1 files changed, 100 insertions, 0 deletions
diff --git a/src/nftutils.c b/src/nftutils.c
new file mode 100644
index 00000000..ca178aa0
--- /dev/null
+++ b/src/nftutils.c
@@ -0,0 +1,100 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <nft.h>
+
+#include "nftutils.h"
+
+#include <netdb.h>
+
+/* Buffer size used for getprotobynumber_r() and similar. The manual comments
+ * that a buffer of 1024 should be sufficient "for most applications"(??), so
+ * let's double it.  It still fits reasonably on the stack, so no need to
+ * choose a smaller one. */
+#define NETDB_BUFSIZE 2048
+
+bool nft_getprotobynumber(int proto, char *out_name, size_t name_len)
+{
+	const struct protoent *result;
+
+#if HAVE_DECL_GETPROTOBYNUMBER_R
+	struct protoent result_buf;
+	char buf[NETDB_BUFSIZE];
+	int r;
+
+	r = getprotobynumber_r(proto,
+	                       &result_buf,
+	                       buf,
+	                       sizeof(buf),
+	                       (struct protoent **) &result);
+	if (r != 0 || result != &result_buf)
+		result = NULL;
+#else
+	result = getprotobynumber(proto);
+#endif
+
+	if (!result)
+		return false;
+
+	if (strlen(result->p_name) >= name_len)
+		return false;
+	strcpy(out_name, result->p_name);
+	return true;
+}
+
+int nft_getprotobyname(const char *name)
+{
+	const struct protoent *result;
+
+#if HAVE_DECL_GETPROTOBYNAME_R
+	struct protoent result_buf;
+	char buf[NETDB_BUFSIZE];
+	int r;
+
+	r = getprotobyname_r(name,
+	                     &result_buf,
+	                     buf,
+	                     sizeof(buf),
+	                     (struct protoent **) &result);
+	if (r != 0 || result != &result_buf)
+		result = NULL;
+#else
+	result = getprotobyname(name);
+#endif
+
+	if (!result)
+		return -1;
+
+	if (result->p_proto < 0 || result->p_proto > UINT8_MAX)
+		return -1;
+	return (uint8_t) result->p_proto;
+}
+
+bool nft_getservbyport(int port, const char *proto, char *out_name, size_t name_len)
+{
+	const struct servent *result;
+
+#if HAVE_DECL_GETSERVBYPORT_R
+	struct servent result_buf;
+	char buf[NETDB_BUFSIZE];
+	int r;
+
+	r = getservbyport_r(port,
+	                    proto,
+	                    &result_buf,
+	                    buf,
+	                    sizeof(buf),
+	                    (struct servent**) &result);
+	if (r != 0 || result != &result_buf)
+		result = NULL;
+#else
+	result = getservbyport(port, proto);
+#endif
+
+	if (!result)
+		return false;
+
+	if (strlen(result->s_name) >= name_len)
+		return false;
+	strcpy(out_name, result->s_name);
+	return true;
+}