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Date: Fri, 18 Oct 2013 17:44:28 +0800
From: mike <qiudayu@linux.vnet.ibm.com>
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Subject: Re: [Qemu-devel] [PATCH v2] net/net: Change the default mac address
 of nic
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To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, aliguori@amazon.com, Stefan Weil <sw@weilnetz.de>

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On 10/18/2013 05:00 PM, Stefan Hajnoczi wrote:
> On Fri, Oct 18, 2013 at 10:54:13AM +0800, mike wrote:
>>> NACK
>>>
>>> I'm not going to merge this patch:
>>>
>>> If you terminate QEMU and launch it again the NIC gets a different MAC
>>> address.  Some guest operating systems are sensitive to this - under
>> For these users must use -device <nic-model>,mac=XX:XX:XX:XX:XX:XX.
>> I think no body will boot up the guest, which sensitive to this,
>> without mac address.
>>
>> Actually, people use the command line without mac address, mean they mainly
>> don't care about mac address, so give them random mac address is reasonable
>> I think.
>>
>> In my opinion, if we fix this, for qemu side no any issue, we both support
>> mac address set or unset correctly.
>>
>> What am I confuse is, *qemu supports mac address unset, why we force
>> users must set the address when more than one guests*?
>> This is unreasonable.
>>
>>> many Linux distros the network interfaces names change due to the MAC
>>> address change.  As a result firewall configuration will break and other
>>> services may fail to start because they cannot find the interface.
>> Agree, so this mac address should set in qemu command line as
>> libvirt does :)
>>> If you have multiple guests or want control over the MAC address, set it
>>> explicitly using -device <nic-model>,mac=XX:XX:XX:XX:XX:XX.
>> Currently, especially for developers, people mainly use qemu
>> command line directly, and as qemu supports mac address
>> unset, they may try the simplest command line to boot up
>> lots of guests, they will confuse about why all this guest use
>> the same mac address.
> Your argument is weak: *you* want to avoid specifying the MAC address so
> in exchange you want to *break* existing configurations and force other
> people to start specifying a MAC address.
OK, I do not want to break the existing configurations.

I'm fine if you do not want to merge this patch.

But I think this should be an issue of qemu, and need to
do something on it, so I make this patch.

Can we try other solutions to solve this issue?
(if you agree this should be an issue)

Also this potential issue can happens if the user set the same mac address
with more than one guest on one host.

Can we avoid this ?

Thanks
Mike
> This doesn't improve anything, it will just annoy users and cause bug
> reports.
>
> Sorry that there isn't a solution that satisfies everyone, you'll have
> to add a MAC address to your command-line.
>
> Stefan
>
>
>


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    <div class="moz-cite-prefix">On 10/18/2013 05:00 PM, Stefan Hajnoczi
      wrote:<br>
    </div>
    <blockquote
      cite="mid:20131018090044.GI9292@stefanha-thinkpad.redhat.com"
      type="cite">
      <pre wrap="">On Fri, Oct 18, 2013 at 10:54:13AM +0800, mike wrote:
</pre>
      <blockquote type="cite">
        <blockquote type="cite">
          <pre wrap="">NACK

I'm not going to merge this patch:

If you terminate QEMU and launch it again the NIC gets a different MAC
address.  Some guest operating systems are sensitive to this - under
</pre>
        </blockquote>
        <pre wrap="">For these users must use -device &lt;nic-model&gt;,mac=XX:XX:XX:XX:XX:XX.
I think no body will boot up the guest, which sensitive to this,
without mac address.

Actually, people use the command line without mac address, mean they mainly
don't care about mac address, so give them random mac address is reasonable
I think.

In my opinion, if we fix this, for qemu side no any issue, we both support
mac address set or unset correctly.

What am I confuse is, *qemu supports mac address unset, why we force
users must set the address when more than one guests*?
This is unreasonable.

</pre>
        <blockquote type="cite">
          <pre wrap="">many Linux distros the network interfaces names change due to the MAC
address change.  As a result firewall configuration will break and other
services may fail to start because they cannot find the interface.
</pre>
        </blockquote>
        <pre wrap="">Agree, so this mac address should set in qemu command line as
libvirt does :)
</pre>
        <blockquote type="cite">
          <pre wrap="">If you have multiple guests or want control over the MAC address, set it
explicitly using -device &lt;nic-model&gt;,mac=XX:XX:XX:XX:XX:XX.
</pre>
        </blockquote>
        <pre wrap="">Currently, especially for developers, people mainly use qemu
command line directly, and as qemu supports mac address
unset, they may try the simplest command line to boot up
lots of guests, they will confuse about why all this guest use
the same mac address.
</pre>
      </blockquote>
      <pre wrap="">
Your argument is weak: *you* want to avoid specifying the MAC address so
in exchange you want to *break* existing configurations and force other
people to start specifying a MAC address.
</pre>
    </blockquote>
    OK, I do not want to break the existing configurations.<br>
    <br>
    I'm fine if you do not want to merge this patch.<br>
    <br>
    But I think this should be an issue of qemu, and need to<br>
    do something on it, so I make this patch.<br>
    <br>
    Can we try other solutions to solve this issue?<br>
    (if you agree this should be an issue)<br>
    <br>
    Also this potential issue can happens if the user set the same mac
    address<br>
    with more than one guest on one host.<br>
    <br>
    Can we avoid this ?<span style="color: rgb(51, 51, 51); font-family:
      arial; font-size: 13px; font-style: normal; font-variant: normal;
      font-weight: normal; letter-spacing: normal; line-height: 20px;
      orphans: auto; text-align: start; text-indent: 0px;
      text-transform: none; white-space: normal; widows: auto;
      word-spacing: 0px; -webkit-text-stroke-width: 0px;
      background-color: rgb(255, 255, 255); display: inline !important;
      float: none;"></span><span style="color: rgb(51, 51, 51);
      font-family: arial; font-size: 13px; font-style: normal;
      font-variant: normal; font-weight: normal; letter-spacing: normal;
      line-height: 20px; orphans: auto; text-align: start; text-indent:
      0px; text-transform: none; white-space: normal; widows: auto;
      word-spacing: 0px; -webkit-text-stroke-width: 0px;
      background-color: rgb(255, 255, 255); display: inline !important;
      float: none;"><br>
    </span><br>
    Thanks<br>
    Mike<br>
    <blockquote
      cite="mid:20131018090044.GI9292@stefanha-thinkpad.redhat.com"
      type="cite">
      <pre wrap="">
This doesn't improve anything, it will just annoy users and cause bug
reports.

Sorry that there isn't a solution that satisfies everyone, you'll have
to add a MAC address to your command-line.</pre>
    </blockquote>
    <blockquote
      cite="mid:20131018090044.GI9292@stefanha-thinkpad.redhat.com"
      type="cite">
      <pre wrap="">

Stefan



</pre>
    </blockquote>
    <br>
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