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Re: [dhcwg] recommendation on DHCP6 source port numbers

Bernie Volz <bevolz@gmail.com> Fri, 01 March 2024 11:31 UTC

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From: Bernie Volz <bevolz@gmail.com>
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Date: Fri, 01 Mar 2024 06:31:32 -0500
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References: <2D11BD95-831F-4F19-A4DE-17C1D15F9E42@employees.org>
Cc: Tomoyuki Sahara <tsahara@iij.ad.jp>, Lorenzo Colitti <lorenzo@google.com>, dhcwg@ietf.org
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To: Ole Troan <otroan@employees.org>
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Subject: Re: [dhcwg] recommendation on DHCP6 source port numbers
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https://datatracker.ietf.org/doc/html/rfc8415#section-7.2" rel="nofollow">7.2.  UDP Ports

   Clients listen for DHCP messages on UDP port 546.  Servers and relay
   agents listen for DHCP messages on UDP port 547.

From 8415.

- Bernie (from iPad)

On Mar 1, 2024, at 5:56 AM, Ole Troan <otroan@employees.org> wrote:


(b) sends response messages to the source port of the request message.

This server is broken and needs to follow the RFC.

Yes, you could fix this by changing client to send from 546 source port. But it is server that is broken and should be fixed.

And it is usually a lot easier to fix (& update) a few servers than lots of clients.

Which text in RFC8415 does such a server violate?

RFC768 says:
Source Port is an optional field, when meaningful, it indicates the port
of the sending process, and may be assumed to be the port to which a
reply should be addressed in the absence of any other information. If
not used, a value of zero is inserted.


So unless there is text in RFC8414 (or someone has already implemented BOOTP) it would be fair to assume you’d just swap source and dest ports.

O.

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