forked from netbirdio/netbird
/
sock_linux.go
328 lines (279 loc) · 8.53 KB
/
sock_linux.go
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//go:build linux && !android
// Inspired by
// Jason Donenfeld (https://git.zx2c4.com/wireguard-tools/tree/contrib/nat-hole-punching/nat-punch-client.c#n96)
// and @stv0g in https://github.com/stv0g/cunicu/tree/ebpf-poc/ebpf_poc
package sharedsock
import (
"context"
"fmt"
"net"
"sync"
"time"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/google/gopacket/routing"
"github.com/libp2p/go-netroute"
"github.com/mdlayher/socket"
log "github.com/sirupsen/logrus"
"golang.org/x/sync/errgroup"
"golang.org/x/sys/unix"
)
// ErrSharedSockStopped indicates that shared socket has been stopped
var ErrSharedSockStopped = fmt.Errorf("shared socked stopped")
// SharedSocket is a net.PacketConn that initiates two raw sockets (ipv4 and ipv6) and listens to UDP packets filtered
// by BPF instructions (e.g., IncomingSTUNFilter that checks and sends only STUN packets to the listeners (ReadFrom)).
// It is meant to be used when sharing a port with some other process.
type SharedSocket struct {
ctx context.Context
conn4 *socket.Conn
conn6 *socket.Conn
port int
routerMux sync.RWMutex
router routing.Router
packetDemux chan rcvdPacket
cancel context.CancelFunc
}
type rcvdPacket struct {
n int
addr unix.Sockaddr
buf []byte
err error
}
type receiver func(ctx context.Context, p []byte, flags int) (int, unix.Sockaddr, error)
var writeSerializerOptions = gopacket.SerializeOptions{
ComputeChecksums: true,
FixLengths: true,
}
// Listen creates an IPv4 and IPv6 raw sockets, starts a reader and routing table routines
func Listen(port int, filter BPFFilter) (net.PacketConn, error) {
var err error
ctx, cancel := context.WithCancel(context.Background())
rawSock := &SharedSocket{
ctx: ctx,
cancel: cancel,
port: port,
packetDemux: make(chan rcvdPacket),
}
rawSock.router, err = netroute.New()
if err != nil {
return nil, fmt.Errorf("failed to create raw socket router: %v", err)
}
rawSock.conn4, err = socket.Socket(unix.AF_INET, unix.SOCK_RAW, unix.IPPROTO_UDP, "raw_udp4", nil)
if err != nil {
return nil, fmt.Errorf("failed to create ipv4 raw socket: %v", err)
}
rawSock.conn6, err = socket.Socket(unix.AF_INET6, unix.SOCK_RAW, unix.IPPROTO_UDP, "raw_udp6", nil)
if err != nil {
log.Errorf("failed to create ipv6 raw socket: %v", err)
}
ipv4Instructions, ipv6Instructions, err := filter.GetInstructions(uint32(rawSock.port))
if err != nil {
_ = rawSock.Close()
return nil, fmt.Errorf("getBPFInstructions failed with: %rawSock", err)
}
err = rawSock.conn4.SetBPF(ipv4Instructions)
if err != nil {
_ = rawSock.Close()
return nil, fmt.Errorf("socket4.SetBPF failed with: %rawSock", err)
}
if rawSock.conn6 != nil {
err = rawSock.conn6.SetBPF(ipv6Instructions)
if err != nil {
_ = rawSock.Close()
return nil, fmt.Errorf("socket6.SetBPF failed with: %rawSock", err)
}
}
go rawSock.read(rawSock.conn4.Recvfrom)
if rawSock.conn6 != nil {
go rawSock.read(rawSock.conn6.Recvfrom)
}
go rawSock.updateRouter()
return rawSock, nil
}
// updateRouter updates the listener routing table client
// this is needed to avoid outdated information across different client networks
func (s *SharedSocket) updateRouter() {
ticker := time.NewTicker(15 * time.Second)
defer ticker.Stop()
for {
select {
case <-s.ctx.Done():
return
case <-ticker.C:
router, err := netroute.New()
if err != nil {
log.Errorf("failed to create and update packet router for stunListener: %s", err)
continue
}
s.routerMux.Lock()
s.router = router
s.routerMux.Unlock()
}
}
}
// LocalAddr returns an IPv4 address using the supplied port
func (s *SharedSocket) LocalAddr() net.Addr {
// todo check impact on ipv6 discovery
return &net.UDPAddr{
IP: net.IPv4zero,
Port: s.port,
}
}
// SetDeadline sets both the read and write deadlines associated with the ipv4 and ipv6 Conn sockets
func (s *SharedSocket) SetDeadline(t time.Time) error {
err := s.conn4.SetDeadline(t)
if err != nil {
return fmt.Errorf("s.conn4.SetDeadline error: %s", err)
}
if s.conn6 == nil {
return nil
}
err = s.conn6.SetDeadline(t)
if err != nil {
return fmt.Errorf("s.conn6.SetDeadline error: %s", err)
}
return nil
}
// SetReadDeadline sets the read deadline associated with the ipv4 and ipv6 Conn sockets
func (s *SharedSocket) SetReadDeadline(t time.Time) error {
err := s.conn4.SetReadDeadline(t)
if err != nil {
return fmt.Errorf("s.conn4.SetReadDeadline error: %s", err)
}
if s.conn6 == nil {
return nil
}
err = s.conn6.SetReadDeadline(t)
if err != nil {
return fmt.Errorf("s.conn6.SetReadDeadline error: %s", err)
}
return nil
}
// SetWriteDeadline sets the write deadline associated with the ipv4 and ipv6 Conn sockets
func (s *SharedSocket) SetWriteDeadline(t time.Time) error {
err := s.conn4.SetWriteDeadline(t)
if err != nil {
return fmt.Errorf("s.conn4.SetWriteDeadline error: %s", err)
}
if s.conn6 == nil {
return nil
}
err = s.conn6.SetWriteDeadline(t)
if err != nil {
return fmt.Errorf("s.conn6.SetWriteDeadline error: %s", err)
}
return nil
}
// Close closes the underlying ipv4 and ipv6 conn sockets
func (s *SharedSocket) Close() error {
s.cancel()
errGrp := errgroup.Group{}
if s.conn4 != nil {
errGrp.Go(s.conn4.Close)
}
if s.conn6 != nil {
errGrp.Go(s.conn6.Close)
}
return errGrp.Wait()
}
// read start a read loop for a specific receiver and sends the packet to the packetDemux channel
func (s *SharedSocket) read(receiver receiver) {
for {
buf := make([]byte, 1500)
n, addr, err := receiver(s.ctx, buf, 0)
select {
case <-s.ctx.Done():
return
case s.packetDemux <- rcvdPacket{n, addr, buf[:n], err}:
}
}
}
// ReadFrom reads packets received in the packetDemux channel
func (s *SharedSocket) ReadFrom(b []byte) (n int, addr net.Addr, err error) {
var pkt rcvdPacket
select {
case <-s.ctx.Done():
return -1, nil, ErrSharedSockStopped
case pkt = <-s.packetDemux:
}
if pkt.err != nil {
return -1, nil, pkt.err
}
var ip4layer layers.IPv4
var udp layers.UDP
var payload gopacket.Payload
var parser *gopacket.DecodingLayerParser
var ip net.IP
if sa, isIPv4 := pkt.addr.(*unix.SockaddrInet4); isIPv4 {
ip = sa.Addr[:]
parser = gopacket.NewDecodingLayerParser(layers.LayerTypeIPv4, &ip4layer, &udp, &payload)
} else if sa, isIPv6 := pkt.addr.(*unix.SockaddrInet6); isIPv6 {
ip = sa.Addr[:]
parser = gopacket.NewDecodingLayerParser(layers.LayerTypeUDP, &udp, &payload)
} else {
return -1, nil, fmt.Errorf("received invalid address family")
}
decodedLayers := make([]gopacket.LayerType, 0, 3)
err = parser.DecodeLayers(pkt.buf, &decodedLayers)
if err != nil {
return 0, nil, err
}
remoteAddr := &net.UDPAddr{
IP: ip,
Port: int(udp.SrcPort),
}
copy(b, payload)
return int(udp.Length), remoteAddr, nil
}
// WriteTo builds a UDP packet and writes it using the specific IP version writer
func (s *SharedSocket) WriteTo(buf []byte, rAddr net.Addr) (n int, err error) {
rUDPAddr, ok := rAddr.(*net.UDPAddr)
if !ok {
return -1, fmt.Errorf("invalid address type")
}
buffer := gopacket.NewSerializeBuffer()
payload := gopacket.Payload(buf)
udp := &layers.UDP{
SrcPort: layers.UDPPort(s.port),
DstPort: layers.UDPPort(rUDPAddr.Port),
}
s.routerMux.RLock()
defer s.routerMux.RUnlock()
_, _, src, err := s.router.Route(rUDPAddr.IP)
if err != nil {
return 0, fmt.Errorf("got an error while checking route, err: %s", err)
}
rSockAddr, conn, nwLayer := s.getWriterObjects(src, rUDPAddr.IP)
if err := udp.SetNetworkLayerForChecksum(nwLayer); err != nil {
return -1, fmt.Errorf("failed to set network layer for checksum: %w", err)
}
if err := gopacket.SerializeLayers(buffer, writeSerializerOptions, udp, payload); err != nil {
return -1, fmt.Errorf("failed serialize rcvdPacket: %s", err)
}
bufser := buffer.Bytes()
return 0, conn.Sendto(context.TODO(), bufser, 0, rSockAddr)
}
// getWriterObjects returns the specific IP version objects that are used to build a packet and send it using the raw socket
func (s *SharedSocket) getWriterObjects(src, dest net.IP) (sa unix.Sockaddr, conn *socket.Conn, layer gopacket.NetworkLayer) {
if dest.To4() == nil {
sa = &unix.SockaddrInet6{}
copy(sa.(*unix.SockaddrInet6).Addr[:], dest.To16())
conn = s.conn6
layer = &layers.IPv6{
SrcIP: src,
DstIP: dest,
}
} else {
sa = &unix.SockaddrInet4{}
copy(sa.(*unix.SockaddrInet4).Addr[:], dest.To4())
conn = s.conn4
layer = &layers.IPv4{
Version: 4,
TTL: 64,
Protocol: layers.IPProtocolUDP,
SrcIP: src,
DstIP: dest,
}
}
return sa, conn, layer
}