diff --git a/libnetutil/netutil.cc b/libnetutil/netutil.cc
index b75c8dfac..5128736ba 100644
--- a/libnetutil/netutil.cc
+++ b/libnetutil/netutil.cc
@@ -111,6 +111,26 @@
 #endif
 #include <net/if_arp.h>
 
+/* Define CMSG_* symbols for Solaris 9 and earlier. See
+   http://wiki.opencsw.org/porting-faq#toc10. */
+#if defined(__sun) || defined(__sun__)
+# ifndef CMSG_ALIGN
+#   ifdef __sun__
+#     define CMSG_ALIGN(len) _CMSG_DATA_ALIGN (len)
+#   else
+      /* aligning to sizeof (long) is assumed to be portable (fd.o#40235) */
+#     define CMSG_ALIGN(len) (((len) + sizeof (long) - 1) & ~(sizeof (long) - 1))
+#   endif
+# endif
+# ifndef CMSG_SPACE
+#   define CMSG_SPACE(len) (CMSG_ALIGN (sizeof (struct cmsghdr)) + CMSG_ALIGN (len))
+# endif
+# ifndef CMSG_LEN
+#   define CMSG_LEN(len) (CMSG_ALIGN (sizeof (struct cmsghdr)) + (len))
+# endif
+#endif /* Solaris */
+
+
 #if HAVE_NETINET_IN_H
 #include <netinet/in.h>
 #endif