Comment 7 for bug 1588731

Reviewed: https://review.openstack.org/347062
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=0036bc07e7ee1d59e713df604d73645b8764d025
Submitter: Jenkins
Branch: stable/liberty

commit 0036bc07e7ee1d59e713df604d73645b8764d025
Author: Hynek Mlnarik <email address hidden>
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
    (cherry picked from commit 2dcacaae88970365350200ca58982a18e21c703d)