Link flap when adding / removing a vlan (was Re: r360902 breaks VLAN interface on if_em (82579LM))

[mike tancsa]

On 5/31/2020 5:39 PM, Lev Serebryakov wrote:
> Hello Ian,
>
> Thursday, May 28, 2020, 2:45:48 AM, you wrote:
>
>> I noticed that my VLAN interfaces stopped working after a recent build. 
>> tcpdump showed traffic leaving leaving and entering the interface but no 
>> host on the network actually received any packets from this host.  A 
>> binary search led me to r360902 and indeed the following change fixed 
>> the issue for me:
>  Problem is, this change will return terrible situation when adding new VLAN
> will flap connection status.
>
>  It all worked before iflib: hardware VLAN filtering worked, and
> adding/removing new VLAN didn't cause link to flap.
>
>  Now, with iflib, looks like we can not have all good things at once :(

Hi All,

Just came across this thread as I am running into this behaviour on
RELENG_12.  Adding a new vlan causes all vlans on the parent interface
to flap. Not the greatest thing as it bounces a LOT of traffic
potentially, flaps routing etc.  Is there a way around this ?

This is on r367411 releng12

igb0 at pci0:2:0:0:        class=0x020000 card=0x153315d9 chip=0x15338086
rev=0x03 hdr=0x00
    vendor     = 'Intel Corporation'
    device     = 'I210 Gigabit Network Connection'
    class      = network
    subclass   = ethernet

eg. just something simple like

ifconfig vlan16 create 10.1.2.3/29 vlandev igb1 vlan 16

 # dmesg | tail -8
igb1: link state changed to DOWN
vlan16: link state changed to DOWN
vlan2049: link state changed to DOWN
vlan15: link state changed to DOWN
igb1: link state changed to UP
vlan16: link state changed to UP
vlan2049: link state changed to UP
vlan15: link state changed to UP


    ---Mike