Re: [PATCH nft,v4 7/7] intervals: support to partial deletion with automerge

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Wed, Apr 13, 2022 at 04:38:02PM +0200, Phil Sutter wrote:
> On Wed, Apr 13, 2022 at 04:27:07PM +0200, Pablo Neira Ayuso wrote:
> [...]
> > > The one with EXPR_F_REMOVE comes *after* the one to be removed, right?
> > 
> > Right, the other way around actually.
> > 
> > > My question again: Is it possible for 'prev' to have EXPR_F_REMOVE set?
> > > Maybe I miss something, but to me it looks like not although the code
> > > expects it.
> > 
> > prev never has EXPR_F_REMOVE, so it points to an existing element.
> 
> So below change should be fine?

Yes, setelem_adjust() always checks for if (!(prev->flags & EXPR_F_REMOVE))

Your patch looks correct to me.

> diff --git a/src/intervals.c b/src/intervals.c
> index 451bc4dd4dd45..c0077c06880ff 100644
> --- a/src/intervals.c
> +++ b/src/intervals.c
> @@ -265,14 +265,12 @@ static void remove_elem(struct expr *prev, struct set *set, struct expr *purge)
>  {
>  	struct expr *clone;
>  
> -	if (!(prev->flags & EXPR_F_REMOVE)) {
> -		if (prev->flags & EXPR_F_KERNEL) {
> -			clone = expr_clone(prev);
> -			list_move_tail(&clone->list, &purge->expressions);
> -		} else {
> -			list_del(&prev->list);
> -			expr_free(prev);
> -		}
> +	if (prev->flags & EXPR_F_KERNEL) {
> +		clone = expr_clone(prev);
> +		list_move_tail(&clone->list, &purge->expressions);
> +	} else {
> +		list_del(&prev->list);
> +		expr_free(prev);
>  	}
>  }
>  
> @@ -360,18 +358,15 @@ static int setelem_adjust(struct set *set, struct expr *add, struct expr *purge,
>  {
>  	if (mpz_cmp(prev_range->low, range->low) == 0 &&
>  	    mpz_cmp(prev_range->high, range->high) > 0) {
> -		if (!(prev->flags & EXPR_F_REMOVE) &&
> -		    i->flags & EXPR_F_REMOVE)
> +		if (i->flags & EXPR_F_REMOVE)
>  			adjust_elem_left(set, prev, i, add, purge);
>  	} else if (mpz_cmp(prev_range->low, range->low) < 0 &&
>  		   mpz_cmp(prev_range->high, range->high) == 0) {
> -		if (!(prev->flags & EXPR_F_REMOVE) &&
> -		    i->flags & EXPR_F_REMOVE)
> +		if (i->flags & EXPR_F_REMOVE)
>  			adjust_elem_right(set, prev, i, add, purge);
>  	} else if (mpz_cmp(prev_range->low, range->low) < 0 &&
>  		   mpz_cmp(prev_range->high, range->high) > 0) {
> -		if (!(prev->flags & EXPR_F_REMOVE) &&
> -		    i->flags & EXPR_F_REMOVE)
> +		if (i->flags & EXPR_F_REMOVE)
>  			split_range(set, prev, i, add, purge);
>  	} else {
>  		return -1;
> @@ -417,8 +412,7 @@ static int setelem_delete(struct list_head *msgs, struct set *set,
>  
>  		if (mpz_cmp(prev_range.low, range.low) == 0 &&
>  		    mpz_cmp(prev_range.high, range.high) == 0) {
> -			if (!(prev->flags & EXPR_F_REMOVE) &&
> -			    i->flags & EXPR_F_REMOVE) {
> +			if (i->flags & EXPR_F_REMOVE) {
>  				list_move_tail(&prev->list, &purge->expressions);
>  				list_del(&i->list);
>  				expr_free(i);