MFC r265691:

For some UDP packets (for example with 200 byte payload) and IP options,
the IP header and the UDP header are not in the same mbuf.
Add code to in_delayed_cksum() to deal with this case.

MFC r265713:

Use KASSERTs as suggested by glebius@

1 files changed, 6 insertions, 10 deletions

diff --git a/sys/netinet/ip_output.c b/sys/netinet/ip_output.c
index 69832d4..c0a6ffd 100644
--- a/sys/netinet/ip_output.c
+++ b/sys/netinet/ip_output.c
@@ -864,17 +864,13 @@ in_delayed_cksum(struct mbuf *m)
 		csum = 0xffff;
 	offset += m->m_pkthdr.csum_data;	/* checksum offset */
 
-	if (offset + sizeof(u_short) > m->m_len) {
-		printf("delayed m_pullup, m->len: %d  off: %d  p: %d\n",
-		    m->m_len, offset, ip->ip_p);
-		/*
-		 * XXX
-		 * this shouldn't happen, but if it does, the
-		 * correct behavior may be to insert the checksum
-		 * in the appropriate next mbuf in the chain.
-		 */
-		return;
+	/* find the mbuf in the chain where the checksum starts*/
+	while ((m != NULL) && (offset >= m->m_len)) {
+		offset -= m->m_len;
+		m = m->m_next;
 	}
+	KASSERT(m != NULL, ("in_delayed_cksum: checksum outside mbuf chain."));
+	KASSERT(offset + sizeof(u_short) <= m->m_len, ("in_delayed_cksum: checksum split between mbufs."));
 	*(u_short *)(m->m_data + offset) = csum;
 }