JENKINS-64954 Explicitly preserve docker connection used for a specific image

src/main/java/org/jenkinsci/plugins/docker/workflow/WithContainerStep.java

@@ -42,6 +42,7 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
@@ -206,8 +207,9 @@ public Execution() {
             }
 
             ImageAction.add(step.image, run);
+            String dockerHost = envHost.get("DOCKER_HOST", "unix:///var/run/docker.sock");
             getContext().newBodyInvoker().
-                    withContext(BodyInvoker.mergeLauncherDecorators(getContext().get(LauncherDecorator.class), new Decorator(container, envHost, ws, toolName, dockerVersion))).
+                    withContext(BodyInvoker.mergeLauncherDecorators(getContext().get(LauncherDecorator.class), new Decorator(container, dockerHost, envHost, ws, toolName, dockerVersion))).
                     withCallback(new Callback(container, toolName)).
                     start();
             return false;
@@ -240,14 +242,16 @@ private static class Decorator extends LauncherDecorator implements Serializable
 
         private static final long serialVersionUID = 1;
         private final String container;
+        private final String dockerHost;
         private final String[] envHost;
         private final String ws;
         private final @CheckForNull String toolName;
         private final boolean hasEnv;
         private final boolean hasWorkdir;
 
-        Decorator(String container, EnvVars envHost, String ws, String toolName, VersionNumber dockerVersion) {
+        Decorator(String container, String dockerHost, EnvVars envHost, String ws, String toolName, VersionNumber dockerVersion) {
             this.container = container;
+            this.dockerHost = dockerHost;
             this.envHost = Util.mapToEnv(envHost);
             this.ws = ws;
             this.toolName = toolName;
@@ -332,6 +336,8 @@ private static class Decorator extends LauncherDecorator implements Serializable
                     System.arraycopy(originalMasks, 0, masks, prefix.size(), originalMasks.length);
                     starter.masks(masks);
 
+                    starter.envs(Collections.singletonMap("DOCKER_HOST", dockerHost));
+
                     return super.launch(starter);
                 }
                 @Override public void kill(Map<String,String> modelEnvVars) throws IOException, InterruptedException {

src/test/java/org/jenkinsci/plugins/docker/workflow/WithContainerStepTest.java

@@ -455,4 +455,23 @@ private static final class Execution extends SynchronousNonBlockingStepExecution
         }
     }
 
+    @Test
+    @Issue("JENKINS-64954")
+    public void dockerConnectionTracking() {
+        story.then(r -> {
+            DockerTestUtil.assumeDocker();
+            WorkflowJob p = r.jenkins.createProject(WorkflowJob.class, "p");
+            p.setDefinition(new CpsFlowDefinition("node {\n"
+                + "    docker.image(\"docker:dind\").withRun(\"--privileged\", \"dockerd --tls=false --host 0.0.0.0\") { dockerContainer ->\n"
+                + "        docker.image(\"docker:dind\").inside(\"--link ${dockerContainer.id}:docker --entrypoint=''\") {\n"
+                + "            docker.withServer(\"tcp://docker\") {\n"
+                + "                sh \"echo with nested docker\"\n"
+                + "            }\n"
+                + "        }\n"
+                + "    }\n"
+                + "}", true));
+            WorkflowRun b = story.j.assertBuildStatusSuccess(p.scheduleBuild2(0));
+            story.j.assertLogContains("with nested docker", b);
+        });
+    }
 }