Kea 2.2.0
option6_pdexclude.cc
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1// Copyright (C) 2016-2022 Internet Systems Consortium, Inc. ("ISC")
2//
3// This Source Code Form is subject to the terms of the Mozilla Public
4// License, v. 2.0. If a copy of the MPL was not distributed with this
5// file, You can obtain one at http://mozilla.org/MPL/2.0/.
6
7#include <config.h>
8
10#include <dhcp/dhcp6.h>
13#include <util/encode/hex.h>
14#include <util/io_utilities.h>
15
16#include <boost/dynamic_bitset.hpp>
17#include <iostream>
18#include <stdint.h>
19
20using namespace std;
21using namespace isc;
22using namespace isc::dhcp;
23using namespace isc::asiolink;
24using namespace isc::util;
25
26namespace isc {
27namespace dhcp {
28
30 const uint8_t delegated_prefix_length,
31 const isc::asiolink::IOAddress& excluded_prefix,
32 const uint8_t excluded_prefix_length)
34 excluded_prefix_length_(excluded_prefix_length),
35 subnet_id_() {
36
37 // Expecting v6 prefixes of sane length.
38 if (!delegated_prefix.isV6() || !excluded_prefix.isV6() ||
39 (delegated_prefix_length > 128) || (excluded_prefix_length_ > 128)) {
40 isc_throw(BadValue, "invalid delegated or excluded prefix values specified: "
41 << delegated_prefix << "/"
42 << static_cast<int>(delegated_prefix_length) << ", "
43 << excluded_prefix << "/"
44 << static_cast<int>(excluded_prefix_length_));
45 }
46
47 // Excluded prefix must be longer than or equal to the delegated prefix.
48 if (excluded_prefix_length_ <= delegated_prefix_length) {
49 isc_throw(BadValue, "length of the excluded prefix "
50 << excluded_prefix << "/"
51 << static_cast<int>(excluded_prefix_length_)
52 << " must be greater than the length of the"
53 " delegated prefix " << delegated_prefix << "/"
54 << static_cast<int>(delegated_prefix_length));
55 }
56
57 // Both prefixes must share common part with a length equal to the
58 // delegated prefix length.
59 std::vector<uint8_t> delegated_prefix_bytes = delegated_prefix.toBytes();
60 boost::dynamic_bitset<uint8_t> delegated_prefix_bits(delegated_prefix_bytes.rbegin(),
61 delegated_prefix_bytes.rend());
62
63 std::vector<uint8_t> excluded_prefix_bytes = excluded_prefix.toBytes();
64 boost::dynamic_bitset<uint8_t> excluded_prefix_bits(excluded_prefix_bytes.rbegin(),
65 excluded_prefix_bytes.rend());
66
67
68 // See RFC6603, section 4.2: assert(p1>>s == p2>>s)
69 const uint8_t delta = 128 - delegated_prefix_length;
70
71 if ((delegated_prefix_bits >> delta) != (excluded_prefix_bits >> delta)) {
72 isc_throw(BadValue, "excluded prefix "
73 << excluded_prefix << "/"
74 << static_cast<int>(excluded_prefix_length_)
75 << " must have the same common prefix part of "
76 << static_cast<int>(delegated_prefix_length)
77 << " as the delegated prefix "
78 << delegated_prefix << "/"
79 << static_cast<int>(delegated_prefix_length));
80 }
81
82
83 // Shifting prefix by delegated prefix length leaves us with only a
84 // subnet id part of the excluded prefix.
85 excluded_prefix_bits <<= delegated_prefix_length;
86
87 // Calculate subnet id length.
88 const uint8_t subnet_id_length = getSubnetIDLength(delegated_prefix_length,
89 excluded_prefix_length);
90 for (uint8_t i = 0; i < subnet_id_length; ++i) {
91 // Retrieve bit representation of the current byte.
92 const boost::dynamic_bitset<uint8_t> first_byte = excluded_prefix_bits >> 120;
93
94 // Convert it to a numeric value.
95 uint8_t val = static_cast<uint8_t>(first_byte.to_ulong());
96
97 // Zero padded excluded_prefix_bits follow when excluded_prefix_length_ is
98 // not divisible by 8.
99 if (i == subnet_id_length - 1) {
100 uint8_t length_delta = excluded_prefix_length_ - delegated_prefix_length;
101 if (length_delta % 8 != 0) {
102 uint8_t mask = 0xFF;
103 mask <<= (8 - (length_delta % 8));
104 val &= mask;
105 }
106 }
107 // Store calculated value in a buffer.
108 subnet_id_.push_back(val);
109
110 // Go to the next byte.
111 excluded_prefix_bits <<= 8;
112 }
113}
114
117 : Option(V6, D6O_PD_EXCLUDE),
118 excluded_prefix_length_(0),
119 subnet_id_() {
120 unpack(begin, end);
121}
122
125 return (cloneInternal<Option6PDExclude>());
126}
127
128void
130 // Make sure that the subnet identifier is valid. It should never
131 // be empty.
132 if ((excluded_prefix_length_ == 0) || subnet_id_.empty()) {
133 isc_throw(BadValue, "subnet identifier of a Prefix Exclude option"
134 " must not be empty");
135 }
136
137 // Header = option code and length.
138 packHeader(buf);
139
140 // Excluded prefix length is always 1 byte long field.
141 buf.writeUint8(excluded_prefix_length_);
142
143 // Write the subnet identifier.
144 buf.writeData(static_cast<const void*>(&subnet_id_[0]), subnet_id_.size());
145}
146
147void
150
151 // At this point we don't know the excluded prefix length, but the
152 // minimum requirement is that reminder of this option includes the
153 // excluded prefix length and at least 1 byte of the IPv6 subnet id.
154 if (std::distance(begin, end) < 2) {
155 isc_throw(BadValue, "truncated Prefix Exclude option");
156 }
157
158 // We can safely read the excluded prefix length and move forward.
159 uint8_t excluded_prefix_length = *begin++;
160 if (excluded_prefix_length == 0) {
161 isc_throw(BadValue, "excluded prefix length must not be 0");
162 }
163
164 std::vector<uint8_t> subnet_id_bytes(begin, end);
165
166 // Subnet id parsed, proceed to the end of the option.
167 begin = end;
168
169 uint8_t last_bits_num = excluded_prefix_length % 8;
170 if (last_bits_num > 0) {
171 *subnet_id_bytes.rbegin() = (*subnet_id_bytes.rbegin() >> (8 - last_bits_num)
172 << (8 - (last_bits_num)));
173 }
174
175 excluded_prefix_length_ = excluded_prefix_length;
176 subnet_id_.swap(subnet_id_bytes);
177}
178
179uint16_t
181 return (getHeaderLen() + sizeof(excluded_prefix_length_) + subnet_id_.size());
182}
183
184std::string
185Option6PDExclude::toText(int indent) const {
186 std::ostringstream s;
187 s << headerToText(indent) << ": ";
188 s << "excluded-prefix-len=" << static_cast<unsigned>(excluded_prefix_length_)
189 << ", subnet-id=0x" << util::encode::encodeHex(subnet_id_);
190 return (s.str());
191}
192
195 const uint8_t delegated_prefix_length) const {
196 // Get binary representation of the delegated prefix.
197 std::vector<uint8_t> delegated_prefix_bytes = delegated_prefix.toBytes();
198 // We need to calculate how many bytes include the useful data and assign
199 // zeros to remaining bytes (beyond the prefix length).
200 const uint8_t bytes_length = (delegated_prefix_length / 8) +
201 static_cast<uint8_t>(delegated_prefix_length % 8 != 0);
202 std::fill(delegated_prefix_bytes.begin() + bytes_length,
203 delegated_prefix_bytes.end(), 0);
204
205 // Convert the delegated prefix to bit format.
206 boost::dynamic_bitset<uint8_t> bits(delegated_prefix_bytes.rbegin(),
207 delegated_prefix_bytes.rend());
208
209 boost::dynamic_bitset<uint8_t> subnet_id_bits(subnet_id_.rbegin(),
210 subnet_id_.rend());
211
212 // Concatenate the delegated prefix with subnet id. The resulting prefix
213 // is an excluded prefix in bit format.
214 for (int i = subnet_id_bits.size() - 1; i >= 0; --i) {
215 bits.set(128 - delegated_prefix_length - subnet_id_bits.size() + i,
216 subnet_id_bits.test(i));
217 }
218
219 // Convert the prefix to binary format.
220 std::vector<uint8_t> bytes(V6ADDRESS_LEN);
221 boost::to_block_range(bits, bytes.rbegin());
222
223 // And create a prefix object from bytes.
224 return (IOAddress::fromBytes(AF_INET6, &bytes[0]));
225}
226
227uint8_t
228Option6PDExclude::getSubnetIDLength(const uint8_t delegated_prefix_length,
229 const uint8_t excluded_prefix_length) const {
230 uint8_t subnet_id_length_bits = excluded_prefix_length -
231 delegated_prefix_length - 1;
232 uint8_t subnet_id_length = (subnet_id_length_bits / 8) + 1;
233 return (subnet_id_length);
234}
235
236} // end of namespace isc::dhcp
237} // end of namespace isc
A generic exception that is thrown if a parameter given to a method is considered invalid in that con...
virtual OptionPtr clone() const
Copies this option and returns a pointer to the copy.
asiolink::IOAddress getExcludedPrefix(const asiolink::IOAddress &delegated_prefix, const uint8_t delegated_prefix_length) const
Returns excluded prefix.
virtual std::string toText(int indent=0) const
Returns Prefix Exclude option in textual format.
Option6PDExclude(const isc::asiolink::IOAddress &delegated_prefix, const uint8_t delegated_prefix_length, const isc::asiolink::IOAddress &excluded_prefix, const uint8_t excluded_prefix_length)
Constructor.
virtual uint16_t len() const
Returns length of the complete option (data length + DHCPv6 option header)
virtual void pack(isc::util::OutputBuffer &buf, bool check=true) const
Writes option in wire-format to a buffer.
virtual void unpack(OptionBufferConstIter begin, OptionBufferConstIter end)
Parses received buffer.
std::string headerToText(const int indent=0, const std::string &type_name="") const
Returns option header in the textual format.
Definition: option.cc:288
virtual uint16_t getHeaderLen() const
Returns length of header (2 for v4, 4 for v6)
Definition: option.cc:321
void packHeader(isc::util::OutputBuffer &buf, bool check=true) const
Store option's header in a buffer.
Definition: option.cc:119
The OutputBuffer class is a buffer abstraction for manipulating mutable data.
Definition: buffer.h:294
void writeUint8(uint8_t data)
Write an unsigned 8-bit integer into the buffer.
Definition: buffer.h:466
void writeData(const void *data, size_t len)
Copy an arbitrary length of data into the buffer.
Definition: buffer.h:550
@ D6O_PD_EXCLUDE
Definition: dhcp6.h:87
#define isc_throw(type, stream)
A shortcut macro to insert known values into exception arguments.
OptionBuffer::const_iterator OptionBufferConstIter
const_iterator for walking over OptionBuffer
Definition: option.h:30
boost::shared_ptr< Option > OptionPtr
Definition: option.h:36
string encodeHex(const vector< uint8_t > &binary)
Encode binary data in the base16 ('hex') format.
Definition: base_n.cc:469
Definition: edns.h:19
Defines the logger used by the top-level component of kea-lfc.