[PATCH 2/2 nft] src: allow variable in chain policy

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This patch introduces the use of nft input files variables in chain policy.
e.g.

define default_policy = "accept"

add table ip foo
add chain ip foo bar {type filter hook input priority filter; policy $default_policy}

table ip foo {
	chain bar {
		type filter hook input priority filter; policy accept;
	}
}

Signed-off-by: Fernando Fernandez Mancera <ffmancera@xxxxxxxxxx>
---
 include/rule.h                                |  2 +-
 src/evaluate.c                                | 51 +++++++++++++++++++
 src/json.c                                    |  5 +-
 src/mnl.c                                     |  9 ++--
 src/netlink.c                                 |  8 ++-
 src/parser_bison.y                            | 19 +++++--
 src/parser_json.c                             | 17 +++++--
 src/rule.c                                    | 13 +++--
 .../testcases/nft-f/0025policy_variable_0     | 17 +++++++
 .../testcases/nft-f/0026policy_variable_0     | 17 +++++++
 .../testcases/nft-f/0027policy_variable_1     | 18 +++++++
 .../testcases/nft-f/0028policy_variable_1     | 18 +++++++
 .../nft-f/dumps/0025policy_variable_0.nft     |  5 ++
 .../nft-f/dumps/0026policy_variable_0.nft     |  5 ++
 14 files changed, 186 insertions(+), 18 deletions(-)
 create mode 100755 tests/shell/testcases/nft-f/0025policy_variable_0
 create mode 100755 tests/shell/testcases/nft-f/0026policy_variable_0
 create mode 100755 tests/shell/testcases/nft-f/0027policy_variable_1
 create mode 100755 tests/shell/testcases/nft-f/0028policy_variable_1
 create mode 100644 tests/shell/testcases/nft-f/dumps/0025policy_variable_0.nft
 create mode 100644 tests/shell/testcases/nft-f/dumps/0026policy_variable_0.nft

diff --git a/include/rule.h b/include/rule.h
index c6e8716..b12165a 100644
--- a/include/rule.h
+++ b/include/rule.h
@@ -209,7 +209,7 @@ struct chain {
 	const char		*hookstr;
 	unsigned int		hooknum;
 	struct prio_spec	priority;
-	int			policy;
+	struct expr		*policy;
 	const char		*type;
 	const char		*dev;
 	struct scope		scope;
diff --git a/src/evaluate.c b/src/evaluate.c
index d2faee8..4d8bfbf 100755
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -3415,6 +3415,52 @@ static uint32_t str2hooknum(uint32_t family, const char *hook)
 	return NF_INET_NUMHOOKS;
 }
 
+static bool evaluate_policy(struct eval_ctx *ctx, struct expr **policy)
+{
+	char policy_str[NFT_NAME_MAXLEN];
+	struct location loc;
+	int policy_num;
+
+	ctx->ectx.len = NFT_NAME_MAXLEN * BITS_PER_BYTE;
+	if (expr_evaluate(ctx, policy) < 0)
+		return false;
+	if ((*policy)->etype != EXPR_VALUE) {
+		expr_error(ctx->msgs, *policy, "%s is not a valid "
+			   "policy expression", expr_name(*policy));
+		return false;
+	}
+
+	if ((*policy)->dtype->type == TYPE_STRING) {
+		mpz_export_data(policy_str, (*policy)->value,
+				BYTEORDER_HOST_ENDIAN,
+				NFT_NAME_MAXLEN);
+		loc = (*policy)->location;
+		if (!strcmp(policy_str, "accept")) {
+			expr_free(*policy);
+			policy_num = NF_ACCEPT;
+			*policy = constant_expr_alloc(&loc,
+						      &integer_type,
+						      BYTEORDER_HOST_ENDIAN,
+						      sizeof(int) * BITS_PER_BYTE,
+						      &policy_num);
+		} else if (!strcmp(policy_str, "drop")) {
+			expr_free(*policy);
+			policy_num = NF_DROP;
+			*policy = constant_expr_alloc(&(*policy)->location,
+						      &integer_type,
+						      BYTEORDER_HOST_ENDIAN,
+						      sizeof(int) * BITS_PER_BYTE,
+						      &policy_num);
+		} else {
+			expr_error(ctx->msgs, *policy, "%s is not a valid policy"
+				   " value", policy_str);
+			return false;
+		}
+	}
+
+	return true;
+}
+
 static int chain_evaluate(struct eval_ctx *ctx, struct chain *chain)
 {
 	struct table *table;
@@ -3448,6 +3494,11 @@ static int chain_evaluate(struct eval_ctx *ctx, struct chain *chain)
 			return __stmt_binary_error(ctx, &chain->priority.loc, NULL,
 						   "invalid priority expression %s in this context.",
 						   expr_name(chain->priority.expr));
+		if (chain->policy) {
+			if (!evaluate_policy(ctx, &chain->policy))
+				return chain_error(ctx, chain, "invalid policy expression %s",
+						   expr_name(chain->policy));
+		}
 	}
 
 	list_for_each_entry(rule, &chain->rules, list) {
diff --git a/src/json.c b/src/json.c
index 33e0ec1..ff2e06e 100644
--- a/src/json.c
+++ b/src/json.c
@@ -223,6 +223,7 @@ static json_t *rule_print_json(struct output_ctx *octx,
 static json_t *chain_print_json(const struct chain *chain)
 {
 	json_t *root, *tmp;
+	int policy;
 
 	root = json_pack("{s:s, s:s, s:s, s:I}",
 			 "family", family2str(chain->handle.family),
@@ -231,12 +232,14 @@ static json_t *chain_print_json(const struct chain *chain)
 			 "handle", chain->handle.handle.id);
 
 	if (chain->flags & CHAIN_F_BASECHAIN) {
+		mpz_export_data(&policy, chain->policy->value,
+				BYTEORDER_HOST_ENDIAN, sizeof(int));
 		tmp = json_pack("{s:s, s:s, s:i, s:s}",
 				"type", chain->type,
 				"hook", hooknum2str(chain->handle.family,
 						    chain->hooknum),
 				"prio", chain->priority.num,
-				"policy", chain_policy2str(chain->policy));
+				"policy", chain_policy2str(policy));
 		if (chain->dev)
 			json_object_set_new(tmp, "dev", json_string(chain->dev));
 		json_object_update(root, tmp);
diff --git a/src/mnl.c b/src/mnl.c
index eab8d54..ab71a00 100644
--- a/src/mnl.c
+++ b/src/mnl.c
@@ -518,6 +518,7 @@ int mnl_nft_chain_add(struct netlink_ctx *ctx, const struct cmd *cmd,
 {
 	struct nftnl_chain *nlc;
 	struct nlmsghdr *nlh;
+	int policy;
 
 	nlc = nftnl_chain_alloc();
 	if (nlc == NULL)
@@ -536,9 +537,11 @@ int mnl_nft_chain_add(struct netlink_ctx *ctx, const struct cmd *cmd,
 			nftnl_chain_set_str(nlc, NFTNL_CHAIN_TYPE,
 					    cmd->chain->type);
 		}
-		if (cmd->chain->policy != -1)
-			nftnl_chain_set_u32(nlc, NFTNL_CHAIN_POLICY,
-					    cmd->chain->policy);
+		if (cmd->chain->policy) {
+			mpz_export_data(&policy, cmd->chain->policy->value,
+					BYTEORDER_HOST_ENDIAN, sizeof(int));
+			nftnl_chain_set_u32(nlc, NFTNL_CHAIN_POLICY, policy);
+		}
 		if (cmd->chain->dev != NULL)
 			nftnl_chain_set_str(nlc, NFTNL_CHAIN_DEV,
 					    cmd->chain->dev);
diff --git a/src/netlink.c b/src/netlink.c
index 14b0df4..d2be63c 100644
--- a/src/netlink.c
+++ b/src/netlink.c
@@ -369,6 +369,7 @@ struct chain *netlink_delinearize_chain(struct netlink_ctx *ctx,
 					const struct nftnl_chain *nlc)
 {
 	struct chain *chain;
+	int policy;
 
 	chain = chain_alloc(nftnl_chain_get_str(nlc, NFTNL_CHAIN_NAME));
 	chain->handle.family =
@@ -390,7 +391,12 @@ struct chain *netlink_delinearize_chain(struct netlink_ctx *ctx,
 			nftnl_chain_get_s32(nlc, NFTNL_CHAIN_PRIO);
 		chain->type          =
 			xstrdup(nftnl_chain_get_str(nlc, NFTNL_CHAIN_TYPE));
-		chain->policy          =
+		policy = nftnl_chain_get_u32(nlc, NFTNL_CHAIN_POLICY);
+		chain->policy = constant_expr_alloc(&netlink_location,
+						    &string_type,
+						    BYTEORDER_HOST_ENDIAN,
+						    sizeof(int) * BITS_PER_BYTE,
+						    &policy);
 			nftnl_chain_get_u32(nlc, NFTNL_CHAIN_POLICY);
 		if (nftnl_chain_is_set(nlc, NFTNL_CHAIN_DEV)) {
 			chain->dev	=
diff --git a/src/parser_bison.y b/src/parser_bison.y
index ed7bd89..2a7cc9f 100644
--- a/src/parser_bison.y
+++ b/src/parser_bison.y
@@ -636,8 +636,8 @@ int nft_lex(void *, void *, void *);
 %type <stmt>			meter_stmt meter_stmt_alloc flow_stmt_legacy_alloc
 %destructor { stmt_free($$); }	meter_stmt meter_stmt_alloc flow_stmt_legacy_alloc
 
-%type <expr>			symbol_expr verdict_expr integer_expr variable_expr chain_expr prio_expr
-%destructor { expr_free($$); }	symbol_expr verdict_expr integer_expr variable_expr chain_expr prio_expr
+%type <expr>			symbol_expr verdict_expr integer_expr variable_expr chain_expr prio_expr policy_expr
+%destructor { expr_free($$); }	symbol_expr verdict_expr integer_expr variable_expr chain_expr prio_expr policy_expr
 %type <expr>			primary_expr shift_expr and_expr
 %destructor { expr_free($$); }	primary_expr shift_expr and_expr
 %type <expr>			exclusive_or_expr inclusive_or_expr
@@ -2019,17 +2019,28 @@ dev_spec		:	DEVICE	string		{ $$ = $2; }
 			|	/* empty */		{ $$ = NULL; }
 			;
 
-policy_spec		:	POLICY		chain_policy
+policy_spec		:	POLICY		policy_expr
 			{
-				if ($<chain>0->policy != -1) {
+				if ($<chain>0->policy) {
 					erec_queue(error(&@$, "you cannot set chain policy twice"),
 						   state->msgs);
+					expr_free($2);
 					YYERROR;
 				}
 				$<chain>0->policy	= $2;
 			}
 			;
 
+policy_expr		:	variable_expr
+			|	chain_policy
+			{
+				$$ = constant_expr_alloc(&@$, &integer_type,
+							 BYTEORDER_HOST_ENDIAN,
+							 sizeof(int) *
+							 BITS_PER_BYTE, &$1);
+			}
+			;
+
 chain_policy		:	ACCEPT		{ $$ = NF_ACCEPT; }
 			|	DROP		{ $$ = NF_DROP;   }
 			;
diff --git a/src/parser_json.c b/src/parser_json.c
index 76c0a5c..a227b17 100644
--- a/src/parser_json.c
+++ b/src/parser_json.c
@@ -2530,13 +2530,20 @@ static struct cmd *json_parse_cmd_add_table(struct json_ctx *ctx, json_t *root,
 	return cmd_alloc(op, obj, &h, int_loc, NULL);
 }
 
-static int parse_policy(const char *policy)
+static struct expr *parse_policy(const char *policy)
 {
+	int policy_num;
+
 	if (!strcmp(policy, "accept"))
-		return NF_ACCEPT;
-	if (!strcmp(policy, "drop"))
-		return NF_DROP;
-	return -1;
+		policy_num = NF_ACCEPT;
+	else if (!strcmp(policy, "drop"))
+		policy_num = NF_DROP;
+	else
+		return NULL;
+
+	return constant_expr_alloc(int_loc, &integer_type,
+				   BYTEORDER_HOST_ENDIAN, sizeof(int)
+				   * BITS_PER_BYTE, &policy_num);
 }
 
 static struct cmd *json_parse_cmd_add_chain(struct json_ctx *ctx, json_t *root,
diff --git a/src/rule.c b/src/rule.c
index 23011d9..afa46e9 100644
--- a/src/rule.c
+++ b/src/rule.c
@@ -800,7 +800,7 @@ struct chain *chain_alloc(const char *name)
 	if (name != NULL)
 		chain->handle.chain.name = xstrdup(name);
 
-	chain->policy = -1;
+	chain->policy = NULL;
 	return chain;
 }
 
@@ -824,6 +824,7 @@ void chain_free(struct chain *chain)
 	if (chain->dev != NULL)
 		xfree(chain->dev);
 	expr_free(chain->priority.expr);
+	expr_free(chain->policy);
 	xfree(chain);
 }
 
@@ -1099,12 +1100,15 @@ static void chain_print_declaration(const struct chain *chain,
 				    struct output_ctx *octx)
 {
 	char priobuf[STD_PRIO_BUFSIZE];
+	int policy;
 
 	nft_print(octx, "\tchain %s {", chain->handle.chain.name);
 	if (nft_output_handle(octx))
 		nft_print(octx, " # handle %" PRIu64, chain->handle.handle.id);
 	nft_print(octx, "\n");
 	if (chain->flags & CHAIN_F_BASECHAIN) {
+		mpz_export_data(&policy, chain->policy->value,
+				BYTEORDER_HOST_ENDIAN, sizeof(int));
 		nft_print(octx, "\t\ttype %s hook %s", chain->type,
 			  hooknum2str(chain->handle.family, chain->hooknum));
 		if (chain->dev != NULL)
@@ -1113,7 +1117,7 @@ static void chain_print_declaration(const struct chain *chain,
 			  prio2str(octx, priobuf, sizeof(priobuf),
 				   chain->handle.family, chain->hooknum,
 				   chain->priority.num),
-			  chain_policy2str(chain->policy));
+			  chain_policy2str(policy));
 	}
 }
 
@@ -1134,17 +1138,20 @@ static void chain_print(const struct chain *chain, struct output_ctx *octx)
 void chain_print_plain(const struct chain *chain, struct output_ctx *octx)
 {
 	char priobuf[STD_PRIO_BUFSIZE];
+	int policy;
 
 	nft_print(octx, "chain %s %s %s", family2str(chain->handle.family),
 		  chain->handle.table.name, chain->handle.chain.name);
 
 	if (chain->flags & CHAIN_F_BASECHAIN) {
+		mpz_export_data(&policy, chain->policy->value,
+				BYTEORDER_HOST_ENDIAN, 4);
 		nft_print(octx, " { type %s hook %s priority %s; policy %s; }",
 			  chain->type, chain->hookstr,
 			  prio2str(octx, priobuf, sizeof(priobuf),
 				   chain->handle.family, chain->hooknum,
 				   chain->priority.num),
-			  chain_policy2str(chain->policy));
+			  chain_policy2str(policy));
 	}
 	if (nft_output_handle(octx))
 		nft_print(octx, " # handle %" PRIu64, chain->handle.handle.id);
diff --git a/tests/shell/testcases/nft-f/0025policy_variable_0 b/tests/shell/testcases/nft-f/0025policy_variable_0
new file mode 100755
index 0000000..b88e968
--- /dev/null
+++ b/tests/shell/testcases/nft-f/0025policy_variable_0
@@ -0,0 +1,17 @@
+#!/bin/bash
+
+# Tests use of variables in chain policy
+
+set -e
+
+RULESET="
+define default_policy = \"accept\"
+
+table inet global {
+    chain prerouting {
+        type filter hook prerouting priority filter
+        policy \$default_policy
+    }
+}"
+
+$NFT -f - <<< "$RULESET"
diff --git a/tests/shell/testcases/nft-f/0026policy_variable_0 b/tests/shell/testcases/nft-f/0026policy_variable_0
new file mode 100755
index 0000000..d4d98ed
--- /dev/null
+++ b/tests/shell/testcases/nft-f/0026policy_variable_0
@@ -0,0 +1,17 @@
+#!/bin/bash
+
+# Tests use of variables in chain policy
+
+set -e
+
+RULESET="
+define default_policy = \"drop\"
+
+table inet global {
+    chain prerouting {
+        type filter hook prerouting priority filter
+        policy \$default_policy
+    }
+}"
+
+$NFT -f - <<< "$RULESET"
diff --git a/tests/shell/testcases/nft-f/0027policy_variable_1 b/tests/shell/testcases/nft-f/0027policy_variable_1
new file mode 100755
index 0000000..ae35516
--- /dev/null
+++ b/tests/shell/testcases/nft-f/0027policy_variable_1
@@ -0,0 +1,18 @@
+#!/bin/bash
+
+# Tests use of variables in chain policy
+
+set -e
+
+RULESET="
+define default_policy = { 127.0.0.1 }
+
+table inet global {
+    chain prerouting {
+        type filter hook prerouting priority filter
+        policy \$default_policy
+    }
+}"
+
+$NFT -f - <<< "$RULESET" && exit 1
+exit 0
diff --git a/tests/shell/testcases/nft-f/0028policy_variable_1 b/tests/shell/testcases/nft-f/0028policy_variable_1
new file mode 100755
index 0000000..027eb01
--- /dev/null
+++ b/tests/shell/testcases/nft-f/0028policy_variable_1
@@ -0,0 +1,18 @@
+#!/bin/bash
+
+# Tests use of variables in priority specification
+
+set -e
+
+RULESET="
+define default_policy = *
+
+table inet global {
+    chain prerouting {
+        type filter hook prerouting priority filter
+        policy \$default_policy
+    }
+}"
+
+$NFT -f - <<< "$RULESET" && exit 1
+exit 0
diff --git a/tests/shell/testcases/nft-f/dumps/0025policy_variable_0.nft b/tests/shell/testcases/nft-f/dumps/0025policy_variable_0.nft
new file mode 100644
index 0000000..f409309
--- /dev/null
+++ b/tests/shell/testcases/nft-f/dumps/0025policy_variable_0.nft
@@ -0,0 +1,5 @@
+table inet global {
+	chain prerouting {
+		type filter hook prerouting priority filter; policy accept;
+	}
+}
diff --git a/tests/shell/testcases/nft-f/dumps/0026policy_variable_0.nft b/tests/shell/testcases/nft-f/dumps/0026policy_variable_0.nft
new file mode 100644
index 0000000..d729e1e
--- /dev/null
+++ b/tests/shell/testcases/nft-f/dumps/0026policy_variable_0.nft
@@ -0,0 +1,5 @@
+table inet global {
+	chain prerouting {
+		type filter hook prerouting priority filter; policy drop;
+	}
+}
-- 
2.20.1




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