From eb06054a7b1e9d429b69d1c205ea81058468f60d Mon Sep 17 00:00:00 2001
From: Juan Font Alonso <juanfontalonso@gmail.com>
Date: Sun, 6 Mar 2022 17:25:21 +0100
Subject: [PATCH] Make DERP Region configurable

---
 app.go                     | 17 ++++++++++-------
 cmd/headscale/cli/utils.go | 22 ++++++++++++++--------
 config-example.yaml        |  9 +++++++++
 derp_server.go             | 14 ++++++++------
 4 files changed, 41 insertions(+), 21 deletions(-)

diff --git a/app.go b/app.go
index 82e87cf0..f1426bbb 100644
--- a/app.go
+++ b/app.go
@@ -120,13 +120,16 @@ type OIDCConfig struct {
 }
 
 type DERPConfig struct {
-	ServerEnabled   bool
-	STUNEnabled     bool
-	STUNAddr        string
-	URLs            []url.URL
-	Paths           []string
-	AutoUpdate      bool
-	UpdateFrequency time.Duration
+	ServerEnabled    bool
+	ServerRegionID   int
+	ServerRegionCode string
+	ServerRegionName string
+	STUNEnabled      bool
+	STUNAddr         string
+	URLs             []url.URL
+	Paths            []string
+	AutoUpdate       bool
+	UpdateFrequency  time.Duration
 }
 
 type CLIConfig struct {
diff --git a/cmd/headscale/cli/utils.go b/cmd/headscale/cli/utils.go
index e6dce3a1..dc7a4e9f 100644
--- a/cmd/headscale/cli/utils.go
+++ b/cmd/headscale/cli/utils.go
@@ -117,7 +117,10 @@ func LoadConfig(path string) error {
 }
 
 func GetDERPConfig() headscale.DERPConfig {
-	enabled := viper.GetBool("derp.server.enabled")
+	serverEnabled := viper.GetBool("derp.server.enabled")
+	serverRegionID := viper.GetInt("derp.server.region_id")
+	serverRegionCode := viper.GetString("derp.server.region_code")
+	serverRegionName := viper.GetString("derp.server.region_name")
 	stunEnabled := viper.GetBool("derp.server.stun.enabled")
 	stunAddr := viper.GetString("derp.server.stun.listen_addr")
 
@@ -142,13 +145,16 @@ func GetDERPConfig() headscale.DERPConfig {
 	updateFrequency := viper.GetDuration("derp.update_frequency")
 
 	return headscale.DERPConfig{
-		ServerEnabled:   enabled,
-		STUNEnabled:     stunEnabled,
-		STUNAddr:        stunAddr,
-		URLs:            urls,
-		Paths:           paths,
-		AutoUpdate:      autoUpdate,
-		UpdateFrequency: updateFrequency,
+		ServerEnabled:    serverEnabled,
+		ServerRegionID:   serverRegionID,
+		ServerRegionCode: serverRegionCode,
+		ServerRegionName: serverRegionName,
+		STUNEnabled:      stunEnabled,
+		STUNAddr:         stunAddr,
+		URLs:             urls,
+		Paths:            paths,
+		AutoUpdate:       autoUpdate,
+		UpdateFrequency:  updateFrequency,
 	}
 }
 
diff --git a/config-example.yaml b/config-example.yaml
index 57b43fd4..1ab92dca 100644
--- a/config-example.yaml
+++ b/config-example.yaml
@@ -60,6 +60,15 @@ derp:
     # The Headscale server_url defined above MUST be using https, DERP requires TLS to be in place
     enabled: false
 
+    # Region ID to use for the embedded DERP server.
+    # The local DERP prevails if the region ID collides with other region ID coming from
+    # the regular DERP config.
+    region_id: 999
+
+    # Region code and name are displayed in the Tailscale UI to identify a DERP region
+    region_code: "headscale"
+    region_name: "Headscale Embedded DERP"
+
     # If enabled, also listens in the configured address for STUN connections to help on NAT traversal
     # For more details on how this works, check this great article: https://tailscale.com/blog/how-tailscale-works/
     stun:
diff --git a/derp_server.go b/derp_server.go
index aeb4877a..8995ca8b 100644
--- a/derp_server.go
+++ b/derp_server.go
@@ -62,14 +62,14 @@ func (h *Headscale) generateRegionLocalDERP() (tailcfg.DERPRegion, error) {
 	}
 
 	localDERPregion := tailcfg.DERPRegion{
-		RegionID:   999,
-		RegionCode: "headscale",
-		RegionName: "Headscale Embedded DERP",
+		RegionID:   h.cfg.DERP.ServerRegionID,
+		RegionCode: h.cfg.DERP.ServerRegionCode,
+		RegionName: h.cfg.DERP.ServerRegionName,
 		Avoid:      false,
 		Nodes: []*tailcfg.DERPNode{
 			{
-				Name:     "999a",
-				RegionID: 999,
+				Name:     fmt.Sprintf("%d", h.cfg.DERP.ServerRegionID),
+				RegionID: h.cfg.DERP.ServerRegionID,
 				HostName: host,
 				DERPPort: port,
 			},
@@ -108,6 +108,7 @@ func (h *Headscale) DERPHandler(ctx *gin.Context) {
 	if !ok {
 		log.Error().Caller().Msg("DERP requires Hijacker interface from Gin")
 		ctx.String(http.StatusInternalServerError, "HTTP does not support general TCP support")
+
 		return
 	}
 
@@ -115,6 +116,7 @@ func (h *Headscale) DERPHandler(ctx *gin.Context) {
 	if err != nil {
 		log.Error().Caller().Err(err).Msgf("Hijack failed")
 		ctx.String(http.StatusInternalServerError, "HTTP does not support general TCP support")
+
 		return
 	}
 
@@ -169,7 +171,7 @@ func (h *Headscale) DERPBootstrapDNSHandler(ctx *gin.Context) {
 	ctx.JSON(http.StatusOK, dnsEntries)
 }
 
-// ServeSTUN starts a STUN server on the configured addr
+// ServeSTUN starts a STUN server on the configured addr.
 func (h *Headscale) ServeSTUN() {
 	packetConn, err := net.ListenPacket("udp", h.cfg.DERP.STUNAddr)
 	if err != nil {