examples: add libnftables example program

Create an example folder to add example source code files to show how to
use libnftables. Add first example program using the buffer API.

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

2 files changed, 37 insertions, 0 deletions

diff --git a/examples/Makefile.am b/examples/Makefile.am
new file mode 100644
index 00000000..dd637fe3
--- /dev/null
+++ b/examples/Makefile.am
@@ -0,0 +1,3 @@
+noinst_PROGRAMS	= nft-buffer
+
+LDADD = $(top_builddir)/src/libnftables.la
diff --git a/examples/nft-buffer.c b/examples/nft-buffer.c
new file mode 100644
index 00000000..1c4b1e04
--- /dev/null
+++ b/examples/nft-buffer.c
@@ -0,0 +1,34 @@
+/* gcc nft-buffer.c -o nft-buffer -lnftables */
+#include <stdlib.h>
+#include <nftables/libnftables.h>
+
+const char ruleset[] =
+	"flush ruleset;"
+	"add table x;"
+	"add chain x y { type filter hook input priority 0; };"
+	"add rule x y counter;";
+
+int main(void)
+{
+	struct nft_ctx *ctx;
+	int err;
+
+	ctx = nft_ctx_new(0);
+	if (!ctx) {
+		perror("cannot allocate nft context");
+		return EXIT_FAILURE;
+	}
+
+	/* create ruleset: all commands in the buffer are atomically applied */
+	err = nft_run_cmd_from_buffer(ctx, ruleset);
+	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;
+}