diff --git a/lib/ChangeLog b/lib/ChangeLog
index b662aed..f5471b4 100644
--- a/lib/ChangeLog
+++ b/lib/ChangeLog
@@ -1,3 +1,11 @@
+2004-11-15  Greg Troxel  <gdt@fnord.ir.bbn.com>
+
+	* sockopt.h: Avoid CMSG_ALIGN, and declare that sizes are without
+	alignment (users should use CMSG_SPACE).
+
+	* zebra.h: Rationalize CMSG_SPACE compatibility defines.  Warn if
+	asumming 4-byte alignment, since this isn't safe.
+
 2004-11-15 Andrew J. Schorr <ajschorr@alumni.princeton.edu>
 
 	* memory.c: (zerror) Use zlog_err instead of fprintf to stderr.
diff --git a/lib/sockopt.h b/lib/sockopt.h
index bec2616..df199c1 100644
--- a/lib/sockopt.h
+++ b/lib/sockopt.h
@@ -44,7 +44,7 @@
  * Size defines for control messages used to get ifindex.  We define
  * values for each method, and define a macro that can be used by code
  * that is unaware of which method is in use.
- * XXX Needs to use CMSG_DATA and CMSG_ALIGN.
+ * These values are without any alignment needed (see CMSG_SPACE in RFC3542).
  */
 #if defined (IP_PKTINFO)
 /* Linux in_pktinfo. */
@@ -61,8 +61,7 @@
 #if defined (SUNOS_5)
 #define SOPT_SIZE_CMSG_RECVIF_IPV4()  (sizeof (uint_t))
 #else
-#define SOPT_SIZE_CMSG_RECVIF_IPV4()	\
-	__CMSG_ALIGN((sizeof (struct sockaddr_dl)))
+#define SOPT_SIZE_CMSG_RECVIF_IPV4()	(sizeof (struct sockaddr_dl))
 #endif /* SUNOS_5 */
 #endif /* IP_RECVIF */
 
diff --git a/lib/zebra.h b/lib/zebra.h
index 6980529..f2c396d 100644
--- a/lib/zebra.h
+++ b/lib/zebra.h
@@ -210,7 +210,13 @@
 #endif /* BSDI_NRL */
 
 /* 
- * RFC 2553-bis defines not available on some systems.
+ * RFC 3542 defines several macros for using struct cmsghdr.
+ * Here, we define those that are not present
+ */
+
+/*
+ * Internal defines, for use only in this file.
+ * These are likely wrong on other than ILP32 machines, so warn.
  */
 #ifndef _CMSG_DATA_ALIGN
 #define _CMSG_DATA_ALIGN(n)           (((n) + 3) & ~3)
@@ -220,16 +226,24 @@
 #define _CMSG_HDR_ALIGN(n)            (((n) + 3) & ~3)
 #endif /* _CMSG_HDR_ALIGN */
 
+/*
+ * CMSG_SPACE and CMSG_LEN are required in RFC3542, but were new in that
+ * version.
+ */
 #ifndef CMSG_SPACE
 #define CMSG_SPACE(l)       (_CMSG_DATA_ALIGN(sizeof(struct cmsghdr)) + \
                               _CMSG_HDR_ALIGN(l))
+#warning "assuming 4-byte alignment for CMSG_SPACE"
 #endif  /* CMSG_SPACE */
 
 
 #ifndef CMSG_LEN
 #define CMSG_LEN(l)         (_CMSG_DATA_ALIGN(sizeof(struct cmsghdr)) + (l))
+#warning "assuming 4-byte alignment for CMSG_LEN"
 #endif /* CMSG_LEN */
 
+
+
 #if !(defined(__GNUC__) || defined(VTYSH_EXTRACT_PL)) 
 #define __attribute__(x)
 #endif  /* !__GNUC__ */