From: Ben Greear <greearb@candelatech•com>
To: WeipingPan <panweiping3@gmail•com>
Cc: herbert@gondor•hengli.com.au,
"open list:NETWORKING [GENERAL]" <netdev@vger•kernel.org>
Subject: Re: [PATCH net] vlan:make mtu of vlan equal to physical dev
Date: Tue, 18 Oct 2011 19:51:42 -0700 [thread overview]
Message-ID: <4E9E3B3E.2070902@candelatech.com> (raw)
In-Reply-To: <4E9E30B8.5030904@gmail.com>
On 10/18/2011 07:06 PM, WeipingPan wrote:
> Hi, Herbert,
>
> What do you think of this patch ?
>
> thanks
> Weiping Pan
> On 10/08/2011 06:12 PM, Weiping Pan wrote:
>> Default mtu of vlan device is the same with mtu of physical device,
>> for example 1500, but when change physics mtu to 1600,
>> VLAN device's mtu is still 1500.
>> Certainly, you can change vlan device's mtu to 1600 manually,
>> but I think when you change physics device's mtu, VLAN's mtu should be changed
>> automatically instead of by manually.
I don't like the idea. It's perfectly valid to have the physical dev with 9000 MTU
and have vlans with 1500 MTU.
>> Steps to Reproduce:
>> 1.vconfig add eth4 3
>> 2.ifconfig eth4 mtu 1600
>> 3.check mtu on eth4.3
>>
>> And what's worse is that if you decrease mtu of pyhsical device,
>> and when you want to increase it, the mtu of vlan device won't be changed.
That *might* be worth fixing, but even so, some NICs might handle that
just fine, so my opinion is that this should not change either.
Thanks,
Ben
>>
>> Steps to Reproduce:
>> 1.vconfig add eth4 3
>> 2.ifconfig eth4 mtu 100
>> 3.ifconfig eth4 mtu 1500
>> 4.the mtu of eth4.3 is still 100
>>
>> This bug is reported by Liang Zheng(lzheng@redhat•com).
>>
>> Signed-off-by: Weiping Pan<panweiping3@gmail•com>
>> ---
>> net/8021q/vlan.c | 3 ---
>> 1 files changed, 0 insertions(+), 3 deletions(-)
>>
>> diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
>> index 8970ba1..f6072b4 100644
>> --- a/net/8021q/vlan.c
>> +++ b/net/8021q/vlan.c
>> @@ -417,9 +417,6 @@ static int vlan_device_event(struct notifier_block *unused, unsigned long event,
>> if (!vlandev)
>> continue;
>>
>> - if (vlandev->mtu<= dev->mtu)
>> - continue;
>> -
>> dev_set_mtu(vlandev, dev->mtu);
>> }
>> break;
>
> --
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--
Ben Greear <greearb@candelatech•com>
Candela Technologies Inc http://www.candelatech.com
next prev parent reply other threads:[~2011-10-19 2:51 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-08 10:12 [PATCH net] vlan:make mtu of vlan equal to physical dev Weiping Pan
2011-10-10 4:00 ` David Miller
2011-10-19 2:06 ` WeipingPan
2011-10-19 2:51 ` Ben Greear [this message]
2011-10-21 14:48 ` Herbert Xu
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