TUN-4425: --overwrite-dns flag for in adhoc and route dns cmds

CHANGES.md

@@ -1,5 +1,12 @@
 **Experimental**: This is a new format for release notes. The format and availability is subject to change.
 
+## 2021.5.8
+### New Features
+- When creating a DNS record to point a hostname at a tunnel, you can now use --overwrite-dns to overwrite any existing
+  DNS records with that hostname. This works when using the CLI to provision DNS, and when starting an adhoc tunnel, e.g.
+  - `cloudflared route --overwrite-dns dns foo foo.example.com`
+  - `cloudflared tunnel --overwrite-dns --name foo --hostname foo.example.com`
+
 ## 2021.5.7
 ### New Features
 - Named Tunnels will automatically select the protocol to connect to Cloudflare's edge network.

cmd/cloudflared/tunnel/cmd.go

@@ -87,6 +87,10 @@ const (
 var (
 	graceShutdownC chan struct{}
 	version        string
+
+	routeFailMsg = fmt.Sprintf("failed to provision routing, please create it manually via Cloudflare dashboard or UI; "+
+		"most likely you already have a conflicting record there. You can also rerun this command with --%s to overwrite "+
+		"any existing DNS records for this hostname.", overwriteDNSFlag)
 )
 
 func Flags() []cli.Flag {
@@ -181,7 +185,7 @@ func runAdhocNamedTunnel(sc *subcommandContext, name, credentialsOutputPath stri
 
 	if r, ok := routeFromFlag(sc.c); ok {
 		if res, err := sc.route(tunnel.ID, r); err != nil {
-			sc.log.Err(err).Str("route", r.String()).Msg("failed to provision routing, please create it manually via Cloudflare dashboard or UI; most likely you already have a conflicting record there")
+			sc.log.Err(err).Str("route", r.String()).Msg(routeFailMsg)
 		} else {
 			sc.log.Info().Msg(res.SuccessSummary())
 		}
@@ -199,12 +203,12 @@ func runClassicTunnel(sc *subcommandContext) error {
 	return StartServer(sc.c, version, nil, sc.log, sc.isUIEnabled)
 }
 
-func routeFromFlag(c *cli.Context) (tunnelstore.Route, bool) {
+func routeFromFlag(c *cli.Context) (route tunnelstore.Route, ok bool) {
 	if hostname := c.String("hostname"); hostname != "" {
 		if lbPool := c.String("lb-pool"); lbPool != "" {
 			return tunnelstore.NewLBRoute(hostname, lbPool), true
 		}
-		return tunnelstore.NewDNSRoute(hostname), true
+		return tunnelstore.NewDNSRoute(hostname, c.Bool(overwriteDNSFlagName)), true
 	}
 	return nil, false
 }
@@ -613,6 +617,7 @@ func tunnelFlags(shouldHide bool) []cli.Flag {
 			Hidden: shouldHide,
 		}),
 		selectProtocolFlag,
+		overwriteDNSFlag,
 	}...)
 
 	return flags

cmd/cloudflared/tunnel/subcommands.go

@@ -33,6 +33,7 @@ const (
 	connsSortByOptions   = "id, startedAt, numConnections, version"
 	CredFileFlagAlias    = "cred-file"
 	CredFileFlag         = "credentials-file"
+	overwriteDNSFlagName = "overwrite-dns"
 
 	LogFieldTunnelID = "tunnelID"
 )
@@ -133,6 +134,12 @@ var (
 		Usage:   `Constraints the cleanup to stop the connections of a single Connector (by its ID). You can find the various Connectors (and their IDs) currently connected to your tunnel via 'cloudflared tunnel info <name>'.`,
 		EnvVars: []string{"TUNNEL_CLEANUP_CONNECTOR"},
 	}
+	overwriteDNSFlag = &cli.BoolFlag{
+		Name:    overwriteDNSFlagName,
+		Aliases: []string{"f"},
+		Usage:   `Overwrites existing DNS records with this hostname`,
+		EnvVars: []string{"TUNNEL_FORCE_PROVISIONING_DNS"},
+	}
 )
 
 func buildCreateCommand() *cli.Command {
@@ -670,10 +677,11 @@ Further information about managing Cloudflare WARP traffic to your tunnel is ava
 		Subcommands: []*cli.Command{
 			buildRouteIPSubcommand(),
 		},
+		Flags: []cli.Flag{overwriteDNSFlag},
 	}
 }
 
-func dnsRouteFromArg(c *cli.Context) (tunnelstore.Route, error) {
+func dnsRouteFromArg(c *cli.Context, overwriteExisting bool) (tunnelstore.Route, error) {
 	const (
 		userHostnameIndex = 2
 		expectedNArgs     = 3
@@ -687,7 +695,7 @@ func dnsRouteFromArg(c *cli.Context) (tunnelstore.Route, error) {
 	} else if !validateHostname(userHostname, true) {
 		return nil, errors.Errorf("%s is not a valid hostname", userHostname)
 	}
-	return tunnelstore.NewDNSRoute(userHostname), nil
+	return tunnelstore.NewDNSRoute(userHostname, overwriteExisting), nil
 }
 
 func lbRouteFromArg(c *cli.Context) (tunnelstore.Route, error) {
@@ -756,7 +764,7 @@ func routeCommand(c *cli.Context) error {
 		if err != nil {
 			return err
 		}
-		route, err = dnsRouteFromArg(c)
+		route, err = dnsRouteFromArg(c, c.Bool(overwriteDNSFlagName))
 		if err != nil {
 			return err
 		}

tunnelstore/client.go

@@ -82,6 +82,7 @@ type RouteResult interface {
 
 type DNSRoute struct {
 	userHostname      string
+	overwriteExisting bool
 }
 
 type DNSRouteResult struct {
@@ -89,9 +90,10 @@ type DNSRouteResult struct {
 	CName Change `json:"cname"`
 }
 
-func NewDNSRoute(userHostname string) Route {
+func NewDNSRoute(userHostname string, overwriteExisting bool) Route {
 	return &DNSRoute{
 		userHostname:      userHostname,
+		overwriteExisting: overwriteExisting,
 	}
 }
 
@@ -99,9 +101,11 @@ func (dr *DNSRoute) MarshalJSON() ([]byte, error) {
 	s := struct {
 		Type              string `json:"type"`
 		UserHostname      string `json:"user_hostname"`
+		OverwriteExisting bool   `json:"overwrite_existing"`
 	}{
 		Type:              dr.RecordType(),
 		UserHostname:      dr.userHostname,
+		OverwriteExisting: dr.overwriteExisting,
 	}
 	return json.Marshal(&s)
 }