ipv6: Should use consistent conditional judgement for ip6 fragment between __ip6_append_data and ip6_finish_output

Zheng Li · davem330 · commit e4c5e13aa45c · 2016-12-29T11:55:17.000-05:00
There is an inconsistent conditional judgement between __ip6_append_data
and ip6_finish_output functions, the variable length in __ip6_append_data
just include the length of application's payload and udp6 header, don't
include the length of ipv6 header, but in ip6_finish_output use
(skb-&gt;len &gt; ip6_skb_dst_mtu(skb)) as judgement, and skb-&gt;len include the
length of ipv6 header.

That causes some particular application's udp6 payloads whose length are
between (MTU - IPv6 Header) and MTU were fragmented by ip6_fragment even
though the rst-&gt;dev support UFO feature.

Add the length of ipv6 header to length in __ip6_append_data to keep
consistent conditional judgement as ip6_finish_output for ip6 fragment.

Signed-off-by: Zheng Li &lt;james.z.li@ericsson.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
@@ -1373,7 +1373,7 @@ static int __ip6_append_data(struct sock *sk,
 	 */
 
 	cork->length += length;
-	if (((length > mtu) ||
+	if ((((length + fragheaderlen) > mtu) ||
 	     (skb && skb_is_gso(skb))) &&
 	    (sk->sk_protocol == IPPROTO_UDP) &&
 	    (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len &&
