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Re: [Xen-devel] xen-netback notify DomU to send ARP.

On 2013-1-8 21:42, Ian Campbell wrote:
On Tue, 2013-01-08 at 13:13 +0000, Jan Beulich wrote:
On 08.01.13 at 12:57, jianhai luan <jianhai.luan@xxxxxxxxxx> wrote:
ÂÂÂ When Xen Dom0's network circumstance changed, DomU
should be notified in some special condition. For
example the below circumstance:
ÂÂÂ ping from Guest A to DomU:
ÂÂÂ Guest A --> eth0 - bond0 - xenbr0 --VIF(DOMU)
ÂÂÂ when eth0 inactive, and eth1 active.
How is eth0 failing? Are you unplugging it, un-enslaving it or taking
some other sort of administrative action?
In my emulation environment, i unplug it or ifdown the interface, while eth0 maybe wrong in productive environment.

Which bonding mode are you using?
Bond running in active-backup mode.

Doesn't this state change cause the switch to which eth0 and eth1 are
attached to forget the MAC tables associated with the eth0 port, meaning
that subsequent traffic will be flooded until it learns that eth1 is the
new port?

ÂÂÂ Guest A --> eth0ÂÂ bond0 - xenbr0 --VIF(DOMU)
ÂÂÂ Guest A will don't reach to DomU. After Guest A
ÂÂÂ send ARP request and DomU respond, Guest A will
ÂÂÂ reach DomU. But some more second will be elapsed.
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ eth0ÂÂ bond0 - xenbr0 --VIF(DOMU)
ÂÂÂ Guest A --> eth1/
Isn't a change to the availability of the bonds supposed to be
transparent to Guest A _and_ DomU? I.e. aren't you trying to fix
an eventual problem here in the wrong place?
In non-virtualised bonding the bonding drive can take care of some of
this because it knows its own MAC address and can send appropriate
gratuitous frames (depends on the bonding mode) to paper over things. In
the virtualised case it (most likely) doesn't know VIF(DOMU)s MAC
 If you have know all ip and mac before modprobe bond, you can configure the bond argument. But you don't know all ip and mac before start new virtual.
 If bond want to know all DomU's ip and mac which pass through, it must check all skb. it's not good idea.

If Xen netback watch the network change, will notify
DomU by change it own status. So netfront will watch
netback's change, and DomU send ARP initiative.
Your patch is, at least according to what I see, completely
unusable - line breaks dropped, line order reversed, and
(guessing) some UTF-16/UCS-2 characters inserted at the top.
Please attach patches as plain ASCII.
ÂFrom the name it looks to me like it is the vi temp file created while
you have the file open rather than the actual patch file...



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