libnftables: Implement JSON output support

Although technically there already is support for JSON output via 'nft
export json' command, it is hardly useable since it exports all the gory
details of nftables VM. Also, libnftables has no control over what is
exported since the content comes directly from libnftnl.

Instead, implement JSON format support for regular 'nft list' commands.

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

1 files changed, 10 insertions, 1 deletions

diff --git a/src/main.c b/src/main.c
index d26ea018..f3615974 100644
--- a/src/main.c
+++ b/src/main.c
@@ -31,6 +31,7 @@ enum opt_vals {
 	OPT_FILE		= 'f',
 	OPT_INTERACTIVE		= 'i',
 	OPT_INCLUDEPATH		= 'I',
+	OPT_JSON		= 'j',
 	OPT_NUMERIC		= 'n',
 	OPT_STATELESS		= 's',
 	OPT_IP2NAME		= 'N',
@@ -40,7 +41,7 @@ enum opt_vals {
 	OPT_INVALID		= '?',
 };
 
-#define OPTSTRING	"hvcf:iI:vnsNae"
+#define OPTSTRING	"hvcf:iI:jvnsNae"
 
 static const struct option options[] = {
 	{
@@ -95,6 +96,10 @@ static const struct option options[] = {
 		.val		= OPT_ECHO,
 	},
 	{
+		.name		= "json",
+		.val		= OPT_JSON,
+	},
+	{
 		.name		= NULL
 	}
 };
@@ -112,6 +117,7 @@ static void show_help(const char *name)
 "  -f, --file <filename>		Read input from <filename>\n"
 "  -i, --interactive		Read input from interactive CLI\n"
 "\n"
+"  -j, --json			Format output in JSON\n"
 "  -n, --numeric			When specified once, show network addresses numerically (default behaviour).\n"
 "  				Specify twice to also show Internet services (port numbers) numerically.\n"
 "				Specify three times to also show protocols, user IDs, and group IDs numerically.\n"
@@ -255,6 +261,9 @@ int main(int argc, char * const *argv)
 		case OPT_ECHO:
 			nft_ctx_output_set_echo(nft, true);
 			break;
+		case OPT_JSON:
+			nft_ctx_output_set_json(nft, true);
+			break;
 		case OPT_INVALID:
 			exit(EXIT_FAILURE);
 		}