Add blacklisting of drivers

client/client.go

@@ -786,9 +786,11 @@ func (c *Client) fingerprintPeriodic(name string, f fingerprint.Fingerprint, d t
 
 // setupDrivers is used to find the available drivers
 func (c *Client) setupDrivers() error {
-	// Build the whitelist of drivers.
+	// Build the white/blacklists of drivers.
 	whitelist := c.config.ReadStringListToMap("driver.whitelist")
 	whitelistEnabled := len(whitelist) > 0
+	blacklist := c.config.ReadStringListToMap("driver.blacklist")
+	blacklistEnabled := len(blacklist) > 0
 
 	var avail []string
 	var skipped []string
@@ -800,6 +802,11 @@ func (c *Client) setupDrivers() error {
 			skipped = append(skipped, name)
 			continue
 		}
+		// Skip fingerprinting drivers that are in the blacklist if it is enabled.
+		if _, ok := blacklist[name]; blacklistEnabled && ok {
+			skipped = append(skipped, name)
+			continue
+		}
 
 		d, err := driver.NewDriver(name, driverCtx)
 		if err != nil {
@@ -825,7 +832,7 @@ func (c *Client) setupDrivers() error {
 	c.logger.Printf("[DEBUG] client: available drivers %v", avail)
 
 	if len(skipped) != 0 {
-		c.logger.Printf("[DEBUG] client: drivers skipped due to whitelist: %v", skipped)
+		c.logger.Printf("[DEBUG] client: drivers skipped due to white/blacklist: %v", skipped)
 	}
 
 	return nil

client/client_test.go

@@ -313,6 +313,27 @@ func TestClient_Drivers_InWhitelist(t *testing.T) {
 	}
 }
 
+func TestClient_Drivers_InBlacklist(t *testing.T) {
+	c := testClient(t, func(c *config.Config) {
+		if c.Options == nil {
+			c.Options = make(map[string]string)
+		}
+
+		// Weird spacing to test trimming
+		c.Options["driver.blacklist"] = "   exec ,  foo	"
+	})
+	defer c.Shutdown()
+
+	node := c.Node()
+	if node.Attributes["driver.exec"] != "" {
+		if v, ok := osExecDriverSupport[runtime.GOOS]; !v && ok {
+			t.Fatalf("exec driver loaded despite blacklist")
+		} else {
+			t.Skipf("missing exec driver, no OS support")
+		}
+	}
+}
+
 func TestClient_Drivers_OutOfWhitelist(t *testing.T) {
 	c := testClient(t, func(c *config.Config) {
 		if c.Options == nil {
@@ -329,6 +350,29 @@ func TestClient_Drivers_OutOfWhitelist(t *testing.T) {
 	}
 }
 
+func TestClient_Drivers_WhitelistBlacklistCombination(t *testing.T) {
+	c := testClient(t, func(c *config.Config) {
+		if c.Options == nil {
+			c.Options = make(map[string]string)
+		}
+
+		// Expected output is set difference (raw_exec)
+		c.Options["driver.whitelist"] = "raw_exec,exec"
+		c.Options["driver.blacklist"] = "exec"
+	})
+	defer c.Shutdown()
+
+	node := c.Node()
+	// Check expected present
+	if node.Attributes["driver.raw_exec"] == "" {
+		t.Fatalf("missing raw_exec driver")
+	}
+	// Check expected absent
+	if node.Attributes["driver.exec"] != "" {
+		t.Fatalf("exec driver loaded despite blacklist")
+	}
+}
+
 func TestClient_Register(t *testing.T) {
 	s1, _ := testServer(t, nil)
 	defer s1.Shutdown()

website/source/docs/agent/configuration/client.html.md

@@ -133,6 +133,19 @@ see the [drivers documentation](/docs/drivers/index.html).
     }
     ```
 
+- `"driver.blacklist"` `(string: "")` - Specifies a comma-separated list of
+  blacklisted drivers . If specified, drivers in the blacklist will be
+  disabled. If the blacklist is empty, all drivers are fingerprinted and enabled
+  where applicable.
+
+    ```hcl
+    client {
+      options = {
+        "driver.blacklist" = "docker,qemu"
+      }
+    }
+    ```
+
 - `"env.blacklist"` `(string: see below)` - Specifies a comma-separated list of
   environment variable keys not to pass to these tasks. Nomad passes the host
   environment variables to `exec`, `raw_exec` and `java` tasks. If specified,