lwip: Route LWIP socket POSIX I/O functions via IDF VFS layer

No more conflicts between LWIP & newlib read(), write(), fcntl(), etc.

select() still only works if all of the fds are sockets.

Closes https://github.com/espressif/esp-idf/issues/273

components/lwip/include/lwip/port/arch/sys_arch.h

@@ -37,6 +37,7 @@
 #include "freertos/task.h"
 #include "freertos/queue.h"
 #include "freertos/semphr.h"
+#include "arch/vfs_lwip.h"
 
 #ifdef __cplusplus
 extern "C" {

components/lwip/include/lwip/port/arch/vfs_lwip.h

@@ -0,0 +1,28 @@
+// Copyright 2017 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Internal declarations used to ingreate LWIP port layer
+   to ESP-IDF VFS for POSIX I/O.
+*/
+extern unsigned lwip_socket_offset;
+
+void esp_vfs_lwip_sockets_register();
+
+#ifdef __cplusplus
+}
+#endif

components/lwip/include/lwip/port/lwipopts.h

@@ -34,6 +34,7 @@
 
 #include <stdlib.h>
 #include <time.h>
+#include <unistd.h>
 #include <sys/time.h>
 #include <sys/fcntl.h>
 #include "esp_task.h"
@@ -687,6 +688,19 @@
 #define ETHARP_TRUST_IP_MAC             CONFIG_LWIP_ETHARP_TRUST_IP_MAC
 
 
+/**
+ * POSIX I/O functions are mapped to LWIP via the VFS layer
+ * (see port/vfs_lwip.c)
+ */
+#define LWIP_POSIX_SOCKETS_IO_NAMES     0
+
+
+/**
+ * Socket offset is also determined via the VFS layer at
+ * filesystem registration time (see port/vfs_lwip.c)
+ */
+#define LWIP_SOCKET_OFFSET              lwip_socket_offset
+
 /* Enable all Espressif-only options */
 
 #define ESP_LWIP                        1

components/lwip/port/freertos/sys_arch.c

@@ -433,6 +433,7 @@ sys_init(void)
     if (ERR_OK != sys_mutex_new(&g_lwip_protect_mutex)) {
         ESP_LOGE(TAG, "sys_init: failed to init lwip protect mutex\n");
     }
+    esp_vfs_lwip_sockets_register();
 }
 
 /*-----------------------------------------------------------------------------------*/

components/lwip/port/vfs_lwip.c

@@ -0,0 +1,78 @@
+// Copyright 2017 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <string.h>
+#include <stdbool.h>
+#include <stdarg.h>
+#include <sys/errno.h>
+#include <sys/lock.h>
+#include <sys/fcntl.h>
+#include "esp_vfs.h"
+#include "esp_vfs_dev.h"
+#include "esp_attr.h"
+#include "soc/uart_struct.h"
+#include "lwip/sockets.h"
+#include "sdkconfig.h"
+
+/* LWIP is a special case for VFS use.
+
+   From the LWIP side:
+   - We set LWIP_SOCKET_OFFSET dynamically at VFS registration time so that native LWIP socket functions & VFS functions
+   see the same fd space. This is necessary to mix POSIX file operations defined in VFS with POSIX socket operations defined
+   in LWIP, without needing to wrap all of them.
+
+   From the VFS side:
+   - ESP_VFS_FLAG_SHARED_FD_SPACE is set, so unlike other VFS implementations the FDs that the LWIP "VFS" sees and the
+   FDs that the user sees are the same FDs.
+*/
+
+unsigned lwip_socket_offset;
+
+static int lwip_fcntl_r_wrapper(int fd, int cmd, va_list args);
+static int lwip_ioctl_r_wrapper(int fd, int cmd, va_list args);
+
+void esp_vfs_lwip_sockets_register()
+{
+    esp_vfs_t vfs = {
+        .fd_offset = 0,
+        .flags = ESP_VFS_FLAG_DEFAULT | ESP_VFS_FLAG_SHARED_FD_SPACE,
+        .write = &lwip_write_r,
+        .open = NULL,
+        .fstat = NULL,
+        .close = &lwip_close_r,
+        .read = &lwip_read_r,
+        .fcntl = &lwip_fcntl_r_wrapper,
+        .ioctl = &lwip_ioctl_r_wrapper,
+    };
+    unsigned max_fd;
+
+    ESP_ERROR_CHECK(esp_vfs_register_socket_space(&vfs, NULL, &lwip_socket_offset, &max_fd));
+
+    /* LWIP can't be allowed to create more sockets than fit in the per-VFS fd space. Currently this isn't configurable
+     * but it's set much larger than CONFIG_LWIP_MAX_SOCKETS should ever be (max 2^12 FDs).
+     */
+    assert(CONFIG_LWIP_MAX_SOCKETS <= max_fd - lwip_socket_offset);
+}
+
+static int lwip_fcntl_r_wrapper(int fd, int cmd, va_list args)
+{
+    return lwip_fcntl_r(fd, cmd, va_arg(args, int));
+}
+
+static int lwip_ioctl_r_wrapper(int fd, int cmd, va_list args)
+{
+    return lwip_ioctl_r(fd, cmd, va_arg(args, void *));
+}
+
+