- With ICMPv4 Type 3 Code 4 (fragmentation needed) to ICMPv6

  translation, adjust the MTU size for the difference between the IPv4
  and IPv6 header size.  MTU size is to increase with this adjustment,
  but turns high limit into ETHERMTU.

kame/sys/netinet6/natpt_trans.c

@@ -1,4 +1,4 @@
-/*	$KAME: natpt_trans.c,v 1.133 2002/07/02 15:29:01 fujisawa Exp $	*/
+/*	$KAME: natpt_trans.c,v 1.134 2002/07/05 06:27:13 fujisawa Exp $	*/
 
 /*
  * Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000 and 2001 WIDE Project.
@@ -43,6 +43,7 @@
 #include <sys/socket.h>
 #include <sys/syslog.h>
 
+#include <net/ethernet.h>		/* for #define ETHERMTU */
 #include <net/route.h>			/* for <netinet6/ip6_var.h> */
 
 #include <netinet/in.h>
@@ -1072,7 +1073,10 @@ natpt_icmp4Unreach(struct icmp *icmp4, struct icmp6_hdr *icmp6)
 		if (icmp4->icmp_nextmtu == 0)
 			icmp6->icmp6_mtu = IPV6_MMTU;	/* xxx */
 		else
-			icmp6->icmp6_mtu = ntohs(icmp4->icmp_nextmtu);	/* xxx */
+			icmp6->icmp6_mtu =
+				min(ETHERMTU,
+				    ntohs(icmp4->icmp_nextmtu) +
+				    (sizeof(struct ip6_hdr) - sizeof(struct ip)));
 		HTONL(icmp6->icmp6_mtu);
 		break;