Reviewed: https://review.openstack.org/325170 Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=2dcacaae88970365350200ca58982a18e21c703d Submitter: Jenkins Branch: master
commit 2dcacaae88970365350200ca58982a18e21c703d Author: Hynek Mlnarik <[email protected]> Date: Fri Jun 3 11:30:17 2016 +0200 Fix of ping usage in net_helpers.async_ping() net_helpers.async_ping() should pass when each of the ICMP echo requests is matched by a corresponding ICMP echo reply, and it should fail if a response is not received for some request. The async_ping implementation relies on the ping exit code: when ping returns nonzero exit code, RuntimeException would be consequentially thrown and async_ping assertion would thus fail. Current implementation of net_helpers.async_ping() is broken due to its usage of -c parameter of ping command and assumption that if _some_ of the ICMP replies does not arrive, ping would return nonzero exit code. However, Linux ping works in the way that if _at least one_ reply is received from any number of ICMP ping requests, result code is 0 (success) and thus no RuntimeException is thrown. This commit fixes assert_ping to be a reliable assertion guaranteeing that no ping request stays without reply. For simple bash reproducer and more thorough discussion of possible solutions, see the bug description. Closes-Bug: #1588731 Change-Id: I9257b94a8ebbfaf1c4266c1f8ce3097657bacee5 ** 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/1588731 Title: net_helpers.async_ping() is unreliable Status in neutron: Fix Released Bug description: Current implementation of net_helpers.async_ping() is broken due its usage of -c parameter of ping and expectation that if some of the ICMP replies does not arrive, RuntimeException would be thrown. Linux ping works in the way that if at least one reply is received from any number of ICMP ping requests, result code is 0 (success) and no RuntimeException is thrown. Shell reproducer of current net_helpers.async_ping() behaviour: ip a add 10.20.30.5/24 dev lo ; \ ( sleep 0.5 ; ip a del 10.20.30.5/24 dev lo ; sleep 1 ; ip a add 10.20.30.5/24 dev lo ; sleep 2 ; ip a del 10.20.30.5/24 dev lo ) & \ ping 10.20.30.5 -W 1 -c 3 ; \ echo "ping return code = $?" The return code is always 0 although one of the ICMP replies is lost. Man page suggests to use -w parameter. However this does not help: When using -w parameter, it is still possible that one ICMP reply is missed (even when using -c) while ping resulting in 0: e.g. "ping -c 3 -w 3" would send _four_ icmp requests and receive three responses if e.g. second response is missed and the other responses would be fast enough. Because three responses would be received, ping would return 0 status code even though there was a single packet loss, and that would lead to false conclusion that ping test passes correctly. Shell reproducer of net_helpers.async_ping() behaviour with -w: ip a add 10.20.30.5/24 dev lo ; \ ( sleep 0.5 ; ip a del 10.20.30.5/24 dev lo ; sleep 1 ; ip a add 10.20.30.5/24 dev lo ; sleep 2 ; ip a del 10.20.30.5/24 dev lo ) & \ ping 10.20.30.5 -W 1 -c 3 -w 3 ; \ echo "ping return code = $?" The return code is 0 and 1 roughly at similar rate, hence using -w is not an option for reliable net_helpers.async_ping(). Hence net_helpers.async_ping() needs to use ping only for a single ICMP request/reply test, only in that case the result code is reliable. Multiple ICMP requests/replies need to be handled in the code. This happens with ping at least from iputils-s20121221 and iputils-s20140519. It seems a ping issue as one would expect that -c would limit the number of ICMP requests sent. Yet neutron tests should account for this behaviour. To manage notifications about this bug go to: https://bugs.launchpad.net/neutron/+bug/1588731/+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
