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udp.go
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udp.go
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package shadowsocks
import (
"errors"
"fmt"
"net"
"strconv"
"sync"
"time"
sscore "github.com/shadowsocks/go-shadowsocks2/core"
sssocks "github.com/shadowsocks/go-shadowsocks2/socks"
"github.com/eycorsican/go-tun2socks/common/dns"
"github.com/eycorsican/go-tun2socks/common/log"
"github.com/eycorsican/go-tun2socks/core"
)
type udpHandler struct {
sync.Mutex
cipher sscore.Cipher
remoteAddr net.Addr
conns map[core.UDPConn]net.PacketConn
dnsCache dns.DnsCache
fakeDns dns.FakeDns
timeout time.Duration
}
func NewUDPHandler(server, cipher, password string, timeout time.Duration, dnsCache dns.DnsCache, fakeDns dns.FakeDns) core.UDPConnHandler {
ciph, err := sscore.PickCipher(cipher, []byte{}, password)
if err != nil {
log.Errorf("failed to pick a cipher: %v", err)
}
remoteAddr, err := net.ResolveUDPAddr("udp", server)
if err != nil {
log.Errorf("failed to resolve udp address: %v", err)
}
return &udpHandler{
cipher: ciph,
remoteAddr: remoteAddr,
conns: make(map[core.UDPConn]net.PacketConn, 16),
dnsCache: dnsCache,
fakeDns: fakeDns,
timeout: timeout,
}
}
func (h *udpHandler) fetchUDPInput(conn core.UDPConn, input net.PacketConn) {
buf := core.NewBytes(core.BufSize)
defer func() {
h.Close(conn)
core.FreeBytes(buf)
}()
for {
input.SetDeadline(time.Now().Add(h.timeout))
n, _, err := input.ReadFrom(buf)
if err != nil {
// log.Printf("read remote failed: %v", err)
return
}
addr := sssocks.SplitAddr(buf[:])
resolvedAddr, err := net.ResolveUDPAddr("udp", addr.String())
if err != nil {
return
}
_, err = conn.WriteFrom(buf[int(len(addr)):n], resolvedAddr)
if err != nil {
log.Warnf("write local failed: %v", err)
return
}
if h.dnsCache != nil {
_, port, err := net.SplitHostPort(addr.String())
if err != nil {
panic("impossible error")
}
if port == strconv.Itoa(dns.COMMON_DNS_PORT) {
h.dnsCache.Store(buf[int(len(addr)):n])
return // DNS response
}
}
}
}
func (h *udpHandler) Connect(conn core.UDPConn, target *net.UDPAddr) error {
pc, err := net.ListenPacket("udp", "")
if err != nil {
return err
}
pc = h.cipher.PacketConn(pc)
h.Lock()
h.conns[conn] = pc
h.Unlock()
go h.fetchUDPInput(conn, pc)
if target != nil {
log.Infof("new proxy connection for target: %s:%s", target.Network(), target.String())
}
return nil
}
func (h *udpHandler) ReceiveTo(conn core.UDPConn, data []byte, addr *net.UDPAddr) error {
h.Lock()
pc, ok1 := h.conns[conn]
h.Unlock()
if addr.Port == dns.COMMON_DNS_PORT {
if h.fakeDns != nil {
resp, err := h.fakeDns.GenerateFakeResponse(data)
if err == nil {
_, err = conn.WriteFrom(resp, addr)
if err != nil {
return errors.New(fmt.Sprintf("write dns answer failed: %v", err))
}
h.Close(conn)
return nil
}
}
if h.dnsCache != nil {
if answer := h.dnsCache.Query(data); answer != nil {
_, err := conn.WriteFrom(answer, addr)
if err != nil {
return errors.New(fmt.Sprintf("cache dns answer failed: %v", err))
}
h.Close(conn)
return nil
}
}
}
if ok1 {
// Replace with a domain name if target address IP is a fake IP.
var targetHost string
if h.fakeDns != nil && h.fakeDns.IsFakeIP(addr.IP) {
targetHost = h.fakeDns.QueryDomain(addr.IP)
} else {
targetHost = addr.IP.String()
}
dest := net.JoinHostPort(targetHost, strconv.Itoa(addr.Port))
buf := append([]byte{0, 0, 0}, sssocks.ParseAddr(dest)...)
buf = append(buf, data[:]...)
_, err := pc.WriteTo(buf[3:], h.remoteAddr)
if err != nil {
h.Close(conn)
return errors.New(fmt.Sprintf("write remote failed: %v", err))
}
return nil
} else {
h.Close(conn)
return errors.New(fmt.Sprintf("proxy connection %v->%v does not exists", conn.LocalAddr(), addr))
}
}
func (h *udpHandler) Close(conn core.UDPConn) {
conn.Close()
h.Lock()
defer h.Unlock()
if pc, ok := h.conns[conn]; ok {
pc.Close()
delete(h.conns, conn)
}
}