Make IP Prefix configurable and available ip deterministic

README.md

@@ -113,9 +113,10 @@ Headscale's configuration file is named `config.json` or `config.yaml`. Headscal
 ```
     "server_url": "http://192.168.1.12:8080",
     "listen_addr": "0.0.0.0:8080",
+    "ip_prefix": "100.64.0.0/10"
 ```
 
-`server_url` is the external URL via which Headscale is reachable. `listen_addr` is the IP address and port the Headscale program should listen on.
+`server_url` is the external URL via which Headscale is reachable. `listen_addr` is the IP address and port the Headscale program should listen on. `ip_prefix` is the IP prefix (range) in which IP addresses for nodes will be allocated.
 
 ```
     "private_key_path": "private.key",

api.go

@@ -445,6 +445,7 @@ func (h *Headscale) handleAuthKey(c *gin.Context, db *gorm.DB, idKey wgkey.Key,
 		log.Println(err)
 		return
 	}
+	log.Printf("Assigning %s to %s", ip, m.Name)
 
 	m.AuthKeyID = uint(pak.ID)
 	m.IPAddress = ip.String()

app.go

@@ -13,6 +13,7 @@ import (
 	"github.com/gin-gonic/gin"
 	"golang.org/x/crypto/acme/autocert"
 	"gorm.io/gorm"
+	"inet.af/netaddr"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/wgkey"
 )
@@ -24,6 +25,7 @@ type Config struct {
 	PrivateKeyPath                 string
 	DerpMap                        *tailcfg.DERPMap
 	EphemeralNodeInactivityTimeout time.Duration
+	IPPrefix                       netaddr.IPPrefix
 
 	DBtype string
 	DBpath string

app_test.go

@@ -6,6 +6,7 @@ import (
 	"testing"
 
 	"gopkg.in/check.v1"
+	"inet.af/netaddr"
 )
 
 func Test(t *testing.T) {
@@ -36,7 +37,9 @@ func (s *Suite) ResetDB(c *check.C) {
 	if err != nil {
 		c.Fatal(err)
 	}
-	cfg := Config{}
+	cfg := Config{
+		IPPrefix: netaddr.MustParseIPPrefix("10.27.0.0/23"),
+	}
 
 	h = Headscale{
 		cfg:      cfg,

cli_test.go

@@ -15,6 +15,7 @@ func (s *Suite) TestRegisterMachine(c *check.C) {
 		DiscoKey:    "faa",
 		Name:        "testmachine",
 		NamespaceID: n.ID,
+		IPAddress:   "10.0.0.1",
 	}
 	h.db.Save(&m)
 

cmd/headscale/cli/utils.go

@@ -14,6 +14,7 @@ import (
 	"github.com/juanfont/headscale"
 	"github.com/spf13/viper"
 	"gopkg.in/yaml.v2"
+	"inet.af/netaddr"
 	"tailscale.com/tailcfg"
 )
 
@@ -36,6 +37,8 @@ func LoadConfig(path string) error {
 	viper.SetDefault("tls_letsencrypt_cache_dir", "/var/www/.cache")
 	viper.SetDefault("tls_letsencrypt_challenge_type", "HTTP-01")
 
+	viper.SetDefault("ip_prefix", "100.64.0.0/10")
+
 	err := viper.ReadInConfig()
 	if err != nil {
 		return fmt.Errorf("Fatal error reading config file: %s \n", err)
@@ -97,6 +100,7 @@ func getHeadscaleApp() (*headscale.Headscale, error) {
 		Addr:           viper.GetString("listen_addr"),
 		PrivateKeyPath: absPath(viper.GetString("private_key_path")),
 		DerpMap:        derpMap,
+		IPPrefix:       netaddr.MustParseIPPrefix(viper.GetString("ip_prefix")),
 
 		EphemeralNodeInactivityTimeout: viper.GetDuration("ephemeral_node_inactivity_timeout"),
 

utils.go

@@ -7,18 +7,12 @@ package headscale
 
 import (
 	"crypto/rand"
-	"encoding/binary"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"io"
-	"net"
-	"time"
-
-	mathrand "math/rand"
 
 	"golang.org/x/crypto/nacl/box"
-	"gorm.io/gorm"
+	"inet.af/netaddr"
 	"tailscale.com/types/wgkey"
 )
 
@@ -77,47 +71,71 @@ func encodeMsg(b []byte, pubKey *wgkey.Key, privKey *wgkey.Private) ([]byte, err
 	return msg, nil
 }
 
-func (h *Headscale) getAvailableIP() (*net.IP, error) {
-	i := 0
+func (h *Headscale) getAvailableIP() (*netaddr.IP, error) {
+	ipPrefix := h.cfg.IPPrefix
+
+	usedIps, err := h.getUsedIPs()
+	if err != nil {
+		return nil, err
+	}
+
+	// Get the first IP in our prefix
+	ip := ipPrefix.IP()
+
 	for {
-		ip, err := getRandomIP()
-		if err != nil {
-			return nil, err
+		if !ipPrefix.Contains(ip) {
+			return nil, fmt.Errorf("could not find any suitable IP in %s", ipPrefix)
+		}
+
+		// Some OS (including Linux) does not like when IPs ends with 0 or 255, which
+		// is typically called network or broadcast. Lets avoid them and continue
+		// to look when we get one of those traditionally reserved IPs.
+		ipRaw := ip.As4()
+		if ipRaw[3] == 0 || ipRaw[3] == 255 {
+			ip = ip.Next()
+			continue
+		}
+
+		if ip.IsZero() &&
+			ip.IsLoopback() {
+
+			ip = ip.Next()
+			continue
 		}
-		m := Machine{}
-		if result := h.db.First(&m, "ip_address = ?", ip.String()); errors.Is(result.Error, gorm.ErrRecordNotFound) {
-			return ip, nil
+
+		if !containsIPs(usedIps, ip) {
+			return &ip, nil
 		}
-		i++
-		if i == 100 { // really random number
-			break
+
+		ip = ip.Next()
+	}
+}
+
+func (h *Headscale) getUsedIPs() ([]netaddr.IP, error) {
+	var addresses []string
+	h.db.Model(&Machine{}).Pluck("ip_address", &addresses)
+
+	ips := make([]netaddr.IP, len(addresses))
+	for index, addr := range addresses {
+		if addr != "" {
+			ip, err := netaddr.ParseIP(addr)
+			if err != nil {
+				return nil, fmt.Errorf("failed to parse ip from database, %w", err)
+			}
+
+			ips[index] = ip
 		}
 	}
-	return nil, errors.New("Could not find an available IP address in 100.64.0.0/10")
+
+	return ips, nil
 }
 
-func getRandomIP() (*net.IP, error) {
-	mathrand.Seed(time.Now().Unix())
-	ipo, ipnet, err := net.ParseCIDR("100.64.0.0/10")
-	if err == nil {
-		ip := ipo.To4()
-		// fmt.Println("In Randomize IPAddr: IP ", ip, " IPNET: ", ipnet)
-		// fmt.Println("Final address is ", ip)
-		// fmt.Println("Broadcast address is ", ipb)
-		// fmt.Println("Network address is ", ipn)
-		r := mathrand.Uint32()
-		ipRaw := make([]byte, 4)
-		binary.LittleEndian.PutUint32(ipRaw, r)
-		// ipRaw[3] = 254
-		// fmt.Println("ipRaw is ", ipRaw)
-		for i, v := range ipRaw {
-			// fmt.Println("IP Before: ", ip[i], " v is ", v, " Mask is: ", ipnet.Mask[i])
-			ip[i] = ip[i] + (v &^ ipnet.Mask[i])
-			// fmt.Println("IP After: ", ip[i])
+func containsIPs(ips []netaddr.IP, ip netaddr.IP) bool {
+	for _, v := range ips {
+		if v == ip {
+			return true
 		}
-		// fmt.Println("FINAL IP: ", ip.String())
-		return &ip, nil
 	}
 
-	return nil, err
+	return false
 }

utils_test.go

@@ -0,0 +1,155 @@
+package headscale
+
+import (
+	"gopkg.in/check.v1"
+	"inet.af/netaddr"
+)
+
+func (s *Suite) TestGetAvailableIp(c *check.C) {
+	ip, err := h.getAvailableIP()
+
+	c.Assert(err, check.IsNil)
+
+	expected := netaddr.MustParseIP("10.27.0.1")
+
+	c.Assert(ip.String(), check.Equals, expected.String())
+}
+
+func (s *Suite) TestGetUsedIps(c *check.C) {
+	ip, err := h.getAvailableIP()
+	c.Assert(err, check.IsNil)
+
+	n, err := h.CreateNamespace("test_ip")
+	c.Assert(err, check.IsNil)
+
+	pak, err := h.CreatePreAuthKey(n.Name, false, false, nil)
+	c.Assert(err, check.IsNil)
+
+	_, err = h.GetMachine("test", "testmachine")
+	c.Assert(err, check.NotNil)
+
+	m := Machine{
+		ID:             0,
+		MachineKey:     "foo",
+		NodeKey:        "bar",
+		DiscoKey:       "faa",
+		Name:           "testmachine",
+		NamespaceID:    n.ID,
+		Registered:     true,
+		RegisterMethod: "authKey",
+		AuthKeyID:      uint(pak.ID),
+		IPAddress:      ip.String(),
+	}
+	h.db.Save(&m)
+
+	ips, err := h.getUsedIPs()
+
+	c.Assert(err, check.IsNil)
+
+	expected := netaddr.MustParseIP("10.27.0.1")
+
+	c.Assert(ips[0], check.Equals, expected)
+
+	m1, err := h.GetMachineByID(0)
+	c.Assert(err, check.IsNil)
+
+	c.Assert(m1.IPAddress, check.Equals, expected.String())
+}
+
+func (s *Suite) TestGetMultiIp(c *check.C) {
+	n, err := h.CreateNamespace("test-ip-multi")
+	c.Assert(err, check.IsNil)
+
+	for i := 1; i <= 350; i++ {
+		ip, err := h.getAvailableIP()
+		c.Assert(err, check.IsNil)
+
+		pak, err := h.CreatePreAuthKey(n.Name, false, false, nil)
+		c.Assert(err, check.IsNil)
+
+		_, err = h.GetMachine("test", "testmachine")
+		c.Assert(err, check.NotNil)
+
+		m := Machine{
+			ID:             uint64(i),
+			MachineKey:     "foo",
+			NodeKey:        "bar",
+			DiscoKey:       "faa",
+			Name:           "testmachine",
+			NamespaceID:    n.ID,
+			Registered:     true,
+			RegisterMethod: "authKey",
+			AuthKeyID:      uint(pak.ID),
+			IPAddress:      ip.String(),
+		}
+		h.db.Save(&m)
+	}
+
+	ips, err := h.getUsedIPs()
+
+	c.Assert(err, check.IsNil)
+
+	c.Assert(len(ips), check.Equals, 350)
+
+	c.Assert(ips[0], check.Equals, netaddr.MustParseIP("10.27.0.1"))
+	c.Assert(ips[9], check.Equals, netaddr.MustParseIP("10.27.0.10"))
+	c.Assert(ips[300], check.Equals, netaddr.MustParseIP("10.27.1.47"))
+
+	// Check that we can read back the IPs
+	m1, err := h.GetMachineByID(1)
+	c.Assert(err, check.IsNil)
+	c.Assert(m1.IPAddress, check.Equals, netaddr.MustParseIP("10.27.0.1").String())
+
+	m50, err := h.GetMachineByID(50)
+	c.Assert(err, check.IsNil)
+	c.Assert(m50.IPAddress, check.Equals, netaddr.MustParseIP("10.27.0.50").String())
+
+	expectedNextIP := netaddr.MustParseIP("10.27.1.97")
+	nextIP, err := h.getAvailableIP()
+	c.Assert(err, check.IsNil)
+
+	c.Assert(nextIP.String(), check.Equals, expectedNextIP.String())
+
+	// If we call get Available again, we should receive
+	// the same IP, as it has not been reserved.
+	nextIP2, err := h.getAvailableIP()
+	c.Assert(err, check.IsNil)
+
+	c.Assert(nextIP2.String(), check.Equals, expectedNextIP.String())
+}
+
+func (s *Suite) TestGetAvailableIpMachineWithoutIP(c *check.C) {
+	ip, err := h.getAvailableIP()
+	c.Assert(err, check.IsNil)
+
+	expected := netaddr.MustParseIP("10.27.0.1")
+
+	c.Assert(ip.String(), check.Equals, expected.String())
+
+	n, err := h.CreateNamespace("test_ip")
+	c.Assert(err, check.IsNil)
+
+	pak, err := h.CreatePreAuthKey(n.Name, false, false, nil)
+	c.Assert(err, check.IsNil)
+
+	_, err = h.GetMachine("test", "testmachine")
+	c.Assert(err, check.NotNil)
+
+	m := Machine{
+		ID:             0,
+		MachineKey:     "foo",
+		NodeKey:        "bar",
+		DiscoKey:       "faa",
+		Name:           "testmachine",
+		NamespaceID:    n.ID,
+		Registered:     true,
+		RegisterMethod: "authKey",
+		AuthKeyID:      uint(pak.ID),
+	}
+	h.db.Save(&m)
+
+	ip2, err := h.getAvailableIP()
+	c.Assert(err, check.IsNil)
+
+	c.Assert(ip2.String(), check.Equals, expected.String())
+}