1 /*
2 * Copyright 2018 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 #include "pc/sdp_serializer.h"
12
13 #include <algorithm>
14 #include <map>
15 #include <string>
16 #include <utility>
17 #include <vector>
18
19 #include "absl/algorithm/container.h"
20 #include "absl/types/optional.h"
21 #include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
22 #include "rtc_base/checks.h"
23 #include "rtc_base/string_encode.h"
24 #include "rtc_base/string_to_number.h"
25 #include "rtc_base/strings/string_builder.h"
26
27 using cricket::RidDescription;
28 using cricket::RidDirection;
29 using cricket::SimulcastDescription;
30 using cricket::SimulcastLayer;
31 using cricket::SimulcastLayerList;
32
33 namespace webrtc {
34
35 namespace {
36
37 // delimiters
38 const char kDelimiterComma[] = ",";
39 const char kDelimiterCommaChar = ',';
40 const char kDelimiterEqual[] = "=";
41 const char kDelimiterEqualChar = '=';
42 const char kDelimiterSemicolon[] = ";";
43 const char kDelimiterSemicolonChar = ';';
44 const char kDelimiterSpace[] = " ";
45 const char kDelimiterSpaceChar = ' ';
46
47 // https://tools.ietf.org/html/draft-ietf-mmusic-sdp-simulcast-13#section-5.1
48 // https://tools.ietf.org/html/draft-ietf-mmusic-rid-15#section-10
49 const char kSimulcastPausedStream[] = "~";
50 const char kSimulcastPausedStreamChar = '~';
51 const char kSendDirection[] = "send";
52 const char kReceiveDirection[] = "recv";
53 const char kPayloadType[] = "pt";
54
ParseError(const std::string & message)55 RTCError ParseError(const std::string& message) {
56 return RTCError(RTCErrorType::SYNTAX_ERROR, message);
57 }
58
59 // These methods serialize simulcast according to the specification:
60 // https://tools.ietf.org/html/draft-ietf-mmusic-sdp-simulcast-13#section-5.1
operator <<(rtc::StringBuilder & builder,const SimulcastLayer & simulcast_layer)61 rtc::StringBuilder& operator<<(rtc::StringBuilder& builder,
62 const SimulcastLayer& simulcast_layer) {
63 if (simulcast_layer.is_paused) {
64 builder << kSimulcastPausedStream;
65 }
66 builder << simulcast_layer.rid;
67 return builder;
68 }
69
operator <<(rtc::StringBuilder & builder,const std::vector<SimulcastLayer> & layer_alternatives)70 rtc::StringBuilder& operator<<(
71 rtc::StringBuilder& builder,
72 const std::vector<SimulcastLayer>& layer_alternatives) {
73 bool first = true;
74 for (const SimulcastLayer& rid : layer_alternatives) {
75 if (!first) {
76 builder << kDelimiterComma;
77 }
78 builder << rid;
79 first = false;
80 }
81 return builder;
82 }
83
operator <<(rtc::StringBuilder & builder,const SimulcastLayerList & simulcast_layers)84 rtc::StringBuilder& operator<<(rtc::StringBuilder& builder,
85 const SimulcastLayerList& simulcast_layers) {
86 bool first = true;
87 for (const auto& alternatives : simulcast_layers) {
88 if (!first) {
89 builder << kDelimiterSemicolon;
90 }
91 builder << alternatives;
92 first = false;
93 }
94 return builder;
95 }
96 // This method deserializes simulcast according to the specification:
97 // https://tools.ietf.org/html/draft-ietf-mmusic-sdp-simulcast-13#section-5.1
98 // sc-str-list = sc-alt-list *( ";" sc-alt-list )
99 // sc-alt-list = sc-id *( "," sc-id )
100 // sc-id-paused = "~"
101 // sc-id = [sc-id-paused] rid-id
102 // rid-id = 1*(alpha-numeric / "-" / "_") ; see: I-D.ietf-mmusic-rid
ParseSimulcastLayerList(const std::string & str)103 RTCErrorOr<SimulcastLayerList> ParseSimulcastLayerList(const std::string& str) {
104 std::vector<std::string> tokens;
105 rtc::tokenize_with_empty_tokens(str, kDelimiterSemicolonChar, &tokens);
106 if (tokens.empty()) {
107 return ParseError("Layer list cannot be empty.");
108 }
109
110 SimulcastLayerList result;
111 for (const std::string& token : tokens) {
112 if (token.empty()) {
113 return ParseError("Simulcast alternative layer list is empty.");
114 }
115
116 std::vector<std::string> rid_tokens;
117 rtc::tokenize_with_empty_tokens(token, kDelimiterCommaChar, &rid_tokens);
118
119 if (rid_tokens.empty()) {
120 return ParseError("Simulcast alternative layer list is malformed.");
121 }
122
123 std::vector<SimulcastLayer> layers;
124 for (const std::string& rid_token : rid_tokens) {
125 if (rid_token.empty() || rid_token == kSimulcastPausedStream) {
126 return ParseError("Rid must not be empty.");
127 }
128
129 bool paused = rid_token[0] == kSimulcastPausedStreamChar;
130 std::string rid = paused ? rid_token.substr(1) : rid_token;
131 layers.push_back(SimulcastLayer(rid, paused));
132 }
133
134 result.AddLayerWithAlternatives(layers);
135 }
136
137 return std::move(result);
138 }
139
ParseRidPayloadList(const std::string & payload_list,RidDescription * rid_description)140 webrtc::RTCError ParseRidPayloadList(const std::string& payload_list,
141 RidDescription* rid_description) {
142 RTC_DCHECK(rid_description);
143 std::vector<int>& payload_types = rid_description->payload_types;
144 // Check that the description doesn't have any payload types or restrictions.
145 // If the pt= field is specified, it must be first and must not repeat.
146 if (!payload_types.empty()) {
147 return ParseError("Multiple pt= found in RID Description.");
148 }
149 if (!rid_description->restrictions.empty()) {
150 return ParseError("Payload list must appear first in the restrictions.");
151 }
152
153 // If the pt= field is specified, it must have a value.
154 if (payload_list.empty()) {
155 return ParseError("Payload list must have at least one value.");
156 }
157
158 // Tokenize the ',' delimited list
159 std::vector<std::string> string_payloads;
160 rtc::tokenize(payload_list, kDelimiterCommaChar, &string_payloads);
161 if (string_payloads.empty()) {
162 return ParseError("Payload list must have at least one value.");
163 }
164
165 for (const std::string& payload_type : string_payloads) {
166 absl::optional<int> value = rtc::StringToNumber<int>(payload_type);
167 if (!value.has_value()) {
168 return ParseError("Invalid payload type: " + payload_type);
169 }
170
171 // Check if the value already appears in the payload list.
172 if (absl::c_linear_search(payload_types, value.value())) {
173 return ParseError("Duplicate payload type in list: " + payload_type);
174 }
175 payload_types.push_back(value.value());
176 }
177
178 return RTCError::OK();
179 }
180
181 } // namespace
182
SerializeSimulcastDescription(const cricket::SimulcastDescription & simulcast) const183 std::string SdpSerializer::SerializeSimulcastDescription(
184 const cricket::SimulcastDescription& simulcast) const {
185 rtc::StringBuilder sb;
186 std::string delimiter;
187
188 if (!simulcast.send_layers().empty()) {
189 sb << kSendDirection << kDelimiterSpace << simulcast.send_layers();
190 delimiter = kDelimiterSpace;
191 }
192
193 if (!simulcast.receive_layers().empty()) {
194 sb << delimiter << kReceiveDirection << kDelimiterSpace
195 << simulcast.receive_layers();
196 }
197
198 return sb.str();
199 }
200
201 // https://tools.ietf.org/html/draft-ietf-mmusic-sdp-simulcast-13#section-5.1
202 // a:simulcast:<send> <streams> <recv> <streams>
203 // Formal Grammar
204 // sc-value = ( sc-send [SP sc-recv] ) / ( sc-recv [SP sc-send] )
205 // sc-send = %s"send" SP sc-str-list
206 // sc-recv = %s"recv" SP sc-str-list
207 // sc-str-list = sc-alt-list *( ";" sc-alt-list )
208 // sc-alt-list = sc-id *( "," sc-id )
209 // sc-id-paused = "~"
210 // sc-id = [sc-id-paused] rid-id
211 // rid-id = 1*(alpha-numeric / "-" / "_") ; see: I-D.ietf-mmusic-rid
DeserializeSimulcastDescription(absl::string_view string) const212 RTCErrorOr<SimulcastDescription> SdpSerializer::DeserializeSimulcastDescription(
213 absl::string_view string) const {
214 std::vector<std::string> tokens;
215 rtc::tokenize(std::string(string), kDelimiterSpaceChar, &tokens);
216
217 if (tokens.size() != 2 && tokens.size() != 4) {
218 return ParseError("Must have one or two <direction, streams> pairs.");
219 }
220
221 bool bidirectional = tokens.size() == 4; // indicates both send and recv
222
223 // Tokens 0, 2 (if exists) should be send / recv
224 if ((tokens[0] != kSendDirection && tokens[0] != kReceiveDirection) ||
225 (bidirectional && tokens[2] != kSendDirection &&
226 tokens[2] != kReceiveDirection) ||
227 (bidirectional && tokens[0] == tokens[2])) {
228 return ParseError("Valid values: send / recv.");
229 }
230
231 // Tokens 1, 3 (if exists) should be alternative layer lists
232 RTCErrorOr<SimulcastLayerList> list1, list2;
233 list1 = ParseSimulcastLayerList(tokens[1]);
234 if (!list1.ok()) {
235 return list1.MoveError();
236 }
237
238 if (bidirectional) {
239 list2 = ParseSimulcastLayerList(tokens[3]);
240 if (!list2.ok()) {
241 return list2.MoveError();
242 }
243 }
244
245 // Set the layers so that list1 is for send and list2 is for recv
246 if (tokens[0] != kSendDirection) {
247 std::swap(list1, list2);
248 }
249
250 // Set the layers according to which pair is send and which is recv
251 // At this point if the simulcast is unidirectional then
252 // either |list1| or |list2| will be in 'error' state indicating that
253 // the value should not be used.
254 SimulcastDescription simulcast;
255 if (list1.ok()) {
256 simulcast.send_layers() = list1.MoveValue();
257 }
258
259 if (list2.ok()) {
260 simulcast.receive_layers() = list2.MoveValue();
261 }
262
263 return std::move(simulcast);
264 }
265
SerializeRidDescription(const RidDescription & rid_description) const266 std::string SdpSerializer::SerializeRidDescription(
267 const RidDescription& rid_description) const {
268 RTC_DCHECK(!rid_description.rid.empty());
269 RTC_DCHECK(rid_description.direction == RidDirection::kSend ||
270 rid_description.direction == RidDirection::kReceive);
271
272 rtc::StringBuilder builder;
273 builder << rid_description.rid << kDelimiterSpace
274 << (rid_description.direction == RidDirection::kSend
275 ? kSendDirection
276 : kReceiveDirection);
277
278 const auto& payload_types = rid_description.payload_types;
279 const auto& restrictions = rid_description.restrictions;
280
281 // First property is separated by ' ', the next ones by ';'.
282 const char* propertyDelimiter = kDelimiterSpace;
283
284 // Serialize any codecs in the description.
285 if (!payload_types.empty()) {
286 builder << propertyDelimiter << kPayloadType << kDelimiterEqual;
287 propertyDelimiter = kDelimiterSemicolon;
288 const char* formatDelimiter = "";
289 for (int payload_type : payload_types) {
290 builder << formatDelimiter << payload_type;
291 formatDelimiter = kDelimiterComma;
292 }
293 }
294
295 // Serialize any restrictions in the description.
296 for (const auto& pair : restrictions) {
297 // Serialize key=val pairs. =val part is ommitted if val is empty.
298 builder << propertyDelimiter << pair.first;
299 if (!pair.second.empty()) {
300 builder << kDelimiterEqual << pair.second;
301 }
302
303 propertyDelimiter = kDelimiterSemicolon;
304 }
305
306 return builder.str();
307 }
308
309 // https://tools.ietf.org/html/draft-ietf-mmusic-rid-15#section-10
310 // Formal Grammar
311 // rid-syntax = %s"a=rid:" rid-id SP rid-dir
312 // [ rid-pt-param-list / rid-param-list ]
313 // rid-id = 1*(alpha-numeric / "-" / "_")
314 // rid-dir = %s"send" / %s"recv"
315 // rid-pt-param-list = SP rid-fmt-list *( ";" rid-param )
316 // rid-param-list = SP rid-param *( ";" rid-param )
317 // rid-fmt-list = %s"pt=" fmt *( "," fmt )
318 // rid-param = 1*(alpha-numeric / "-") [ "=" param-val ]
319 // param-val = *( %x20-58 / %x60-7E )
320 // ; Any printable character except semicolon
DeserializeRidDescription(absl::string_view string) const321 RTCErrorOr<RidDescription> SdpSerializer::DeserializeRidDescription(
322 absl::string_view string) const {
323 std::vector<std::string> tokens;
324 rtc::tokenize(std::string(string), kDelimiterSpaceChar, &tokens);
325
326 if (tokens.size() < 2) {
327 return ParseError("RID Description must contain <RID> <direction>.");
328 }
329
330 if (tokens.size() > 3) {
331 return ParseError("Invalid RID Description format. Too many arguments.");
332 }
333
334 if (!IsLegalRsidName(tokens[0])) {
335 return ParseError("Invalid RID value: " + tokens[0] + ".");
336 }
337
338 if (tokens[1] != kSendDirection && tokens[1] != kReceiveDirection) {
339 return ParseError("Invalid RID direction. Supported values: send / recv.");
340 }
341
342 RidDirection direction = tokens[1] == kSendDirection ? RidDirection::kSend
343 : RidDirection::kReceive;
344
345 RidDescription rid_description(tokens[0], direction);
346
347 // If there is a third argument it is a payload list and/or restriction list.
348 if (tokens.size() == 3) {
349 std::vector<std::string> restrictions;
350 rtc::tokenize(tokens[2], kDelimiterSemicolonChar, &restrictions);
351
352 // Check for malformed restriction list, such as ';' or ';;;' etc.
353 if (restrictions.empty()) {
354 return ParseError("Invalid RID restriction list: " + tokens[2]);
355 }
356
357 // Parse the restrictions. The payload indicator (pt) can only appear first.
358 for (const std::string& restriction : restrictions) {
359 std::vector<std::string> parts;
360 rtc::tokenize(restriction, kDelimiterEqualChar, &parts);
361 if (parts.empty() || parts.size() > 2) {
362 return ParseError("Invalid format for restriction: " + restriction);
363 }
364
365 // |parts| contains at least one value and it does not contain a space.
366 // Note: |parts| and other values might still contain tab, newline,
367 // unprintable characters, etc. which will not generate errors here but
368 // will (most-likely) be ignored by components down stream.
369 if (parts[0] == kPayloadType) {
370 RTCError error = ParseRidPayloadList(
371 parts.size() > 1 ? parts[1] : std::string(), &rid_description);
372 if (!error.ok()) {
373 return std::move(error);
374 }
375
376 continue;
377 }
378
379 // Parse |parts| as a key=value pair which allows unspecified values.
380 if (rid_description.restrictions.find(parts[0]) !=
381 rid_description.restrictions.end()) {
382 return ParseError("Duplicate restriction specified: " + parts[0]);
383 }
384
385 rid_description.restrictions[parts[0]] =
386 parts.size() > 1 ? parts[1] : std::string();
387 }
388 }
389
390 return std::move(rid_description);
391 }
392
393 } // namespace webrtc
394