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

[Eric Joyner]

Could you reply to that issue with what you've found?

Though, as far as I can recall, igb(4) devices are not supposed to do
the iflib reset talked about in the bug, so I wouldn't expect to see a link
flap on those.

- Eric

On Fri, Nov 6, 2020 at 12:48 PM mike tancsa <mike at sentex.net> wrote:

> On 11/6/2020 2:17 PM, mike tancsa wrote:
> > 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 :(
>
>
> Looks like this is captured in
>
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=240818
>
>
> > 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
> >
> >
> >
> >
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