netdev - Re: [PATCH] ipvlan: add the check of ip header checksum

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Date:   Tue, 21 Jul 2020 12:39:03 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     guodeqing <geffrey.guo@...wei.com>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Mahesh Bandewar <maheshb@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH] ipvlan: add the check of ip header checksum

On Tue, Jul 21, 2020 at 6:17 AM guodeqing <geffrey.guo@...wei.com> wrote:
>
> The ip header checksum can be error in the following steps.
> $ ip netns add ns1
> $ ip link add gw link eth0 type ipvlan
> $ ip addr add 168.16.0.1/24 dev gw
> $ ip link set dev gw up
> $ ip link add ip1 link eth0 type ipvlan
> $ ip link set ip1 netns ns1
> $ ip netns exec ns1 ip link set ip1 up
> $ ip netns exec ns1 ip addr add 168.16.0.2/24 dev ip1
> $ ip netns exec ns1 tc qdisc add dev ip1 root netem corrupt 50%
> $ ip netns exec ns1 ping 168.16.0.1
>
> The ip header of a packet maybe modified when it steps in
> ipvlan_process_v4_outbound because of the netem, the corruptted
> packets should be dropped.

This does not make much sense, as you intentionally corrupt
the header. More importantly, the check you add is too late, right?
ipvlan_xmit_mode_l3() already does the addr lookup with IP header,

Thanks.