src: Support intra-transaction rule references

A rule may be added before or after another one using index keyword. To
support for the other rule being added within the same batch, one has to
make use of NFTNL_RULE_ID and NFTNL_RULE_POSITION_ID attributes. This
patch does just that among a few more crucial things:

* If cache is complete enough to contain rules, update cache when
  evaluating rule commands so later index references resolve correctly.

* Reduce rule_translate_index() to its core code which is the actual
  linking of rules and consequently rename the function. The removed
  bits are pulled into the calling rule_evaluate() to reduce code
  duplication in between cache updates with and without rule reference.

* Pass the current command op to rule_evaluate() as indicator whether to
  insert before or after a referenced rule or at beginning or end of
  chain in cache. Exploit this from chain_evaluate() to avoid adding
  the chain's rules a second time.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

8 files changed, 139 insertions, 20 deletions

diff --git a/include/rule.h b/include/rule.h
index 8ccdc2e1..dd9df9ec 100644
--- a/include/rule.h
+++ b/include/rule.h
@@ -73,6 +73,8 @@ struct handle {
 	struct position_spec	position;
 	struct position_spec	index;
 	uint32_t		set_id;
+	uint32_t		rule_id;
+	uint32_t		position_id;
 };
 
 extern void handle_merge(struct handle *dst, const struct handle *src);
diff --git a/src/evaluate.c b/src/evaluate.c
index b9660d77..39101b48 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -3180,13 +3180,29 @@ static int flowtable_evaluate(struct eval_ctx *ctx, struct flowtable *ft)
 	return 0;
 }
 
-/* Convert rule's handle.index into handle.position. */
-static int rule_translate_index(struct eval_ctx *ctx, struct rule *rule)
+/* make src point at dst, either via handle.position or handle.position_id */
+static void link_rules(struct rule *src, struct rule *dst)
 {
+	static uint32_t ref_id = 0;
+
+	if (dst->handle.handle.id) {
+		/* dst is in kernel, make src reference it by handle */
+		src->handle.position.id = dst->handle.handle.id;
+		src->handle.position.location = src->handle.index.location;
+		return;
+	}
+
+	/* dst is not in kernel, make src reference it by per-transaction ID */
+	if (!dst->handle.rule_id)
+		dst->handle.rule_id = ++ref_id;
+	src->handle.position_id = dst->handle.rule_id;
+}
+
+static int rule_cache_update(struct eval_ctx *ctx, enum cmd_ops op)
+{
+	struct rule *rule = ctx->rule, *ref = NULL;
 	struct table *table;
 	struct chain *chain;
-	uint64_t index = 0;
-	struct rule *r;
 
 	table = table_lookup(&rule->handle, &ctx->nft->cache);
 	if (!table)
@@ -3196,21 +3212,59 @@ static int rule_translate_index(struct eval_ctx *ctx, struct rule *rule)
 	if (!chain)
 		return chain_not_found(ctx);
 
-	list_for_each_entry(r, &chain->rules, list) {
-		if (++index < rule->handle.index.id)
-			continue;
-		rule->handle.position.id = r->handle.handle.id;
-		rule->handle.position.location = rule->handle.index.location;
+	if (rule->handle.index.id) {
+		ref = rule_lookup_by_index(chain, rule->handle.index.id);
+		if (!ref)
+			return cmd_error(ctx, &rule->handle.index.location,
+					 "Could not process rule: %s",
+					 strerror(ENOENT));
+
+		link_rules(rule, ref);
+	} else if (rule->handle.handle.id) {
+		ref = rule_lookup(chain, rule->handle.handle.id);
+		if (!ref)
+			return cmd_error(ctx, &rule->handle.handle.location,
+					 "Could not process rule: %s",
+					 strerror(ENOENT));
+	} else if (rule->handle.position.id) {
+		ref = rule_lookup(chain, rule->handle.position.id);
+		if (!ref)
+			return cmd_error(ctx, &rule->handle.position.location,
+					 "Could not process rule: %s",
+					 strerror(ENOENT));
+	}
+
+	switch (op) {
+	case CMD_INSERT:
+		rule_get(rule);
+		if (ref)
+			list_add_tail(&rule->list, &ref->list);
+		else
+			list_add(&rule->list, &chain->rules);
+		break;
+	case CMD_ADD:
+		rule_get(rule);
+		if (ref)
+			list_add(&rule->list, &ref->list);
+		else
+			list_add_tail(&rule->list, &chain->rules);
+		break;
+	case CMD_REPLACE:
+		rule_get(rule);
+		list_add(&rule->list, &ref->list);
+		/* fall through */
+	case CMD_DELETE:
+		list_del(&ref->list);
+		rule_free(ref);
+		break;
+	default:
 		break;
 	}
-	if (!rule->handle.position.id)
-		return cmd_error(ctx, &rule->handle.index.location,
-				"Could not process rule: %s",
-				strerror(ENOENT));
 	return 0;
 }
 
-static int rule_evaluate(struct eval_ctx *ctx, struct rule *rule)
+static int rule_evaluate(struct eval_ctx *ctx, struct rule *rule,
+			 enum cmd_ops op)
 {
 	struct stmt *stmt, *tstmt = NULL;
 	struct error_record *erec;
@@ -3238,11 +3292,11 @@ static int rule_evaluate(struct eval_ctx *ctx, struct rule *rule)
 		return -1;
 	}
 
-	if (rule->handle.index.id &&
-	    rule_translate_index(ctx, rule))
-		return -1;
+	/* add rules to cache only if it is complete enough to contain them */
+	if (!cache_is_complete(&ctx->nft->cache, CMD_LIST))
+		return 0;
 
-	return 0;
+	return rule_cache_update(ctx, op);
 }
 
 static uint32_t str2hooknum(uint32_t family, const char *hook)
@@ -3323,7 +3377,7 @@ static int chain_evaluate(struct eval_ctx *ctx, struct chain *chain)
 
 	list_for_each_entry(rule, &chain->rules, list) {
 		handle_merge(&rule->handle, &chain->handle);
-		if (rule_evaluate(ctx, rule) < 0)
+		if (rule_evaluate(ctx, rule, CMD_INVALID) < 0)
 			return -1;
 	}
 	return 0;
@@ -3410,7 +3464,7 @@ static int cmd_evaluate_add(struct eval_ctx *ctx, struct cmd *cmd)
 		return set_evaluate(ctx, cmd->set);
 	case CMD_OBJ_RULE:
 		handle_merge(&cmd->rule->handle, &cmd->handle);
-		return rule_evaluate(ctx, cmd->rule);
+		return rule_evaluate(ctx, cmd->rule, cmd->op);
 	case CMD_OBJ_CHAIN:
 		return chain_evaluate(ctx, cmd->chain);
 	case CMD_OBJ_TABLE:
diff --git a/src/mnl.c b/src/mnl.c
index 83dfb9d2..6ebad28b 100644
--- a/src/mnl.c
+++ b/src/mnl.c
@@ -378,6 +378,10 @@ int mnl_nft_rule_add(struct netlink_ctx *ctx, const struct cmd *cmd,
 	nftnl_rule_set_str(nlr, NFTNL_RULE_CHAIN, h->chain.name);
 	if (h->position.id)
 		nftnl_rule_set_u64(nlr, NFTNL_RULE_POSITION, h->position.id);
+	if (h->rule_id)
+		nftnl_rule_set_u32(nlr, NFTNL_RULE_ID, h->rule_id);
+	if (h->position_id)
+		nftnl_rule_set_u32(nlr, NFTNL_RULE_POSITION_ID, h->position_id);
 
 	netlink_linearize_rule(ctx, nlr, rule);
 	nlh = nftnl_nlmsg_build_hdr(nftnl_batch_buffer(ctx->batch),
diff --git a/tests/shell/testcases/cache/0003_cache_update_0 b/tests/shell/testcases/cache/0003_cache_update_0
index fa9b5df3..05edc9c7 100755
--- a/tests/shell/testcases/cache/0003_cache_update_0
+++ b/tests/shell/testcases/cache/0003_cache_update_0
@@ -34,6 +34,9 @@ EOF
 # add rule ip t4 c meta l4proto icmp accept -> rule to reference in next step
 # add rule ip t4 c index 0 drop -> index 0 is not found due to rule cache not
 #                                  being updated
+# add rule ip t4 c index 2 drop -> index 2 is not found due to igmp rule being
+#                                  in same transaction and therefore not having
+#                                  an allocated handle
 $NFT -i >/dev/null <<EOF
 add table ip t4; add chain ip t4 c
 add rule ip t4 c meta l4proto icmp accept
@@ -41,3 +44,7 @@ EOF
 $NFT -f - >/dev/null <<EOF
 add rule ip t4 c index 0 drop
 EOF
+$NFT -f - >/dev/null <<EOF
+add rule ip t4 c meta l4proto igmp accept
+add rule ip t4 c index 2 drop
+EOF
diff --git a/tests/shell/testcases/transactions/0024rule_0 b/tests/shell/testcases/transactions/0024rule_0
new file mode 100755
index 00000000..4c1ac41d
--- /dev/null
+++ b/tests/shell/testcases/transactions/0024rule_0
@@ -0,0 +1,17 @@
+#!/bin/bash
+
+RULESET="flush ruleset
+add table x
+add chain x y
+add rule x y accept comment rule1
+add rule x y accept comment rule4
+add rule x y index 0 accept comment rule2
+insert rule x y index 2 accept comment rule3"
+
+$NFT -f - <<< "$RULESET" && \
+	$NFT -f - <<< "$RULESET" && \
+	echo "$RULESET" | tr '\n' ';' | $NFT -i >/dev/null && \
+	exit 0
+echo "E: intra-transaction rule reference failed"
+exit 1
+
diff --git a/tests/shell/testcases/transactions/0025rule_0 b/tests/shell/testcases/transactions/0025rule_0
new file mode 100755
index 00000000..d72d5cfc
--- /dev/null
+++ b/tests/shell/testcases/transactions/0025rule_0
@@ -0,0 +1,21 @@
+#!/bin/bash
+
+# make sure stored delete/replace rule commands are correctly applied
+
+set -e
+
+$NFT -f - <<EOF
+flush ruleset
+table x {
+	chain y {
+		accept
+		log
+	}
+}
+EOF
+
+$NFT -f - <<EOF
+replace rule x y handle 2 log
+delete rule x y handle 3
+add rule x y index 0 drop
+EOF
diff --git a/tests/shell/testcases/transactions/dumps/0024rule_0.nft b/tests/shell/testcases/transactions/dumps/0024rule_0.nft
new file mode 100644
index 00000000..7860ff65
--- /dev/null
+++ b/tests/shell/testcases/transactions/dumps/0024rule_0.nft
@@ -0,0 +1,8 @@
+table ip x {
+	chain y {
+		accept comment "rule1"
+		accept comment "rule2"
+		accept comment "rule3"
+		accept comment "rule4"
+	}
+}
diff --git a/tests/shell/testcases/transactions/dumps/0025rule_0.nft b/tests/shell/testcases/transactions/dumps/0025rule_0.nft
new file mode 100644
index 00000000..dcb61ae6
--- /dev/null
+++ b/tests/shell/testcases/transactions/dumps/0025rule_0.nft
@@ -0,0 +1,6 @@
+table ip x {
+	chain y {
+		log
+		drop
+	}
+}