linux-kernel - Re: [PATCH] openvswitch: Fix L4 checksum handling when dealing with IP fragments

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Message-ID: <CALnjE+p-y8i5h1Dnk0BHnhdq94Ndys=uQ=UXy3uLWmNA48SeJg@mail.gmail.com>
Date:	Mon, 3 Aug 2015 09:25:53 -0700
From:	Pravin Shelar <pshelar@...ira.com>
To:	Glenn Griffin <ggriffin.kernel@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	"dev@...nvswitch.org" <dev@...nvswitch.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] openvswitch: Fix L4 checksum handling when dealing with
 IP fragments

On Sat, Aug 1, 2015 at 6:31 PM, Glenn Griffin <ggriffin.kernel@...il.com> wrote:
> openvswitch modifies the L4 checksum of a packet when modifying
> the ip address. When an IP packet is fragmented only the first
> fragment contains an L4 header and checksum. Prior to this change
> openvswitch would modify all fragments, modifying application data
> in non-first fragments, causing checksum failures in the
> reassembled packet.
>
> Signed-off-by: Glenn Griffin <ggriffin.kernel@...il.com>

Patch looks good. I have one following comment.
> ---
>  net/openvswitch/actions.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
> index 8a8c0b8..bfffb1a 100644
> --- a/net/openvswitch/actions.c
> +++ b/net/openvswitch/actions.c
> @@ -273,28 +273,36 @@ static int set_eth_addr(struct sk_buff *skb, struct sw_flow_key *flow_key,
>         return 0;
>  }
>
> -static void set_ip_addr(struct sk_buff *skb, struct iphdr *nh,
> -                       __be32 *addr, __be32 new_addr)
> +static void update_ip_l4_checksum(struct sk_buff *skb, struct iphdr *nh,
> +                                 __be32 addr, __be32 new_addr)
>  {
>         int transport_len = skb->len - skb_transport_offset(skb);
>
> +       if (ntohs(nh->frag_off) & IP_OFFSET)
> +               return;

It is efficient to check frag-offset in network byte order.
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