		      __u32 group, gfp_t allocation);
> -int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb,
> -			       __u32 portid, __u32 group, gfp_t allocation,
> -			       int (*filter)(struct sock *dsk, struct sk_buff *skb, void *data),
> -			       void *filter_data);
>  int netlink_set_err(struct sock *ssk, __u32 portid, __u32 group, int code);
>  int netlink_register_notifier(struct notifier_block *nb);
>  int netlink_unregister_notifier(struct notifier_block *nb);
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index dd488938447f..b462fdc87e9b 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -1405,8 +1405,6 @@ struct netlink_broadcast_data {
>  	int delivered;
>  	gfp_t allocation;
>  	struct sk_buff *skb, *skb2;
> -	int (*tx_filter)(struct sock *dsk, struct sk_buff *skb, void *data);
> -	void *tx_data;
>  };
>  
>  static void do_one_broadcast(struct sock *sk,
> @@ -1460,11 +1458,6 @@ static void do_one_broadcast(struct sock *sk,
>  			p->delivery_failure = 1;
>  		goto out;
>  	}
> -	if (p->tx_filter && p->tx_filter(sk, p->skb2, p->tx_data)) {
> -		kfree_skb(p->skb2);
> -		p->skb2 = NULL;
> -		goto out;
> -	}
>  	if (sk_filter(sk, p->skb2)) {
>  		kfree_skb(p->skb2);
>  		p->skb2 = NULL;
> @@ -1487,10 +1480,8 @@ static void do_one_broadcast(struct sock *sk,
>  	sock_put(sk);
>  }
>  
> -int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb, u32 portid,
> -	u32 group, gfp_t allocation,
> -	int (*filter)(struct sock *dsk, struct sk_buff *skb, void *data),
> -	void *filter_data)
> +int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, u32 portid,
> +		      u32 group, gfp_t allocation)
>  {
>  	struct net *net = sock_net(ssk);
>  	struct netlink_broadcast_data info;
> @@ -1509,8 +1500,6 @@ int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb, u32 portid
>  	info.allocation = allocation;
>  	info.skb = skb;
>  	info.skb2 = NULL;
> -	info.tx_filter = filter;
> -	info.tx_data = filter_data;
>  
>  	/* While we sleep in clone, do not allow to change socket list */
>  
> @@ -1536,14 +1525,7 @@ int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb, u32 portid
>  	}
>  	return -ESRCH;
>  }
> -EXPORT_SYMBOL(netlink_broadcast_filtered);
>  
> -int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, u32 portid,
> -		      u32 group, gfp_t allocation)
> -{
> -	return netlink_broadcast_filtered(ssk, skb, portid, group, allocation,
> -		NULL, NULL);
> -}
>  EXPORT_SYMBOL(netlink_broadcast);
>  
>  struct netlink_set_err_data {
> 


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