Merge pull request #51507 from zhangguanzhang/fix-pause-restart

libnet: setupDNS: don't overwrite user-modified resolv.conf

integration/networking/resolvconf_test.go

@@ -212,3 +212,41 @@ func TestNslookupWindows(t *testing.T) {
 	// can only be changed in daemon.json using feature flag "windows-dns-proxy".
 	assert.Check(t, is.Contains(res.Stdout.String(), "Addresses:"))
 }
+
+// TestResolvConfPreservedOnRestart verifies that external modifications to
+// /etc/resolv.conf are preserved when a non-host network container is restarted.
+// Regression test for https://github.com/moby/moby/issues/51490
+func TestResolvConfPreservedOnRestart(t *testing.T) {
+	skip.If(t, testEnv.DaemonInfo.OSType == "windows", "No /etc/resolv.conf on Windows")
+
+	ctx := setupTest(t)
+
+	d := daemon.New(t, daemon.WithResolvConf(network.GenResolvConf("8.8.8.8")))
+	d.StartWithBusybox(ctx, t)
+	defer d.Stop(t)
+
+	c := d.NewClientT(t)
+	defer c.Close()
+
+	const ctrName = "test-resolvconf-preserved-on-restart"
+	id := container.Run(ctx, t, c, container.WithName(ctrName))
+	defer c.ContainerRemove(ctx, id, client.ContainerRemoveOptions{Force: true})
+
+	appendContent := `# hello`
+	res, err := container.Exec(ctx, c, ctrName, []string{
+		"sh", "-c",
+		"echo '" + appendContent + "' >> /etc/resolv.conf",
+	})
+	assert.NilError(t, err)
+	assert.Check(t, is.Equal(res.ExitCode, 0))
+
+	// Restart the container.
+	_, err = c.ContainerRestart(ctx, ctrName, client.ContainerRestartOptions{})
+	assert.Assert(t, is.Nil(err))
+
+	// Verify the modification was preserved
+	res, err = container.Exec(ctx, c, ctrName, []string{"tail", "-n", "1", "/etc/resolv.conf"})
+	assert.NilError(t, err)
+	assert.Check(t, is.Equal(res.ExitCode, 0))
+	assert.Check(t, is.Contains(res.Stdout(), appendContent))
+}