On 1/12/15, 1:29 PM, Ben Greear wrote:
On 01/12/2015 11:22 AM, Mike Christie wrote:
On 1/9/15, 8:28 PM, Thomas Dwyer III wrote:
Hi folks,
I spent some time browsing through this forum but I was unable to find an
explanation for this comment referring to the disabled bind_src_by_address()
function in io.c:
*This is not supported for now, because it is not exactly what we want.*
*It also turns out that targets will send packets to other interfaces*
*causing all types of weird things to happen.*
I found several posts from people referring to this specific comment but I
did not find an explanation. Is it possible that the author of this comment
was referring to the ARP flux issue, which may cause a target to associate
the bound IP address with the MAC address from an interface other than the
one specified with SO_BINDTODEVICE? If so, I don't see how avoiding the
call to bind() solves this problem. I would appreciate a reply from anyone
who might know what "weird things" means in this context.
bind_src_by_address() only did a bind() and was expecting all traffic to flow
through the interface with the specified ip address. If you have multiple
interfaces on the same subnet, the network layer would send/recv on any of
them. This ended up causing issues with packets not getting sent/received or
received
in incorrect orders to the iscsi layers on the initiator/target side.
If you add additional routing logic based on source-addresses, then this method
will indeed
bind to a particular interface, so please leave that logic in place.
The basic problem, people wanted to solved was the case where they have
multiple interfaces on the same subnet. They then wanted to be able to
create iscsi connections/sessions through all those interfaces and have
the multipath layer round robin over them. If you just tried to do
bind() the network layer would send/recv over any of the interfaces on
the same subnet.
What additional logic can you add to make this work on a per connection
basis? I have seen where you can manually manipulate the routing table
to send all traffic through specific nics, but not where I can control
it on per connection level.
BINDTODEVICE is also very useful, of course, but it will not be so useful if
you have
multiple IPs on the same interface.
Did you mean subnet or interface? For subnet, we are currently using
BINDTODEVICE (no bind() or other calls) when we have multiple IPs on the
same subnet for the multipath case I described above.
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