netdev - Re: [PATCH net v2] net: vrf: Fix ping failed when vrf mtu is set to 0

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Date:   Mon, 8 Apr 2019 09:58:56 +0800
From:   linmiaohe <linmiaohe@...wei.com>
To:     David Ahern <dsa@...ulusnetworks.com>
CC:     Shrijeet Mukherjee <shrijeet@...il.com>, <davem@...emloft.net>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Mingfangsen <mingfangsen@...wei.com>
Subject: Re: [PATCH net v2] net: vrf: Fix ping failed when vrf mtu is set to 0



On 2019/4/7 22:30, David Ahern wrote:
> On 4/6/19 11:46 PM, linmiaohe wrote:
>> diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
>> index 7c1430ed0244..4d35d37f225a 100644
>> --- a/drivers/net/vrf.c
>> +++ b/drivers/net/vrf.c
>> @@ -43,6 +43,12 @@
>>
>>  #define FIB_RULE_PREF  1000       /* default preference for FIB rules */
>>
>> +/* The MTU is really irrelevant for VRF except for odd cases, so limit it
>> + * to a reasonable range which both works for IPV4 and IPV6.
>> + */
>> +#define VRF_MIN_MTU	1280      /* same as IPV6_MIN_MTU */
>> +#define VRF_MAX_MTU	0xFFFFU   /* same as IP_MAX_MTU */
> 
> Since VRF does not care about MTU, there is no reason for VRF specific
> macros.
> 
>> +
>>  static unsigned int vrf_net_id;
>>
>>  struct net_vrf {
>> @@ -1274,8 +1280,8 @@ static void vrf_setup(struct net_device *dev)
>>  	/* default to no qdisc; user can add if desired */
>>  	dev->priv_flags |= IFF_NO_QUEUE;
>>
>> -	dev->min_mtu = 0;
>> -	dev->max_mtu = 0;
>> +	dev->min_mtu = VRF_MIN_MTU;
>> +	dev->max_mtu = VRF_MAX_MTU;
> 
> Set these to IPV6_MIN_MTU and ETH_MAX_MTU and add a comment that VRF
> devices do not care about MTU, but if the MTU is set too low then the
> ipv4 and ipv6 protocols are disabled which breaks networking.
> 
> 

Thanks a lot for your advice. I will send v3 latter.