2016-12-12 01:56:22

by James Lee

Subject: [PATCH v2] ipv4: Should use consistent conditional judgement for ip fragment in __ip_append_data and ip_finish_output

From: zheng li <[email protected]>

There is an inconsistent conditional judgement in __ip_append_data and
ip_finish_output functions, the variable length in __ip_append_data just
include the length of application's payload and udp header, don't include
the length of ip header, but in ip_finish_output use
(skb->len > ip_skb_dst_mtu(skb)) as judgement, and skb->len include the
length of ip header.

That causes some particular application's udp payload whose length is
between (MTU - IP Header) and MTU were fragmented by ip_fragment even
though the rst->dev support UFO feature.

Add the length of ip header to length in __ip_append_data to keep
consistent conditional judgement as ip_finish_output for ip fragment.

Signed-off-by: Zheng Li <[email protected]>
---
net/ipv4/ip_output.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 877bdb0..12a0149 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -936,7 +936,7 @@ static int __ip_append_data(struct sock *sk,
csummode = CHECKSUM_PARTIAL;

cork->length += length;
- if (((length > mtu) || (skb && skb_is_gso(skb))) &&
+ 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 &&
(sk->sk_type == SOCK_DGRAM) && !sk->sk_no_check_tx) {
--
2.7.4

2016-12-20 15:46:20

by David Miller

Subject: Re: [PATCH v2] ipv4: Should use consistent conditional judgement for ip fragment in __ip_append_data and ip_finish_output

From: Zheng Li <[email protected]>
Date: Mon, 12 Dec 2016 09:56:05 +0800

> From: zheng li <[email protected]>
>
> There is an inconsistent conditional judgement in __ip_append_data and
> ip_finish_output functions, the variable length in __ip_append_data just
> include the length of application's payload and udp header, don't include
> the length of ip header, but in ip_finish_output use
> (skb->len > ip_skb_dst_mtu(skb)) as judgement, and skb->len include the
> length of ip header.
>
> That causes some particular application's udp payload whose length is
> between (MTU - IP Header) and MTU were fragmented by ip_fragment even
> though the rst->dev support UFO feature.
>
> Add the length of ip header to length in __ip_append_data to keep
> consistent conditional judgement as ip_finish_output for ip fragment.
>
> Signed-off-by: Zheng Li <[email protected]>

Applied, thanks.