forked from jpillora/chisel
/
tunnel_in_proxy_udp.go
189 lines (180 loc) · 4.73 KB
/
tunnel_in_proxy_udp.go
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package tunnel
import (
"context"
"encoding/gob"
"fmt"
"io"
"net"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/JackieKu/chisel/share/cio"
"github.com/JackieKu/chisel/share/settings"
"github.com/jpillora/sizestr"
"golang.org/x/crypto/ssh"
"golang.org/x/sync/errgroup"
)
//listenUDP is a special listener which forwards packets via
//the bound ssh connection. tricky part is multiplexing lots of
//udp clients through the entry node. each will listen on its
//own source-port for a response:
// (random)
// src-1 1111->... dst-1 6345->7777
// src-2 2222->... <---> udp <---> udp <-> dst-1 7543->7777
// src-3 3333->... listener handler dst-1 1444->7777
//
//we must store these mappings (1111-6345, etc) in memory for a length
//of time, so that when the exit node receives a response on 6345, it
//knows to return it to 1111.
func listenUDP(l *cio.Logger, sshTun sshTunnel, remote *settings.Remote) (*udpListener, error) {
a, err := net.ResolveUDPAddr("udp", remote.Local())
if err != nil {
return nil, l.Errorf("resolve: %s", err)
}
conn, err := net.ListenUDP("udp", a)
if err != nil {
return nil, l.Errorf("listen: %s", err)
}
//ready
u := &udpListener{
Logger: l,
sshTun: sshTun,
remote: remote,
inbound: conn,
}
return u, nil
}
type udpListener struct {
*cio.Logger
sshTun sshTunnel
remote *settings.Remote
inbound *net.UDPConn
outboundMut sync.Mutex
outbound *udpChannel
sent, recv int64
}
func (u *udpListener) run(ctx context.Context) error {
defer u.inbound.Close()
//udp doesnt accept connections,
//udp simply forwards packets
//and therefore only needs to listen
eg, ctx := errgroup.WithContext(ctx)
eg.Go(func() error {
return u.runInbound(ctx)
})
eg.Go(func() error {
return u.runOutbound(ctx)
})
if err := eg.Wait(); err != nil {
u.Debugf("listen: %s", err)
return err
}
u.Debugf("Close (sent %s received %s)", sizestr.ToString(u.sent), sizestr.ToString(u.recv))
return nil
}
func (u *udpListener) runInbound(ctx context.Context) error {
const maxMTU = 9012
buff := make([]byte, maxMTU)
for !isDone(ctx) {
//read from inbound udp
u.inbound.SetReadDeadline(time.Now().Add(time.Second))
n, addr, err := u.inbound.ReadFromUDP(buff)
if e, ok := err.(net.Error); ok && (e.Timeout() || e.Temporary()) {
continue
}
if err != nil {
return u.Errorf("read error: %w", err)
}
//upsert ssh channel
uc, err := u.getUDPChan(ctx)
if err != nil {
if strings.HasSuffix(err.Error(), "EOF") {
continue
}
return u.Errorf("inbound-udpchan: %w", err)
}
//send over channel, including source address
b := buff[:n]
if err := uc.encode(addr.String(), b); err != nil {
if strings.HasSuffix(err.Error(), "EOF") {
continue //dropped packet...
}
return u.Errorf("encode error: %w", err)
}
//stats
atomic.AddInt64(&u.sent, int64(n))
}
return nil
}
func (u *udpListener) runOutbound(ctx context.Context) error {
for !isDone(ctx) {
//upsert ssh channel
uc, err := u.getUDPChan(ctx)
if err != nil {
if strings.HasSuffix(err.Error(), "EOF") {
continue
}
return u.Errorf("outbound-udpchan: %w", err)
}
//receive from channel, including source address
p := udpPacket{}
if err := uc.decode(&p); err == io.EOF {
//outbound ssh disconnected, get new connection...
continue
} else if err != nil {
return u.Errorf("decode error: %w", err)
}
//write back to inbound udp
addr, err := net.ResolveUDPAddr("udp", p.Src)
if err != nil {
return u.Errorf("resolve error: %w", err)
}
n, err := u.inbound.WriteToUDP(p.Payload, addr)
if err != nil {
return u.Errorf("write error: %w", err)
}
//stats
atomic.AddInt64(&u.recv, int64(n))
}
return nil
}
func (u *udpListener) getUDPChan(ctx context.Context) (*udpChannel, error) {
u.outboundMut.Lock()
defer u.outboundMut.Unlock()
//cached
if u.outbound != nil {
return u.outbound, nil
}
//not cached, bind
sshConn := u.sshTun.getSSH(ctx)
if sshConn == nil {
return nil, fmt.Errorf("ssh-conn nil")
}
//ssh request for udp packets for this proxy's remote,
//just "udp" since the remote address is sent with each packet
dstAddr := u.remote.Remote() + "/udp"
rwc, reqs, err := sshConn.OpenChannel("chisel", []byte(dstAddr))
if err != nil {
return nil, fmt.Errorf("ssh-chan error: %s", err)
}
go ssh.DiscardRequests(reqs)
//remove on disconnect
go u.unsetUDPChan(sshConn)
//ready
o := &udpChannel{
r: gob.NewDecoder(rwc),
w: gob.NewEncoder(rwc),
c: rwc,
}
u.outbound = o
u.Debugf("aquired channel")
return o, nil
}
func (u *udpListener) unsetUDPChan(sshConn ssh.Conn) {
sshConn.Wait()
u.Debugf("lost channel")
u.outboundMut.Lock()
u.outbound = nil
u.outboundMut.Unlock()
}