[XFRM] STATE: Support non-fragment outbound transformation headers.

For originated outbound IPv6 packets which will fragment, ip6_append_data()
should know length of extension headers before sending them and
the length is carried by dst_entry.
IPv6 IPsec headers fragment then transformation was
designed to place all headers after fragment header.
OTOH Mobile IPv6 extension headers do not fragment then
it is a good idea to make dst_entry have non-fragment length to tell it
to ip6_append_data().

Signed-off-by: Masahide NAKAMURA <nakam@linux-ipv6.org>
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 2a376b7..258e3e4 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -971,7 +971,7 @@
 
 	hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
 
-	fragheaderlen = sizeof(struct ipv6hdr) + (opt ? opt->opt_nflen : 0);
+	fragheaderlen = sizeof(struct ipv6hdr) + rt->u.dst.nfheader_len + (opt ? opt->opt_nflen : 0);
 	maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen - sizeof(struct frag_hdr);
 
 	if (mtu <= sizeof(struct ipv6hdr) + IPV6_MAXPLEN) {