pc/ice_server_parsing.cc - src - Git at Google

 /*
  *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */

 #include "pc/ice_server_parsing.h"

 #include <stddef.h>

 #include <cctype>  // For std::isdigit.
 #include <string>
 #include <tuple>

 #include "p2p/base/port_interface.h"
 #include "rtc_base/arraysize.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/ip_address.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/socket_address.h"
 #include "rtc_base/string_encode.h"
 #include "rtc_base/string_to_number.h"

 namespace webrtc {

 namespace {
 // Number of tokens must be preset when TURN uri has transport param.
 const size_t kTurnTransportTokensNum = 2;
 // The default stun port.
 const int kDefaultStunPort = 3478;
 const int kDefaultStunTlsPort = 5349;
 const char kTransport[] = "transport";

 // Allowed characters in hostname per RFC 3986 Appendix A "reg-name"
 const char kRegNameCharacters[] =
     "abcdefghijklmnopqrstuvwxyz"
     "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
     "0123456789"
     "-._~"          // unreserved
     "%"             // pct-encoded
     "!$&'()*+,;=";  // sub-delims

 // NOTE: Must be in the same order as the ServiceType enum.
 const char* kValidIceServiceTypes[] = {"stun", "stuns", "turn", "turns"};

 // NOTE: A loop below assumes that the first value of this enum is 0 and all
 // other values are incremental.
 enum class ServiceType {
   STUN = 0,  // Indicates a STUN server.
   STUNS,     // Indicates a STUN server used with a TLS session.
   TURN,      // Indicates a TURN server
   TURNS,     // Indicates a TURN server used with a TLS session.
   INVALID,   // Unknown.
 };
 static_assert(static_cast<size_t>(ServiceType::INVALID) ==
                   arraysize(kValidIceServiceTypes),
               "kValidIceServiceTypes must have as many strings as ServiceType "
               "has values.");

 // `in_str` should follow of RFC 7064/7065 syntax, but with an optional
 // "?transport=" already stripped. I.e.,
 // stunURI       = scheme ":" host [ ":" port ]
 // scheme        = "stun" / "stuns" / "turn" / "turns"
 // host          = IP-literal / IPv4address / reg-name
 // port          = *DIGIT

 // Return tuple is service_type, host, with service_type == ServiceType::INVALID
 // on failure.
 std::tuple<ServiceType, absl::string_view> GetServiceTypeAndHostnameFromUri(
     absl::string_view in_str) {
   const auto colonpos = in_str.find(':');
   if (colonpos == absl::string_view::npos) {
     RTC_LOG(LS_WARNING) << "Missing ':' in ICE URI: " << in_str;
     return {ServiceType::INVALID, ""};
   }
   if ((colonpos + 1) == in_str.length()) {
     RTC_LOG(LS_WARNING) << "Empty hostname in ICE URI: " << in_str;
     return {ServiceType::INVALID, ""};
   }
   for (size_t i = 0; i < arraysize(kValidIceServiceTypes); ++i) {
     if (in_str.compare(0, colonpos, kValidIceServiceTypes[i]) == 0) {
       return {static_cast<ServiceType>(i), in_str.substr(colonpos + 1)};
     }
   }
   return {ServiceType::INVALID, ""};
 }

 absl::optional<int> ParsePort(absl::string_view in_str) {
   // Make sure port only contains digits. StringToNumber doesn't check this.
   for (const char& c : in_str) {
     if (!std::isdigit(static_cast<unsigned char>(c))) {
       return false;
     }
   }
   return rtc::StringToNumber<int>(in_str);
 }

 // This method parses IPv6 and IPv4 literal strings, along with hostnames in
 // standard hostname:port format.
 // Consider following formats as correct.
 // `hostname:port`, |[IPV6 address]:port|, |IPv4 address|:port,
 // `hostname`, |[IPv6 address]|, |IPv4 address|.

 // Return tuple is success, host, port.
 std::tuple<bool, absl::string_view, int> ParseHostnameAndPortFromString(
     absl::string_view in_str,
     int default_port) {
   if (in_str.empty()) {
     return {false, "", 0};
   }
   absl::string_view host;
   int port = default_port;

   if (in_str.at(0) == '[') {
     // IP_literal syntax
     auto closebracket = in_str.rfind(']');
     if (closebracket == absl::string_view::npos) {
       return {false, "", 0};
     }
     auto colonpos = in_str.find(':', closebracket);
     if (absl::string_view::npos != colonpos) {
       if (absl::optional<int> opt_port =
               ParsePort(in_str.substr(closebracket + 2))) {
         port = *opt_port;
       } else {
         return {false, "", 0};
       }
     }
     host = in_str.substr(1, closebracket - 1);
   } else {
     // IPv4address or reg-name syntax
     auto colonpos = in_str.find(':');
     if (absl::string_view::npos != colonpos) {
       if (absl::optional<int> opt_port =
               ParsePort(in_str.substr(colonpos + 1))) {
         port = *opt_port;
       } else {
         return {false, "", 0};
       }
       host = in_str.substr(0, colonpos);
     } else {
       host = in_str;
     }
     // RFC 3986 section 3.2.2 and Appendix A - "reg-name" syntax
     if (host.find_first_not_of(kRegNameCharacters) != absl::string_view::npos) {
       return {false, "", 0};
     }
   }
   return {!host.empty(), host, port};
 }

 // Adds a STUN or TURN server to the appropriate list,
 // by parsing `url` and using the username/password in `server`.
 RTCErrorType ParseIceServerUrl(
     const PeerConnectionInterface::IceServer& server,
     absl::string_view url,
     cricket::ServerAddresses* stun_servers,
     std::vector<cricket::RelayServerConfig>* turn_servers) {
   // RFC 7064
   // stunURI       = scheme ":" host [ ":" port ]
   // scheme        = "stun" / "stuns"

   // RFC 7065
   // turnURI       = scheme ":" host [ ":" port ]
   //                 [ "?transport=" transport ]
   // scheme        = "turn" / "turns"
   // transport     = "udp" / "tcp" / transport-ext
   // transport-ext = 1*unreserved

   // RFC 3986
   // host     = IP-literal / IPv4address / reg-name
   // port     = *DIGIT

   RTC_DCHECK(stun_servers != nullptr);
   RTC_DCHECK(turn_servers != nullptr);
   cricket::ProtocolType turn_transport_type = cricket::PROTO_UDP;
   RTC_DCHECK(!url.empty());
   std::vector<absl::string_view> tokens = rtc::split(url, '?');
   absl::string_view uri_without_transport = tokens[0];
   // Let's look into transport= param, if it exists.
   if (tokens.size() == kTurnTransportTokensNum) {  // ?transport= is present.
     std::vector<absl::string_view> transport_tokens =
         rtc::split(tokens[1], '=');
     if (transport_tokens[0] != kTransport) {
       RTC_LOG(LS_WARNING) << "Invalid transport parameter key.";
       return RTCErrorType::SYNTAX_ERROR;
     }
     if (transport_tokens.size() < 2) {
       RTC_LOG(LS_WARNING) << "Transport parameter missing value.";
       return RTCErrorType::SYNTAX_ERROR;
     }

     absl::optional<cricket::ProtocolType> proto =
         cricket::StringToProto(transport_tokens[1]);
     if (!proto ||
         (*proto != cricket::PROTO_UDP && *proto != cricket::PROTO_TCP)) {
       RTC_LOG(LS_WARNING) << "Transport parameter should always be udp or tcp.";
       return RTCErrorType::SYNTAX_ERROR;
     }
     turn_transport_type = *proto;
   }

   auto [service_type, hoststring] =
       GetServiceTypeAndHostnameFromUri(uri_without_transport);
   if (service_type == ServiceType::INVALID) {
     RTC_LOG(LS_WARNING) << "Invalid transport parameter in ICE URI: " << url;
     return RTCErrorType::SYNTAX_ERROR;
   }

   // GetServiceTypeAndHostnameFromUri should never give an empty hoststring
   RTC_DCHECK(!hoststring.empty());

   int default_port = kDefaultStunPort;
   if (service_type == ServiceType::TURNS) {
     default_port = kDefaultStunTlsPort;
     turn_transport_type = cricket::PROTO_TLS;
   }

   if (hoststring.find('@') != absl::string_view::npos) {
     RTC_LOG(LS_WARNING) << "Invalid url: " << uri_without_transport;
     RTC_LOG(LS_WARNING)
         << "Note that user-info@ in turn:-urls is long-deprecated.";
     return RTCErrorType::SYNTAX_ERROR;
   }

   auto [success, address, port] =
       ParseHostnameAndPortFromString(hoststring, default_port);
   if (!success) {
     RTC_LOG(LS_WARNING) << "Invalid hostname format: " << uri_without_transport;
     return RTCErrorType::SYNTAX_ERROR;
   }

   if (port <= 0 || port > 0xffff) {
     RTC_LOG(LS_WARNING) << "Invalid port: " << port;
     return RTCErrorType::SYNTAX_ERROR;
   }

   switch (service_type) {
     case ServiceType::STUN:
     case ServiceType::STUNS:
       stun_servers->insert(rtc::SocketAddress(address, port));
       break;
     case ServiceType::TURN:
     case ServiceType::TURNS: {
       if (server.username.empty() || server.password.empty()) {
         // The WebRTC spec requires throwing an InvalidAccessError when username
         // or credential are ommitted; this is the native equivalent.
         RTC_LOG(LS_WARNING) << "TURN server with empty username or password";
         return RTCErrorType::INVALID_PARAMETER;
       }
       // If the hostname field is not empty, then the server address must be
       // the resolved IP for that host, the hostname is needed later for TLS
       // handshake (SNI and Certificate verification).
       absl::string_view hostname =
           server.hostname.empty() ? address : server.hostname;
       rtc::SocketAddress socket_address(hostname, port);
       if (!server.hostname.empty()) {
         rtc::IPAddress ip;
         if (!IPFromString(address, &ip)) {
           // When hostname is set, the server address must be a
           // resolved ip address.
           RTC_LOG(LS_WARNING)
               << "IceServer has hostname field set, but URI does not "
                  "contain an IP address.";
           return RTCErrorType::INVALID_PARAMETER;
         }
         socket_address.SetResolvedIP(ip);
       }
       cricket::RelayServerConfig config =
           cricket::RelayServerConfig(socket_address, server.username,
                                      server.password, turn_transport_type);
       if (server.tls_cert_policy ==
           PeerConnectionInterface::kTlsCertPolicyInsecureNoCheck) {
         config.tls_cert_policy =
             cricket::TlsCertPolicy::TLS_CERT_POLICY_INSECURE_NO_CHECK;
       }
       config.tls_alpn_protocols = server.tls_alpn_protocols;
       config.tls_elliptic_curves = server.tls_elliptic_curves;

       turn_servers->push_back(config);
       break;
     }
     default:
       // We shouldn't get to this point with an invalid service_type, we should
       // have returned an error already.
       RTC_DCHECK_NOTREACHED() << "Unexpected service type";
       return RTCErrorType::INTERNAL_ERROR;
   }
   return RTCErrorType::NONE;
 }

 }  // namespace

 RTCErrorType ParseIceServers(
     const PeerConnectionInterface::IceServers& servers,
     cricket::ServerAddresses* stun_servers,
     std::vector<cricket::RelayServerConfig>* turn_servers) {
   for (const PeerConnectionInterface::IceServer& server : servers) {
     if (!server.urls.empty()) {
       for (const std::string& url : server.urls) {
         if (url.empty()) {
           RTC_LOG(LS_WARNING) << "Empty uri.";
           return RTCErrorType::SYNTAX_ERROR;
         }
         RTCErrorType err =
             ParseIceServerUrl(server, url, stun_servers, turn_servers);
         if (err != RTCErrorType::NONE) {
           return err;
         }
       }
     } else if (!server.uri.empty()) {
       // Fallback to old .uri if new .urls isn't present.
       RTCErrorType err =
           ParseIceServerUrl(server, server.uri, stun_servers, turn_servers);
       if (err != RTCErrorType::NONE) {
         return err;
       }
     } else {
       RTC_LOG(LS_WARNING) << "Empty uri.";
       return RTCErrorType::SYNTAX_ERROR;
     }
   }
   // Candidates must have unique priorities, so that connectivity checks
   // are performed in a well-defined order.
   int priority = static_cast<int>(turn_servers->size() - 1);
   for (cricket::RelayServerConfig& turn_server : *turn_servers) {
     // First in the list gets highest priority.
     turn_server.priority = priority--;
   }
   return RTCErrorType::NONE;
 }

 }  // namespace webrtc
	/*
	* Copyright 2017 The WebRTC project authors. All Rights Reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/

	#include "pc/ice_server_parsing.h"

	#include <stddef.h>

	#include <cctype> // For std::isdigit.
	#include <string>
	#include <tuple>

	#include "p2p/base/port_interface.h"
	#include "rtc_base/arraysize.h"
	#include "rtc_base/checks.h"
	#include "rtc_base/ip_address.h"
	#include "rtc_base/logging.h"
	#include "rtc_base/socket_address.h"
	#include "rtc_base/string_encode.h"
	#include "rtc_base/string_to_number.h"

	namespace webrtc {

	namespace {
	// Number of tokens must be preset when TURN uri has transport param.
	const size_t kTurnTransportTokensNum = 2;
	// The default stun port.
	const int kDefaultStunPort = 3478;
	const int kDefaultStunTlsPort = 5349;
	const char kTransport[] = "transport";

	// Allowed characters in hostname per RFC 3986 Appendix A "reg-name"
	const char kRegNameCharacters[] =
	"abcdefghijklmnopqrstuvwxyz"
	"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
	"0123456789"
	"-._~" // unreserved
	"%" // pct-encoded
	"!$&'()*+,;="; // sub-delims

	// NOTE: Must be in the same order as the ServiceType enum.
	const char* kValidIceServiceTypes[] = {"stun", "stuns", "turn", "turns"};

	// NOTE: A loop below assumes that the first value of this enum is 0 and all
	// other values are incremental.
	enum class ServiceType {
	STUN = 0, // Indicates a STUN server.
	STUNS, // Indicates a STUN server used with a TLS session.
	TURN, // Indicates a TURN server
	TURNS, // Indicates a TURN server used with a TLS session.
	INVALID, // Unknown.
	};
	static_assert(static_cast<size_t>(ServiceType::INVALID) ==
	arraysize(kValidIceServiceTypes),
	"kValidIceServiceTypes must have as many strings as ServiceType "
	"has values.");

	// `in_str` should follow of RFC 7064/7065 syntax, but with an optional
	// "?transport=" already stripped. I.e.,
	// stunURI = scheme ":" host [ ":" port ]
	// scheme = "stun" / "stuns" / "turn" / "turns"
	// host = IP-literal / IPv4address / reg-name
	// port = *DIGIT

	// Return tuple is service_type, host, with service_type == ServiceType::INVALID
	// on failure.
	std::tuple<ServiceType, absl::string_view> GetServiceTypeAndHostnameFromUri(
	absl::string_view in_str) {
	const auto colonpos = in_str.find(':');
	if (colonpos == absl::string_view::npos) {
	RTC_LOG(LS_WARNING) << "Missing ':' in ICE URI: " << in_str;
	return {ServiceType::INVALID, ""};
	}
	if ((colonpos + 1) == in_str.length()) {
	RTC_LOG(LS_WARNING) << "Empty hostname in ICE URI: " << in_str;
	return {ServiceType::INVALID, ""};
	}
	for (size_t i = 0; i < arraysize(kValidIceServiceTypes); ++i) {
	if (in_str.compare(0, colonpos, kValidIceServiceTypes[i]) == 0) {
	return {static_cast<ServiceType>(i), in_str.substr(colonpos + 1)};
	}
	}
	return {ServiceType::INVALID, ""};
	}

	absl::optional<int> ParsePort(absl::string_view in_str) {
	// Make sure port only contains digits. StringToNumber doesn't check this.
	for (const char& c : in_str) {
	if (!std::isdigit(static_cast<unsigned char>(c))) {
	return false;
	}
	}
	return rtc::StringToNumber<int>(in_str);
	}

	// This method parses IPv6 and IPv4 literal strings, along with hostnames in
	// standard hostname:port format.
	// Consider following formats as correct.
	// `hostname:port`, \|[IPV6 address]:port\|, \|IPv4 address\|:port,
	// `hostname`, \|[IPv6 address]\|, \|IPv4 address\|.

	// Return tuple is success, host, port.
	std::tuple<bool, absl::string_view, int> ParseHostnameAndPortFromString(
	absl::string_view in_str,
	int default_port) {
	if (in_str.empty()) {
	return {false, "", 0};
	}
	absl::string_view host;
	int port = default_port;

	if (in_str.at(0) == '[') {
	// IP_literal syntax
	auto closebracket = in_str.rfind(']');
	if (closebracket == absl::string_view::npos) {
	return {false, "", 0};
	}
	auto colonpos = in_str.find(':', closebracket);
	if (absl::string_view::npos != colonpos) {
	if (absl::optional<int> opt_port =
	ParsePort(in_str.substr(closebracket + 2))) {
	port = *opt_port;
	} else {
	return {false, "", 0};
	}
	}
	host = in_str.substr(1, closebracket - 1);
	} else {
	// IPv4address or reg-name syntax
	auto colonpos = in_str.find(':');
	if (absl::string_view::npos != colonpos) {
	if (absl::optional<int> opt_port =
	ParsePort(in_str.substr(colonpos + 1))) {
	port = *opt_port;
	} else {
	return {false, "", 0};
	}
	host = in_str.substr(0, colonpos);
	} else {
	host = in_str;
	}
	// RFC 3986 section 3.2.2 and Appendix A - "reg-name" syntax
	if (host.find_first_not_of(kRegNameCharacters) != absl::string_view::npos) {
	return {false, "", 0};
	}
	}
	return {!host.empty(), host, port};
	}

	// Adds a STUN or TURN server to the appropriate list,
	// by parsing `url` and using the username/password in `server`.
	RTCErrorType ParseIceServerUrl(
	const PeerConnectionInterface::IceServer& server,
	absl::string_view url,
	cricket::ServerAddresses* stun_servers,
	std::vector<cricket::RelayServerConfig>* turn_servers) {
	// RFC 7064
	// stunURI = scheme ":" host [ ":" port ]
	// scheme = "stun" / "stuns"

	// RFC 7065
	// turnURI = scheme ":" host [ ":" port ]
	// [ "?transport=" transport ]
	// scheme = "turn" / "turns"
	// transport = "udp" / "tcp" / transport-ext
	// transport-ext = 1*unreserved

	// RFC 3986
	// host = IP-literal / IPv4address / reg-name
	// port = *DIGIT

	RTC_DCHECK(stun_servers != nullptr);
	RTC_DCHECK(turn_servers != nullptr);
	cricket::ProtocolType turn_transport_type = cricket::PROTO_UDP;
	RTC_DCHECK(!url.empty());
	std::vector<absl::string_view> tokens = rtc::split(url, '?');
	absl::string_view uri_without_transport = tokens[0];
	// Let's look into transport= param, if it exists.
	if (tokens.size() == kTurnTransportTokensNum) { // ?transport= is present.
	std::vector<absl::string_view> transport_tokens =
	rtc::split(tokens[1], '=');
	if (transport_tokens[0] != kTransport) {
	RTC_LOG(LS_WARNING) << "Invalid transport parameter key.";
	return RTCErrorType::SYNTAX_ERROR;
	}
	if (transport_tokens.size() < 2) {
	RTC_LOG(LS_WARNING) << "Transport parameter missing value.";
	return RTCErrorType::SYNTAX_ERROR;
	}

	absl::optional<cricket::ProtocolType> proto =
	cricket::StringToProto(transport_tokens[1]);
	if (!proto \|\|
	(proto != cricket::PROTO_UDP && proto != cricket::PROTO_TCP)) {
	RTC_LOG(LS_WARNING) << "Transport parameter should always be udp or tcp.";
	return RTCErrorType::SYNTAX_ERROR;
	}
	turn_transport_type = *proto;
	}

	auto [service_type, hoststring] =
	GetServiceTypeAndHostnameFromUri(uri_without_transport);
	if (service_type == ServiceType::INVALID) {
	RTC_LOG(LS_WARNING) << "Invalid transport parameter in ICE URI: " << url;
	return RTCErrorType::SYNTAX_ERROR;
	}

	// GetServiceTypeAndHostnameFromUri should never give an empty hoststring
	RTC_DCHECK(!hoststring.empty());

	int default_port = kDefaultStunPort;
	if (service_type == ServiceType::TURNS) {
	default_port = kDefaultStunTlsPort;
	turn_transport_type = cricket::PROTO_TLS;
	}

	if (hoststring.find('@') != absl::string_view::npos) {
	RTC_LOG(LS_WARNING) << "Invalid url: " << uri_without_transport;
	RTC_LOG(LS_WARNING)
	<< "Note that user-info@ in turn:-urls is long-deprecated.";
	return RTCErrorType::SYNTAX_ERROR;
	}

	auto [success, address, port] =
	ParseHostnameAndPortFromString(hoststring, default_port);
	if (!success) {
	RTC_LOG(LS_WARNING) << "Invalid hostname format: " << uri_without_transport;
	return RTCErrorType::SYNTAX_ERROR;
	}

	if (port <= 0 \|\| port > 0xffff) {
	RTC_LOG(LS_WARNING) << "Invalid port: " << port;
	return RTCErrorType::SYNTAX_ERROR;
	}

	switch (service_type) {
	case ServiceType::STUN:
	case ServiceType::STUNS:
	stun_servers->insert(rtc::SocketAddress(address, port));
	break;
	case ServiceType::TURN:
	case ServiceType::TURNS: {
	if (server.username.empty() \|\| server.password.empty()) {
	// The WebRTC spec requires throwing an InvalidAccessError when username
	// or credential are ommitted; this is the native equivalent.
	RTC_LOG(LS_WARNING) << "TURN server with empty username or password";
	return RTCErrorType::INVALID_PARAMETER;
	}
	// If the hostname field is not empty, then the server address must be
	// the resolved IP for that host, the hostname is needed later for TLS
	// handshake (SNI and Certificate verification).
	absl::string_view hostname =
	server.hostname.empty() ? address : server.hostname;
	rtc::SocketAddress socket_address(hostname, port);
	if (!server.hostname.empty()) {
	rtc::IPAddress ip;
	if (!IPFromString(address, &ip)) {
	// When hostname is set, the server address must be a
	// resolved ip address.
	RTC_LOG(LS_WARNING)
	<< "IceServer has hostname field set, but URI does not "
	"contain an IP address.";
	return RTCErrorType::INVALID_PARAMETER;
	}
	socket_address.SetResolvedIP(ip);
	}
	cricket::RelayServerConfig config =
	cricket::RelayServerConfig(socket_address, server.username,
	server.password, turn_transport_type);
	if (server.tls_cert_policy ==
	PeerConnectionInterface::kTlsCertPolicyInsecureNoCheck) {
	config.tls_cert_policy =
	cricket::TlsCertPolicy::TLS_CERT_POLICY_INSECURE_NO_CHECK;
	}
	config.tls_alpn_protocols = server.tls_alpn_protocols;
	config.tls_elliptic_curves = server.tls_elliptic_curves;

	turn_servers->push_back(config);
	break;
	}
	default:
	// We shouldn't get to this point with an invalid service_type, we should
	// have returned an error already.
	RTC_DCHECK_NOTREACHED() << "Unexpected service type";
	return RTCErrorType::INTERNAL_ERROR;
	}
	return RTCErrorType::NONE;
	}

	} // namespace

	RTCErrorType ParseIceServers(
	const PeerConnectionInterface::IceServers& servers,
	cricket::ServerAddresses* stun_servers,
	std::vector<cricket::RelayServerConfig>* turn_servers) {
	for (const PeerConnectionInterface::IceServer& server : servers) {
	if (!server.urls.empty()) {
	for (const std::string& url : server.urls) {
	if (url.empty()) {
	RTC_LOG(LS_WARNING) << "Empty uri.";
	return RTCErrorType::SYNTAX_ERROR;
	}
	RTCErrorType err =
	ParseIceServerUrl(server, url, stun_servers, turn_servers);
	if (err != RTCErrorType::NONE) {
	return err;
	}
	}
	} else if (!server.uri.empty()) {
	// Fallback to old .uri if new .urls isn't present.
	RTCErrorType err =
	ParseIceServerUrl(server, server.uri, stun_servers, turn_servers);
	if (err != RTCErrorType::NONE) {
	return err;
	}
	} else {
	RTC_LOG(LS_WARNING) << "Empty uri.";
	return RTCErrorType::SYNTAX_ERROR;
	}
	}
	// Candidates must have unique priorities, so that connectivity checks
	// are performed in a well-defined order.
	int priority = static_cast<int>(turn_servers->size() - 1);
	for (cricket::RelayServerConfig& turn_server : *turn_servers) {
	// First in the list gets highest priority.
	turn_server.priority = priority--;
	}
	return RTCErrorType::NONE;
	}

	} // namespace webrtc