netdev - Re: [PATCH net-next 3/4] nexthop: Do not return invalid nexthop object during multipath selection

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Message-ID: <eb6a1866-7c71-53c6-241f-0a38a4047f7e@kernel.org>
Date: Tue, 30 May 2023 09:08:01 -0600
From: David Ahern <dsahern@...nel.org>
To: Benjamin Poirier <bpoirier@...dia.com>, netdev@...r.kernel.org
Cc: Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
 Ido Schimmel <idosch@...dia.com>
Subject: Re: [PATCH net-next 3/4] nexthop: Do not return invalid nexthop
 object during multipath selection

On 5/29/23 2:19 PM, Benjamin Poirier wrote:
> diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
> index c12acbf39659..ca501ced04fb 100644
> --- a/net/ipv4/nexthop.c
> +++ b/net/ipv4/nexthop.c
> @@ -1186,6 +1186,7 @@ static struct nexthop *nexthop_select_path_fdb(struct nh_group *nhg, int hash)
>  static struct nexthop *nexthop_select_path_hthr(struct nh_group *nhg, int hash)
>  {
>  	struct nexthop *rc = NULL;
> +	bool first = false;
>  	int i;
>  
>  	if (nhg->fdb_nh)
> @@ -1194,20 +1195,24 @@ static struct nexthop *nexthop_select_path_hthr(struct nh_group *nhg, int hash)
>  	for (i = 0; i < nhg->num_nh; ++i) {
>  		struct nh_grp_entry *nhge = &nhg->nh_entries[i];
>  
> -		if (hash > atomic_read(&nhge->hthr.upper_bound))
> -			continue;
> -
>  		/* nexthops always check if it is good and does
>  		 * not rely on a sysctl for this behavior
>  		 */
> -		if (nexthop_is_good_nh(nhge->nh))
> -			return nhge->nh;
> +		if (!nexthop_is_good_nh(nhge->nh))
> +			continue;
>  
> -		if (!rc)
> +		if (!first) {

Setting 'first' and 'rc' are equivalent, so 'first' is not needed. As I
recall it was used in fib_select_multipath before the nexthop
refactoring (eba618abacade) because nhsel == 0 is valid, so the loop
could not rely on it.



>  			rc = nhge->nh;
> +			first = true;
> +		}
> +
> +		if (hash > atomic_read(&nhge->hthr.upper_bound))
> +			continue;
> +
> +		return nhge->nh;
>  	}
>  
> -	return rc;
> +	return rc ? : nhg->nh_entries[0].nh;
>  }
>  
>  static struct nexthop *nexthop_select_path_res(struct nh_group *nhg, int hash)