diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 4acdb63495db..e6f931997996 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1193,11 +1193,35 @@ int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to,
 
 	fragheaderlen = sizeof(struct ipv6hdr) + rt->rt6i_nfheader_len +
 			(opt ? opt->opt_nflen : 0);
-	maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen - sizeof(struct frag_hdr);
+	maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen -
+		     sizeof(struct frag_hdr);
 
 	if (mtu <= sizeof(struct ipv6hdr) + IPV6_MAXPLEN) {
-		if (cork->length + length > sizeof(struct ipv6hdr) + IPV6_MAXPLEN - fragheaderlen) {
-			ipv6_local_error(sk, EMSGSIZE, fl6, mtu-exthdrlen);
+		unsigned int maxnonfragsize, headersize;
+
+		headersize = sizeof(struct ipv6hdr) +
+			     (opt ? opt->tot_len : 0) +
+			     (dst_allfrag(&rt->dst) ?
+			      sizeof(struct frag_hdr) : 0) +
+			     rt->rt6i_nfheader_len;
+
+		maxnonfragsize = (np->pmtudisc >= IPV6_PMTUDISC_DO) ?
+				 mtu : sizeof(struct ipv6hdr) + IPV6_MAXPLEN;
+
+		/* dontfrag active */
+		if ((cork->length + length > mtu - headersize) && dontfrag &&
+		    (sk->sk_protocol == IPPROTO_UDP ||
+		     sk->sk_protocol == IPPROTO_RAW)) {
+			ipv6_local_rxpmtu(sk, fl6, mtu - headersize +
+						   sizeof(struct ipv6hdr));
+			goto emsgsize;
+		}
+
+		if (cork->length + length > maxnonfragsize - headersize) {
+emsgsize:
+			ipv6_local_error(sk, EMSGSIZE, fl6,
+					 mtu - headersize +
+					 sizeof(struct ipv6hdr));
 			return -EMSGSIZE;
 		}
 	}
@@ -1222,12 +1246,6 @@ int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to,
 	 * --yoshfuji
 	 */
 
-	if ((length > mtu) && dontfrag && (sk->sk_protocol == IPPROTO_UDP ||
-					   sk->sk_protocol == IPPROTO_RAW)) {
-		ipv6_local_rxpmtu(sk, fl6, mtu-exthdrlen);
-		return -EMSGSIZE;
-	}
-
 	skb = skb_peek_tail(&sk->sk_write_queue);
 	cork->length += length;
 	if (((length > mtu) ||