netdev - Re: [PATCH net] vrf: fix maximum MTU

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Date:   Tue, 8 Jun 2021 09:22:28 -0600
From:   David Ahern <dsahern@...il.com>
To:     Nicolas Dichtel <nicolas.dichtel@...nd.com>, davem@...emloft.net,
        kuba@...nel.org
Cc:     netdev@...r.kernel.org, Miaohe Lin <linmiaohe@...wei.com>
Subject: Re: [PATCH net] vrf: fix maximum MTU

On 6/8/21 8:59 AM, Nicolas Dichtel wrote:
> My initial goal was to fix the default MTU, which is set to 65536, ie above
> the maximum defined in the driver: 65535 (ETH_MAX_MTU).
> 
> In fact, it's seems more consistent, wrt min_mtu, to set the max_mtu to
> IP6_MAX_MTU (65535 + sizeof(struct ipv6hdr)) and use it by default.
> 
> Let's also, for consistency, set the mtu in vrf_setup(). This function
> calls ether_setup(), which set the mtu to 1500. Thus, the whole mtu config
> is done in the same function.
> 
> Before the patch:
> $ ip link add blue type vrf table 1234
> $ ip link list blue
> 9: blue: <NOARP,MASTER> mtu 65536 qdisc noop state DOWN mode DEFAULT group default qlen 1000
>     link/ether fa:f5:27:70:24:2a brd ff:ff:ff:ff:ff:ff
> $ ip link set dev blue mtu 65535
> $ ip link set dev blue mtu 65536
> Error: mtu greater than device maximum.
> 
> Fixes: 5055376a3b44 ("net: vrf: Fix ping failed when vrf mtu is set to 0")
> CC: Miaohe Lin <linmiaohe@...wei.com>
> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>
> ---
>  drivers/net/vrf.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@...il.com>