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udp.go
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udp.go
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// Copyright 2015 CoreOS, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package udp
import (
"encoding/json"
"fmt"
"net"
"os"
"sync"
"syscall"
log "github.com/coreos/flannel/Godeps/_workspace/src/github.com/golang/glog"
"github.com/coreos/flannel/Godeps/_workspace/src/github.com/vishvananda/netlink"
"github.com/coreos/flannel/Godeps/_workspace/src/golang.org/x/net/context"
"github.com/coreos/flannel/backend"
"github.com/coreos/flannel/pkg/ip"
"github.com/coreos/flannel/subnet"
)
const (
encapOverhead = 28 // 20 bytes IP hdr + 8 bytes UDP hdr
defaultPort = 8285
)
type UdpBackend struct {
sm subnet.Manager
network string
config *subnet.Config
cfg struct {
Port int
}
lease *subnet.Lease
ctl *os.File
ctl2 *os.File
tun *os.File
conn *net.UDPConn
mtu int
tunNet ip.IP4Net
ctx context.Context
cancel context.CancelFunc
wg sync.WaitGroup
}
func New(sm subnet.Manager, network string, config *subnet.Config) backend.Backend {
ctx, cancel := context.WithCancel(context.Background())
be := UdpBackend{
sm: sm,
network: network,
config: config,
ctx: ctx,
cancel: cancel,
}
be.cfg.Port = defaultPort
return &be
}
func (m *UdpBackend) Init(extIface *net.Interface, extIaddr net.IP, extEaddr net.IP) (*backend.SubnetDef, error) {
// Parse our configuration
if len(m.config.Backend) > 0 {
if err := json.Unmarshal(m.config.Backend, &m.cfg); err != nil {
return nil, fmt.Errorf("error decoding UDP backend config: %v", err)
}
}
// Acquire the lease form subnet manager
attrs := subnet.LeaseAttrs{
PublicIP: ip.FromIP(extEaddr),
}
l, err := m.sm.AcquireLease(m.ctx, m.network, &attrs)
switch err {
case nil:
m.lease = l
case context.Canceled, context.DeadlineExceeded:
return nil, err
default:
return nil, fmt.Errorf("failed to acquire lease: %v", err)
}
// Tunnel's subnet is that of the whole overlay network (e.g. /16)
// and not that of the individual host (e.g. /24)
m.tunNet = ip.IP4Net{
IP: l.Subnet.IP,
PrefixLen: m.config.Network.PrefixLen,
}
// TUN MTU will be smaller b/c of encap (IP+UDP hdrs)
m.mtu = extIface.MTU - encapOverhead
if err = m.initTun(); err != nil {
return nil, err
}
m.conn, err = net.ListenUDP("udp4", &net.UDPAddr{Port: m.cfg.Port})
if err != nil {
return nil, fmt.Errorf("failed to start listening on UDP socket: %v", err)
}
m.ctl, m.ctl2, err = newCtlSockets()
if err != nil {
return nil, fmt.Errorf("failed to create control socket: %v", err)
}
return &backend.SubnetDef{
Net: l.Subnet,
MTU: m.mtu,
}, nil
}
func (m *UdpBackend) Run() {
// one for each goroutine below
m.wg.Add(2)
go func() {
runCProxy(m.tun, m.conn, m.ctl2, m.tunNet.IP, m.mtu)
m.wg.Done()
}()
go func() {
subnet.LeaseRenewer(m.ctx, m.sm, m.network, m.lease)
m.wg.Done()
}()
m.monitorEvents()
m.wg.Wait()
}
func (m *UdpBackend) Stop() {
if m.ctl != nil {
stopProxy(m.ctl)
}
m.cancel()
}
func (m *UdpBackend) Name() string {
return "UDP"
}
func newCtlSockets() (*os.File, *os.File, error) {
fds, err := syscall.Socketpair(syscall.AF_UNIX, syscall.SOCK_SEQPACKET, 0)
if err != nil {
return nil, nil, err
}
f1 := os.NewFile(uintptr(fds[0]), "ctl")
f2 := os.NewFile(uintptr(fds[1]), "ctl")
return f1, f2, nil
}
func (m *UdpBackend) initTun() error {
var tunName string
var err error
m.tun, tunName, err = ip.OpenTun("flannel%d")
if err != nil {
return fmt.Errorf("Failed to open TUN device: %v", err)
}
err = configureIface(tunName, m.tunNet, m.mtu)
if err != nil {
return err
}
return nil
}
func configureIface(ifname string, ipn ip.IP4Net, mtu int) error {
iface, err := netlink.LinkByName(ifname)
if err != nil {
return fmt.Errorf("failed to lookup interface %v", ifname)
}
err = netlink.AddrAdd(iface, &netlink.Addr{ipn.ToIPNet(), ""})
if err != nil {
return fmt.Errorf("failed to add IP address %v to %v: %v", ipn.String(), ifname, err)
}
err = netlink.LinkSetMTU(iface, mtu)
if err != nil {
return fmt.Errorf("failed to set MTU for %v: %v", ifname, err)
}
err = netlink.LinkSetUp(iface)
if err != nil {
return fmt.Errorf("failed to set interface %v to UP state: %v", ifname, err)
}
// explicitly add a route since there might be a route for a subnet already
// installed by Docker and then it won't get auto added
err = netlink.RouteAdd(&netlink.Route{
LinkIndex: iface.Attrs().Index,
Scope: netlink.SCOPE_UNIVERSE,
Dst: ipn.Network().ToIPNet(),
})
if err != nil && err != syscall.EEXIST {
return fmt.Errorf("Failed to add route (%v -> %v): %v", ipn.Network().String(), ifname, err)
}
return nil
}
func (m *UdpBackend) monitorEvents() {
log.Info("Watching for new subnet leases")
evts := make(chan []subnet.Event)
m.wg.Add(1)
go func() {
subnet.WatchLeases(m.ctx, m.sm, m.network, m.lease, evts)
m.wg.Done()
}()
for {
select {
case evtBatch := <-evts:
m.processSubnetEvents(evtBatch)
case <-m.ctx.Done():
return
}
}
}
func (m *UdpBackend) processSubnetEvents(batch []subnet.Event) {
for _, evt := range batch {
switch evt.Type {
case subnet.SubnetAdded:
log.Info("Subnet added: ", evt.Lease.Subnet)
setRoute(m.ctl, evt.Lease.Subnet, evt.Lease.Attrs.PublicIP, m.cfg.Port)
case subnet.SubnetRemoved:
log.Info("Subnet removed: ", evt.Lease.Subnet)
removeRoute(m.ctl, evt.Lease.Subnet)
default:
log.Error("Internal error: unknown event type: ", int(evt.Type))
}
}
}