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Re: [dhcwg] [v6ops] Operational Headache: DHCP V6 Relay

Sander Steffann <sander@steffann.nl> Thu, 27 June 2019 14:16 UTC

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From: Sander Steffann <sander@steffann.nl>
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Date: Thu, 27 Jun 2019 16:16:02 +0200
In-Reply-To: <218CA62E-75FC-462A-A04E-7B3377631F5E@gmail.com>
Cc: Fred Templin <Fred.L.Templin@boeing.com>, "dhcwg@ietf.org" <dhcwg@ietf.org>, v6ops list <v6ops@ietf.org>
To: Fred Baker <fredbaker.ietf@gmail.com>
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Subject: Re: [dhcwg] [v6ops] Operational Headache: DHCP V6 Relay
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Hi Fred,

> I don't see a prohibition of this sort of design, but it seems unnecessarily complex. The relay protocol is designed to communicate from a relay to another relay or to a server. Adding a relay process just to communicate with the server process via localhost seems an unnecessary step.

When implementing DHCPKit I implemented it in roughly the same way (although I did it inside a single process). Wrapping every incoming message inside a relay message makes it possible to handle layer-2 information uniformly.

The process/function that listens on the multicast address generates an internal relay message with all relevant information (interface, mac address, source link-local address etc) and sends that to the main server to be processed. The server can then always get all relevant information from the DHCPv6 packet stack, independent of how it was received. Otherwise you'd have to have an extra channel to communicate all that metadata to the server process.

Cheers,
Sander

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