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// Copyright 2016 Cong Ding
//
// 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 stun
import (
"bytes"
"encoding/hex"
"errors"
"net"
"time"
)
const (
numRetransmit = 9
defaultTimeout = 100
maxTimeout = 1600
maxPacketSize = 1024
)
func (c *Client) sendBindingReq(conn net.PacketConn, addr net.Addr, changeIP bool, changePort bool) (*response, error) {
// Construct packet.
pkt, err := newPacket()
if err != nil {
return nil, err
}
pkt.types = typeBindingRequest
attribute := newSoftwareAttribute(c.softwareName)
pkt.addAttribute(*attribute)
if changeIP || changePort {
attribute = newChangeReqAttribute(changeIP, changePort)
pkt.addAttribute(*attribute)
}
// length of fingerprint attribute must be included into crc,
// so we add it before calculating crc, then subtract it after calculating crc.
pkt.length += 8
attribute = newFingerprintAttribute(pkt)
pkt.length -= 8
pkt.addAttribute(*attribute)
// Send packet.
return c.send(pkt, conn, addr)
}
// RFC 3489: Clients SHOULD retransmit the request starting with an interval
// of 100ms, doubling every retransmit until the interval reaches 1.6s.
// Retransmissions continue with intervals of 1.6s until a response is
// received, or a total of 9 requests have been sent.
func (c *Client) send(pkt *packet, conn net.PacketConn, addr net.Addr) (*response, error) {
c.logger.Info("\n" + hex.Dump(pkt.bytes()))
timeout := defaultTimeout
packetBytes := make([]byte, maxPacketSize)
for i := 0; i < numRetransmit; i++ {
// Send packet to the server.
length, err := conn.WriteTo(pkt.bytes(), addr)
if err != nil {
return nil, err
}
if length != len(pkt.bytes()) {
return nil, errors.New("Error in sending data.")
}
err = conn.SetReadDeadline(time.Now().Add(time.Duration(timeout) * time.Millisecond))
if err != nil {
return nil, err
}
if timeout < maxTimeout {
timeout *= 2
}
for {
// Read from the port.
length, raddr, err := conn.ReadFrom(packetBytes)
if err != nil {
if nerr, ok := err.(net.Error); ok && nerr.Timeout() {
break
}
return nil, err
}
p, err := newPacketFromBytes(packetBytes[0:length])
if err != nil {
return nil, err
}
// If transId mismatches, keep reading until get a
// matched packet or timeout.
if !bytes.Equal(pkt.transID, p.transID) {
continue
}
c.logger.Info("\n" + hex.Dump(packetBytes[0:length]))
resp := newResponse(p, conn)
resp.serverAddr = newHostFromStr(raddr.String())
return resp, err
}
}
return nil, nil
}
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