+void *sk_getxdmdata(void *sock, int *lenp);
+
+/*
+ * Function provided by front ends, and called by uxnet.c to indicate
+ * that net_pending_errors() would like to be called back when the
+ * front end has a spare moment and isn't deep in any other recursion.
+ */
+void frontend_net_error_pending(void);
+
+/*
+ * General helpful Unix stuff: more helpful version of the FD_SET
+ * macro, which also handles maxfd.
+ */
+#define FD_SET_MAX(fd, max, set) do { \
+ FD_SET(fd, &set); \
+ if (max < fd + 1) max = fd + 1; \
+} while (0)
+
+/*
+ * Exports from winser.c.
+ */
+extern Backend serial_backend;