[dhcwg] Fwd: RFC 8415 question: unicast Information-request

[Felix Hamme <[e-mail]>]

Dear DHCPv6 experts,


does RFC8415 permit Information-request messages with an IPv6 unicast
destination address?


Section 16 states:
"A server MUST discard any Solicit, Confirm, Rebind, or
Information-request messages it receives with a Layer 3 unicast
destination address."
(unicast Information-request forbidden)

Section 18.2 states:
"If the client has a source address of sufficient scope that can be
used by the server as a return address and the client has received a
Server Unicast option (see Section 21.12) from the server, the client
SHOULD unicast any Request, Renew, Release, and Decline messages to
the server."
(unicast Information-request not mentioned)

Section 18.4 states:
"For example, unicast transmission is not allowed for Solicit, Confirm,
and Rebind messages (see Sections 18.3.1, 18.3.3, and 18.3.5,
respectively), even if the Server Unicast option (see Section 21.12) is
configured. For Request, Renew, Information-request, Release, and
Decline messages, it is allowed only if the Server Unicast option is
configured."
(unicast Information-request allowed if a Server Unicast option was
received)

Appendix B ("informational") does not permit a Server Unicast option in
a Reconfigure message.


I am not sure how to interpret those statements in total.

When sending an Information-request message in response to a Reconfigure
message, a client needs to include a Server Identifier option (see
section 18.2.6) to address a specific server. It appears reasonable to
me to permit a Server Unicast option in a Reconfigure message so that a
client can respond with an Information-request message with an unicast
destination address.

What if the Information-request message is sent after a
Solicit-Advertise-Request-Reply message exchange, in which the server
sent a Server Unicast option? May a client unicast Information-request
messages in that case?


Sincerely,
Felix Hamme