|  | // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 
|  | // Use of this source code is governed by a BSD-style license that can be | 
|  | // found in the LICENSE file. | 
|  |  | 
|  | #ifndef QUICHE_QUIC_CORE_CRYPTO_CRYPTO_PROTOCOL_H_ | 
|  | #define QUICHE_QUIC_CORE_CRYPTO_CRYPTO_PROTOCOL_H_ | 
|  |  | 
|  | #include <cstddef> | 
|  | #include <string> | 
|  |  | 
|  | #include "net/third_party/quiche/src/quic/core/quic_tag.h" | 
|  |  | 
|  | // Version and Crypto tags are written to the wire with a big-endian | 
|  | // representation of the name of the tag.  For example | 
|  | // the client hello tag (CHLO) will be written as the | 
|  | // following 4 bytes: 'C' 'H' 'L' 'O'.  Since it is | 
|  | // stored in memory as a little endian uint32_t, we need | 
|  | // to reverse the order of the bytes. | 
|  | // | 
|  | // We use a macro to ensure that no static initialisers are created. Use the | 
|  | // MakeQuicTag function in normal code. | 
|  | #define TAG(a, b, c, d) \ | 
|  | static_cast<QuicTag>((d << 24) + (c << 16) + (b << 8) + a) | 
|  |  | 
|  | namespace quic { | 
|  |  | 
|  | typedef std::string ServerConfigID; | 
|  |  | 
|  | // The following tags have been deprecated and should not be reused: | 
|  | // "1CON", "BBQ4", "NCON", "RCID", "SREJ", "TBKP", "TB10" | 
|  |  | 
|  | // clang-format off | 
|  | const QuicTag kCHLO = TAG('C', 'H', 'L', 'O');   // Client hello | 
|  | const QuicTag kSHLO = TAG('S', 'H', 'L', 'O');   // Server hello | 
|  | const QuicTag kSCFG = TAG('S', 'C', 'F', 'G');   // Server config | 
|  | const QuicTag kREJ  = TAG('R', 'E', 'J', '\0');  // Reject | 
|  | const QuicTag kCETV = TAG('C', 'E', 'T', 'V');   // Client encrypted tag-value | 
|  | // pairs | 
|  | const QuicTag kPRST = TAG('P', 'R', 'S', 'T');   // Public reset | 
|  | const QuicTag kSCUP = TAG('S', 'C', 'U', 'P');   // Server config update | 
|  | const QuicTag kALPN = TAG('A', 'L', 'P', 'N');   // Application-layer protocol | 
|  |  | 
|  | // Key exchange methods | 
|  | const QuicTag kP256 = TAG('P', '2', '5', '6');   // ECDH, Curve P-256 | 
|  | const QuicTag kC255 = TAG('C', '2', '5', '5');   // ECDH, Curve25519 | 
|  |  | 
|  | // AEAD algorithms | 
|  | const QuicTag kAESG = TAG('A', 'E', 'S', 'G');   // AES128 + GCM-12 | 
|  | const QuicTag kCC20 = TAG('C', 'C', '2', '0');   // ChaCha20 + Poly1305 RFC7539 | 
|  |  | 
|  | // Congestion control feedback types | 
|  | const QuicTag kQBIC = TAG('Q', 'B', 'I', 'C');   // TCP cubic | 
|  |  | 
|  | // Connection options (COPT) values | 
|  | const QuicTag kAFCW = TAG('A', 'F', 'C', 'W');   // Auto-tune flow control | 
|  | // receive windows. | 
|  | const QuicTag kIFW5 = TAG('I', 'F', 'W', '5');   // Set initial size | 
|  | // of stream flow control | 
|  | // receive window to | 
|  | // 32KB. (2^5 KB). | 
|  | const QuicTag kIFW6 = TAG('I', 'F', 'W', '6');   // Set initial size | 
|  | // of stream flow control | 
|  | // receive window to | 
|  | // 64KB. (2^6 KB). | 
|  | const QuicTag kIFW7 = TAG('I', 'F', 'W', '7');   // Set initial size | 
|  | // of stream flow control | 
|  | // receive window to | 
|  | // 128KB. (2^7 KB). | 
|  | const QuicTag kIFW8 = TAG('I', 'F', 'W', '8');   // Set initial size | 
|  | // of stream flow control | 
|  | // receive window to | 
|  | // 256KB. (2^8 KB). | 
|  | const QuicTag kIFW9 = TAG('I', 'F', 'W', '9');   // Set initial size | 
|  | // of stream flow control | 
|  | // receive window to | 
|  | // 512KB. (2^9 KB). | 
|  | const QuicTag kIFWA = TAG('I', 'F', 'W', 'a');   // Set initial size | 
|  | // of stream flow control | 
|  | // receive window to | 
|  | // 1MB. (2^0xa KB). | 
|  | const QuicTag kTBBR = TAG('T', 'B', 'B', 'R');   // Reduced Buffer Bloat TCP | 
|  | const QuicTag k1RTT = TAG('1', 'R', 'T', 'T');   // STARTUP in BBR for 1 RTT | 
|  | const QuicTag k2RTT = TAG('2', 'R', 'T', 'T');   // STARTUP in BBR for 2 RTTs | 
|  | const QuicTag kLRTT = TAG('L', 'R', 'T', 'T');   // Exit STARTUP in BBR on loss | 
|  | const QuicTag kBBS1 = TAG('B', 'B', 'S', '1');   // Rate-based recovery in | 
|  | // BBR STARTUP | 
|  | const QuicTag kBBS2 = TAG('B', 'B', 'S', '2');   // More aggressive packet | 
|  | // conservation in BBR STARTUP | 
|  | const QuicTag kBBS3 = TAG('B', 'B', 'S', '3');   // Slowstart packet | 
|  | // conservation in BBR STARTUP | 
|  | const QuicTag kBBS4 = TAG('B', 'B', 'S', '4');   // Reduce rate in STARTUP by | 
|  | // bytes_lost / CWND. | 
|  | const QuicTag kBBS5 = TAG('B', 'B', 'S', '5');   // Reduce rate in STARTUP by | 
|  | // 2 * bytes_lost / CWND. | 
|  | const QuicTag kBBRR = TAG('B', 'B', 'R', 'R');   // Rate-based recovery in BBR | 
|  | const QuicTag kBBR1 = TAG('B', 'B', 'R', '1');   // DEPRECATED | 
|  | const QuicTag kBBR2 = TAG('B', 'B', 'R', '2');   // DEPRECATED | 
|  | const QuicTag kBBR3 = TAG('B', 'B', 'R', '3');   // Fully drain the queue once | 
|  | // per cycle | 
|  | const QuicTag kBBR4 = TAG('B', 'B', 'R', '4');   // 20 RTT ack aggregation | 
|  | const QuicTag kBBR5 = TAG('B', 'B', 'R', '5');   // 40 RTT ack aggregation | 
|  | const QuicTag kBBR9 = TAG('B', 'B', 'R', '9');   // Ignore app-limited calls in | 
|  | // BBR if enough inflight. | 
|  | const QuicTag kBBRS = TAG('B', 'B', 'R', 'S');   // Use 1.5x pacing in startup | 
|  | // after a loss has occurred. | 
|  | const QuicTag kBBQ1 = TAG('B', 'B', 'Q', '1');   // BBR with lower 2.77 STARTUP | 
|  | // pacing and CWND gain. | 
|  | const QuicTag kBBQ2 = TAG('B', 'B', 'Q', '2');   // BBR with lower 2.0 STARTUP | 
|  | // CWND gain. | 
|  | const QuicTag kBBQ3 = TAG('B', 'B', 'Q', '3');   // BBR with ack aggregation | 
|  | // compensation in STARTUP. | 
|  | const QuicTag kBBQ5 = TAG('B', 'B', 'Q', '5');   // Expire ack aggregation upon | 
|  | // bandwidth increase in | 
|  | // STARTUP. | 
|  | const QuicTag kRENO = TAG('R', 'E', 'N', 'O');   // Reno Congestion Control | 
|  | const QuicTag kTPCC = TAG('P', 'C', 'C', '\0');  // Performance-Oriented | 
|  | // Congestion Control | 
|  | const QuicTag kBYTE = TAG('B', 'Y', 'T', 'E');   // TCP cubic or reno in bytes | 
|  | const QuicTag kIW03 = TAG('I', 'W', '0', '3');   // Force ICWND to 3 | 
|  | const QuicTag kIW10 = TAG('I', 'W', '1', '0');   // Force ICWND to 10 | 
|  | const QuicTag kIW20 = TAG('I', 'W', '2', '0');   // Force ICWND to 20 | 
|  | const QuicTag kIW50 = TAG('I', 'W', '5', '0');   // Force ICWND to 50 | 
|  | const QuicTag kB2ON = TAG('B', '2', 'O', 'N');   // Enable BBRv2 | 
|  | const QuicTag kB2NA = TAG('B', '2', 'N', 'A');   // For BBRv2, do not add ack | 
|  | // height to queueing threshold | 
|  | const QuicTag kB2RP = TAG('B', '2', 'R', 'P');   // For BBRv2, run PROBE_RTT on | 
|  | // the regular schedule | 
|  | const QuicTag kBSAO = TAG('B', 'S', 'A', 'O');   // Avoid Overestimation in | 
|  | // Bandwidth Sampler with ack | 
|  | // aggregation | 
|  | const QuicTag kNTLP = TAG('N', 'T', 'L', 'P');   // No tail loss probe | 
|  | const QuicTag k1TLP = TAG('1', 'T', 'L', 'P');   // 1 tail loss probe | 
|  | const QuicTag k1RTO = TAG('1', 'R', 'T', 'O');   // Send 1 packet upon RTO | 
|  | const QuicTag kNRTO = TAG('N', 'R', 'T', 'O');   // CWND reduction on loss | 
|  | const QuicTag kTIME = TAG('T', 'I', 'M', 'E');   // Time based loss detection | 
|  | const QuicTag kATIM = TAG('A', 'T', 'I', 'M');   // Adaptive time loss detection | 
|  | const QuicTag kMIN1 = TAG('M', 'I', 'N', '1');   // Min CWND of 1 packet | 
|  | const QuicTag kMIN4 = TAG('M', 'I', 'N', '4');   // Min CWND of 4 packets, | 
|  | // with a min rate of 1 BDP. | 
|  | const QuicTag kTLPR = TAG('T', 'L', 'P', 'R');   // Tail loss probe delay of | 
|  | // 0.5RTT. | 
|  | const QuicTag kMAD0 = TAG('M', 'A', 'D', '0');   // Ignore ack delay | 
|  | const QuicTag kMAD1 = TAG('M', 'A', 'D', '1');   // 25ms initial max ack delay | 
|  | const QuicTag kMAD2 = TAG('M', 'A', 'D', '2');   // No min TLP | 
|  | const QuicTag kMAD3 = TAG('M', 'A', 'D', '3');   // No min RTO | 
|  | const QuicTag kMAD4 = TAG('M', 'A', 'D', '4');   // IETF style TLP | 
|  | const QuicTag kMAD5 = TAG('M', 'A', 'D', '5');   // IETF style TLP with 2x mult | 
|  | const QuicTag k1ACK = TAG('1', 'A', 'C', 'K');   // 1 fast ack for reordering | 
|  | const QuicTag kACD0 = TAG('A', 'D', 'D', '0');   // Disable ack decimation | 
|  | const QuicTag kACKD = TAG('A', 'C', 'K', 'D');   // Ack decimation style acking. | 
|  | const QuicTag kAKD2 = TAG('A', 'K', 'D', '2');   // Ack decimation tolerating | 
|  | // out of order packets. | 
|  | const QuicTag kAKD3 = TAG('A', 'K', 'D', '3');   // Ack decimation style acking | 
|  | // with 1/8 RTT acks. | 
|  | const QuicTag kAKD4 = TAG('A', 'K', 'D', '4');   // Ack decimation with 1/8 RTT | 
|  | // tolerating out of order. | 
|  | const QuicTag kAKDU = TAG('A', 'K', 'D', 'U');   // Unlimited number of packets | 
|  | // received before acking | 
|  | const QuicTag kACKQ = TAG('A', 'C', 'K', 'Q');   // Send an immediate ack after | 
|  | // 1 RTT of not receiving. | 
|  | const QuicTag kSSLR = TAG('S', 'S', 'L', 'R');   // Slow Start Large Reduction. | 
|  | const QuicTag kNPRR = TAG('N', 'P', 'R', 'R');   // Pace at unity instead of PRR | 
|  | const QuicTag k5RTO = TAG('5', 'R', 'T', 'O');   // Close connection on 5 RTOs | 
|  | const QuicTag kCONH = TAG('C', 'O', 'N', 'H');   // Conservative Handshake | 
|  | // Retransmissions. | 
|  | const QuicTag kLFAK = TAG('L', 'F', 'A', 'K');   // Don't invoke FACK on the | 
|  | // first ack. | 
|  | const QuicTag kSTMP = TAG('S', 'T', 'M', 'P');   // Send and process timestamps | 
|  | const QuicTag kEACK = TAG('E', 'A', 'C', 'K');   // Bundle ack-eliciting frame | 
|  | // with an ACK after PTO/RTO | 
|  |  | 
|  | const QuicTag kILD0 = TAG('I', 'L', 'D', '0');   // IETF style loss detection | 
|  | // (default with 1/8 RTT time | 
|  | // threshold) | 
|  | const QuicTag kILD1 = TAG('I', 'L', 'D', '1');   // IETF style loss detection | 
|  | // with 1/4 RTT time threshold | 
|  | const QuicTag kILD2 = TAG('I', 'L', 'D', '2');   // IETF style loss detection | 
|  | // with adaptive packet | 
|  | // threshold | 
|  | const QuicTag kILD3 = TAG('I', 'L', 'D', '3');   // IETF style loss detection | 
|  | // with 1/4 RTT time threshold | 
|  | // and adaptive packet | 
|  | // threshold | 
|  | const QuicTag kILD4 = TAG('I', 'L', 'D', '4');   // IETF style loss detection | 
|  | // with both adaptive time | 
|  | // threshold (default 1/4 RTT) | 
|  | // and adaptive packet | 
|  | // threshold | 
|  | const QuicTag kRUNT = TAG('R', 'U', 'N', 'T');   // No packet threshold loss | 
|  | // detection for "runt" packet. | 
|  | // TODO(fayang): Remove this connection option when QUIC_VERSION_35, is removed | 
|  | // Since MAX_HEADER_LIST_SIZE settings frame is supported instead. | 
|  | const QuicTag kSMHL = TAG('S', 'M', 'H', 'L');   // Support MAX_HEADER_LIST_SIZE | 
|  | // settings frame. | 
|  | const QuicTag kNSTP = TAG('N', 'S', 'T', 'P');   // No stop waiting frames. | 
|  | const QuicTag kNRTT = TAG('N', 'R', 'T', 'T');   // Ignore initial RTT | 
|  |  | 
|  | const QuicTag k1PTO = TAG('1', 'P', 'T', 'O');   // Send 1 packet upon PTO. | 
|  | const QuicTag k2PTO = TAG('2', 'P', 'T', 'O');   // Send 2 packets upon PTO. | 
|  |  | 
|  | const QuicTag k6PTO = TAG('6', 'P', 'T', 'O');   // Closes connection on 6 | 
|  | // consecutive PTOs. | 
|  | const QuicTag k7PTO = TAG('7', 'P', 'T', 'O');   // Closes connection on 7 | 
|  | // consecutive PTOs. | 
|  | const QuicTag k8PTO = TAG('8', 'P', 'T', 'O');   // Closes connection on 8 | 
|  | // consecutive PTOs. | 
|  | const QuicTag kPTOS = TAG('P', 'T', 'O', 'S');   // Skip packet number before | 
|  | // sending the last PTO. | 
|  | const QuicTag kPTOA = TAG('P', 'T', 'O', 'A');   // Do not add max ack delay | 
|  | // when computing PTO timeout | 
|  | // if an immediate ACK is | 
|  | // expected. | 
|  | const QuicTag kPEB1 = TAG('P', 'E', 'B', '1');   // Start exponential backoff | 
|  | // since 1st PTO. | 
|  | const QuicTag kPEB2 = TAG('P', 'E', 'B', '2');   // Start exponential backoff | 
|  | // since 2nd PTO. | 
|  | const QuicTag kPVS1 = TAG('P', 'V', 'S', '1');   // Use 2 * rttvar when | 
|  | // calculating PTO timeout. | 
|  | const QuicTag kPAG1 = TAG('P', 'A', 'G', '1');   // Make 1st PTO more aggressive | 
|  | const QuicTag kPAG2 = TAG('P', 'A', 'G', '2');   // Make first 2 PTOs more | 
|  | // aggressive | 
|  | const QuicTag kPSDA = TAG('P', 'S', 'D', 'A');   // Use standard deviation when | 
|  | // calculating PTO timeout. | 
|  | const QuicTag kPLE1 = TAG('P', 'L', 'E', '1');   // Arm the 1st PTO with | 
|  | // earliest in flight sent time | 
|  | // and at least 0.5*srtt from | 
|  | // last sent packet. | 
|  | const QuicTag kPLE2 = TAG('P', 'L', 'E', '2');   // Arm the 1st PTO with | 
|  | // earliest in flight sent time | 
|  | // and at least 1.5*srtt from | 
|  | // last sent packet. | 
|  |  | 
|  | // Optional support of truncated Connection IDs.  If sent by a peer, the value | 
|  | // is the minimum number of bytes allowed for the connection ID sent to the | 
|  | // peer. | 
|  | const QuicTag kTCID = TAG('T', 'C', 'I', 'D');   // Connection ID truncation. | 
|  |  | 
|  | // Multipath option. | 
|  | const QuicTag kMPTH = TAG('M', 'P', 'T', 'H');   // Enable multipath. | 
|  |  | 
|  | const QuicTag kNCMR = TAG('N', 'C', 'M', 'R');   // Do not attempt connection | 
|  | // migration. | 
|  |  | 
|  | // Disable Pacing offload option. | 
|  | const QuicTag kNPCO = TAG('N', 'P', 'C', 'O');    // No pacing offload. | 
|  |  | 
|  | // Enable bandwidth resumption experiment. | 
|  | const QuicTag kBWRE = TAG('B', 'W', 'R', 'E');  // Bandwidth resumption. | 
|  | const QuicTag kBWMX = TAG('B', 'W', 'M', 'X');  // Max bandwidth resumption. | 
|  | const QuicTag kBWRS = TAG('B', 'W', 'R', 'S');  // Server bandwidth resumption. | 
|  | const QuicTag kBWS2 = TAG('B', 'W', 'S', '2');  // Server bw resumption v2. | 
|  | const QuicTag kBWS3 = TAG('B', 'W', 'S', '3');  // QUIC Initial CWND - Control. | 
|  | const QuicTag kBWS4 = TAG('B', 'W', 'S', '4');  // QUIC Initial CWND - Enabled. | 
|  | const QuicTag kBWS5 = TAG('B', 'W', 'S', '5');  // QUIC Initial CWND up and down | 
|  | const QuicTag kBWS6 = TAG('B', 'W', 'S', '6');  // QUIC Initial CWND - Enabled | 
|  | // with 0.5 * default | 
|  | // multiplier. | 
|  | const QuicTag kBWS7 = TAG('B', 'W', 'S', '7');  // QUIC Initial CWND - Enabled | 
|  | // with 0.75 * default | 
|  | // multiplier. | 
|  | const QuicTag kBWM3 = TAG('B', 'W', 'M', '3');  // Consider overshooting if | 
|  | // bytes lost after bandwidth | 
|  | // resumption * 3 > IW. | 
|  | const QuicTag kBWM4 = TAG('B', 'W', 'M', '4');  // Consider overshooting if | 
|  | // bytes lost after bandwidth | 
|  | // resumption * 4 > IW. | 
|  | const QuicTag kICW1 = TAG('I', 'C', 'W', '1');  // Max initial congestion window | 
|  | // 100. | 
|  |  | 
|  | // Enable path MTU discovery experiment. | 
|  | const QuicTag kMTUH = TAG('M', 'T', 'U', 'H');  // High-target MTU discovery. | 
|  | const QuicTag kMTUL = TAG('M', 'T', 'U', 'L');  // Low-target MTU discovery. | 
|  |  | 
|  | // Enable Priority scheme experiment. | 
|  | const QuicTag kH2PR = TAG('H', '2', 'P', 'R');  // HTTP2 priorities. | 
|  | const QuicTag kFIFO = TAG('F', 'I', 'F', 'O');  // Stream with the smallest ID | 
|  | // has the highest priority. | 
|  | const QuicTag kLIFO = TAG('L', 'I', 'F', 'O');  // Stream with the largest ID | 
|  | // has the highest priority. | 
|  | const QuicTag kRRWS = TAG('R', 'R', 'W', 'S');  // Round robin write scheduling. | 
|  |  | 
|  | // Proof types (i.e. certificate types) | 
|  | // NOTE: although it would be silly to do so, specifying both kX509 and kX59R | 
|  | // is allowed and is equivalent to specifying only kX509. | 
|  | const QuicTag kX509 = TAG('X', '5', '0', '9');   // X.509 certificate, all key | 
|  | // types | 
|  | const QuicTag kX59R = TAG('X', '5', '9', 'R');   // X.509 certificate, RSA keys | 
|  | // only | 
|  | const QuicTag kCHID = TAG('C', 'H', 'I', 'D');   // Channel ID. | 
|  |  | 
|  | // Client hello tags | 
|  | const QuicTag kVER  = TAG('V', 'E', 'R', '\0');  // Version | 
|  | const QuicTag kNONC = TAG('N', 'O', 'N', 'C');   // The client's nonce | 
|  | const QuicTag kNONP = TAG('N', 'O', 'N', 'P');   // The client's proof nonce | 
|  | const QuicTag kKEXS = TAG('K', 'E', 'X', 'S');   // Key exchange methods | 
|  | const QuicTag kAEAD = TAG('A', 'E', 'A', 'D');   // Authenticated | 
|  | // encryption algorithms | 
|  | const QuicTag kCOPT = TAG('C', 'O', 'P', 'T');   // Connection options | 
|  | const QuicTag kCLOP = TAG('C', 'L', 'O', 'P');   // Client connection options | 
|  | const QuicTag kICSL = TAG('I', 'C', 'S', 'L');   // Idle network timeout | 
|  | const QuicTag kSCLS = TAG('S', 'C', 'L', 'S');   // Silently close on timeout | 
|  | const QuicTag kMIBS = TAG('M', 'I', 'D', 'S');   // Max incoming bidi streams | 
|  | const QuicTag kMIUS = TAG('M', 'I', 'U', 'S');   // Max incoming unidi streams | 
|  | const QuicTag kADE  = TAG('A', 'D', 'E', 0);     // Ack Delay Exponent (IETF | 
|  | // QUIC ACK Frame Only). | 
|  | const QuicTag kIRTT = TAG('I', 'R', 'T', 'T');   // Estimated initial RTT in us. | 
|  | const QuicTag kSNI  = TAG('S', 'N', 'I', '\0');  // Server name | 
|  | // indication | 
|  | const QuicTag kPUBS = TAG('P', 'U', 'B', 'S');   // Public key values | 
|  | const QuicTag kSCID = TAG('S', 'C', 'I', 'D');   // Server config id | 
|  | const QuicTag kORBT = TAG('O', 'B', 'I', 'T');   // Server orbit. | 
|  | const QuicTag kPDMD = TAG('P', 'D', 'M', 'D');   // Proof demand. | 
|  | const QuicTag kPROF = TAG('P', 'R', 'O', 'F');   // Proof (signature). | 
|  | const QuicTag kCCS  = TAG('C', 'C', 'S', 0);     // Common certificate set | 
|  | const QuicTag kCCRT = TAG('C', 'C', 'R', 'T');   // Cached certificate | 
|  | const QuicTag kEXPY = TAG('E', 'X', 'P', 'Y');   // Expiry | 
|  | const QuicTag kSTTL = TAG('S', 'T', 'T', 'L');   // Server Config TTL | 
|  | const QuicTag kSFCW = TAG('S', 'F', 'C', 'W');   // Initial stream flow control | 
|  | // receive window. | 
|  | const QuicTag kCFCW = TAG('C', 'F', 'C', 'W');   // Initial session/connection | 
|  | // flow control receive window. | 
|  | const QuicTag kUAID = TAG('U', 'A', 'I', 'D');   // Client's User Agent ID. | 
|  | const QuicTag kXLCT = TAG('X', 'L', 'C', 'T');   // Expected leaf certificate. | 
|  |  | 
|  | const QuicTag kMAD  = TAG('M', 'A', 'D', 0);     // Max Ack Delay (IETF QUIC) | 
|  |  | 
|  | // Rejection tags | 
|  | const QuicTag kRREJ = TAG('R', 'R', 'E', 'J');   // Reasons for server sending | 
|  |  | 
|  | // Server hello tags | 
|  | const QuicTag kCADR = TAG('C', 'A', 'D', 'R');   // Client IP address and port | 
|  | const QuicTag kASAD = TAG('A', 'S', 'A', 'D');   // Alternate Server IP address | 
|  | // and port. | 
|  | const QuicTag kSRST = TAG('S', 'R', 'S', 'T');   // Stateless reset token used | 
|  | // in IETF public reset packet | 
|  |  | 
|  | // CETV tags | 
|  | const QuicTag kCIDK = TAG('C', 'I', 'D', 'K');   // ChannelID key | 
|  | const QuicTag kCIDS = TAG('C', 'I', 'D', 'S');   // ChannelID signature | 
|  |  | 
|  | // Public reset tags | 
|  | const QuicTag kRNON = TAG('R', 'N', 'O', 'N');   // Public reset nonce proof | 
|  | const QuicTag kRSEQ = TAG('R', 'S', 'E', 'Q');   // Rejected packet number | 
|  |  | 
|  | // Universal tags | 
|  | const QuicTag kPAD  = TAG('P', 'A', 'D', '\0');  // Padding | 
|  |  | 
|  | // Stats collection tags | 
|  | const QuicTag kEPID = TAG('E', 'P', 'I', 'D');  // Endpoint identifier. | 
|  |  | 
|  | // clang-format on | 
|  |  | 
|  | // These tags have a special form so that they appear either at the beginning | 
|  | // or the end of a handshake message. Since handshake messages are sorted by | 
|  | // tag value, the tags with 0 at the end will sort first and those with 255 at | 
|  | // the end will sort last. | 
|  | // | 
|  | // The certificate chain should have a tag that will cause it to be sorted at | 
|  | // the end of any handshake messages because it's likely to be large and the | 
|  | // client might be able to get everything that it needs from the small values at | 
|  | // the beginning. | 
|  | // | 
|  | // Likewise tags with random values should be towards the beginning of the | 
|  | // message because the server mightn't hold state for a rejected client hello | 
|  | // and therefore the client may have issues reassembling the rejection message | 
|  | // in the event that it sent two client hellos. | 
|  | const QuicTag kServerNonceTag = TAG('S', 'N', 'O', 0);  // The server's nonce | 
|  | const QuicTag kSourceAddressTokenTag = | 
|  | TAG('S', 'T', 'K', 0);  // Source-address token | 
|  | const QuicTag kCertificateTag = TAG('C', 'R', 'T', 255);  // Certificate chain | 
|  | const QuicTag kCertificateSCTTag = | 
|  | TAG('C', 'S', 'C', 'T');  // Signed cert timestamp (RFC6962) of leaf cert. | 
|  |  | 
|  | #undef TAG | 
|  |  | 
|  | const size_t kMaxEntries = 128;  // Max number of entries in a message. | 
|  |  | 
|  | const size_t kNonceSize = 32;  // Size in bytes of the connection nonce. | 
|  |  | 
|  | const size_t kOrbitSize = 8;  // Number of bytes in an orbit value. | 
|  |  | 
|  | // kProofSignatureLabel is prepended to the CHLO hash and server configs before | 
|  | // signing to avoid any cross-protocol attacks on the signature. | 
|  | const char kProofSignatureLabel[] = "QUIC CHLO and server config signature"; | 
|  |  | 
|  | // kClientHelloMinimumSize is the minimum size of a client hello. Client hellos | 
|  | // will have PAD tags added in order to ensure this minimum is met and client | 
|  | // hellos smaller than this will be an error. This minimum size reduces the | 
|  | // amplification factor of any mirror DoS attack. | 
|  | // | 
|  | // A client may pad an inchoate client hello to a size larger than | 
|  | // kClientHelloMinimumSize to make it more likely to receive a complete | 
|  | // rejection message. | 
|  | const size_t kClientHelloMinimumSize = 1024; | 
|  |  | 
|  | }  // namespace quic | 
|  |  | 
|  | #endif  // QUICHE_QUIC_CORE_CRYPTO_CRYPTO_PROTOCOL_H_ |