netdev - Re: [RFC PATCH net-next 17/22] nexthop: Replay nexthops when registering a notifier

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Date:   Tue, 8 Sep 2020 09:37:10 -0600
From:   David Ahern <dsahern@...il.com>
To:     Ido Schimmel <idosch@...sch.org>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, roopa@...dia.com,
        mlxsw@...dia.com, Ido Schimmel <idosch@...dia.com>
Subject: Re: [RFC PATCH net-next 17/22] nexthop: Replay nexthops when
 registering a notifier

On 9/8/20 3:10 AM, Ido Schimmel wrote:
> From: Ido Schimmel <idosch@...dia.com>
> 
> When registering a new notifier to the nexthop notification chain,
> replay all the existing nexthops to the new notifier so that it will
> have a complete picture of the available nexthops.
> 
> Signed-off-by: Ido Schimmel <idosch@...dia.com>
> ---
>  net/ipv4/nexthop.c | 54 ++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 52 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
> index b40c343ca969..6505a0a28df2 100644
> --- a/net/ipv4/nexthop.c
> +++ b/net/ipv4/nexthop.c
> @@ -156,6 +156,27 @@ static int call_nexthop_notifiers(struct net *net,
>  	return notifier_to_errno(err);
>  }
>  
> +static int call_nexthop_notifier(struct notifier_block *nb, struct net *net,
> +				 enum nexthop_event_type event_type,
> +				 struct nexthop *nh,
> +				 struct netlink_ext_ack *extack)
> +{
> +	struct nh_notifier_info info = {
> +		.net = net,
> +		.extack = extack,
> +	};
> +	int err;
> +
> +	err = nh_notifier_info_init(&info, nh);
> +	if (err)
> +		return err;
> +
> +	err = nb->notifier_call(nb, event_type, &info);
> +	nh_notifier_info_fini(&info);
> +
> +	return notifier_to_errno(err);
> +}
> +
>  static unsigned int nh_dev_hashfn(unsigned int val)
>  {
>  	unsigned int mask = NH_DEV_HASHSIZE - 1;
> @@ -2116,11 +2137,40 @@ static struct notifier_block nh_netdev_notifier = {
>  	.notifier_call = nh_netdev_event,
>  };
>  
> +static int nexthops_dump(struct net *net, struct notifier_block *nb,
> +			 struct netlink_ext_ack *extack)
> +{
> +	struct rb_root *root = &net->nexthop.rb_root;
> +	struct rb_node *node;
> +	int err = 0;
> +
> +	for (node = rb_first(root); node; node = rb_next(node)) {
> +		struct nexthop *nh;
> +
> +		nh = rb_entry(node, struct nexthop, rb_node);
> +		err = call_nexthop_notifier(nb, net, NEXTHOP_EVENT_REPLACE, nh,
> +					    extack);
> +		if (err)
> +			break;
> +	}
> +
> +	return err;
> +}
> +
>  int register_nexthop_notifier(struct net *net, struct notifier_block *nb,
>  			      struct netlink_ext_ack *extack)
>  {
> -	return blocking_notifier_chain_register(&net->nexthop.notifier_chain,
> -						nb);
> +	int err;
> +
> +	rtnl_lock();
> +	err = nexthops_dump(net, nb, extack);

can the unlock be moved here? register function below should not need it.

> +	if (err)
> +		goto unlock;
> +	err = blocking_notifier_chain_register(&net->nexthop.notifier_chain,
> +					       nb);
> +unlock:
> +	rtnl_unlock();
> +	return err;
>  }
>  EXPORT_SYMBOL(register_nexthop_notifier);
>  
>