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net.go
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net.go
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package ovpm
import (
"encoding/binary"
"errors"
"fmt"
"log"
"net"
"time"
"github.com/Sirupsen/logrus"
"github.com/asaskevich/govalidator"
"github.com/coreos/go-iptables/iptables"
"github.com/jinzhu/gorm"
)
// NetworkType distinguishes different types of networks that is defined in the networks table.
type NetworkType uint
// NetworkTypes
const (
UNDEFINEDNET NetworkType = iota
SERVERNET
ROUTE
)
var networkTypes = [...]struct {
Type NetworkType
String string
Description string
}{
{UNDEFINEDNET, "UNDEFINEDNET", "unknown network type"},
{SERVERNET, "SERVERNET", "network behind vpn server"},
{ROUTE, "ROUTE", "network to be pushed as route"},
}
// NetworkTypeFromString returns string representation of the network type.
func NetworkTypeFromString(typ string) NetworkType {
for _, v := range networkTypes {
if v.String == typ {
return v.Type
}
}
return UNDEFINEDNET
}
// GetAllNetworkTypes returns all network types defined in the system.
func GetAllNetworkTypes() []NetworkType {
var networkTypeList []NetworkType
for _, v := range networkTypes {
networkTypeList = append(networkTypeList, v.Type)
}
return networkTypeList
}
func (nt NetworkType) String() string {
for _, v := range networkTypes {
if v.Type == nt {
return v.String
}
}
return "UNDEFINEDNET"
}
// Description gives description about the network type.
func (nt NetworkType) Description() string {
for _, v := range networkTypes {
if v.Type == nt {
return v.Description
}
}
return "UNDEFINEDNET"
}
// IsNetworkType returns if the s is a valid network type or not.
func IsNetworkType(s string) bool {
for _, v := range networkTypes {
if s == v.String {
return true
}
}
return false
}
// dbNetworkModel is database model for external networks on the VPN server.
type dbNetworkModel struct {
gorm.Model
ServerID uint
Server dbServerModel
Name string `gorm:"unique_index"`
CIDR string
Type NetworkType
Via string
Users []*dbUserModel `gorm:"many2many:network_users;"`
}
// Network represents a VPN related network.
type Network struct {
dbNetworkModel
}
// GetNetwork returns a network specified by its name.
func GetNetwork(name string) (*Network, error) {
if svr := TheServer(); !svr.IsInitialized() {
return nil, fmt.Errorf("you first need to create server")
}
// Validate user input.
if govalidator.IsNull(name) {
return nil, fmt.Errorf("validation error: %s can not be null", name)
}
var network dbNetworkModel
db.Preload("Users").Where(&dbNetworkModel{Name: name}).First(&network)
if db.NewRecord(&network) {
return nil, fmt.Errorf("network not found %s", name)
}
return &Network{dbNetworkModel: network}, nil
}
// GetAllNetworks returns all networks defined in the system.
func GetAllNetworks() []*Network {
var networks []*Network
var dbNetworks []*dbNetworkModel
db.Preload("Users").Find(&dbNetworks)
for _, n := range dbNetworks {
networks = append(networks, &Network{dbNetworkModel: *n})
}
return networks
}
// CreateNewNetwork creates a new network definition in the system.
func CreateNewNetwork(name, cidr string, nettype NetworkType, via string) (*Network, error) {
if svr := TheServer(); !svr.IsInitialized() {
return nil, fmt.Errorf("you first need to create server")
}
// Validate user input.
if govalidator.IsNull(name) {
return nil, fmt.Errorf("validation error: %s can not be null", name)
}
if !govalidator.Matches(name, "^([\\w\\.]+)$") { // allow alphanumeric, underscore and dot
return nil, fmt.Errorf("validation error: `%s` can only contain letters, numbers, underscores and dots", name)
}
if !govalidator.IsCIDR(cidr) {
return nil, fmt.Errorf("validation error: `%s` must be a network in the CIDR form", cidr)
}
if via != "" && !govalidator.IsIPv4(via) {
return nil, fmt.Errorf("validation error: `%s` must be a network in the IPv4 form", via)
}
if nettype == UNDEFINEDNET {
return nil, fmt.Errorf("validation error: `%s` must be a valid network type", nettype)
}
_, ipnet, err := net.ParseCIDR(cidr)
if err != nil {
return nil, fmt.Errorf("can not parse CIDR %s: %v", cidr, err)
}
// Overwrite via with the parsed IPv4 string.
if nettype == ROUTE && via != "" {
viaIP := net.ParseIP(via).To4()
if err != nil {
return nil, fmt.Errorf("can not parse IPv4 %s: %v", via, err)
}
via = viaIP.String()
} else {
via = ""
}
network := dbNetworkModel{
Name: name,
CIDR: ipnet.String(),
Type: nettype,
Users: []*dbUserModel{},
Via: via,
}
db.Save(&network)
if db.NewRecord(&network) {
return nil, fmt.Errorf("can not create network in the db")
}
TheServer().EmitWithRestart()
logrus.Infof("network defined: %s (%s)", network.Name, network.CIDR)
return &Network{dbNetworkModel: network}, nil
}
// Delete deletes a network definition in the system.
func (n *Network) Delete() error {
svr := TheServer()
if !svr.IsInitialized() {
return fmt.Errorf("you first need to create server")
}
db.Unscoped().Delete(n.dbNetworkModel)
svr.EmitWithRestart()
logrus.Infof("network deleted: %s", n.Name)
return nil
}
// Associate allows the given user access to this network.
func (n *Network) Associate(username string) error {
if svr := TheServer(); !svr.IsInitialized() {
return fmt.Errorf("you first need to create server")
}
user, err := GetUser(username)
if err != nil {
return fmt.Errorf("user can not be fetched: %v", err)
}
var users []dbUserModel
userAssoc := db.Model(&n.dbNetworkModel).Association("Users")
userAssoc.Find(&users)
var found bool
for _, u := range users {
if u.ID == user.ID {
found = true
break
}
}
if found {
return fmt.Errorf("user %s is already associated with the network %s", user.Username, n.Name)
}
userAssoc.Append(user.dbUserModel)
if userAssoc.Error != nil {
return fmt.Errorf("association failed: %v", userAssoc.Error)
}
TheServer().EmitWithRestart()
logrus.Infof("user '%s' is associated with the network '%s'", user.GetUsername(), n.Name)
return nil
}
// Dissociate breaks up the given users association to the said network.
func (n *Network) Dissociate(username string) error {
svr := TheServer()
if !svr.IsInitialized() {
return fmt.Errorf("you first need to create server")
}
user, err := GetUser(username)
if err != nil {
return fmt.Errorf("user can not be fetched: %v", err)
}
var users []dbUserModel
userAssoc := db.Model(&n.dbNetworkModel).Association("Users")
userAssoc.Find(&users)
var found bool
for _, u := range users {
if u.ID == user.ID {
found = true
break
}
}
if !found {
return fmt.Errorf("user %s is already not associated with the network %s", user.Username, n.Name)
}
userAssoc.Delete(user.dbUserModel)
if userAssoc.Error != nil {
return fmt.Errorf("disassociation failed: %v", userAssoc.Error)
}
svr.EmitWithRestart()
logrus.Infof("user '%s' is dissociated with the network '%s'", user.GetUsername(), n.Name)
return nil
}
// GetName returns network's name.
func (n *Network) GetName() string {
return n.Name
}
// GetCIDR returns network's CIDR.
func (n *Network) GetCIDR() string {
return n.CIDR
}
// GetCreatedAt returns network's name.
func (n *Network) GetCreatedAt() string {
return n.CreatedAt.Format(time.UnixDate)
}
// GetType returns network's network type.
func (n *Network) GetType() NetworkType {
return NetworkType(n.Type)
}
// GetAssociatedUsers returns network's associated users.
func (n *Network) GetAssociatedUsers() []*User {
var users []*User
for _, u := range n.Users {
users = append(users, &User{dbUserModel: *u})
}
return users
}
// GetAssociatedUsernames returns network's associated user names.
func (n *Network) GetAssociatedUsernames() []string {
var usernames []string
for _, user := range n.GetAssociatedUsers() {
usernames = append(usernames, user.Username)
}
return usernames
}
// GetVia returns network' via.
func (n *Network) GetVia() string {
return n.Via
}
// interfaceOfIP returns a network interface that has the given IP.
func interfaceOfIP(ipnet *net.IPNet) *net.Interface {
ifaces, err := net.Interfaces()
if err != nil {
return nil
}
for _, iface := range ifaces {
addrs, err := iface.Addrs()
if err != nil {
logrus.Error(err)
return nil
}
for _, addr := range addrs {
switch addr := addr.(type) {
case *net.IPAddr:
if ip := addr.IP; ip != nil {
if ipnet.Contains(ip) {
return &iface
}
}
case *net.IPNet:
if ip := addr.IP; ip != nil {
if ipnet.Contains(ip) {
return &iface
}
}
}
}
}
return nil
}
// routedInterface returns the interface who has a routable IP address on it.
func routedInterface(network string, flags net.Flags) *net.Interface {
switch network {
case "ip", "ip4", "ip6":
default:
return nil
}
ift, err := net.Interfaces()
if err != nil {
return nil
}
for _, ifi := range ift {
if ifi.Flags&flags != flags {
continue
}
if _, ok := hasRoutableIP(network, &ifi); !ok {
continue
}
return &ifi
}
return nil
}
// getOutboundInterface will return the outbound interface if there is one.
func getOutboundInterface() *net.Interface {
conn, err := net.Dial("udp", "8.8.8.8:80")
if err != nil {
log.Fatal(err)
}
defer conn.Close()
localAddr := conn.LocalAddr().(*net.UDPAddr)
ipnet := net.IPNet{
IP: localAddr.IP.To4(),
Mask: localAddr.IP.To4().DefaultMask(),
}
return interfaceOfIP(&ipnet)
}
// hasRoutableIP returns if the received interface has a routable IP
// address attached on it.
func hasRoutableIP(network string, ifi *net.Interface) (net.IP, bool) {
ifat, err := ifi.Addrs()
if err != nil {
return nil, false
}
for _, ifa := range ifat {
switch ifa := ifa.(type) {
case *net.IPAddr:
if ip := routableIP(network, ifa.IP); ip != nil {
return ip, true
}
case *net.IPNet:
if ip := routableIP(network, ifa.IP); ip != nil {
return ip, true
}
}
}
return nil, false
}
// vpnInterface returns the interface which belongs to the VPN server.
func vpnInterface() *net.Interface {
svr := TheServer()
mask := net.IPMask(net.ParseIP(svr.Mask))
prefix := net.ParseIP(svr.Net)
netw := prefix.Mask(mask).To4()
netw[3] = byte(1) // Server is always gets xxx.xxx.xxx.1
ipnet := net.IPNet{IP: netw, Mask: mask}
return interfaceOfIP(&ipnet)
}
// routableIP returns if the received IP is routable.
func routableIP(network string, ip net.IP) net.IP {
if !ip.IsLoopback() && !ip.IsLinkLocalUnicast() && !ip.IsGlobalUnicast() {
return nil
}
switch network {
case "ip4":
if ip := ip.To4(); ip != nil {
return ip
}
case "ip6":
if ip.IsLoopback() { // addressing scope of the loopback address depends on each implementation
return nil
}
if ip := ip.To16(); ip != nil && ip.To4() == nil {
return ip
}
default:
if ip := ip.To4(); ip != nil {
return ip
}
if ip := ip.To16(); ip != nil {
return ip
}
}
return nil
}
// ensureNatEnabled launches a goroutine that constantly tries to enable nat.
func ensureNatEnabled() {
// Nat enablerer
go func() {
for {
err := enableNat()
if err == nil {
logrus.Debug("nat is enabled")
return
}
logrus.Debugf("can not enable nat: %v", err)
// TODO(cad): employ a exponential back-off approach here
// instead of sleeping for the constant duration.
time.Sleep(1 * time.Second)
}
}()
}
// enableNat is an idempotent command that ensures nat is enabled for the vpn server.
func enableNat() error {
if Testing {
return nil
}
// rif := routedInterface("ip", net.FlagUp|net.FlagBroadcast)
// if rif == nil {
// return fmt.Errorf("can not get routable network interface")
// }
rif := getOutboundInterface()
if rif == nil {
return fmt.Errorf("can not get default gw interface")
}
vpnIfc := vpnInterface()
if vpnIfc == nil {
return fmt.Errorf("can not get vpn network interface on the system")
}
// Enable ip forwarding.
TheServer().emitToFile("/proc/sys/net/ipv4/ip_forward", "1", 0)
ipt, err := iptables.NewWithProtocol(iptables.ProtocolIPv4)
if err != nil {
return fmt.Errorf("can not create new iptables object: %v", err)
}
svr := TheServer()
mask := net.IPMask(net.ParseIP(svr.Mask))
prefix := net.ParseIP(svr.Net)
netw := prefix.Mask(mask).To4()
netw[3] = byte(1) // Server is always gets xxx.xxx.xxx.1
ipnet := net.IPNet{IP: netw, Mask: mask}
// Append iptables nat rules.
if err := ipt.AppendUnique("nat", "POSTROUTING", "-s", ipnet.String(), "-o", rif.Name, "-j", "MASQUERADE"); err != nil {
return err
}
if err := ipt.AppendUnique("filter", "FORWARD", "-i", rif.Name, "-o", vpnIfc.Name, "-m", "state", "--state", "RELATED,ESTABLISHED", "-j", "ACCEPT"); err != nil {
return err
}
if err := ipt.AppendUnique("filter", "FORWARD", "-i", vpnIfc.Name, "-o", rif.Name, "-j", "ACCEPT"); err != nil {
return err
}
return nil
}
// HostID2IP converts a host id (32-bit unsigned integer) to an IP address.
func HostID2IP(hostid uint32) net.IP {
ip := make([]byte, 4)
binary.BigEndian.PutUint32(ip, hostid)
return net.IP(ip).To4()
}
// IP2HostID converts an IP address to a host id (32-bit unsigned integer).
func IP2HostID(ip net.IP) uint32 {
hostid := binary.BigEndian.Uint32(ip.To4())
return hostid
}
// IncrementIP will return next ip address within the network.
func IncrementIP(ip, mask string) (string, error) {
if !govalidator.IsIPv4(ip) {
return "", fmt.Errorf("'ip' is expected to be a valid IPv4 %s", ip)
}
if !govalidator.IsIPv4(ip) {
return "", fmt.Errorf("'mask' is expected to be a valid IPv4 %s", mask)
}
ipAddr := net.ParseIP(ip).To4()
netMask := net.IPMask(net.ParseIP(mask).To4())
ipNet := net.IPNet{IP: ipAddr, Mask: netMask}
for i := len(ipAddr) - 1; i >= 0; i-- {
ipAddr[i]++
if ip[i] != 0 {
break
}
}
if !ipNet.Contains(ipAddr) {
return ip, errors.New("overflowed CIDR while incrementing IP")
}
return ipAddr.String(), nil
}