netdev - Re: [RFC PATCH net-next 11/22] nexthop: Emit a notification when a nexthop is added

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Message-ID: <8568a626-0597-0904-c67c-a8badc4e270a@gmail.com>
Date:   Tue, 8 Sep 2020 09:21:08 -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 11/22] nexthop: Emit a notification when a
 nexthop is added

On 9/8/20 3:10 AM, Ido Schimmel wrote:
> From: Ido Schimmel <idosch@...dia.com>
> 
> Emit a notification in the nexthop notification chain when a new nexthop
> is added (not replaced). The nexthop can either be a new group or a
> single nexthop.

Add a comment about why EVENT_REPLACE is generated on an 'added (not
replaced)' event.

> 
> The notification is sent after the nexthop is inserted into the
> red-black tree, as listeners might need to callback into the nexthop
> code with the nexthop ID in order to mark the nexthop as offloaded.
> 
> Signed-off-by: Ido Schimmel <idosch@...dia.com>
> ---
>  include/net/nexthop.h | 3 ++-
>  net/ipv4/nexthop.c    | 6 +++++-
>  2 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/include/net/nexthop.h b/include/net/nexthop.h
> index 4147681e86d2..6431ff8cdb89 100644
> --- a/include/net/nexthop.h
> +++ b/include/net/nexthop.h
> @@ -106,7 +106,8 @@ struct nexthop {
>  
>  enum nexthop_event_type {
>  	NEXTHOP_EVENT_ADD,

looks like the ADD event is not used and can be removed.

> -	NEXTHOP_EVENT_DEL
> +	NEXTHOP_EVENT_DEL,
> +	NEXTHOP_EVENT_REPLACE,
>  };
>  
>  struct nh_notifier_single_info {
> diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
> index 71605c612458..1fa249facd46 100644
> --- a/net/ipv4/nexthop.c
> +++ b/net/ipv4/nexthop.c
> @@ -1277,7 +1277,11 @@ static int insert_nexthop(struct net *net, struct nexthop *new_nh,
>  
>  	rb_link_node_rcu(&new_nh->rb_node, parent, pp);
>  	rb_insert_color(&new_nh->rb_node, root);
> -	rc = 0;
> +
> +	rc = call_nexthop_notifiers(net, NEXTHOP_EVENT_REPLACE, new_nh, extack);
> +	if (rc)
> +		rb_erase(&new_nh->rb_node, &net->nexthop.rb_root);
> +
>  out:
>  	if (!rc) {
>  		nh_base_seq_inc(net);
>