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Date:      Mon, 1 May 2023 16:08:18 +0200
From:      Arnaud Houdelette-Langlois <arnaud.houdelette@normandie-univ.fr>
To:        freebsd-net@freebsd.org
Subject:   Re: Duplicates IP packets when using CARP and ECMP routes.
Message-ID:  <a82f72e5-a309-e209-d08f-540e4fb0adcc@normandie-univ.fr>
In-Reply-To: <3f3507f6-fc53-444b-8730-d61143ba3c1e@app.fastmail.com>
References:  <e57135b2-90a2-b71e-8a7d-b80a2f638b9f@normandie-univ.fr> <3f3507f6-fc53-444b-8730-d61143ba3c1e@app.fastmail.com>

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Thanks for the info.

I opened the PR : https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=271168


Arnaud Houdelette-Langlois
Administrateur des infrastructures systèmes et réseaux
Normandie Université
+33 2 31 56 69 54

Le 29/04/2023 à 23:44, Alexander Chernikov a écrit :
>
>
> On Sat, 29 Apr 2023, at 11:01 AM, Arnaud Houdelette-Langlois wrote:
>>
>> Hi.
>>
>> We got a freebsd router with both ospf/bpg and multipath routes 
>> (ECMP) (using the new bird2 with netlink) .
>>
>> The router got an interface with carp enabled on it (gateway for 
>> admin vlan).
>>
>> Packets received on the carp address gets routed on all known routes 
>> towards destination. Thus, the destination host receives duplicates 
>> ip packets. (which disrupts most udp based protocols)
>>
>> Using a simple alias instead of carp solve the problem. Is this a 
>> known problem, or should I fill a PR ?
>>
> No, that’s not a known problem.
> Please do open the PR with details.
>> -- 
>> Arnaud Houdelette-Langlois
>> Administrateur des infrastructures systèmes et réseaux
>> Normandie Université
>> +33 2 31 56 69 54
>>
>
> /Alexander
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    <p>Thanks for the info. <br>
    </p>
    <p>I opened the PR :
      <a class="moz-txt-link-freetext" href="https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=271168">https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=271168</a></p>;
    <p><br>
    </p>
    <pre class="moz-signature" cols="72">Arnaud Houdelette-Langlois
Administrateur des infrastructures systèmes et réseaux
Normandie Université
+33 2 31 56 69 54</pre>
    <div class="moz-cite-prefix">Le 29/04/2023 à 23:44, Alexander
      Chernikov a écrit :<br>
    </div>
    <blockquote type="cite"
      cite="mid:3f3507f6-fc53-444b-8730-d61143ba3c1e@app.fastmail.com">
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      <div>On Sat, 29 Apr 2023, at 11:01 AM, Arnaud Houdelette-Langlois
        wrote:<br>
      </div>
      <blockquote type="cite" id="qt" style="">
        <p>Hi.<br>
        </p>
        <p>We got a freebsd router with both ospf/bpg and multipath
          routes (ECMP) (using the new bird2 with netlink) .<br>
        </p>
        <p>The router got an interface with carp enabled on it (gateway
          for admin vlan).<br>
        </p>
        <p>Packets received on the carp address gets routed on all known
          routes towards destination. Thus, the destination host
          receives duplicates ip packets. (which disrupts most udp based
          protocols)<br>
        </p>
        <p>Using a simple alias instead of carp solve the problem. Is
          this a known problem, or should I fill a PR ?<br>
        </p>
      </blockquote>
      <div>No, that’s not a known problem. <br>
      </div>
      <div>Please do open the PR with details.</div>
      <blockquote type="cite" id="qt" style="">
        <pre class="qt-moz-signature" cols="72">-- 
Arnaud Houdelette-Langlois
Administrateur des infrastructures systèmes et réseaux
Normandie Université
+33 2 31 56 69 54
</pre>
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        <div class="signature">/Alexander<br>
        </div>
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