dhcpcd: Respect IPV6_PREFERRED_ONLY flag regardless of state #307
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rsmarples
requested changes
Mar 28, 2024
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https://datatracker.ietf.org/doc/html/rfc8925#section-3.2
If the client is in any other state, it SHOULD continue to use the assigned IPv4 address until further DHCPv4 reconfiguration events.
So we need to add the NONE state to the list, not just remove the list.
Current IPv6_PREFERRED_ONLY (option 108) handling code is only effective when current state is DHS_DISCOVER and DHS_REBOOT. However, when we receive multiple ACKs upon our REQUEST, the first ACK will trigger the use_v6only code path and dhcp_drop() us into DHS_NONE state, as a result the option 108 on the second ACK won't be handled correctly and we'll bind to the lease instead. This patch fixes the issue by adding DHS_NONE as a state to respect option 108 as well.
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Thanks for the RFC pointer. I've updated the patch. |
rsmarples
approved these changes
Apr 2, 2024
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Thanks! |
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Current IPv6_PREFERRED_ONLY (option 108) handling code is only effective when current state is DHS_DISCOVER or DHS_REBOOT. However the assumption that we'll only receive OFFER and ACK with option 108 in those two states is not true. Particularly, when we receive multiple ACKs upon our REQUEST, the first ACK will trigger the use_v6only code path and dhcp_drop() us into DHS_NONE state, therefore the option 108 on second ACK won't be handled correctly and we'll bind to the lease incorrectly.
DHS_NONE is not the only possible state, considering the corner cases of server configuration change and multiple servers. Thus we should just remove the state check here.