--- dist/pf/net/pf.orig.c	2007-09-22 17:43:14.000000000 +0300
+++ dist/pf/net/pf.c	2007-09-22 17:50:31.000000000 +0300
@@ -5057,9 +5057,6 @@
 	struct pf_addr		 naddr;
 	struct pf_src_node	*sn = NULL;
 	int			 error = 0;
-#ifdef __NetBSD__
-	struct tcphdr		 th;
-#endif
 
 	if (m == NULL || *m == NULL || r == NULL ||
 	    (dir != PF_IN && dir != PF_OUT) || oifp == NULL)
@@ -5178,10 +5175,10 @@
 		}
 	}
 #else
-	m_copydata(m0, sizeof(*ip), sizeof(th), &th);
-	th.th_sum = 0;
-	m_copyback(m0, sizeof(*ip), sizeof(th), &th);
-	in4_cksum(m0, IPPROTO_TCP, sizeof(*ip), m0->m_pkthdr.len - sizeof(*ip));
+	if (m0->m_pkthdr.csum_flags & (M_CSUM_TCPv4|M_CSUM_UDPv4)) {
+		 in_delayed_cksum(m0);
+		 m0->m_pkthdr.csum_flags &= ~(M_CSUM_TCPv4|M_CSUM_UDPv4);
+	}
 #endif
 
 	if (ntohs(ip->ip_len) <= ifp->if_mtu) {