[nft v3 PATCH 3/4] src: add input flag NFT_CTX_INPUT_JSON to enable JSON parsing

[Thomas Haller <thaller@redhat.com>]

By default, the input is parsed using the nftables grammar. When setting
NFT_CTX_OUTPUT_JSON flag, nftables will first try to parse the input as
JSON before falling back to the nftables grammar.

But NFT_CTX_OUTPUT_JSON flag also turns on JSON for the output. Add a
flag NFT_CTX_INPUT_JSON which allows to treat only the input in JSON
format, but keep the output mode unchanged.

Signed-off-by: Thomas Haller <thaller@redhat.com>
---
 doc/libnftables.adoc           | 6 ++++++
 include/nftables/libnftables.h | 1 +
 src/libnftables.c              | 6 ++++--
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/doc/libnftables.adoc b/doc/libnftables.adoc
index 77f3a0fd5659..27e230281edb 100644
--- a/doc/libnftables.adoc
+++ b/doc/libnftables.adoc
@@ -87,6 +87,7 @@ The flags setting controls the input format.
 ----
 enum {
         NFT_CTX_INPUT_NO_DNS = (1 << 0),
+        NFT_CTX_INPUT_JSON   = (1 << 1),
 };
 ----
 
@@ -94,6 +95,11 @@ NFT_CTX_INPUT_NO_DNS::
 	Avoid resolving IP addresses with blocking getaddrinfo(). In that case,
 	only plain IP addresses are accepted.
 
+NFT_CTX_INPUT_JSON:
+	When parsing the input, first try to interpret the input as JSON before
+	falling back to the nftables format. This behavior is implied when setting
+	the NFT_CTX_OUTPUT_JSON flag.
+
 The *nft_ctx_input_get_flags*() function returns the input flags setting's value in 'ctx'.
 
 The *nft_ctx_input_set_flags*() function sets the input flags setting in 'ctx' to the value of 'val'.
diff --git a/include/nftables/libnftables.h b/include/nftables/libnftables.h
index 2f5f079efff0..152c7a5b75da 100644
--- a/include/nftables/libnftables.h
+++ b/include/nftables/libnftables.h
@@ -50,6 +50,7 @@ void nft_ctx_set_optimize(struct nft_ctx *ctx, uint32_t flags);
 
 enum {
 	NFT_CTX_INPUT_NO_DNS		= (1 << 0),
+	NFT_CTX_INPUT_JSON		= (1 << 1),
 };
 
 unsigned int nft_ctx_input_get_flags(struct nft_ctx *ctx);
diff --git a/src/libnftables.c b/src/libnftables.c
index 6832f0486d6d..a2e0ae6b5843 100644
--- a/src/libnftables.c
+++ b/src/libnftables.c
@@ -578,7 +578,8 @@ int nft_run_cmd_from_buffer(struct nft_ctx *nft, const char *buf)
 	nlbuf = xzalloc(strlen(buf) + 2);
 	sprintf(nlbuf, "%s\n", buf);
 
-	if (nft_output_json(&nft->output))
+	if (nft_output_json(&nft->output) ||
+	    (nft_ctx_input_get_flags(nft) & NFT_CTX_INPUT_JSON))
 		rc = nft_parse_json_buffer(nft, nlbuf, &msgs, &cmds);
 	if (rc == -EINVAL)
 		rc = nft_parse_bison_buffer(nft, nlbuf, &msgs, &cmds,
@@ -677,7 +678,8 @@ static int __nft_run_cmd_from_filename(struct nft_ctx *nft, const char *filename
 		goto err;
 
 	rc = -EINVAL;
-	if (nft_output_json(&nft->output))
+	if (nft_output_json(&nft->output) ||
+	    (nft_ctx_input_get_flags(nft) & NFT_CTX_INPUT_JSON))
 		rc = nft_parse_json_filename(nft, filename, &msgs, &cmds);
 	if (rc == -EINVAL)
 		rc = nft_parse_bison_filename(nft, filename, &msgs, &cmds);
-- 
2.41.0