--- lwip-2.0.2/src/include/lwip/sockets.h   (original)
+++ lwip-2.0.2/src/include/lwip/sockets.h   (patched)
@@ -47,6 +47,7 @@
 #include "lwip/err.h"
 #include "lwip/inet.h"
 #include "lwip/errno.h"
+#include "lwip/sys.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -157,6 +158,32 @@
   void         *msg_control;
   socklen_t     msg_controllen;
   int           msg_flags;
+};
+
+#if LWIP_NETCONN_SEM_PER_THREAD
+#define SELECT_SEM_T        sys_sem_t*
+#define SELECT_SEM_PTR(sem) (sem)
+#else /* LWIP_NETCONN_SEM_PER_THREAD */
+#define SELECT_SEM_T        sys_sem_t
+#define SELECT_SEM_PTR(sem) (&(sem))
+#endif /* LWIP_NETCONN_SEM_PER_THREAD */
+
+/** Description for a task waiting in select */
+struct lwip_select_cb {
+  /** Pointer to the next waiting task */
+  struct lwip_select_cb *next;
+  /** Pointer to the previous waiting task */
+  struct lwip_select_cb *prev;
+  /** readset passed to select */
+  fd_set *readset;
+  /** writeset passed to select */
+  fd_set *writeset;
+  /** unimplemented: exceptset passed to select */
+  fd_set *exceptset;
+  /** don't signal the same semaphore twice: set to 1 when signalled */
+  int sem_signalled;
+  /** semaphore to wake up a task waiting for select */
+  SELECT_SEM_T sem;
 };
 
 /* Socket protocol types (TCP/UDP/RAW) */