posix: net: implement if_nameindex() et al

Implement if_indextoname(), if_freenameindex(), if_nameindex(),
and if_nametoindex() by wrapping around networking subystem
calls.

Signed-off-by: Chris Friedt <chrisfriedt@gmail.com>

include/zephyr/posix/net/if.h

@@ -6,12 +6,26 @@
 #ifndef ZEPHYR_INCLUDE_POSIX_NET_IF_H_
 #define ZEPHYR_INCLUDE_POSIX_NET_IF_H_
 
-#include <zephyr/net/socket.h>
+#ifdef CONFIG_NET_INTERFACE_NAME_LEN
+#define IF_NAMESIZE CONFIG_NET_INTERFACE_NAME_LEN
+#else
+#define IF_NAMESIZE 1
+#endif
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+struct if_nameindex {
+	unsigned int if_index;
+	char *if_name;
+};
+
+char *if_indextoname(unsigned int ifindex, char *ifname);
+void if_freenameindex(struct if_nameindex *ptr);
+struct if_nameindex *if_nameindex(void);
+unsigned int if_nametoindex(const char *ifname);
+
 #ifdef __cplusplus
 }
 #endif

lib/posix/options/net.c

@@ -6,9 +6,12 @@
 
 #include <ctype.h>
 #include <stdio.h>
+#include <stdlib.h>
 
+#include <zephyr/net/net_if.h>
 #include <zephyr/posix/arpa/inet.h>
 #include <zephyr/posix/netinet/in.h>
+#include <zephyr/posix/net/if.h>
 
 in_addr_t inet_addr(const char *cp)
 {
@@ -76,3 +79,98 @@ char *inet_ntoa(struct in_addr in)
 
 	return buf;
 }
+
+char *if_indextoname(unsigned int ifindex, char *ifname)
+{
+	int ret;
+
+	if (!IS_ENABLED(CONFIG_NET_INTERFACE_NAME)) {
+		errno = ENOTSUP;
+		return NULL;
+	}
+
+	ret = net_if_get_name(net_if_get_by_index(ifindex), ifname, IF_NAMESIZE);
+	if (ret < 0) {
+		errno = ENXIO;
+		return NULL;
+	}
+
+	return ifname;
+}
+
+void if_freenameindex(struct if_nameindex *ptr)
+{
+	size_t n;
+
+	if (ptr == NULL || !IS_ENABLED(CONFIG_NET_INTERFACE_NAME)) {
+		return;
+	}
+
+	NET_IFACE_COUNT(&n);
+
+	for (size_t i = 0; i < n; ++i) {
+		if (IS_ENABLED(CONFIG_NET_INTERFACE_NAME) && ptr[i].if_name != NULL) {
+			free(ptr[i].if_name);
+		}
+	}
+
+	free(ptr);
+}
+
+struct if_nameindex *if_nameindex(void)
+{
+	size_t n;
+	char *name;
+	struct if_nameindex *ni;
+
+	if (!IS_ENABLED(CONFIG_NET_INTERFACE_NAME)) {
+		errno = ENOTSUP;
+		return NULL;
+	}
+
+	/* FIXME: would be nice to use this without malloc */
+	NET_IFACE_COUNT(&n);
+	ni = malloc((n + 1) * sizeof(*ni));
+	if (ni == NULL) {
+		goto return_err;
+	}
+
+	for (size_t i = 0; i < n; ++i) {
+		ni[i].if_index = i + 1;
+
+		ni[i].if_name = malloc(IF_NAMESIZE);
+		if (ni[i].if_name == NULL) {
+			goto return_err;
+		}
+
+		name = if_indextoname(i + 1, ni[i].if_name);
+		__ASSERT_NO_MSG(name != NULL);
+	}
+
+	ni[n].if_index = 0;
+	ni[n].if_name = NULL;
+
+	return ni;
+
+return_err:
+	if_freenameindex(ni);
+	errno = ENOBUFS;
+
+	return NULL;
+}
+
+unsigned int if_nametoindex(const char *ifname)
+{
+	int ret;
+
+	if (!IS_ENABLED(CONFIG_NET_INTERFACE_NAME)) {
+		return 0;
+	}
+
+	ret = net_if_get_by_name(ifname);
+	if (ret < 0) {
+		return 0;
+	}
+
+	return ret;
+}