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From:   William Tu <u9012063@gmail.com>
Date:   Thu, 3 Oct 2019 11:29:24 -0700
Message-ID: <CALDO+SYz1NkyeJvfGr17nMHmG-grWakDhJB6cFvXKn2Zy4c5hg@mail.gmail.com>
Subject: Re: [PATCH] erspan: remove the incorrect mtu limit for erspan
To:     Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Cc:     "David S. Miller" <davem@davemloft.net>,
        Linux Kernel Network Developers <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Thu, Sep 26, 2019 at 11:59 PM Haishuang Yan
<yanhaishuang@cmss.chinamobile.com> wrote:
>
> erspan driver calls ether_setup(), after commit 61e84623ace3
> ("net: centralize net_device min/max MTU checking"), the range
> of mtu is [min_mtu, max_mtu], which is [68, 1500] by default.
>
> It causes the dev mtu of the erspan device to not be greater
> than 1500, this limit value is not correct for ipgre tap device.
>
> Tested:
> Before patch:
> # ip link set erspan0 mtu 1600
> Error: mtu greater than device maximum.
> After patch:
> # ip link set erspan0 mtu 1600
> # ip -d link show erspan0
> 21: erspan0@NONE: <BROADCAST,MULTICAST> mtu 1600 qdisc noop state DOWN
> mode DEFAULT group default qlen 1000
>     link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 0
>
> Fixes: 61e84623ace3 ("net: centralize net_device min/max MTU checking")
> Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
> ---

Thanks for the patch!
Acked-by: William Tu <u9012063@gmail.com>


>  net/ipv4/ip_gre.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
> index a53a543..52690bb 100644
> --- a/net/ipv4/ip_gre.c
> +++ b/net/ipv4/ip_gre.c
> @@ -1446,6 +1446,7 @@ static void erspan_setup(struct net_device *dev)
>         struct ip_tunnel *t = netdev_priv(dev);
>
>         ether_setup(dev);
> +       dev->max_mtu = 0;
>         dev->netdev_ops = &erspan_netdev_ops;
>         dev->priv_flags &= ~IFF_TX_SKB_SHARING;
>         dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
> --
> 1.8.3.1
>
>
>