infra: use IFA_F_NODAD for control plane tap addresses - #679
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The accept_dad sysctl set on the control plane tap is ineffective because the kernel evaluates max(conf/all/accept_dad, conf/<iface>/accept_dad). Since conf/all/accept_dad defaults to 1, DAD still runs after link flaps. When DAD runs, the kernel sends a NS probe on the control plane tap. Grout's datapath answers with a NA (it owns the same address), and the kernel marks the address as dadfailed. The address never recovers, sendmsg() returns EINVAL permanently and OSPF6 never converges. Set IFA_F_NODAD in the netlink RTM_NEWADDR message when adding IPv6 addresses to the control plane tap. This is a per-address flag that unconditionally prevents DAD regardless of any sysctl setting. Fixes: 0480bdf ("infra: disable DAD on control plane TAPs") Signed-off-by: Robin Jarry <rjarry@redhat.com>
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The accept_dad sysctl set on the control plane tap is ineffective because the kernel evaluates max(conf/all/accept_dad, conf//accept_dad). Since conf/all/accept_dad defaults to 1, DAD still runs after link flaps.
When DAD runs, the kernel sends a NS probe on the control plane tap. Grout's datapath answers with a NA (it owns the same address), and the kernel marks the address as dadfailed. The address never recovers, sendmsg() returns EINVAL permanently and OSPF6 never converges.
Set IFA_F_NODAD in the netlink RTM_NEWADDR message when adding IPv6 addresses to the control plane tap. This is a per-address flag that unconditionally prevents DAD regardless of any sysctl setting.
Fixes: 0480bdf ("infra: disable DAD on control plane TAPs")