A number of tests in the TestDockerDaemonSuite create a custom bridge as part
of the test. In some cases, an existing `docker0` bridge could interfere with
those tests. For example, the `TestDaemonICCLinkExpose` and `TestDaemonICCPing`
verify that no "icc" communication is possible, and for this create a new
bridge with a custom IP-range.
However, depending on which tests ran before the test, a default `docker0` bridge
may exist (e.g., if the`TestDefaultGatewayIPv4Implicit`) with the same IP-range,
in which iptables rules may have been set up that allow communication, and thus
make the "icc" tests fail.
This patch removes the `docker0` interface at the start of tests that create
their own bridge to prevent it from interfering.
Note that alternatively, we could update those tests to use an IP-range that's
less likely to overlap, but this may be more brittle (but could still be done
in addition to this change as a follow-up).
To verify these changes;
make DOCKER_GRAPHDRIVER=vfs TEST_SKIP_INTEGRATION=1 TESTFLAGS='-test.run TestDockerDaemonSuite/TestDaemon(DefaultGatewayIPv4|ICC)' test-integration-cli
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
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