107 lines
3.5 KiB
Go
107 lines
3.5 KiB
Go
// Copyright 2013, Cong Ding. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// Author: Cong Ding <dinggnu@gmail.com>
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package stun
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import (
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"encoding/binary"
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"hash/crc32"
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"net"
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)
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type attribute struct {
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types uint16
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length uint16
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value []byte
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}
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func newAttribute(types uint16, value []byte) *attribute {
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att := new(attribute)
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att.types = types
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att.value = padding(value)
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att.length = uint16(len(att.value))
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return att
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}
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func newFingerprintAttribute(packet *packet) *attribute {
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crc := crc32.ChecksumIEEE(packet.bytes()) ^ fingerprint
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buf := make([]byte, 4)
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binary.BigEndian.PutUint32(buf, crc)
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return newAttribute(attributeFingerprint, buf)
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}
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func newSoftwareAttribute(name string) *attribute {
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return newAttribute(attributeSoftware, []byte(name))
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}
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func newChangeReqAttribute(changeIP bool, changePort bool) *attribute {
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value := make([]byte, 4)
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if changeIP {
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value[3] |= 0x04
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}
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if changePort {
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value[3] |= 0x02
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}
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return newAttribute(attributeChangeRequest, value)
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}
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// 0 1 2 3
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// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// |x x x x x x x x| Family | X-Port |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | X-Address (Variable)
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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//
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// Figure 6: Format of XOR-MAPPED-ADDRESS Attribute
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func (v *attribute) xorAddr(transID []byte) *Host {
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xorIP := make([]byte, 16)
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for i := 0; i < len(v.value)-4; i++ {
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xorIP[i] = v.value[i+4] ^ transID[i]
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}
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family := uint16(v.value[1])
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port := binary.BigEndian.Uint16(v.value[2:4])
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// Truncate if IPv4, otherwise net.IP sometimes renders it as an IPv6 address.
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if family == attributeFamilyIPv4 {
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xorIP = xorIP[:4]
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}
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x := binary.BigEndian.Uint16(transID[:2])
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return &Host{family, net.IP(xorIP).String(), port ^ x}
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}
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// 0 1 2 3
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// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// |0 0 0 0 0 0 0 0| Family | Port |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | |
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// | Address (32 bits or 128 bits) |
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// | |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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//
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// Figure 5: Format of MAPPED-ADDRESS Attribute
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func (v *attribute) rawAddr() *Host {
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host := new(Host)
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host.family = uint16(v.value[1])
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host.port = binary.BigEndian.Uint16(v.value[2:4])
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// Truncate if IPv4, otherwise net.IP sometimes renders it as an IPv6 address.
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if host.family == attributeFamilyIPv4 {
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v.value = v.value[:8]
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}
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host.ip = net.IP(v.value[4:]).String()
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return host
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}
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