+#ifndef __dead
+# define __dead __attribute__((noreturn))
+#endif
+
+#if !defined(HAVE_ATTRIBUTE__SENTINEL__) && !defined(__sentinel__)
+# define __sentinel__
+#endif
+
+#if !defined(HAVE_ATTRIBUTE__BOUNDED__) && !defined(__bounded__)
+# define __bounded__(x, y, z)
+#endif
+
+#if !defined(HAVE_ATTRIBUTE__NONNULL__) && !defined(__nonnull__)
+# define __nonnull__(x)
+#endif
+
+/* *-*-nto-qnx doesn't define this macro in the system headers */
+#ifdef MISSING_HOWMANY
+# define howmany(x,y) (((x)+((y)-1))/(y))
+#endif
+
+#ifndef OSSH_ALIGNBYTES
+#define OSSH_ALIGNBYTES (sizeof(int) - 1)
+#endif
+#ifndef __CMSG_ALIGN
+#define __CMSG_ALIGN(p) (((u_int)(p) + OSSH_ALIGNBYTES) &~ OSSH_ALIGNBYTES)
+#endif
+
+/* Length of the contents of a control message of length len */
+#ifndef CMSG_LEN
+#define CMSG_LEN(len) (__CMSG_ALIGN(sizeof(struct cmsghdr)) + (len))
+#endif
+
+/* Length of the space taken up by a padded control message of length len */
+#ifndef CMSG_SPACE
+#define CMSG_SPACE(len) (__CMSG_ALIGN(sizeof(struct cmsghdr)) + __CMSG_ALIGN(len))
+#endif
+
+/* given pointer to struct cmsghdr, return pointer to data */
+#ifndef CMSG_DATA
+#define CMSG_DATA(cmsg) ((u_char *)(cmsg) + __CMSG_ALIGN(sizeof(struct cmsghdr)))
+#endif /* CMSG_DATA */
+
+/*
+ * RFC 2292 requires to check msg_controllen, in case that the kernel returns
+ * an empty list for some reasons.
+ */
+#ifndef CMSG_FIRSTHDR
+#define CMSG_FIRSTHDR(mhdr) \
+ ((mhdr)->msg_controllen >= sizeof(struct cmsghdr) ? \
+ (struct cmsghdr *)(mhdr)->msg_control : \
+ (struct cmsghdr *)NULL)
+#endif /* CMSG_FIRSTHDR */
+
+#if defined(HAVE_DECL_OFFSETOF) && HAVE_DECL_OFFSETOF == 0
+# define offsetof(type, member) ((size_t) &((type *)0)->member)
+#endif
+
+/* Set up BSD-style BYTE_ORDER definition if it isn't there already */
+/* XXX: doesn't try to cope with strange byte orders (PDP_ENDIAN) */
+#ifndef BYTE_ORDER
+# ifndef LITTLE_ENDIAN
+# define LITTLE_ENDIAN 1234
+# endif /* LITTLE_ENDIAN */
+# ifndef BIG_ENDIAN
+# define BIG_ENDIAN 4321
+# endif /* BIG_ENDIAN */
+# ifdef WORDS_BIGENDIAN
+# define BYTE_ORDER BIG_ENDIAN
+# else /* WORDS_BIGENDIAN */
+# define BYTE_ORDER LITTLE_ENDIAN
+# endif /* WORDS_BIGENDIAN */
+#endif /* BYTE_ORDER */