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vender/github.com/ccding/go-stun/stun/attribute.go

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+// Copyright 2013, Cong Ding. All rights reserved.
+//
+// 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.
+//
+// Author: Cong Ding <dinggnu@gmail.com>
+
+package stun
+
+import (
+	"encoding/binary"
+	"hash/crc32"
+	"net"
+)
+
+type attribute struct {
+	types  uint16
+	length uint16
+	value  []byte
+}
+
+func newAttribute(types uint16, value []byte) *attribute {
+	att := new(attribute)
+	att.types = types
+	att.value = padding(value)
+	att.length = uint16(len(att.value))
+	return att
+}
+
+func newFingerprintAttribute(packet *packet) *attribute {
+	crc := crc32.ChecksumIEEE(packet.bytes()) ^ fingerprint
+	buf := make([]byte, 4)
+	binary.BigEndian.PutUint32(buf, crc)
+	return newAttribute(attributeFingerprint, buf)
+}
+
+func newSoftwareAttribute(name string) *attribute {
+	return newAttribute(attributeSoftware, []byte(name))
+}
+
+func newChangeReqAttribute(changeIP bool, changePort bool) *attribute {
+	value := make([]byte, 4)
+	if changeIP {
+		value[3] |= 0x04
+	}
+	if changePort {
+		value[3] |= 0x02
+	}
+	return newAttribute(attributeChangeRequest, value)
+}
+
+//      0                   1                   2                   3
+//      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
+//     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//     |x x x x x x x x|    Family     |         X-Port                |
+//     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//     |                X-Address (Variable)
+//     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//
+//             Figure 6: Format of XOR-MAPPED-ADDRESS Attribute
+func (v *attribute) xorAddr(transID []byte) *Host {
+	xorIP := make([]byte, 16)
+	for i := 0; i < len(v.value)-4; i++ {
+		xorIP[i] = v.value[i+4] ^ transID[i]
+	}
+	family := uint16(v.value[1])
+	port := binary.BigEndian.Uint16(v.value[2:4])
+	// Truncate if IPv4, otherwise net.IP sometimes renders it as an IPv6 address.
+	if family == attributeFamilyIPv4 {
+		xorIP = xorIP[:4]
+	}
+	x := binary.BigEndian.Uint16(transID[:2])
+	return &Host{family, net.IP(xorIP).String(), port ^ x}
+}
+
+//       0                   1                   2                   3
+//       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
+//      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//      |0 0 0 0 0 0 0 0|    Family     |           Port                |
+//      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//      |                                                               |
+//      |                 Address (32 bits or 128 bits)                 |
+//      |                                                               |
+//      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//
+//               Figure 5: Format of MAPPED-ADDRESS Attribute
+func (v *attribute) rawAddr() *Host {
+	host := new(Host)
+	host.family = uint16(v.value[1])
+	host.port = binary.BigEndian.Uint16(v.value[2:4])
+	// Truncate if IPv4, otherwise net.IP sometimes renders it as an IPv6 address.
+	if host.family == attributeFamilyIPv4 {
+		v.value = v.value[:8]
+	}
+	host.ip = net.IP(v.value[4:]).String()
+	return host
+}