Reviewed: https://review.opendev.org/c/openstack/neutron/+/866489 Committed: https://opendev.org/openstack/neutron/commit/74224e79e031636018b970fac9c2aa72516eb12d Submitter: "Zuul (22348)" Branch: master
commit 74224e79e031636018b970fac9c2aa72516eb12d Author: Sebastian Lohff <[email protected]> Date: Fri Dec 2 17:36:44 2022 +0100 Gracefully restart dnsmasq to not break tcp DNS When talking to dnsmasq using DNS over tcp dnsmasq will fork out for TCP connections. Forked processes will stay until all connections have been closed, meaning that dangling connections will keep the processes and with that will also keep the tcp/53 port in listening state. On dnsmasq restart (e.g. on network update, subnet create, ...) the parent process is killed with SIGKILL and a new process is started. This new process cannot listen on tcp/53, as it is still in use by the old child with the dangling connection. To prevent dangling dnsmasq connections on tcp we need to properly shutdown the child. This is done by first sending SIGTERM and only send a SIGKILL if the process is not shutting down properly. With that we get proper cleanup of all children and tcp will come up after a restart. Change-Id: Ie633148c512f5124e978648c50a4c6318c61baa8 Closes-bug: #1998621 ** Changed in: neutron Status: In Progress => Fix Released -- You received this bug notification because you are a member of Yahoo! Engineering Team, which is subscribed to neutron. https://bugs.launchpad.net/bugs/1998621 Title: dnsmasq on DHCP Agent does not listen on tcp/53 after dnsmasq restart Status in neutron: Fix Released Bug description: When talking to dnsmasq using DNS over tcp dnsmasq will fork out for TCP connections. Forked processes will stay until all connections have been closed, meaning that dangling connections will keep the processes and with that will also keep the tcp/53 port in listening state. On dnsmasq restart (e.g. on network update, subnet create, ...) the parent process is killed with SIGKILL and a new process is started. This new process cannot listen on tcp/53, as it is still in use by the old child with the dangling connection. This could be prevented by sending SIGTERM instead of SIGKILL, as dnsmasq then does a proper cleanup of its forks and all tcp/53 connections are properly closed. This only happens when starting the dnsmasq with --bind-dynamic, as with this flag dnsmasq will ignore any errors resulting form it not being able to bind on tcp/53, see here: https://github.com/imp/dnsmasq/blob/f186bdcbc76cd894133a043b115b4510c0ee1fcf/src/network.c#L725-L726 The flag has been introduced here: https://bugs.launchpad.net/neutron/+bug/1828473 To manage notifications about this bug go to: https://bugs.launchpad.net/neutron/+bug/1998621/+subscriptions -- Mailing list: https://launchpad.net/~yahoo-eng-team Post to : [email protected] Unsubscribe : https://launchpad.net/~yahoo-eng-team More help : https://help.launchpad.net/ListHelp
