Index: sys/mbuf.h
===================================================================
RCS file: /space2/ncvs/src/sys/sys/mbuf.h,v
retrieving revision 1.115
diff -u -p -r1.115 mbuf.h
--- sys/mbuf.h	26 Mar 2003 10:35:31 -0000	1.115
+++ sys/mbuf.h	26 Mar 2003 15:11:12 -0000
@@ -332,6 +332,15 @@ struct mbstat {
 #define	M_WRITABLE(m)	(!((m)->m_flags & M_RDONLY) && (!((m)->m_flags  \
 			    & M_EXT) || !MEXT_IS_REF(m)))
 
+
+/*
+ * Sanity check an mbuf chain containing a packet.
+ */
+#define M_PKTCHECK(m) do {						\
+	KASSERT((m)->m_flags & M_PKTHDR, ("no packet header"));		\
+	KASSERT((m)->m_pkthdr.len == m_length(m, NULL), ("bad header length"));\
+} while (0)
+
 /*
  * Set the m_data pointer of a newly-allocated mbuf (m_get/MGET) to place
  * an object of the specified size at the end of the mbuf, longword aligned.
Index: net/if_var.h
===================================================================
RCS file: /space2/ncvs/src/sys/net/if_var.h,v
retrieving revision 1.58
diff -u -p -r1.58 if_var.h
--- net/if_var.h	1 Jan 2003 18:48:54 -0000	1.58
+++ net/if_var.h	26 Mar 2003 15:33:16 -0000
@@ -229,6 +229,7 @@ typedef void if_init_f_t(void *);
 #define	_IF_QLEN(ifq)		((ifq)->ifq_len)
 
 #define	_IF_ENQUEUE(ifq, m) do { 				\
+	M_PKTCHECK(m);						\
 	(m)->m_nextpkt = NULL;					\
 	if ((ifq)->ifq_tail == NULL) 				\
 		(ifq)->ifq_head = m; 				\
@@ -245,6 +246,7 @@ typedef void if_init_f_t(void *);
 } while (0)
 
 #define	_IF_PREPEND(ifq, m) do {				\
+	M_PKTCHECK(m);						\
 	(m)->m_nextpkt = (ifq)->ifq_head; 			\
 	if ((ifq)->ifq_tail == NULL) 				\
 		(ifq)->ifq_tail = (m); 				\