On 17 Jul 2006, at 4:15pm, Dong-Hai Han wrote:
It's also the case that this newer version of the code will
loopback
packets that are not accepted for transmission by the MAC driver
(the
loopback happens before the packets are passed down). This differs
from the older code, where the loopback occurred only if the MAC
driver accepted the packets.
Yes, it's changed. Mike and I have dicussed it, our conclusion is
that:
1. Even if MAC driver returns OK, it doesn't mean that the packet
is safe on
the line, or even being sent out.
Whilst this is true, the proposed behaviour does not match what is
generally accepted (or what I wrote). In most instances, if the tx
function indicates that it has accepted the packet, then it's
reasonable to assume that it's queued for transmission.
If we go the way you propose, it seems that snoop could see a variety
of packets that are not accepted for transmission by the driver.
This would be very confusing for an administrator.
2. For xen case, when domUs are communicating with each other, does
it make sense to cut the virtual link when the packet can't go
through the
physical link?
I don't follow this comment, sorry.
With the current Xen backend driver, if the backend and frontend are
not both in the 'Connected' state then attempts to transmit packets
via the backend driver fail. Similarly, if snoop is monitoring the
backend interface before the backend and frontend are both
'Connected' it doesn't see any packets reflected back.
dme.
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