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Clean up localhost resolv logic and add IPv6 support to regexp

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Addresses #5811

This cleans up an error in the logic which removes localhost resolvers
from the host resolv.conf at container creation start time. Specifically
when the determination is made if any nameservers are left after
removing localhost resolvers, it was using a string match on the word
"nameserver", which could have been anywhere (including commented out)
leading to incorrect situations where no nameservers were left but the
default ones were not added.

This also adds some complexity to the regular expressions for finding
nameservers in general, as well as matching on localhost resolvers due
to the recent addition of IPv6 support.  Because of IPv6 support now
available in the Docker daemon, the resolvconf code is now aware of
IPv6 enable/disable state and uses that for both filter/cleaning of
nameservers as well as adding default Google DNS (IPv4 only vs. IPv4
and IPv6 if IPv6 enabled).  For all these changes, tests have been
added/strengthened to test these additional capabilities.

Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com> (github: estesp)
Upstream-commit: 93d51e5e971e001d80e9ffa863439f2d72215b5a
Component: engine
This commit is contained in:
Phil Estes
2015-01-09 12:06:48 -05:00
parent c2ad023d0c
commit 5e93ebec1e
5 changed files with 115 additions and 38 deletions
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34
components/engine/integration-cli/docker_cli_run_test.go
View File

@ -1238,40 +1238,42 @@ func TestRunDisallowBindMountingRootToRoot(t *testing.T) {
logDone("run - bind mount /:/ as volume should fail")
}
// Verify that a container gets default DNS when only localhost resolvers exist
func TestRunDnsDefaultOptions(t *testing.T) {
// ci server has default resolv.conf
// so rewrite it for the test
// preserve original resolv.conf for restoring after test
origResolvConf, err := ioutil.ReadFile("/etc/resolv.conf")
if os.IsNotExist(err) {
t.Fatalf("/etc/resolv.conf does not exist")
}
// test with file
tmpResolvConf := []byte("nameserver 127.0.0.1")
if err := ioutil.WriteFile("/etc/resolv.conf", tmpResolvConf, 0644); err != nil {
t.Fatal(err)
}
// put the old resolvconf back
// defer restored original conf
defer func() {
if err := ioutil.WriteFile("/etc/resolv.conf", origResolvConf, 0644); err != nil {
t.Fatal(err)
}
}()
// test 3 cases: standard IPv4 localhost, commented out localhost, and IPv6 localhost
// 2 are removed from the file at container start, and the 3rd (commented out) one is ignored by
// GetNameservers(), leading to a replacement of nameservers with the default set
tmpResolvConf := []byte("nameserver 127.0.0.1\n#nameserver 127.0.2.1\nnameserver ::1")
if err := ioutil.WriteFile("/etc/resolv.conf", tmpResolvConf, 0644); err != nil {
t.Fatal(err)
}
cmd := exec.Command(dockerBinary, "run", "busybox", "cat", "/etc/resolv.conf")
actual, _, err := runCommandWithOutput(cmd)
if err != nil {
t.Error(err, actual)
return
t.Fatal(err, actual)
}
// check that the actual defaults are there
// if we ever change the defaults from google dns, this will break
expected := "\nnameserver 8.8.8.8\nnameserver 8.8.4.4"
// check that the actual defaults are appended to the commented out
// localhost resolver (which should be preserved)
// NOTE: if we ever change the defaults from google dns, this will break
expected := "#nameserver 127.0.2.1\n\nnameserver 8.8.8.8\nnameserver 8.8.4.4"
if actual != expected {
t.Errorf("expected resolv.conf be: %q, but was: %q", expected, actual)
return
t.Fatalf("expected resolv.conf be: %q, but was: %q", expected, actual)
}
deleteAllContainers()