Re: [Qemu-devel] -net interface association behavior change in current -git.

[Jan Kiszka]

On 2011-05-13 03:49, Rob Landley wrote:
> On 05/12/2011 08:19 PM, Vincent Palatin wrote:
>>>> First of all, as you have 2 totally separated subnets in your setup, I
>>>> think your command-line should use "vlan=" parameter to isolate them,
>>>> else you will end up with some random routing/broadcasting (and random
>>>> tends to change over time).
>>>
>>> Does the kernel need some sort of vlan support compiled into it for this
>>> to work, or can the kernel not care?
>>
>> You don't need anything in your kernel, this is for Qemu network layer
>> configuration.
> 
> Oh good.  (The kernel has a couple different VLAN config options, plus
> cisco has vlan stuff in its routers...  I've been trying not to get any
> of this complexity on me.)
> 
>>>> In my understanding, the Linux kernel might assign interface number
>>>> depending on the order the interfaces are appearing.
>>>
>>> It's going in PCI bus order.  And the _interfaces_ are still happily in
>>> PCI bus order both before and after this commit.  What's changing is the
>>> association between interface and -net user or -net tap.
>>>
>>> The first one, with macaddr 11:11:11, is always eth0.  But before the
>>> patch, eth0 is -net user, and after the patch eth0 is -net tap.
>>
>> So, did you try the vlan parameter which is supposed to associate each
>> interface with the proper thing (IMO the command line order should not
>> have anything to do with it) ?
> 
> Apparently you cannot stick a vlan on -redir, and if you do the error
> message is a bit funky (cannot initialize -net user).  Good to know...
> 
> Yup, that fixed it.  Thanks.
> 
> By the way, does -redir only apply to -net user?

-redir (like all the other free-standing usernet switches) is legacy as
it can only be applied to a single usernet instance. And it's highly
confusing to which it refers. That's also documented in the man page.

>  Actually, reading qemu
> --help it looks like I should be using hostfwd= but the documentation on
> that is REALLY WEIRD:
> 
>   This option can not be given multiple times, but multiple rules may
>   be combined.

Where did you find this? A quick grep did not reveal the location to me.
qemu-options.hx states it clearly:

@item hostfwd=[tcp|udp]:
[...]
This option can be given multiple times.

Jan

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