examples: load ruleset from JSON

Add an example to load a ruleset file expressed in JSON.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

3 files changed, 75 insertions, 1 deletions

diff --git a/examples/Makefile.am b/examples/Makefile.am
index dd637fe3..c972170d 100644
--- a/examples/Makefile.am
+++ b/examples/Makefile.am
@@ -1,3 +1,4 @@
-noinst_PROGRAMS	= nft-buffer
+noinst_PROGRAMS	= nft-buffer		\
+		  nft-json-file
 
 LDADD = $(top_builddir)/src/libnftables.la
diff --git a/examples/json-ruleset.nft b/examples/json-ruleset.nft
new file mode 100644
index 00000000..acea1786
--- /dev/null
+++ b/examples/json-ruleset.nft
@@ -0,0 +1,43 @@
+{
+  "nftables": [
+    {
+      "flush": {
+        "ruleset": {
+          "family": "ip"
+        }
+      }
+    },
+    {
+      "table": {
+        "family": "ip",
+        "name": "x"
+      }
+    },
+    {
+      "chain": {
+        "family": "ip",
+        "table": "x",
+        "name": "y",
+        "type": "filter",
+        "hook": "input",
+        "prio": 0,
+        "policy": "accept"
+      }
+    },
+    {
+      "rule": {
+        "family": "ip",
+        "table": "x",
+        "chain": "y",
+        "expr": [
+          {
+            "counter": {
+              "packets": 0,
+              "bytes": 0
+            }
+          }
+        ]
+      }
+    }
+  ]
+}
diff --git a/examples/nft-json-file.c b/examples/nft-json-file.c
new file mode 100644
index 00000000..0c832f22
--- /dev/null
+++ b/examples/nft-json-file.c
@@ -0,0 +1,30 @@
+/* gcc nft-json-file.c -o nft-json-file -lnftables */
+#include <stdlib.h>
+#include <nftables/libnftables.h>
+
+int main(void)
+{
+	struct nft_ctx *ctx;
+	int err;
+
+	ctx = nft_ctx_new(0);
+	if (!ctx) {
+		perror("cannot allocate nft context");
+		return EXIT_FAILURE;
+	}
+
+	nft_ctx_output_set_flags(ctx, NFT_CTX_OUTPUT_JSON);
+
+	/* create ruleset: all commands in the buffer are atomically applied */
+	err = nft_run_cmd_from_filename(ctx, "json-ruleset.nft");
+	if (err < 0)
+		fprintf(stderr, "failed to run nftables command\n");
+
+	err = nft_run_cmd_from_buffer(ctx, "list ruleset");
+	if (err < 0)
+		fprintf(stderr, "failed to run nftables command\n");
+
+	nft_ctx_free(ctx);
+
+	return EXIT_SUCCESS;
+}