Introduce struct nftnl_str_array

This data structure holds an array of allocated strings for use in
nftnl_chain and nftnl_flowtable structs. For convenience, implement
functions to clear, populate and iterate over contents.

While at it, extend chain and flowtable tests to cover these attributes,
too.

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

1 files changed, 68 insertions, 0 deletions

diff --git a/src/str_array.c b/src/str_array.c
new file mode 100644
index 0000000..63471bd
--- /dev/null
+++ b/src/str_array.c
@@ -0,0 +1,68 @@
+/*
+ * (C) 2024 Red Hat GmbH
+ * Author: Phil Sutter <phil@nwl.cc>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#include <libmnl/libmnl.h>
+#include <linux/netfilter/nf_tables.h>
+
+#include "str_array.h"
+#include "utils.h"
+
+void nftnl_str_array_clear(struct nftnl_str_array *sa)
+{
+	while (sa->len > 0)
+		free(sa->array[--sa->len]);
+	free(sa->array);
+}
+
+int nftnl_str_array_set(struct nftnl_str_array *sa, const char * const *array)
+{
+	int len = 0;
+
+	while (array[len])
+		len++;
+
+	nftnl_str_array_clear(sa);
+	sa->array = calloc(len + 1, sizeof(char *));
+	if (!sa->array)
+		return -1;
+
+	while (sa->len < len) {
+		sa->array[sa->len] = strdup(array[sa->len]);
+		if (!sa->array[sa->len]) {
+			nftnl_str_array_clear(sa);
+			return -1;
+		}
+		sa->len++;
+	}
+	return 0;
+}
+
+int nftnl_parse_devs(struct nftnl_str_array *sa, const struct nlattr *nest)
+{
+	struct nlattr *attr;
+	int len = 0;
+
+	mnl_attr_for_each_nested(attr, nest) {
+		if (mnl_attr_get_type(attr) != NFTA_DEVICE_NAME)
+			return -1;
+		len++;
+	}
+
+	nftnl_str_array_clear(sa);
+	sa->array = calloc(len + 1, sizeof(char *));
+	if (!sa->array)
+		return -1;
+
+	mnl_attr_for_each_nested(attr, nest) {
+		sa->array[sa->len] = strdup(mnl_attr_get_str(attr));
+		if (!sa->array[sa->len]) {
+			nftnl_str_array_clear(sa);
+			return -1;
+		}
+		sa->len++;
+	}
+	return 0;
+}