intervals: support to partial deletion with automerge

Splice the existing set element cache with the elements to be deleted
and merge sort it.  The elements to be deleted are identified by the
EXPR_F_REMOVE flag.

The set elements to be deleted is automerged in first place if the
automerge flag is set on.

There are four possible deletion scenarios:

- Exact match, eg. delete [a-b] and there is a [a-b] range in the kernel set.
- Adjust left side of range, eg. delete [a-b] from range [a-x] where x > b.
- Adjust right side of range, eg. delete [a-b] from range [x-b] where x < a.
- Split range, eg. delete [a-b] from range [x-y] where x < a and b < y.

Update nft_evaluate() to use the safe list variant since new commands
are dynamically registered to the list to update ranges.

This patch also restores the set element existence check for Linux
kernels <= 5.7.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

3 files changed, 254 insertions, 3 deletions

diff --git a/src/evaluate.c b/src/evaluate.c
index eb147585..503b4f03 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -1486,7 +1486,8 @@ static int interval_set_eval(struct eval_ctx *ctx, struct set *set,
 		}
 		break;
 	case CMD_DELETE:
-		set_to_range(init);
+		ret = set_delete(ctx->msgs, ctx->cmd, set, init,
+				 ctx->nft->debug_mask);
 		break;
 	case CMD_GET:
 		break;
diff --git a/src/intervals.c b/src/intervals.c
index 16debf9c..f672d0aa 100644
--- a/src/intervals.c
+++ b/src/intervals.c
@@ -255,6 +255,256 @@ int set_automerge(struct list_head *msgs, struct cmd *cmd, struct set *set,
 	return 0;
 }
 
+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);
+		}
+	}
+}
+
+static void __adjust_elem_left(struct set *set, struct expr *prev, struct expr *i,
+			       struct expr *add)
+{
+	prev->flags &= EXPR_F_KERNEL;
+	expr_free(prev->key->left);
+	prev->key->left = expr_get(i->key->right);
+	mpz_add_ui(prev->key->left->value, prev->key->left->value, 1);
+	list_move(&prev->list, &add->expressions);
+}
+
+static void adjust_elem_left(struct set *set, struct expr *prev, struct expr *i,
+			     struct expr *add, struct expr *purge)
+{
+	struct expr *clone;
+
+	remove_elem(prev, set, purge);
+	__adjust_elem_left(set, prev, i, add);
+
+	list_del(&i->list);
+	expr_free(i);
+
+	clone = expr_clone(prev);
+	list_add_tail(&clone->list, &set->existing_set->init->expressions);
+}
+
+static void __adjust_elem_right(struct set *set, struct expr *prev, struct expr *i,
+				struct expr *add)
+{
+	prev->flags &= EXPR_F_KERNEL;
+	expr_free(prev->key->right);
+	prev->key->right = expr_get(i->key->left);
+	mpz_sub_ui(prev->key->right->value, prev->key->right->value, 1);
+	list_move(&prev->list, &add->expressions);
+}
+
+static void adjust_elem_right(struct set *set, struct expr *prev, struct expr *i,
+			      struct expr *add, struct expr *purge)
+{
+	struct expr *clone;
+
+	remove_elem(prev, set, purge);
+	__adjust_elem_right(set, prev, i, add);
+
+	list_del(&i->list);
+	expr_free(i);
+
+	clone = expr_clone(prev);
+	list_add_tail(&clone->list, &set->existing_set->init->expressions);
+}
+
+static void split_range(struct set *set, struct expr *prev, struct expr *i,
+			struct expr *add, struct expr *purge)
+{
+	struct expr *clone;
+
+	clone = expr_clone(prev);
+	list_move_tail(&clone->list, &purge->expressions);
+
+	prev->flags &= EXPR_F_KERNEL;
+	clone = expr_clone(prev);
+	expr_free(clone->key->left);
+	clone->key->left = expr_get(i->key->right);
+	mpz_add_ui(clone->key->left->value, i->key->right->value, 1);
+	list_move(&clone->list, &add->expressions);
+	clone = expr_clone(clone);
+	list_add_tail(&clone->list, &set->existing_set->init->expressions);
+
+	expr_free(prev->key->right);
+	prev->key->right = expr_get(i->key->left);
+	mpz_sub_ui(prev->key->right->value, i->key->left->value, 1);
+	list_move(&prev->list, &add->expressions);
+	clone = expr_clone(prev);
+	list_add_tail(&clone->list, &set->existing_set->init->expressions);
+
+	list_del(&i->list);
+	expr_free(i);
+}
+
+static int setelem_adjust(struct set *set, struct expr *add, struct expr *purge,
+			  struct range *prev_range, struct range *range,
+			  struct expr *prev, struct expr *i)
+{
+	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)
+			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)
+			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)
+			split_range(set, prev, i, add, purge);
+	} else {
+		return -1;
+	}
+
+	return 0;
+}
+
+static int setelem_delete(struct list_head *msgs, struct set *set,
+			  struct expr *add, struct expr *purge,
+			  struct expr *elems, unsigned int debug_mask)
+{
+	struct expr *i, *next, *prev = NULL;
+	struct range range, prev_range;
+	int err = 0;
+	mpz_t rop;
+
+	mpz_init(prev_range.low);
+	mpz_init(prev_range.high);
+	mpz_init(range.low);
+	mpz_init(range.high);
+	mpz_init(rop);
+
+	list_for_each_entry_safe(i, next, &elems->expressions, list) {
+		if (i->key->etype == EXPR_SET_ELEM_CATCHALL)
+			continue;
+
+		range_expr_value_low(range.low, i);
+		range_expr_value_high(range.high, i);
+
+		if (!prev && i->flags & EXPR_F_REMOVE) {
+			expr_error(msgs, i, "element does not exist");
+			err = -1;
+			goto err;
+		}
+
+		if (!(i->flags & EXPR_F_REMOVE)) {
+			prev = i;
+			mpz_set(prev_range.low, range.low);
+			mpz_set(prev_range.high, range.high);
+			continue;
+		}
+
+		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) {
+				list_move_tail(&prev->list, &purge->expressions);
+				list_del(&i->list);
+				expr_free(i);
+			}
+		} else if (set->automerge &&
+			   setelem_adjust(set, add, purge, &prev_range, &range, prev, i) < 0) {
+			expr_error(msgs, i, "element does not exist");
+			err = -1;
+			goto err;
+		}
+		prev = NULL;
+	}
+err:
+	mpz_clear(prev_range.low);
+	mpz_clear(prev_range.high);
+	mpz_clear(range.low);
+	mpz_clear(range.high);
+	mpz_clear(rop);
+
+	return err;
+}
+
+static void automerge_delete(struct list_head *msgs, struct set *set,
+			     struct expr *init, unsigned int debug_mask)
+{
+	struct set_automerge_ctx ctx = {
+		.set		= set,
+		.init		= init,
+		.debug_mask	= debug_mask,
+	};
+
+	ctx.purge = set_expr_alloc(&internal_location, set);
+	list_expr_sort(&init->expressions);
+	setelem_automerge(&ctx);
+	expr_free(ctx.purge);
+}
+
+/* detection for unexisting intervals already exists in Linux kernels >= 5.7. */
+int set_delete(struct list_head *msgs, struct cmd *cmd, struct set *set,
+	       struct expr *init, unsigned int debug_mask)
+{
+	struct set *existing_set = set->existing_set;
+	struct expr *i, *add;
+	struct handle h = {};
+	struct cmd *add_cmd;
+	int err;
+
+	set_to_range(init);
+	if (set->automerge)
+		automerge_delete(msgs, set, init, debug_mask);
+
+	list_for_each_entry(i, &init->expressions, list)
+		i->flags |= EXPR_F_REMOVE;
+
+	set_to_range(existing_set->init);
+	list_splice_init(&init->expressions, &existing_set->init->expressions);
+
+	list_expr_sort(&existing_set->init->expressions);
+
+	add = set_expr_alloc(&internal_location, set);
+
+	err = setelem_delete(msgs, set, add, init, existing_set->init, debug_mask);
+	if (err < 0) {
+		expr_free(add);
+		return err;
+	}
+
+	if (debug_mask & NFT_DEBUG_SEGTREE) {
+		list_for_each_entry(i, &init->expressions, list)
+			gmp_printf("remove: [%Zx-%Zx]\n",
+				   i->key->left->value, i->key->right->value);
+		list_for_each_entry(i, &add->expressions, list)
+			gmp_printf("add: [%Zx-%Zx]\n",
+				   i->key->left->value, i->key->right->value);
+		list_for_each_entry(i, &existing_set->init->expressions, list)
+			gmp_printf("existing: [%Zx-%Zx]\n",
+				   i->key->left->value, i->key->right->value);
+	}
+
+	if (list_empty(&add->expressions)) {
+		expr_free(add);
+		return 0;
+	}
+
+	handle_merge(&h, &cmd->handle);
+	add_cmd = cmd_alloc(CMD_ADD, CMD_OBJ_ELEMENTS, &h, &cmd->location, add);
+	add_cmd->elem.set = set_get(set);
+	list_add(&add_cmd->list, &cmd->list);
+
+	return 0;
+}
+
 static int setelem_overlap(struct list_head *msgs, struct set *set,
 			   struct expr *init)
 {
diff --git a/src/libnftables.c b/src/libnftables.c
index dc0932bd..6a22ea09 100644
--- a/src/libnftables.c
+++ b/src/libnftables.c
@@ -500,8 +500,8 @@ static int nft_evaluate(struct nft_ctx *nft, struct list_head *msgs,
 			struct list_head *cmds)
 {
 	struct nft_cache_filter *filter;
+	struct cmd *cmd, *next;
 	unsigned int flags;
-	struct cmd *cmd;
 
 	filter = nft_cache_filter_init();
 	flags = nft_cache_evaluate(nft, cmds, filter);
@@ -512,7 +512,7 @@ static int nft_evaluate(struct nft_ctx *nft, struct list_head *msgs,
 
 	nft_cache_filter_fini(filter);
 
-	list_for_each_entry(cmd, cmds, list) {
+	list_for_each_entry_safe(cmd, next, cmds, list) {
 		struct eval_ctx ectx = {
 			.nft	= nft,
 			.msgs	= msgs,