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 2dcacaae88
)
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@ -24,6 +24,7 @@ import select
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import shlex
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import signal
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import subprocess
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import time
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import fixtures
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import netaddr
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@ -95,12 +96,22 @@ def set_namespace_gateway(port_dev, gateway_ip):
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port_dev.route.add_gateway(gateway_ip)
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def assert_ping(src_namespace, dst_ip, timeout=1, count=1):
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def assert_ping(src_namespace, dst_ip, timeout=1, count=1, interval=1):
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ipversion = netaddr.IPAddress(dst_ip).version
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ping_command = 'ping' if ipversion == 4 else 'ping6'
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ns_ip_wrapper = ip_lib.IPWrapper(src_namespace)
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ns_ip_wrapper.netns.execute([ping_command, '-c', count, '-W', timeout,
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dst_ip])
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# See bug 1588731 for explanation why using -c count ping option
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# cannot be used and it needs to be done using the following workaround.
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for _index in range(count):
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start_time = time.time()
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ns_ip_wrapper.netns.execute([ping_command, '-c', '1', '-W', timeout,
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dst_ip])
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end_time = time.time()
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diff = end_time - start_time
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if 0 < diff < interval:
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# wait at most "interval" seconds between individual pings
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time.sleep(interval - diff)
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@contextlib.contextmanager
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