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Hi,</div>
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<br>
</div>
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RFC 8415 section 16.12 requires a server to discard any Information-request</div>
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that includes an IA option. dnsmasq's check tests IA_NA and IA_TA but not</div>
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IA_PD, so an Information-request carrying an IA_PD option is answered with a</div>
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Reply rather than dropped.</div>
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<br>
</div>
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Present in current master: 1f12252 ("Make configuration for DHCPv4 options</div>
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and DHCPv6 options consistent.", 2026-07-27), i.e. v2.93-16-g1f12252.</div>
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<br>
</div>
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Section 16.12:</div>
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<br>
</div>
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Servers MUST discard any received Information-request message that</div>
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meets any of the following conditions:</div>
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<br>
</div>
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- the message includes a Server Identifier option (see</div>
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Section 21.3), and the DUID in the option does not match the</div>
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server's DUID.</div>
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<br>
</div>
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- the message includes an IA option.</div>
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<br>
</div>
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IA_PD is an IA option: section 12 defines an Identity Association as</div>
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covering addresses *or* delegated prefixes, so IA_NA, IA_TA and IA_PD are</div>
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all in scope.</div>
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<br>
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In src/rfc3315.c, the DHCP6IREQ case:</div>
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case DHCP6IREQ:</div>
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{</div>
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/* 3315 para 15.12 */</div>
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if (opt6_find(state->packet_options, state->end, OPTION6_IA_NA, 1) ||</div>
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opt6_find(state->packet_options, state->end, OPTION6_IA_TA, 1))</div>
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return 0;</div>
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<br>
</div>
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OPTION6_IA_PD is missing. The comment's reference explains how: RFC 3315 had</div>
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no prefix delegation (that was RFC 3633), and the merged RFC 8415 renumbered</div>
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the clause to 16.12 and brought IA_PD into its scope.</div>
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<br>
</div>
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The server-id half of 16.12 is implemented correctly, and IA_NA and IA_TA are</div>
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both discarded as they should be -- so only the IA_PD arm of the test is</div>
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absent.</div>
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<br>
</div>
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What I see: an Information-request carrying IA_PD gets a Reply that is</div>
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byte-for-byte identical to the Reply for the same message with no IA option</div>
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at all. The IA_PD is simply ignored rather than acted on.</div>
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<br>
</div>
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Patch below. With it applied, the IA_PD case is dropped, IA_NA and IA_TA stay</div>
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dropped, and an Information-request with no IA option still gets its Reply --</div>
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so it does not over-correct.</div>
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<br>
</div>
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If it is useful I can send a small standalone reproducer: it compiles</div>
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dnsmasq's own sources plus a ~150-line driver that calls dhcp6_reply()</div>
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directly, needs no root or network, and prints each reply. Happy to post it</div>
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or put it somewhere fetchable.</div>
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<br>
</div>
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Found with a conformance checker that builds a reference model from RFC 8415</div>
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and compares dnsmasq's response against the response class the RFC requires.</div>
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This one is invisible to differential testing, since the reply dnsmasq sends</div>
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is a perfectly well-formed Reply with no error status.</div>
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<br>
</div>
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Best regards,</div>
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Zhou Qingyang</div>
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<br>
</div>
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--- a/src/rfc3315.c</div>
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+++ b/src/rfc3315.c</div>
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@@ -1126,9 +1126,14 @@</div>
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<br>
</div>
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case DHCP6IREQ:</div>
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{</div>
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- /* 3315 para 15.12 */</div>
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+ /* RFC 8415 para 16.12: discard an Information-request that includes an</div>
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+ IA option. Para 12 defines an IA as covering addresses *or* delegated</div>
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+ prefixes, so IA_PD counts alongside IA_NA and IA_TA. (The older</div>
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+ reference was to RFC 3315 para 15.12, which predates prefix</div>
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+ delegation.) */</div>
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if (opt6_find(state->packet_options, state->end, OPTION6_IA_NA, 1) ||</div>
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- opt6_find(state->packet_options, state->end, OPTION6_IA_TA, 1))</div>
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+ opt6_find(state->packet_options, state->end, OPTION6_IA_TA, 1) ||</div>
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+ opt6_find(state->packet_options, state->end, OPTION6_IA_PD, 1))</div>
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return 0;</div>
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/* We can't discriminate contexts based on address, as we don't know it.</div>
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