@@ -1,4 +1,4 @@
-/*	$NetBSD: in_offload.c,v 1.4 2011/04/14 15:53:36 yamt Exp $	*/
+/*	$NetBSD: in_offload.c,v 1.5 2011/04/25 22:11:31 yamt Exp $	*/
 
 /*-
  * Copyright (c)2005, 2006 YAMAMOTO Takashi,
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: in_offload.c,v 1.4 2011/04/14 15:53:36 yamt Exp $");
+__KERNEL_RCSID(0, "$NetBSD: in_offload.c,v 1.5 2011/04/25 22:11:31 yamt Exp $");
 
 #include <sys/param.h>
 #include <sys/mbuf.h>
@@ -203,42 +203,44 @@
 void
 ip_undefer_csum(struct mbuf *m, size_t hdrlen, int csum_flags)
 {
-	KASSERT(m->m_flags & M_PKTHDR);
-	KASSERT((m->m_pkthdr.csum_flags & csum_flags) == csum_flags);
+	const size_t iphdrlen = M_CSUM_DATA_IPv4_IPHL(m->m_pkthdr.csum_data);
 	uint16_t csum;
 	uint16_t ip_len;
 	uint16_t *csump;
-	size_t iphdrlen;
 
+	KASSERT(m->m_flags & M_PKTHDR);
+	KASSERT((m->m_pkthdr.csum_flags & csum_flags) == csum_flags);
+
 	if (__predict_true(hdrlen + sizeof(struct ip) <= m->m_len)) {
 		struct ip *ip = (struct ip *)(mtod(m, uint8_t *) + hdrlen);
+
 		ip_len = ip->ip_len;
-		iphdrlen = ip->ip_hl << 2;
 		csump = &ip->ip_sum;
 	} else {
-		uint8_t ip_vhl;
-		const size_t ip_len_offset = hdrlen + offsetof(struct ip, ip_len);
-		m_copydata(m, hdrlen, sizeof(ip_vhl), &ip_vhl);
+		const size_t ip_len_offset =
+		    hdrlen + offsetof(struct ip, ip_len);
+
 		m_copydata(m, ip_len_offset, sizeof(ip_len), &ip_len);
-		iphdrlen = (ip_vhl & 0x0f) << 2;
 		csump = NULL;
 	}
+	ip_len = ntohs(ip_len);
 
 	if (csum_flags & M_CSUM_IPv4) {
-		const size_t offset = hdrlen + offsetof(struct ip, ip_sum);
 		csum = in4_cksum(m, 0, hdrlen, iphdrlen);
 		if (csump != NULL) {
 			*csump = csum;
 		} else {
+			const size_t offset = hdrlen +
+			    offsetof(struct ip, ip_sum);
+
 			m_copyback(m, offset, sizeof(uint16_t), &csum);
 		}
 	}
 
 	if (csum_flags & (M_CSUM_UDPv4|M_CSUM_TCPv4)) {
-		size_t l4offset = hdrlen
-		    + M_CSUM_DATA_IPv4_IPHL(m->m_pkthdr.csum_data);
+		size_t l4offset = hdrlen + iphdrlen;
 
-		csum = in4_cksum(m, 0, hdrlen + l4offset, ip_len - l4offset);
+		csum = in4_cksum(m, 0, l4offset, ip_len - l4offset - hdrlen);
 		if (csum == 0 && (csum_flags & M_CSUM_UDPv4) != 0)
 			csum = 0xffff;