netdev - Re: [PATCH] User mode linux bump maximum MTU tuntap interface [RESAND]

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Date:   Tue, 2 Jul 2019 15:47:13 +0100
From:   Anton Ivanov <anton.ivanov@...-begemot.co.uk>
To:     Richard Weinberger <richard.weinberger@...il.com>,
        Алексей <ne-vlezay80@...dex.ru>
Cc:     netdev@...r.kernel.org, linux-um@...ts.infradead.org
Subject: Re: [PATCH] User mode linux bump maximum MTU tuntap interface
 [RESAND]



On 02/07/2019 15:40, Richard Weinberger wrote:
> CC'ing um folks.
> 
> On Tue, Jul 2, 2019 at 3:01 PM Алексей <ne-vlezay80@...dex.ru> wrote:
>>
>> Hello, the parameter  ETH_MAX_PACKET limited to 1500 bytes is the not
>> support jumbo frames.
>>
>> This patch change ETH_MAX_PACKET the 65535 bytes to jumbo frame support
>> with user mode linux tuntap driver.
>>
>>
>> PATCH:
>>
>> -------------------
>>
>>
>> diff -ruNP ../linux_orig/linux-5.1/arch/um/include/shared/net_user.h
>> ./arch/um/include/shared/net_user.h
>> --- a/arch/um/include/shared/net_user.h    2019-05-06 00:42:58.000000000
>> +0000
>> +++ b/arch/um/include/shared/net_user.h    2019-07-02 07:14:13.593333356
>> +0000
>> @@ -9,7 +9,7 @@
>>   #define ETH_ADDR_LEN (6)
>>   #define ETH_HEADER_ETHERTAP (16)
>>   #define ETH_HEADER_OTHER (26) /* 14 for ethernet + VLAN + MPLS for
>> crazy people */
>> -#define ETH_MAX_PACKET (1500)
>> +#define ETH_MAX_PACKET (65535)
>>
>>   #define UML_NET_VERSION (4)
>>
>> -------------------
>>
>>
> 
> 

The vector version for tap already allows mtu > 1500. It does not have a 
check to limit it to 65535 max though and it should.

I will add this one to the queue of stuff for the network drivers. IMHO 
we should start migrating some of the older ones to vector IO.

-- 
Anton R. Ivanov
https://www.kot-begemot.co.uk/