From: Zheng Li <james.z.li@xxxxxxxxxxxx> [ Upstream commit e4c5e13aa45c23692e4acf56f0b3533f328199b2 ] 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->len > ip6_skb_dst_mtu(skb)) as judgement, and skb->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->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 <james.z.li@xxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx> --- net/ipv6/ip6_output.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index fd649599620e..5a4b8e7bcedd 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1376,7 +1376,7 @@ 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 && -- 2.11.0