net: sockets: Add a socket offload module

This patch enables BSD socket offload to a dedicated
TCP/IP offload engine.

This provides a simpler, more direct mechanism than going
through NET_OFFLOAD (zsock -> net_context -> socket conversions)
for those devices which provide complete TCP/IP offload at the
BSD socket level, and whose use cases do not require
IP routing between multiple network interfaces.

To use, configure CONFIG_NET_SOCKETS_OFFLOAD=y, and register
socket_offload_ops with this module.

Fixes #3706

Signed-off-by: Gil Pitney <gil.pitney@linaro.org>

include/net/socket.h

@@ -186,6 +186,8 @@ int ztls_setsockopt(int sock, int level, int optname,
 #endif /* defined(CONFIG_NET_SOCKETS_SOCKOPT_TLS) */
 
 #if defined(CONFIG_NET_SOCKETS_POSIX_NAMES)
+#define pollfd zsock_pollfd
+#if !defined(CONFIG_NET_SOCKETS_OFFLOAD)
 static inline int socket(int family, int type, int proto)
 {
 #if defined(CONFIG_NET_SOCKETS_SOCKOPT_TLS)
@@ -296,13 +298,6 @@ static inline int poll(struct zsock_pollfd *fds, int nfds, int timeout)
 #endif /* defined(CONFIG_NET_SOCKETS_SOCKOPT_TLS) */
 }
 
-#define pollfd zsock_pollfd
-#define POLLIN ZSOCK_POLLIN
-#define POLLOUT ZSOCK_POLLOUT
-
-#define MSG_PEEK ZSOCK_MSG_PEEK
-#define MSG_DONTWAIT ZSOCK_MSG_DONTWAIT
-
 static inline int getsockopt(int sock, int level, int optname,
 			     void *optval, socklen_t *optlen)
 {
@@ -323,6 +318,16 @@ static inline int setsockopt(int sock, int level, int optname,
 #endif
 }
 
+#else
+#include <net/socket_offload.h>
+#endif /* !defined(CONFIG_NET_SOCKETS_OFFLOAD) */
+
+#define POLLIN ZSOCK_POLLIN
+#define POLLOUT ZSOCK_POLLOUT
+
+#define MSG_PEEK ZSOCK_MSG_PEEK
+#define MSG_DONTWAIT ZSOCK_MSG_DONTWAIT
+
 static inline char *inet_ntop(sa_family_t family, const void *src, char *dst,
 			      size_t size)
 {

include/net/socket_offload.h

@@ -0,0 +1,147 @@
+/*
+ * Copyright (c) 2018 Linaro Limited.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @file
+ * @brief Socket Offload Redirect API
+ */
+
+#ifndef __SOCKET_OFFLOAD_H__
+#define __SOCKET_OFFLOAD_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <net/socket_offload_ops.h>
+
+extern const struct socket_offload *socket_ops;
+
+static inline int socket(int family, int type, int proto)
+{
+	__ASSERT_NO_MSG(socket_ops);
+	__ASSERT_NO_MSG(socket_ops->socket);
+
+	return socket_ops->socket(family, type, proto);
+}
+
+static inline int close(int sock)
+{
+	__ASSERT_NO_MSG(socket_ops);
+	__ASSERT_NO_MSG(socket_ops->close);
+
+	return socket_ops->close(sock);
+}
+
+static inline int accept(int sock, struct sockaddr *addr,
+			 socklen_t *addrlen)
+{
+	__ASSERT_NO_MSG(socket_ops);
+	__ASSERT_NO_MSG(socket_ops->accept);
+
+	return socket_ops->accept(sock, addr, addrlen);
+}
+
+
+static inline int bind(int sock, const struct sockaddr *addr,
+		       socklen_t addrlen)
+{
+	__ASSERT_NO_MSG(socket_ops);
+	__ASSERT_NO_MSG(socket_ops->bind);
+
+	return socket_ops->bind(sock, addr, addrlen);
+}
+
+static inline int listen(int sock, int backlog)
+{
+	__ASSERT_NO_MSG(socket_ops);
+	__ASSERT_NO_MSG(socket_ops->listen);
+
+	return socket_ops->listen(sock, backlog);
+}
+
+static inline int connect(int sock, const struct sockaddr *addr,
+			  socklen_t addrlen)
+{
+	__ASSERT_NO_MSG(socket_ops);
+	__ASSERT_NO_MSG(socket_ops->connect);
+
+	return socket_ops->connect(sock, addr, addrlen);
+}
+
+static inline int poll(struct pollfd *fds, int nfds, int timeout)
+{
+	__ASSERT_NO_MSG(socket_ops);
+	__ASSERT_NO_MSG(socket_ops->poll);
+
+	return socket_ops->poll(fds, nfds, timeout);
+}
+
+static inline int setsockopt(int sock, int level, int optname,
+			     const void *optval,
+			     socklen_t optlen)
+{
+	__ASSERT_NO_MSG(socket_ops);
+	__ASSERT_NO_MSG(socket_ops->setsockopt);
+
+	return socket_ops->setsockopt(sock, level, optname, optval, optlen);
+}
+
+static inline int getsockopt(int sock, int level, int optname,
+			     void *optval, socklen_t *optlen)
+{
+	__ASSERT_NO_MSG(socket_ops);
+	__ASSERT_NO_MSG(socket_ops->getsockopt);
+
+	return socket_ops->getsockopt(sock, level, optname, optval, optlen);
+}
+
+static inline ssize_t recv(int sock, void *buf, size_t max_len,
+				      int flags)
+{
+	__ASSERT_NO_MSG(socket_ops);
+	__ASSERT_NO_MSG(socket_ops->recv);
+
+	return socket_ops->recv(sock, buf, max_len, flags);
+}
+
+static inline ssize_t recvfrom(int sock, void *buf,
+			       short int len,
+			       short int flags,
+			       struct sockaddr *from,
+			       socklen_t *fromlen)
+{
+	__ASSERT_NO_MSG(socket_ops);
+	__ASSERT_NO_MSG(socket_ops->recvfrom);
+
+	return socket_ops->recvfrom(sock, buf, len, flags, from, fromlen);
+}
+
+static inline ssize_t send(int sock, const void *buf, size_t len,
+			   int flags)
+{
+	__ASSERT_NO_MSG(socket_ops);
+	__ASSERT_NO_MSG(socket_ops->send);
+
+	return socket_ops->send(sock, buf, len, flags);
+}
+
+static inline ssize_t sendto(int sock, const void *buf,
+			     size_t len, int flags,
+			     const struct sockaddr *to,
+			     socklen_t tolen)
+{
+	__ASSERT_NO_MSG(socket_ops);
+	__ASSERT_NO_MSG(socket_ops->sendto);
+
+	return socket_ops->sendto(sock, buf, len, flags, to, tolen);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __SOCKET_OFFLOAD_H__ */

include/net/socket_offload_ops.h

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2018 Linaro Limited.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @file
+ * @brief Socket Offload Redirect API
+ */
+
+#ifndef __SOCKET_OFFLOAD_OPS_H__
+#define __SOCKET_OFFLOAD_OPS_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <sys/types.h>
+#include <net/net_ip.h>
+#include <net/socket.h>  /* needed for struct pollfd */
+
+/*
+ * It is assumed that these offload functions follow the
+ * POSIX socket API standard for arguments, return values and setting of errno.
+ */
+struct socket_offload {
+	/* POSIX Socket Functions: */
+	int (*socket)(int family, int type, int proto);
+	int (*close)(int sock);
+	int (*accept)(int sock, struct sockaddr *addr, socklen_t *addrlen);
+	int (*bind)(int sock, const struct sockaddr *addr, socklen_t addrlen);
+	int (*listen)(int sock, int backlog);
+	int (*connect)(int sock, const struct sockaddr *addr,
+		       socklen_t addrlen);
+	int (*poll)(struct pollfd *fds, int nfds, int timeout);
+	int (*setsockopt)(int sock, int level, int optname,
+			  const void *optval, socklen_t optlen);
+	int (*getsockopt)(int sock, int level, int optname, void *optval,
+			  socklen_t *optlen);
+	ssize_t (*recv)(int sock, void *buf, size_t max_len, int flags);
+	ssize_t (*recvfrom)(int sock, void *buf, short int len,
+			    short int flags, struct sockaddr *from,
+			    socklen_t *fromlen);
+	ssize_t (*send)(int sock, const void *buf, size_t len, int flags);
+	ssize_t (*sendto)(int sock, const void *buf, size_t len, int flags,
+			  const struct sockaddr *to, socklen_t tolen);
+};
+
+extern void socket_offload_register(const struct socket_offload *ops);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __SOCKET_OFFLOAD_OPS_H__ */

subsys/net/lib/sockets/CMakeLists.txt

@@ -4,4 +4,5 @@ zephyr_sources(
   sockets.c
   )
 
-zephyr_sources_ifdef(CONFIG_NET_SOCKETS_SOCKOPT_TLS   sockets_tls.c)
+zephyr_sources_ifdef(CONFIG_NET_SOCKETS_SOCKOPT_TLS sockets_tls.c)
+zephyr_sources_ifdef(CONFIG_NET_SOCKETS_OFFLOAD     socket_offload.c)

subsys/net/lib/sockets/Kconfig

@@ -82,6 +82,20 @@ config NET_SOCKETS_TLS_MAX_CIPHERSUITES
 	  By default, all ciphersuites that are available in the system are
 	  available to the socket.
 
+config NET_SOCKETS_OFFLOAD
+	bool "Offload Socket APIs [EXPERIMENTAL]"
+	select NET_SOCKETS_POSIX_NAMES
+	help
+	  Enables direct offloading of socket operations to dedicated TCP/IP
+	  hardware.
+	  This feature is intended to save resources by bypassing the Zephyr
+	  TCP/IP stack in the case where there is only one network interface
+	  required in the system, providing full BSD socket offload capability.
+	  As a result, it bypasses any potential IP routing that Zephyr might
+	  provide between multiple network interfaces.
+	  See NET_OFFLOAD for a more deeply integrated approach which offloads
+	  from the net_context() API within the Zephyr IP stack.
+
 config NET_DEBUG_SOCKETS
 	bool "Debug BSD Sockets compatible API calls"
 	default y if NET_LOG_GLOBAL

subsys/net/lib/sockets/socket_offload.c

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2018 Linaro Limited.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <net/socket_offload.h>
+
+/* Only one provider may register socket operations upon boot. */
+const struct socket_offload *socket_ops;
+
+void socket_offload_register(const struct socket_offload *ops)
+{
+	__ASSERT_NO_MSG(ops);
+	__ASSERT_NO_MSG(socket_ops == NULL);
+
+	socket_ops = ops;
+}