2016-12-28 15:25:22

by James Lee

Subject: [PATCH] ipv6: Should use consistent conditional judgement for ip6 fragment between __ip6_append_data and ip6_finish_output

From: Zheng Li <[email protected]>

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 <[email protected]>
---
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 70d0de40..38122d0 100644
--- 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 &&
--
2.7.4

2016-12-29 16:55:47

by David Miller

Subject: Re: [PATCH] ipv6: Should use consistent conditional judgement for ip6 fragment between __ip6_append_data and ip6_finish_output

From: Zheng Li <[email protected]>
Date: Wed, 28 Dec 2016 23:23:46 +0800

> From: Zheng Li <[email protected]>
>
> 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 <[email protected]>

Applied, thank you.