nftutils: add and use wrappers for getprotoby{name,number}_r(), getservbyport_r()

We should aim to use the thread-safe variants of getprotoby{name,number}
and getservbyport(). However, they may not be available with other libc,
so it requires a configure check. As that is cumbersome, add wrappers
that do that at one place.

These wrappers are thread-safe, if libc provides the reentrant versions.
Use them.

Signed-off-by: Thomas Haller <thaller@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/src/nftutils.h b/src/nftutils.h
new file mode 100644
index 00000000..cb584b9c
--- /dev/null
+++ b/src/nftutils.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef NFTUTILS_H
+#define NFTUTILS_H
+
+#include <stdbool.h>
+#include <stddef.h>
+
+/* The maximum buffer size for (struct protoent).p_name. It is excessively large,
+ * while still reasonably fitting on the stack. Arbitrarily chosen. */
+#define NFT_PROTONAME_MAXSIZE 1024
+
+bool nft_getprotobynumber(int number, char *out_name, size_t name_len);
+int nft_getprotobyname(const char *name);
+
+/* The maximum buffer size for (struct servent).s_name. It is excessively large,
+ * while still reasonably fitting on the stack. Arbitrarily chosen. */
+#define NFT_SERVNAME_MAXSIZE 1024
+
+bool nft_getservbyport(int port, const char *proto, char *out_name, size_t name_len);
+
+#endif /* NFTUTILS_H */