ws: add workaround for Komodia based LSPs that break SIO_BASE_HANDLE

src/ws.c

@@ -1,9 +1,14 @@
 #include <stdlib.h>
 
 #include "error.h"
+#include "util.h"
 #include "win.h"
 #include "ws.h"
 
+#ifndef SIO_BSP_HANDLE_POLL
+#define SIO_BSP_HANDLE_POLL 0x4800001D
+#endif
+
 #ifndef SIO_BASE_HANDLE
 #define SIO_BASE_HANDLE 0x48000022
 #endif
@@ -19,20 +24,54 @@ int ws_global_init(void) {
   return 0;
 }
 
-SOCKET ws_get_base_socket(SOCKET socket) {
+static inline SOCKET ws__ioctl_get_bsp_socket(SOCKET socket, DWORD ioctl) {
-  SOCKET base_socket;
+  SOCKET bsp_socket;
   DWORD bytes;
 
   if (WSAIoctl(socket,
-               SIO_BASE_HANDLE,
+               ioctl,
                NULL,
                0,
-               &base_socket,
+               &bsp_socket,
-               sizeof base_socket,
+               sizeof bsp_socket,
                &bytes,
                NULL,
-               NULL) == SOCKET_ERROR)
+               NULL) != SOCKET_ERROR)
-    return_map_error(INVALID_SOCKET);
+    return bsp_socket;
-
+  else
-  return base_socket;
+    return INVALID_SOCKET;
+}
+
+SOCKET ws_get_base_socket(SOCKET socket) {
+  SOCKET base_socket;
+  DWORD error;
+
+  for (;;) {
+    base_socket = ws__ioctl_get_bsp_socket(socket, SIO_BASE_HANDLE);
+    if (base_socket != INVALID_SOCKET)
+      return base_socket;
+
+    error = GetLastError();
+    if (error == WSAENOTSOCK)
+      return_set_error(INVALID_SOCKET, error);
+
+    /* clang-format off */
+    /* Even though Microsoft documentation clearly states that LSPs should
+     * never intercept the `SIO_BASE_HANDLE` ioctl [1], Komodia based LSPs do
+     * so anyway, breaking it, with the apparent intention of preventing LSP
+     * bypass [2]. Fortunately they don't handle `SIO_BSP_HANDLE_POLL`, which
+     * we can use to obtain the socket associated with the next protocol chain
+     * entry. If this succeeds, loop around and call `SIO_BASE_HANDLE` again
+     * with the retrieved BSP socket to be sure that we actually got all the
+     * way to the base.
+     *  [1] https://docs.microsoft.com/en-us/windows/win32/winsock/winsock-ioctls
+     *  [2] https://www.komodia.com/newwiki/index.php?title=Komodia%27s_Redirector_bug_fixes#Version_2.2.2.6
+     */
+    /* clang-format on */
+    base_socket = ws__ioctl_get_bsp_socket(socket, SIO_BSP_HANDLE_POLL);
+    if (base_socket != INVALID_SOCKET && base_socket != socket)
+      socket = base_socket;
+    else
+      return_set_error(INVALID_SOCKET, error);
+  }
 }