src: enable json echo output when reading native syntax

This patch fixes a bug in which nft did not print any output when
specifying --echo and --json and reading nft native syntax.

This patch respects behavior when input is json, in which the output
would be the identical input plus the handles.

Adds a json_echo member inside struct nft_ctx to build and store the json object
containing the json command objects, the object is built using a mock
monitor to reuse monitor json code. This json object is only used when
we are sure we have not read json from input.

[ added json_alloc_echo() to compile without json support --pablo ]

Fixes: https://bugzilla.netfilter.org/show_bug.cgi?id=1446
Signed-off-by: Jose M. Guisado Gomez <guigom@riseup.net>
Tested-by: Eric Garver <eric@garver.life>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

5 files changed, 65 insertions, 17 deletions

diff --git a/include/json.h b/include/json.h
index 20d6c2a4..41142208 100644
--- a/include/json.h
+++ b/include/json.h
@@ -111,6 +111,7 @@ void monitor_print_rule_json(struct netlink_mon_handler *monh,
 
 int json_events_cb(const struct nlmsghdr *nlh,
 		   struct netlink_mon_handler *monh);
+void json_alloc_echo(struct nft_ctx *ctx);
 void json_print_echo(struct nft_ctx *ctx);
 
 #else /* ! HAVE_LIBJANSSON */
@@ -251,6 +252,11 @@ static inline int json_events_cb(const struct nlmsghdr *nlh,
 	return -1;
 }
 
+static inline void json_alloc_echo(struct nft_ctx *ctx)
+{
+	/* empty */
+}
+
 static inline void json_print_echo(struct nft_ctx *ctx)
 {
 	/* empty */
diff --git a/include/nftables.h b/include/nftables.h
index 3556728d..9095ff3d 100644
--- a/include/nftables.h
+++ b/include/nftables.h
@@ -122,6 +122,7 @@ struct nft_ctx {
 	void			*scanner;
 	struct scope		*top_scope;
 	void			*json_root;
+	json_t			*json_echo;
 };
 
 enum nftables_exit_codes {
diff --git a/src/json.c b/src/json.c
index ac3b1c83..0b398bf0 100644
--- a/src/json.c
+++ b/src/json.c
@@ -1895,9 +1895,15 @@ int do_command_list_json(struct netlink_ctx *ctx, struct cmd *cmd)
 static void monitor_print_json(struct netlink_mon_handler *monh,
 			       const char *cmd, json_t *obj)
 {
+	struct nft_ctx *nft = monh->ctx->nft;
+
 	obj = json_pack("{s:o}", cmd, obj);
-	json_dumpf(obj, monh->ctx->nft->output.output_fp, 0);
-	json_decref(obj);
+	if (nft_output_echo(&nft->output) && !nft->json_root) {
+		json_array_append_new(nft->json_echo, obj);
+	} else {
+		json_dumpf(obj, nft->output.output_fp, 0);
+		json_decref(obj);
+	}
 }
 
 void monitor_print_table_json(struct netlink_mon_handler *monh,
@@ -1941,3 +1947,10 @@ void monitor_print_rule_json(struct netlink_mon_handler *monh,
 
 	monitor_print_json(monh, cmd, rule_print_json(octx, r));
 }
+
+void json_alloc_echo(struct nft_ctx *nft)
+{
+	nft->json_echo = json_array();
+	if (!nft->json_echo)
+		memory_allocation_error();
+}
diff --git a/src/monitor.c b/src/monitor.c
index 3872ebcf..a733a9f0 100644
--- a/src/monitor.c
+++ b/src/monitor.c
@@ -221,12 +221,14 @@ static int netlink_events_table_cb(const struct nlmsghdr *nlh, int type,
 		if (nft_output_handle(&monh->ctx->nft->output))
 			nft_mon_print(monh, " # handle %" PRIu64 "",
 				      t->handle.handle.id);
+		nft_mon_print(monh, "\n");
 		break;
 	case NFTNL_OUTPUT_JSON:
 		monitor_print_table_json(monh, cmd, t);
+		if(!nft_output_echo(&monh->ctx->nft->output))
+			nft_mon_print(monh, "\n");
 		break;
 	}
-	nft_mon_print(monh, "\n");
 	table_free(t);
 	nftnl_table_free(nlt);
 	return MNL_CB_OK;
@@ -258,12 +260,14 @@ static int netlink_events_chain_cb(const struct nlmsghdr *nlh, int type,
 				      c->handle.chain.name);
 			break;
 		}
+		nft_mon_print(monh, "\n");
 		break;
 	case NFTNL_OUTPUT_JSON:
 		monitor_print_chain_json(monh, cmd, c);
+		if(!nft_output_echo(&monh->ctx->nft->output))
+			nft_mon_print(monh, "\n");
 		break;
 	}
-	nft_mon_print(monh, "\n");
 	chain_free(c);
 	nftnl_chain_free(nlc);
 	return MNL_CB_OK;
@@ -304,12 +308,14 @@ static int netlink_events_set_cb(const struct nlmsghdr *nlh, int type,
 				      set->handle.set.name);
 			break;
 		}
+		nft_mon_print(monh, "\n");
 		break;
 	case NFTNL_OUTPUT_JSON:
 		monitor_print_set_json(monh, cmd, set);
+		if(!nft_output_echo(&monh->ctx->nft->output))
+			nft_mon_print(monh, "\n");
 		break;
 	}
-	nft_mon_print(monh, "\n");
 	set_free(set);
 out:
 	nftnl_set_free(nls);
@@ -441,6 +447,7 @@ static int netlink_events_setelem_cb(const struct nlmsghdr *nlh, int type,
 		nft_mon_print(monh, "%s element %s %s %s ",
 			      cmd, family2str(family), table, setname);
 		expr_print(dummyset->init, &monh->ctx->nft->output);
+		nft_mon_print(monh, "\n");
 		break;
 	case NFTNL_OUTPUT_JSON:
 		dummyset->handle.family = family;
@@ -450,9 +457,10 @@ static int netlink_events_setelem_cb(const struct nlmsghdr *nlh, int type,
 		/* prevent set_free() from trying to free those */
 		dummyset->handle.set.name = NULL;
 		dummyset->handle.table.name = NULL;
+		if(!nft_output_echo(&monh->ctx->nft->output))
+			nft_mon_print(monh, "\n");
 		break;
 	}
-	nft_mon_print(monh, "\n");
 	set_free(dummyset);
 out:
 	nftnl_set_free(nls);
@@ -492,12 +500,14 @@ static int netlink_events_obj_cb(const struct nlmsghdr *nlh, int type,
 			       obj->handle.obj.name);
 			break;
 		}
+		nft_mon_print(monh, "\n");
 		break;
 	case NFTNL_OUTPUT_JSON:
 		monitor_print_obj_json(monh, cmd, obj);
+		if(!nft_output_echo(&monh->ctx->nft->output))
+			nft_mon_print(monh, "\n");
 		break;
 	}
-	nft_mon_print(monh, "\n");
 	obj_free(obj);
 	nftnl_obj_free(nlo);
 	return MNL_CB_OK;
@@ -542,12 +552,14 @@ static int netlink_events_rule_cb(const struct nlmsghdr *nlh, int type,
 				      r->handle.handle.id);
 			break;
 		}
+		nft_mon_print(monh, "\n");
 		break;
 	case NFTNL_OUTPUT_JSON:
 		monitor_print_rule_json(monh, cmd, r);
+		if(!nft_output_echo(&monh->ctx->nft->output))
+			nft_mon_print(monh, "\n");
 		break;
 	}
-	nft_mon_print(monh, "\n");
 	rule_free(r);
 	nftnl_rule_free(nlr);
 	return MNL_CB_OK;
@@ -912,6 +924,8 @@ int netlink_echo_callback(const struct nlmsghdr *nlh, void *data)
 {
 	struct netlink_cb_data *nl_cb_data = data;
 	struct netlink_ctx *ctx = nl_cb_data->nl_ctx;
+	struct nft_ctx *nft = ctx->nft;
+
 	struct netlink_mon_handler echo_monh = {
 		.format = NFTNL_OUTPUT_DEFAULT,
 		.ctx = ctx,
@@ -922,8 +936,13 @@ int netlink_echo_callback(const struct nlmsghdr *nlh, void *data)
 	if (!nft_output_echo(&echo_monh.ctx->nft->output))
 		return MNL_CB_OK;
 
-	if (nft_output_json(&ctx->nft->output))
-		return json_events_cb(nlh, &echo_monh);
+	if (nft_output_json(&nft->output)) {
+		if (nft->json_root)
+			return json_events_cb(nlh, &echo_monh);
+
+		json_alloc_echo(nft);
+		echo_monh.format = NFTNL_OUTPUT_JSON;
+	}
 
 	return netlink_events_cb(nlh, &echo_monh);
 }
diff --git a/src/parser_json.c b/src/parser_json.c
index 6ebbb408..2de10993 100644
--- a/src/parser_json.c
+++ b/src/parser_json.c
@@ -4008,11 +4008,20 @@ int json_events_cb(const struct nlmsghdr *nlh, struct netlink_mon_handler *monh)
 
 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_cmd_assoc_free();
-	json_decref(ctx->json_root);
-	ctx->json_root = NULL;
+	if (!ctx->json_root) {
+		if (!ctx->json_echo)
+			return;
+
+		ctx->json_echo = json_pack("{s:o}", "nftables", ctx->json_echo);
+		json_dumpf(ctx->json_echo, ctx->output.output_fp, JSON_PRESERVE_ORDER);
+		json_decref(ctx->json_echo);
+		ctx->json_echo = NULL;
+		fprintf(ctx->output.output_fp, "\n");
+		fflush(ctx->output.output_fp);
+	} else {
+		json_dumpf(ctx->json_root, ctx->output.output_fp, JSON_PRESERVE_ORDER);
+		json_cmd_assoc_free();
+		json_decref(ctx->json_root);
+		ctx->json_root = NULL;
+	}
 }