[jira] [Commented] (CLOUDSTACK-5986) dnsmasq racy condition result in dnsmasq failed to handout IP address

["ASF subversion and git services (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CLOUDSTACK-5986?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13931126#comment-13931126 ] 

ASF subversion and git services commented on CLOUDSTACK-5986:
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Commit 8937434fce6958155e9871caa1648504b7c34999 in cloudstack's branch refs/heads/master from [~yasker]
[ https://git-wip-us.apache.org/repos/asf?p=cloudstack.git;h=8937434 ]

CLOUDSTACK-5986: Fix dnsmasq lease for VPC


> 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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