netdev - Re: [PATCH net-next 3/9] ipv4: Notify route if replacing currently offloaded one

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Date:   Wed, 11 Dec 2019 10:40:09 -0700
From:   David Ahern <dsahern@...il.com>
To:     Ido Schimmel <idosch@...sch.org>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, jiri@...lanox.com, roopa@...ulusnetworks.com,
        mlxsw@...lanox.com, Ido Schimmel <idosch@...lanox.com>
Subject: Re: [PATCH net-next 3/9] ipv4: Notify route if replacing currently
 offloaded one

On 12/10/19 10:23 AM, Ido Schimmel wrote:
> From: Ido Schimmel <idosch@...lanox.com>
> 
> When replacing a route, its replacement should only be notified in case
> the replaced route is of any interest to listeners. In other words, if
> the replaced route is currently used in the data path, which means it is
> the first route in the FIB alias list with the given {prefix, prefix
> length, table ID}.
> 
> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
> ---
>  net/ipv4/fib_trie.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
> index 9264d6628e9f..6822aa90657a 100644
> --- a/net/ipv4/fib_trie.c
> +++ b/net/ipv4/fib_trie.c
> @@ -978,6 +978,27 @@ static struct key_vector *fib_find_node(struct trie *t,
>  	return n;
>  }
>  
> +/* Return the first fib alias matching prefix length and table ID. */
> +static struct fib_alias *fib_find_first_alias(struct hlist_head *fah, u8 slen,
> +					      u32 tb_id)
> +{
> +	struct fib_alias *fa;
> +
> +	hlist_for_each_entry(fa, fah, fa_list) {
> +		if (fa->fa_slen < slen)
> +			continue;
> +		if (fa->fa_slen != slen)
> +			break;
> +		if (fa->tb_id > tb_id)
> +			continue;
> +		if (fa->tb_id != tb_id)
> +			break;
> +		return fa;

Rather than duplicating fib_find_alias, how about adding a 'bool
find_first' argument and bail on it:

		if (find_first)
			return fa;

		continue to tos and priority compares.

> +	}
> +
> +	return NULL;
> +}
> +
>  /* Return the first fib alias matching TOS with
>   * priority less than or equal to PRIO.
>   */
> @@ -1217,6 +1238,17 @@ int fib_table_insert(struct net *net, struct fib_table *tb,
>  			new_fa->tb_id = tb->tb_id;
>  			new_fa->fa_default = -1;
>  
> +			if (fib_find_first_alias(&l->leaf, fa->fa_slen,
> +						 tb->tb_id) == fa) {
> +				enum fib_event_type fib_event;
> +
> +				fib_event = FIB_EVENT_ENTRY_REPLACE_TMP;
> +				err = call_fib_entry_notifiers(net, fib_event,
> +							       key, plen,
> +							       new_fa, extack);
> +				if (err)
> +					goto out_free_new_fa;
> +			}
>  			err = call_fib_entry_notifiers(net,
>  						       FIB_EVENT_ENTRY_REPLACE,
>  						       key, plen, new_fa,
>