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ip_router.go
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ip_router.go
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//go:build linux && !no_ip_router && linux && !no_services
// +build linux,!no_ip_router,linux,!no_services
package services
import (
"bytes"
"fmt"
"math"
"net"
"strings"
"sync"
"time"
"github.com/ansible/receptor/pkg/netceptor"
"github.com/ansible/receptor/pkg/utils"
"github.com/ghjm/cmdline"
"github.com/songgao/water"
"github.com/vishvananda/netlink"
"golang.org/x/net/ipv4"
"golang.org/x/net/ipv6"
)
const adTypeIPRouter = "IP Router"
type ipRoute struct {
dest *net.IPNet
via string
}
// IPRouterService is an IP router service.
type IPRouterService struct {
nc *netceptor.Netceptor
networkName string
tunIfName string
localNet *net.IPNet
advertiseRoutes []*net.IPNet
linkIP net.IP
destIP net.IP
tunIf *water.Interface
link netlink.Link
nConn netceptor.PacketConner
knownRoutes []ipRoute
knownRoutesLock *sync.RWMutex
}
// NewIPRouter creates a new IP router service.
func NewIPRouter(nc *netceptor.Netceptor, networkName string, tunInterface string,
localNet string, routes string,
) (*IPRouterService, error) {
ipr := &IPRouterService{
nc: nc,
networkName: networkName,
tunIfName: tunInterface,
knownRoutes: make([]ipRoute, 0),
knownRoutesLock: &sync.RWMutex{},
}
var err error
_, ipr.localNet, err = net.ParseCIDR(localNet)
if err != nil {
return nil, fmt.Errorf("could not parse %s as a CIDR address", localNet)
}
ones, bits := ipr.localNet.Mask.Size()
if ones != 30 {
return nil, fmt.Errorf("local network %s must be a /30 CIDR", localNet)
}
if bits != 32 {
return nil, fmt.Errorf("local network %s must be IPv4", localNet)
}
ipr.advertiseRoutes = make([]*net.IPNet, 0)
if routes != "" {
routeList := strings.Split(routes, ",")
for i := range routeList {
_, ipNet, err := net.ParseCIDR(routeList[i])
if err != nil {
return nil, fmt.Errorf("could not parse %s as a CIDR address", routeList[i])
}
ipr.advertiseRoutes = append(ipr.advertiseRoutes, ipNet)
}
}
err = ipr.run()
if err != nil {
return nil, err
}
return ipr, nil
}
func (ipr *IPRouterService) updateKnownRoutes() {
newRoutes := make([]ipRoute, 0)
status := ipr.nc.Status()
for i := range status.Advertisements {
ad := status.Advertisements[i]
adType, ok := ad.Tags["type"]
if !ok || adType != adTypeIPRouter {
continue
}
network, ok := ad.Tags["network"]
if !ok || network != ipr.networkName {
continue
}
_, ok = status.RoutingTable[ad.NodeID]
if !ok {
continue
}
for key, value := range ad.Tags {
if strings.HasPrefix(key, "route") {
_, ipNet, err := net.ParseCIDR(value)
if err == nil {
newRoute := ipRoute{
dest: ipNet,
via: ad.NodeID,
}
newRoutes = append(newRoutes, newRoute)
}
}
}
}
ipr.knownRoutesLock.Lock()
ipr.knownRoutes = newRoutes
ipr.knownRoutesLock.Unlock()
}
func (ipr *IPRouterService) reconcileRoutingTable() {
ipr.knownRoutesLock.RLock()
defer ipr.knownRoutesLock.RUnlock()
routes, err := netlink.RouteList(ipr.link, netlink.FAMILY_ALL)
if err != nil {
ipr.nc.Logger.Error("error retrieving kernel routes list: %s", err)
return
}
fmt.Printf("=========\n")
fmt.Printf("Receptor Routes:\n")
for i := range ipr.knownRoutes {
fmt.Printf(" dest %s via %s\n", ipr.knownRoutes[i].dest.String(), ipr.knownRoutes[i].via)
}
fmt.Printf("Kernel Routes:\n")
for i := range routes {
fmt.Printf(" dest %s\n", routes[i].Dst.String())
}
for i := range ipr.knownRoutes {
kr := ipr.knownRoutes[i]
found := false
for j := range routes {
route := routes[j]
if kr.dest.IP.Equal(route.Dst.IP) && bytes.Equal(kr.dest.Mask, route.Dst.Mask) {
found = true
break
}
}
if !found {
ipr.nc.Logger.Debug("Adding route to %s", kr.dest.String())
err := ipr.addRoute(kr.dest)
if err != nil {
ipr.nc.Logger.Error("error adding kernel route to %s: %s", kr.dest.String(), err)
}
}
}
_, ipv6LinkLocal, _ := net.ParseCIDR("fe80::/10")
for i := range routes {
route := routes[i]
if ipr.localNet.Contains(route.Dst.IP) {
continue
}
if ipv6LinkLocal.Contains(route.Dst.IP) {
continue
}
found := false
for j := range ipr.knownRoutes {
kr := ipr.knownRoutes[j]
if kr.dest.IP.Equal(route.Dst.IP) && bytes.Equal(kr.dest.Mask, route.Dst.Mask) {
found = true
break
}
}
if !found {
ipr.nc.Logger.Debug("Removing route to %s", route.Dst.String())
err := netlink.RouteDel(&route)
if err != nil {
ipr.nc.Logger.Error("error deleting kernel route to %s: %s", route.Dst.String(), err)
}
}
}
}
func (ipr *IPRouterService) runAdvertisingWatcher() {
for {
ipr.updateKnownRoutes()
ipr.reconcileRoutingTable()
select {
case <-ipr.nc.Context().Done():
return
case <-time.After(10 * time.Second):
}
}
}
func (ipr *IPRouterService) runTunToNetceptor() {
ipr.nc.Logger.Debug("Running tunnel-to-Receptor forwarder\n")
buf := make([]byte, utils.NormalBufferSize)
for {
if ipr.nc.Context().Err() != nil {
return
}
n, err := ipr.tunIf.Read(buf)
if err != nil {
ipr.nc.Logger.Error("Error reading from tun device: %s\n", err)
continue
}
packet := buf[:n]
// Get the destination address from the received packet
ipVersion := int(packet[0] >> 4)
var destIP net.IP
switch ipVersion {
case 4:
header, err := ipv4.ParseHeader(packet)
if err != nil {
ipr.nc.Logger.Debug("Malformed ipv4 packet received: %s", err)
}
destIP = header.Dst
case 6:
header, err := ipv6.ParseHeader(packet)
if err != nil {
ipr.nc.Logger.Debug("Malformed ipv6 packet received: %s", err)
}
destIP = header.Dst
default:
ipr.nc.Logger.Debug("Packet received with unknown version %d", ipVersion)
continue
}
// Find the lowest cost receptor node that can accept this packet
remoteNode := ""
remoteCost := math.MaxFloat64
ipr.knownRoutesLock.RLock()
for i := range ipr.knownRoutes {
route := ipr.knownRoutes[i]
cost, err := ipr.nc.PathCost(route.via)
if err != nil {
continue
}
if cost < remoteCost && route.dest.Contains(destIP) {
remoteCost = cost
remoteNode = route.via
}
}
ipr.knownRoutesLock.RUnlock()
if remoteNode == "" {
continue
}
// Send the packet via Receptor
remoteAddr := ipr.nc.NewAddr(remoteNode, ipr.networkName)
ipr.nc.Logger.Trace(" Forwarding data length %d to %s via %s\n", n, destIP, remoteAddr.String())
wn, err := ipr.nConn.WriteTo(packet, remoteAddr)
if err != nil || wn != n {
ipr.nc.Logger.Error("Error writing to Receptor network: %s\n", err)
}
}
}
func (ipr *IPRouterService) runNetceptorToTun() {
ipr.nc.Logger.Debug("Running netceptor to tunnel forwarder\n")
buf := make([]byte, utils.NormalBufferSize)
for {
if ipr.nc.Context().Err() != nil {
return
}
n, addr, err := ipr.nConn.ReadFrom(buf)
if err != nil {
ipr.nc.Logger.Error("Error reading from Receptor: %s\n", err)
continue
}
ipr.nc.Logger.Trace(" Forwarding data length %d from %s to %s\n", n,
addr.String(), ipr.tunIf.Name())
wn, err := ipr.tunIf.Write(buf[:n])
if err != nil || wn != n {
ipr.nc.Logger.Error("Error writing to tun device: %s\n", err)
}
}
}
func (ipr *IPRouterService) addRoute(route *net.IPNet) error {
err := netlink.RouteAdd(&netlink.Route{
LinkIndex: ipr.link.Attrs().Index,
Scope: netlink.SCOPE_UNIVERSE,
Dst: route,
Gw: ipr.destIP,
})
if err != nil {
return fmt.Errorf("error adding route to interface: %s", err)
}
return nil
}
// Run runs the IP router.
func (ipr *IPRouterService) run() error {
cfg := water.Config{
DeviceType: water.TUN,
}
cfg.Name = ipr.tunIfName
var err error
ipr.tunIf, err = water.New(water.Config{DeviceType: water.TUN})
if err != nil {
return fmt.Errorf("error opening tun device: %s", err)
}
ipr.link, err = netlink.LinkByName(ipr.tunIf.Name())
if err != nil {
return fmt.Errorf("error accessing link for tun device: %s", err)
}
baseIP := ipr.localNet.IP.To4()
ipr.linkIP = make([]byte, 4)
copy(ipr.linkIP, baseIP)
ipr.linkIP[3]++
ipr.destIP = make([]byte, 4)
copy(ipr.destIP, ipr.linkIP)
ipr.destIP[3]++
if !ipr.localNet.Contains(ipr.linkIP) || !ipr.localNet.Contains(ipr.destIP) {
return fmt.Errorf("error calculating link and remote addresses")
}
addr := &netlink.Addr{
IPNet: netlink.NewIPNet(ipr.linkIP),
Peer: netlink.NewIPNet(ipr.destIP),
}
err = netlink.AddrAdd(ipr.link, addr)
if err != nil {
return fmt.Errorf("error adding IP address to link: %s", err)
}
err = netlink.LinkSetUp(ipr.link)
if err != nil {
return fmt.Errorf("error setting link up: %s", err)
}
advertisement := map[string]string{
"type": adTypeIPRouter,
"network": ipr.networkName,
"route_local": ipr.localNet.String(),
}
for i := range ipr.advertiseRoutes {
advertisement[fmt.Sprintf("route_%d", i)] = ipr.advertiseRoutes[i].String()
}
ipr.nConn, err = ipr.nc.ListenPacketAndAdvertise(ipr.networkName, advertisement)
if err != nil {
return fmt.Errorf("error listening for service %s: %s", ipr.networkName, err)
}
go ipr.runAdvertisingWatcher()
go ipr.runTunToNetceptor()
go ipr.runNetceptorToTun()
return nil
}
// ipRouterCfg is the cmdline configuration object for an IP router.
type ipRouterCfg struct {
NetworkName string `required:"true" description:"Name of this network and service."`
Interface string `description:"Name of the local tun interface"`
LocalNet string `required:"true" description:"Local /30 CIDR address"`
Routes string `description:"Comma separated list of CIDR subnets to advertise"`
}
// Run runs the action.
func (cfg ipRouterCfg) Run() error {
netceptor.MainInstance.Logger.Debug("Running tun router service %s\n", cfg)
_, err := NewIPRouter(netceptor.MainInstance, cfg.NetworkName, cfg.Interface, cfg.LocalNet, cfg.Routes)
if err != nil {
return err
}
return nil
}
func init() {
cmdline.RegisterConfigTypeForApp("receptor-ip-router",
"ip-router", "Run an IP router using a tun interface", ipRouterCfg{}, cmdline.Section(servicesSection))
}