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https://issues.apache.org/jira/browse/CLOUDSTACK-5986?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13932523#comment-13932523
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ASF subversion and git services commented on CLOUDSTACK-5986:
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Commit 92b9951df3050c8934b882b0b4c70828ac01f9af in cloudstack's branch
refs/heads/4.3 from [~yasker]
[ https://git-wip-us.apache.org/repos/asf?p=cloudstack.git;h=92b9951 ]
CLOUDSTACK-5986: Fix dnsmasq lease for VPC
(cherry picked from commit a253ff24682a7d405bfa8428a0833423bf19f9b9)
Signed-off-by: Animesh Chaturvedi <anim...@apache.org>
> dnsmasq racy condition result in dnsmasq failed to handout IP address
> ---------------------------------------------------------------------
>
> Key: CLOUDSTACK-5986
> URL: https://issues.apache.org/jira/browse/CLOUDSTACK-5986
> Project: CloudStack
> Issue Type: Bug
> Security Level: Public(Anyone can view this level - this is the
> default.)
> Components: Virtual Router
> Affects Versions: 4.2.0, 4.2.1
> Reporter: Sheng Yang
> Assignee: Sheng Yang
> Priority: Critical
> Fix For: 4.2.1, 4.3.0
>
>
> In the past, dnsmasq.leases is managed by cloudstack, and would be updated
> after new entry is added(and the entry with same IP or host would be removed).
> In 4.2, we introduced dhcp_release try to speed up the dnsmasq reload
> process, thus result in this issue.
> So in this scenario:
> 1. VM1 would create entry: "mac A, IP A, host A"
> 2. VM2 would create entry: "mac B, IP B, host B"
> 3. VM1 destroyed and VM 2 destroyed, no change to lease file, two records
> still existed.
> 4. VM1 created with IP B: "mac C, IP B, host A".
> At this time, lease file would only contain: "mac C, IP B, host A", because
> the original entries would be removed by either IP match or host name match.
> In fact dnsmasq still holds lease of IP A with mac A in memory, but record is
> already removed from lease file by cloudstack. The lease file is out of sync
> now.
> 5. VM2 recreated with IP A, dhcp_release would be used to release the lease.
> But there is no "mac A, IP A" record in the lease file, so dhcp_release
> failed.
> So result in dnsmasq cannot handle out the IP A to new mac D, because dnsmasq
> was still holding lease for IP A with mac A and haven't been released yet.
> So it only happened when user create and destroy different VMs which share
> the same name but get different IPs.
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