src: restore interface to index cache

nftables used to have a cache to speed up interface name <-> index lookup,
restore it using libmnl.

This reduces netlink traffic since if_nametoindex() and if_indextoname() open,
send a request, receive the list of interface and close a netlink socket for
each call.  I think this is also good for consistency since nft -f will operate
with the same index number when reloading the ruleset.

The cache is populated by when nft_if_nametoindex() and nft_if_indextoname()
are used for first time. Then, it it released in the output path. In the
interactive mode, it is invalidated after each command.

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

1 files changed, 18 insertions, 0 deletions

diff --git a/include/iface.h b/include/iface.h
new file mode 100644
index 00000000..f41ee8be
--- /dev/null
+++ b/include/iface.h
@@ -0,0 +1,18 @@
+#ifndef _NFTABLES_IFACE_H_
+#define _NFTABLES_IFACE_H_
+
+#include <net/if.h>
+
+struct iface {
+	struct list_head	list;
+	char			name[IFNAMSIZ];
+	uint32_t		ifindex;
+};
+
+unsigned int nft_if_nametoindex(const char *name);
+char *nft_if_indextoname(unsigned int ifindex, char *name);
+
+void iface_cache_update(void);
+void iface_cache_release(void);
+
+#endif