net: sockets: Add configurable option to provide raw POSIX API names

With CONFIG_NET_SOCKETS_POSIX_NAMES=y, "raw" POSIX names like
socket(), recv(), close() will be exposed (using macro defines).
The close() is the biggest culprit here, because in POSIX it
applies to any file descriptor, but in this implementation -
only to sockets.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>

include/net/socket.h

@@ -7,6 +7,9 @@
 #ifndef __NET_SOCKET_H
 #define __NET_SOCKET_H
 
+#include <zephyr/types.h>
+#include <net/net_ip.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -14,6 +17,11 @@ extern "C" {
 int zsock_socket(int family, int type, int proto);
 int zsock_close(int sock);
 
+#if defined(CONFIG_NET_SOCKETS_POSIX_NAMES)
+#define socket zsock_socket
+#define close zsock_close
+#endif
+
 #ifdef __cplusplus
 }
 #endif

subsys/net/lib/sockets/Kconfig

@@ -14,6 +14,17 @@ menuconfig NET_SOCKETS
 
 if NET_SOCKETS
 
+config NET_SOCKETS_POSIX_NAMES
+	bool "Standard POSIX names for Sockets API"
+	default n
+	help
+	By default, Sockets API function are prefixed with `zsock_` to avoid
+	namespacing issues. If this option is enabled, they will be provided
+	with standard POSIX names like socket(), recv(), and close(), to help
+	with porting existing code. Note that close() may require a special
+	attention, as in POSIX it closes any file descriptor, while with this
+	option enaled, it will still apply only to sockets.
+
 config NET_DEBUG_SOCKETS
 	bool "Debug BSD Sockets like API calls"
 	default n