JSON: Add support for echo option

The basic principle is to not return a JSON object freshly created from
netlink responses, but just update the existing user-provided one to
make sure callers get back exactly what they expect.

To achieve that, keep the parsed JSON object around in a global variable
('cur_root') and provide a custom callback to insert handles into it
from received netlink messages. The tricky bit here is updating rules
since unique identification is problematic. Therefore drop possibly
present handles from input and later assume updates are received in
order so the first rule not having a handle set is the right one.

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

1 files changed, 267 insertions, 13 deletions

diff --git a/src/parser_json.c b/src/parser_json.c
index e497f0ce..bc682e92 100644
--- a/src/parser_json.c
+++ b/src/parser_json.c
@@ -25,6 +25,10 @@
 #include <linux/netfilter/nf_tables.h>
 #include <jansson.h>
 
+#include <mnl.h>
+#include <libnftnl/rule.h>
+#include <linux/netfilter/nfnetlink.h>
+
 #define CTX_F_RHS	(1 << 0)
 #define CTX_F_STMT	(1 << 1)
 #define CTX_F_PRIMARY	(1 << 2)
@@ -2333,6 +2337,9 @@ static struct cmd *json_parse_cmd_add_table(struct json_ctx *ctx, json_t *root,
 	if (h.table.name)
 		h.table.name = xstrdup(h.table.name);
 
+	if (op == CMD_ADD)
+		json_object_del(root, "handle");
+
 	return cmd_alloc(op, obj, &h, int_loc, NULL);
 }
 
@@ -2404,6 +2411,9 @@ static struct cmd *json_parse_cmd_add_chain(struct json_ctx *ctx, json_t *root,
 		}
 	}
 
+	if (op == CMD_ADD)
+		json_object_del(root, "handle");
+
 	handle_merge(&chain->handle, &h);
 	return cmd_alloc(op, obj, &h, int_loc, chain);
 }
@@ -2474,6 +2484,9 @@ static struct cmd *json_parse_cmd_add_rule(struct json_ctx *ctx, json_t *root,
 		list_add_tail(&stmt->list, &rule->stmts);
 	}
 
+	if (op == CMD_ADD)
+		json_object_del(root, "handle");
+
 	return cmd_alloc(op, obj, &h, int_loc, rule);
 }
 
@@ -2628,6 +2641,10 @@ static struct cmd *json_parse_cmd_add_set(struct json_ctx *ctx, json_t *root,
 	json_unpack(root, "{s:i}", "size", &set->desc.size);
 
 	handle_merge(&set->handle, &h);
+
+	if (op == CMD_ADD)
+		json_object_del(root, "handle");
+
 	return cmd_alloc(op, obj, &h, int_loc, set);
 }
 
@@ -2943,6 +2960,9 @@ static struct cmd *json_parse_cmd_add_object(struct json_ctx *ctx,
 		BUG("Invalid CMD '%d'", cmd_obj);
 	}
 
+	if (op == CMD_ADD)
+		json_object_del(root, "handle");
+
 	return cmd_alloc(op, cmd_obj, &h, int_loc, obj);
 }
 
@@ -3066,6 +3086,9 @@ static struct cmd *json_parse_cmd_replace(struct json_ctx *ctx,
 		list_add_tail(&stmt->list, &rule->stmts);
 	}
 
+	if (op == CMD_REPLACE)
+		json_object_del(root, "handle");
+
 	return cmd_alloc(op, CMD_OBJ_RULE, &h, int_loc, rule);
 }
 
@@ -3298,7 +3321,7 @@ static int json_verify_metainfo(struct json_ctx *ctx, json_t *root)
 	return 0;
 }
 
-static int __json_parse(struct json_ctx *ctx, json_t *root)
+static int __json_parse(struct json_ctx *ctx)
 {
 	struct eval_ctx ectx = {
 		.nft = ctx->nft,
@@ -3307,7 +3330,8 @@ static int __json_parse(struct json_ctx *ctx, json_t *root)
 	json_t *tmp, *value;
 	size_t index;
 
-	if (json_unpack_err(ctx, root, "{s:o}", "nftables", &tmp))
+	if (json_unpack_err(ctx, ctx->nft->json_root,
+			    "{s:o}", "nftables", &tmp))
 		return -1;
 
 	if (!json_is_array(tmp)) {
@@ -3355,7 +3379,6 @@ static int __json_parse(struct json_ctx *ctx, json_t *root)
 	return 0;
 }
 
-
 int nft_parse_json_buffer(struct nft_ctx *nft, const char *buf,
 			  struct list_head *msgs, struct list_head *cmds)
 {
@@ -3368,16 +3391,18 @@ int nft_parse_json_buffer(struct nft_ctx *nft, const char *buf,
 		.msgs = msgs,
 		.cmds = cmds,
 	};
-	json_t *root;
 	int ret;
 
-	root = json_loads(buf, 0, NULL);
-	if (!root)
+	nft->json_root = json_loads(buf, 0, NULL);
+	if (!nft->json_root)
 		return -EINVAL;
 
-	ret = __json_parse(&ctx, root);
+	ret = __json_parse(&ctx);
 
-	json_decref(root);
+	if (!nft->output.echo) {
+		json_decref(nft->json_root);
+		nft->json_root = NULL;
+	}
 	return ret;
 }
 
@@ -3394,15 +3419,244 @@ int nft_parse_json_filename(struct nft_ctx *nft, const char *filename,
 		.cmds = cmds,
 	};
 	json_error_t err;
-	json_t *root;
 	int ret;
 
-	root = json_load_file(filename, 0, &err);
-	if (!root)
+	nft->json_root = json_load_file(filename, 0, &err);
+	if (!nft->json_root)
 		return -EINVAL;
 
-	ret = __json_parse(&ctx, root);
+	ret = __json_parse(&ctx);
 
-	json_decref(root);
+	if (!nft->output.echo) {
+		json_decref(nft->json_root);
+		nft->json_root = NULL;
+	}
 	return ret;
 }
+
+static int json_echo_error(struct netlink_mon_handler *monh,
+			   const char *fmt, ...)
+{
+	struct error_record *erec;
+	va_list ap;
+
+	va_start(ap, fmt);
+	erec = erec_vcreate(EREC_ERROR, int_loc, fmt, ap);
+	va_end(ap);
+	erec_queue(erec, monh->ctx->msgs);
+
+	return MNL_CB_ERROR;
+}
+
+static int obj_prop_check(json_t *obj, const char *key, const char *value)
+{
+	const char *cmp;
+
+	if (!value)
+		return 0;
+
+	if (json_unpack(obj, "{s:s}", key, &cmp) || strcmp(value, cmp))
+		return 1;
+
+	return 0;
+}
+
+static bool obj_info_matches(json_t *obj, const char *family, const char *table,
+			     const char *chain, const char *name)
+{
+	if (obj_prop_check(obj, "family", family) ||
+	    obj_prop_check(obj, "table", table) ||
+	    obj_prop_check(obj, "chain", chain) ||
+	    obj_prop_check(obj, "name", name))
+		return false;
+
+	return true;
+}
+
+static int json_update_table(struct netlink_mon_handler *monh,
+			     json_t *array, const struct nlmsghdr *nlh)
+{
+	const char *family, *name;
+	struct nftnl_table *nlt;
+	uint64_t handle;
+	json_t *value;
+	size_t index;
+
+	nlt = netlink_table_alloc(nlh);
+	family = family2str(nftnl_table_get_u32(nlt, NFTNL_TABLE_FAMILY));
+	name = nftnl_table_get_str(nlt, NFTNL_TABLE_NAME);
+	handle = nftnl_table_get_u64(nlt, NFTNL_TABLE_HANDLE);
+
+	json_array_foreach(array, index, value) {
+		if (json_unpack(value, "{s:{s:o}}", "add", "table", &value) ||
+		    !obj_info_matches(value, family, NULL, NULL, name))
+			continue;
+
+		json_object_set_new(value, "handle", json_integer(handle));
+		return MNL_CB_OK;
+	}
+
+	return json_echo_error(monh, "JSON table object '%s %s' not found.\n",
+			       family, name);
+}
+
+static int json_update_chain(struct netlink_mon_handler *monh,
+			     json_t *array, const struct nlmsghdr *nlh)
+{
+	const char *family, *table, *name;
+	struct nftnl_chain *nlc;
+	uint64_t handle;
+	json_t *value;
+	size_t index;
+
+	nlc = netlink_chain_alloc(nlh);
+	family = family2str(nftnl_chain_get_u32(nlc, NFTNL_CHAIN_FAMILY));
+	table = nftnl_chain_get_str(nlc, NFTNL_CHAIN_TABLE);
+	name = nftnl_chain_get_str(nlc, NFTNL_CHAIN_NAME);
+	handle = nftnl_chain_get_u64(nlc, NFTNL_CHAIN_HANDLE);
+
+	json_array_foreach(array, index, value) {
+		if (json_unpack(value, "{s:{s:o}}", "add", "chain", &value) ||
+		    !obj_info_matches(value, family, table, NULL, name))
+			continue;
+
+		json_object_set_new(value, "handle", json_integer(handle));
+		return MNL_CB_OK;
+	}
+	return json_echo_error(monh,
+			       "JSON chain object '%s %s %s' not found.\n",
+			       family, table, name);
+}
+
+static int json_update_rule(struct netlink_mon_handler *monh,
+			    json_t *array, const struct nlmsghdr *nlh)
+{
+	const char *family, *table, *chain;
+	struct nftnl_rule *nlr;
+	uint64_t handle;
+	json_t *value;
+	size_t index;
+
+	nlr = netlink_rule_alloc(nlh);
+	family = family2str(nftnl_rule_get_u32(nlr, NFTNL_RULE_FAMILY));
+	table = nftnl_rule_get_str(nlr, NFTNL_RULE_TABLE);
+	chain = nftnl_rule_get_str(nlr, NFTNL_RULE_CHAIN);
+	handle = nftnl_rule_get_u64(nlr, NFTNL_RULE_HANDLE);
+
+	json_array_foreach(array, index, value) {
+		if (json_unpack(value, "{s:{s:o}}", "add", "rule", &value) ||
+		    !obj_info_matches(value, family, table, chain, NULL))
+			continue;
+
+		/* this is a hack - assume rules are added in order and caller
+		 * sets the handle for each we previously returned */
+		if (json_object_get(value, "handle"))
+			continue;
+
+		json_object_set_new(value, "handle", json_integer(handle));
+		return MNL_CB_OK;
+	}
+	return json_echo_error(monh,
+			       "JSON rule object in '%s %s %s' without handle not found\n",
+			       family, table, chain);
+}
+
+static int json_update_set(struct netlink_mon_handler *monh,
+			   json_t *array, const struct nlmsghdr *nlh)
+{
+	const char *family, *table, *name;
+	struct nftnl_set *nls;
+	uint64_t handle;
+	uint32_t flags;
+	json_t *value;
+	size_t index;
+
+	nls = netlink_set_alloc(nlh);
+	flags = nftnl_set_get_u32(nls, NFTNL_SET_FLAGS);
+	if (flags & NFT_SET_ANONYMOUS)
+		return MNL_CB_OK;
+
+	family = family2str(nftnl_set_get_u32(nls, NFTNL_SET_FAMILY));
+	table = nftnl_set_get_str(nls, NFTNL_SET_TABLE);
+	name = nftnl_set_get_str(nls, NFTNL_SET_NAME);
+	handle = nftnl_set_get_u64(nls, NFTNL_SET_HANDLE);
+
+	json_array_foreach(array, index, value) {
+		if (json_unpack(value, "{s:{s:o}}", "add", "set", &value) ||
+		    !obj_info_matches(value, family, table, NULL, name))
+			continue;
+
+		json_object_set_new(value, "handle", json_integer(handle));
+		return MNL_CB_OK;
+	}
+	return json_echo_error(monh, "JSON set object '%s %s %s' not found.\n",
+			       family, table, name);
+}
+
+static int json_update_obj(struct netlink_mon_handler *monh,
+			   json_t *array, const struct nlmsghdr *nlh)
+{
+	const char *family, *table, *name, *type;
+	struct nftnl_obj *nlo;
+	uint64_t handle;
+	json_t *value;
+	size_t index;
+
+	nlo = netlink_obj_alloc(nlh);
+	family = family2str(nftnl_obj_get_u32(nlo, NFTNL_OBJ_FAMILY));
+	table = nftnl_obj_get_str(nlo, NFTNL_OBJ_TABLE);
+	name = nftnl_obj_get_str(nlo, NFTNL_OBJ_NAME);
+	type = obj_type_name(nftnl_obj_get_u32(nlo, NFTNL_OBJ_TYPE));
+	handle = nftnl_obj_get_u64(nlo, NFTNL_OBJ_HANDLE);
+
+	json_array_foreach(array, index, value) {
+		if (json_unpack(value, "{s:{s:o}}", "add", type, &value) ||
+		    !obj_info_matches(value, family, table, NULL, name))
+			continue;
+
+		json_object_set_new(value, "handle", json_integer(handle));
+		return MNL_CB_OK;
+	}
+	return json_echo_error(monh, "JSON %s object '%s %s %s' not found.\n",
+			       type, family, table, name);
+}
+
+int json_events_cb(const struct nlmsghdr *nlh, struct netlink_mon_handler *monh)
+{
+	json_t *root = monh->ctx->nft->json_root;
+	json_t *array;
+
+	if (!root)
+		return MNL_CB_OK;
+
+	if (json_unpack(root, "{s:o}", "nftables", &array)) {
+		erec_queue(error(int_loc, "Invalid JSON root element\n"),
+			   monh->ctx->msgs);
+		return MNL_CB_STOP;
+	}
+
+	switch (NFNL_MSG_TYPE(nlh->nlmsg_type)) {
+	case NFT_MSG_NEWTABLE:
+		return json_update_table(monh, array, nlh);
+	case NFT_MSG_NEWCHAIN:
+		return json_update_chain(monh, array, nlh);
+	case NFT_MSG_NEWRULE:
+		return json_update_rule(monh, array, nlh);
+	case NFT_MSG_NEWSET:
+		return json_update_set(monh, array, nlh);
+	case NFT_MSG_NEWOBJ:
+		return json_update_obj(monh, array, nlh);
+	}
+
+	return MNL_CB_OK;
+}
+
+void json_print_echo(struct nft_ctx *ctx)
+{
+	if (!ctx->json_root)
+		return;
+
+	json_dumpf(ctx->json_root, ctx->output.output_fp, JSON_PRESERVE_ORDER);
+	json_decref(ctx->json_root);
+	ctx->json_root = NULL;
+}