[PATCH nft 1/2] parser_json: use stdin buffer if available

[Pablo Neira Ayuso <pablo@netfilter.org>]

Since 5c2b2b0a2ba7 ("src: error reporting with -f and read from stdin")
stdin is stored in a buffer, update json support to use it instead of
reading from /dev/stdin.

Some systems do not provide /dev/stdin symlink to /proc/self/fd/0
according to reporter (that mentions Yocto Linux as example).

Fixes: 935f82e7dd49 ("Support 'nft -f -' to read from stdin")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
v2: remove check for nft_output_json() in nft_run_cmd_from_filename()
    as suggested by Phil Sutter, so JSON support does not really use
    /dev/stdin.

 src/libnftables.c | 3 +--
 src/parser_json.c | 7 +++++++
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/libnftables.c b/src/libnftables.c
index af4734c05004..89317f9f6049 100644
--- a/src/libnftables.c
+++ b/src/libnftables.c
@@ -807,8 +807,7 @@ int nft_run_cmd_from_filename(struct nft_ctx *nft, const char *filename)
 	if (!strcmp(filename, "-"))
 		filename = "/dev/stdin";
 
-	if (!strcmp(filename, "/dev/stdin") &&
-	    !nft_output_json(&nft->output))
+	if (!strcmp(filename, "/dev/stdin"))
 		nft->stdin_buf = stdin_to_buffer();
 
 	if (!nft->stdin_buf &&
diff --git a/src/parser_json.c b/src/parser_json.c
index ee4657ee8044..4912d3608b2b 100644
--- a/src/parser_json.c
+++ b/src/parser_json.c
@@ -4357,6 +4357,13 @@ int nft_parse_json_filename(struct nft_ctx *nft, const char *filename,
 	json_error_t err;
 	int ret;
 
+	if (nft->stdin_buf) {
+		json_indesc.type = INDESC_STDIN;
+		json_indesc.name = "/dev/stdin";
+
+		return nft_parse_json_buffer(nft, nft->stdin_buf, msgs, cmds);
+	}
+
 	json_indesc.type = INDESC_FILE;
 	json_indesc.name = filename;
 
-- 
2.30.2