Public bug reported:
Current DHCP port management in Neutron makes the server to clear the
device_id while the agent is responsible for setting it.
This may cause a potential race condition, for example during network
rescheduling. The server aims to clear the device_id on a DHCP port and
assign the network to another agent while the old agent might just be
taking possession of the port. If the DHCP agent takes possession of the
port (i.e., update port...set the device_id) before the server clears
it, then there is no issue. However, if this happens after the clear
operation by server then the DHCP port would be updated/marked to be
owned by the old agent.
When the new agent takes over the network scheduled to it, it won't be able to
find a port to reuse so that an extra port might need to be created. This leads
to two issues:
1) an extra port is created and never deleted;
2) the extra port creation may fail if there are no available IP addresses.
** Affects: neutron
Importance: Undecided
Assignee: Kailun Qin (kailun.qin)
Status: New
** Changed in: neutron
Assignee: (unassigned) => Kailun Qin (kailun.qin)
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https://bugs.launchpad.net/bugs/1795126
Title:
Race condition of DHCP agent updating port after ownership removed and
given to another agent will cause extra port creation
Status in neutron:
New
Bug description:
Current DHCP port management in Neutron makes the server to clear the
device_id while the agent is responsible for setting it.
This may cause a potential race condition, for example during network
rescheduling. The server aims to clear the device_id on a DHCP port
and assign the network to another agent while the old agent might just
be taking possession of the port. If the DHCP agent takes possession
of the port (i.e., update port...set the device_id) before the server
clears it, then there is no issue. However, if this happens after the
clear operation by server then the DHCP port would be updated/marked
to be owned by the old agent.
When the new agent takes over the network scheduled to it, it won't be able
to find a port to reuse so that an extra port might need to be created. This
leads to two issues:
1) an extra port is created and never deleted;
2) the extra port creation may fail if there are no available IP addresses.
To manage notifications about this bug go to:
https://bugs.launchpad.net/neutron/+bug/1795126/+subscriptions
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