Make globals in quic_constants.h use inline constexpr
As discussed in a recent unrelated CL (cl/457003884), globals protected from ODR only by internal linkage are still a dangerous pattern as explained by go/totw/140#does-this-cause-problems-in-practice. A lot of similarly dangerous code throughout QUICHE, but this CL is a quick bang-for-buck cleanup.
PiperOrigin-RevId: 457746913
diff --git a/quiche/quic/core/quic_constants.h b/quiche/quic/core/quic_constants.h
index 6f89ec1..46af2e8 100644
--- a/quiche/quic/core/quic_constants.h
+++ b/quiche/quic/core/quic_constants.h
@@ -18,106 +18,114 @@
namespace quic {
// Simple time constants.
-const uint64_t kNumSecondsPerMinute = 60;
-const uint64_t kNumSecondsPerHour = kNumSecondsPerMinute * 60;
-const uint64_t kNumSecondsPerWeek = kNumSecondsPerHour * 24 * 7;
-const uint64_t kNumMillisPerSecond = 1000;
-const uint64_t kNumMicrosPerMilli = 1000;
-const uint64_t kNumMicrosPerSecond = kNumMicrosPerMilli * kNumMillisPerSecond;
+inline constexpr uint64_t kNumSecondsPerMinute = 60;
+inline constexpr uint64_t kNumSecondsPerHour = kNumSecondsPerMinute * 60;
+inline constexpr uint64_t kNumSecondsPerWeek = kNumSecondsPerHour * 24 * 7;
+inline constexpr uint64_t kNumMillisPerSecond = 1000;
+inline constexpr uint64_t kNumMicrosPerMilli = 1000;
+inline constexpr uint64_t kNumMicrosPerSecond =
+ kNumMicrosPerMilli * kNumMillisPerSecond;
// Default number of connections for N-connection emulation.
-const uint32_t kDefaultNumConnections = 2;
+inline constexpr uint32_t kDefaultNumConnections = 2;
// Default initial maximum size in bytes of a QUIC packet.
-const QuicByteCount kDefaultMaxPacketSize = 1250;
+inline constexpr QuicByteCount kDefaultMaxPacketSize = 1250;
// Default initial maximum size in bytes of a QUIC packet for servers.
-const QuicByteCount kDefaultServerMaxPacketSize = 1000;
+inline constexpr QuicByteCount kDefaultServerMaxPacketSize = 1000;
// Maximum transmission unit on Ethernet.
-const QuicByteCount kEthernetMTU = 1500;
+inline constexpr QuicByteCount kEthernetMTU = 1500;
// The maximum packet size of any QUIC packet over IPv6, based on ethernet's max
// size, minus the IP and UDP headers. IPv6 has a 40 byte header, UDP adds an
// additional 8 bytes. This is a total overhead of 48 bytes. Ethernet's
// max packet size is 1500 bytes, 1500 - 48 = 1452.
-const QuicByteCount kMaxV6PacketSize = 1452;
+inline constexpr QuicByteCount kMaxV6PacketSize = 1452;
// The maximum packet size of any QUIC packet over IPv4.
// 1500(Ethernet) - 20(IPv4 header) - 8(UDP header) = 1472.
-const QuicByteCount kMaxV4PacketSize = 1472;
+inline constexpr QuicByteCount kMaxV4PacketSize = 1472;
// The maximum incoming packet size allowed.
-const QuicByteCount kMaxIncomingPacketSize = kMaxV4PacketSize;
+inline constexpr QuicByteCount kMaxIncomingPacketSize = kMaxV4PacketSize;
// The maximum outgoing packet size allowed.
-const QuicByteCount kMaxOutgoingPacketSize = kMaxV6PacketSize;
+inline constexpr QuicByteCount kMaxOutgoingPacketSize = kMaxV6PacketSize;
// ETH_MAX_MTU - MAX(sizeof(iphdr), sizeof(ip6_hdr)) - sizeof(udphdr).
-const QuicByteCount kMaxGsoPacketSize = 65535 - 40 - 8;
+inline constexpr QuicByteCount kMaxGsoPacketSize = 65535 - 40 - 8;
// The maximal IETF DATAGRAM frame size we'll accept. Choosing 2^16 ensures
// that it is greater than the biggest frame we could ever fit in a QUIC packet.
-const QuicByteCount kMaxAcceptedDatagramFrameSize = 65536;
+inline constexpr QuicByteCount kMaxAcceptedDatagramFrameSize = 65536;
// Default value of the max_packet_size transport parameter if it is not
// transmitted.
-const QuicByteCount kDefaultMaxPacketSizeTransportParam = 65527;
+inline constexpr QuicByteCount kDefaultMaxPacketSizeTransportParam = 65527;
// Default maximum packet size used in the Linux TCP implementation.
// Used in QUIC for congestion window computations in bytes.
-const QuicByteCount kDefaultTCPMSS = 1460;
-const QuicByteCount kMaxSegmentSize = kDefaultTCPMSS;
+inline constexpr QuicByteCount kDefaultTCPMSS = 1460;
+inline constexpr QuicByteCount kMaxSegmentSize = kDefaultTCPMSS;
// The minimum size of a packet which can elicit a version negotiation packet,
// as per section 8.1 of the QUIC spec.
-const QuicByteCount kMinPacketSizeForVersionNegotiation = 1200;
+inline constexpr QuicByteCount kMinPacketSizeForVersionNegotiation = 1200;
// We match SPDY's use of 32 (since we'd compete with SPDY).
-const QuicPacketCount kInitialCongestionWindow = 32;
+inline constexpr QuicPacketCount kInitialCongestionWindow = 32;
// Do not allow initial congestion window to be greater than 200 packets.
-const QuicPacketCount kMaxInitialCongestionWindow = 200;
+inline constexpr QuicPacketCount kMaxInitialCongestionWindow = 200;
// Do not allow initial congestion window to be smaller than 10 packets.
-const QuicPacketCount kMinInitialCongestionWindow = 10;
+inline constexpr QuicPacketCount kMinInitialCongestionWindow = 10;
// Minimum size of initial flow control window, for both stream and session.
// This is only enforced when version.AllowsLowFlowControlLimits() is false.
-const QuicByteCount kMinimumFlowControlSendWindow = 16 * 1024; // 16 KB
+inline constexpr QuicByteCount kMinimumFlowControlSendWindow =
+ 16 * 1024; // 16 KB
// Default size of initial flow control window, for both stream and session.
-const QuicByteCount kDefaultFlowControlSendWindow = 16 * 1024; // 16 KB
+inline constexpr QuicByteCount kDefaultFlowControlSendWindow =
+ 16 * 1024; // 16 KB
// Maximum flow control receive window limits for connection and stream.
-const QuicByteCount kStreamReceiveWindowLimit = 16 * 1024 * 1024; // 16 MB
-const QuicByteCount kSessionReceiveWindowLimit = 24 * 1024 * 1024; // 24 MB
+inline constexpr QuicByteCount kStreamReceiveWindowLimit =
+ 16 * 1024 * 1024; // 16 MB
+inline constexpr QuicByteCount kSessionReceiveWindowLimit =
+ 24 * 1024 * 1024; // 24 MB
// Minimum size of the CWND, in packets, when doing bandwidth resumption.
-const QuicPacketCount kMinCongestionWindowForBandwidthResumption = 10;
+inline constexpr QuicPacketCount kMinCongestionWindowForBandwidthResumption =
+ 10;
// Default size of the socket receive buffer in bytes.
-const QuicByteCount kDefaultSocketReceiveBuffer = 1024 * 1024;
+inline constexpr QuicByteCount kDefaultSocketReceiveBuffer = 1024 * 1024;
// The lower bound of an untrusted initial rtt value.
-const uint32_t kMinUntrustedInitialRoundTripTimeUs = 10 * kNumMicrosPerMilli;
+inline constexpr uint32_t kMinUntrustedInitialRoundTripTimeUs =
+ 10 * kNumMicrosPerMilli;
// The lower bound of a trusted initial rtt value.
-const uint32_t kMinTrustedInitialRoundTripTimeUs = 5 * kNumMicrosPerMilli;
+inline constexpr uint32_t kMinTrustedInitialRoundTripTimeUs =
+ 5 * kNumMicrosPerMilli;
// Don't allow a client to suggest an RTT longer than 1 second.
-const uint32_t kMaxInitialRoundTripTimeUs = kNumMicrosPerSecond;
+inline constexpr uint32_t kMaxInitialRoundTripTimeUs = kNumMicrosPerSecond;
// Maximum number of open streams per connection.
-const size_t kDefaultMaxStreamsPerConnection = 100;
+inline constexpr size_t kDefaultMaxStreamsPerConnection = 100;
// Number of bytes reserved for public flags in the packet header.
-const size_t kPublicFlagsSize = 1;
+inline constexpr size_t kPublicFlagsSize = 1;
// Number of bytes reserved for version number in the packet header.
-const size_t kQuicVersionSize = 4;
+inline constexpr size_t kQuicVersionSize = 4;
// Minimum number of active connection IDs that an end point can maintain.
-const uint32_t kMinNumOfActiveConnectionIds = 2;
+inline constexpr uint32_t kMinNumOfActiveConnectionIds = 2;
// Length of the retry integrity tag in bytes.
// https://tools.ietf.org/html/draft-ietf-quic-transport-25#section-17.2.5
-const size_t kRetryIntegrityTagLength = 16;
+inline constexpr size_t kRetryIntegrityTagLength = 16;
// By default, UnackedPacketsMap allocates buffer of 64 after the first packet
// is added.
-const int kDefaultUnackedPacketsInitialCapacity = 64;
+inline constexpr int kDefaultUnackedPacketsInitialCapacity = 64;
// Signifies that the QuicPacket will contain version of the protocol.
-const bool kIncludeVersion = true;
+inline constexpr bool kIncludeVersion = true;
// Signifies that the QuicPacket will include a diversification nonce.
-const bool kIncludeDiversificationNonce = true;
+inline constexpr bool kIncludeDiversificationNonce = true;
// Header key used to identify final offset on data stream when sending HTTP/2
// trailing headers over QUIC.
@@ -126,40 +134,40 @@
// Default maximum delayed ack time, in ms.
// Uses a 25ms delayed ack timer. Helps with better signaling
// in low-bandwidth (< ~384 kbps), where an ack is sent per packet.
-const int64_t kDefaultDelayedAckTimeMs = 25;
+inline constexpr int64_t kDefaultDelayedAckTimeMs = 25;
// Default minimum delayed ack time, in ms (used only for sender control of ack
// frequency).
-const uint32_t kDefaultMinAckDelayTimeMs = 5;
+inline constexpr uint32_t kDefaultMinAckDelayTimeMs = 5;
// Default shift of the ACK delay in the IETF QUIC ACK frame.
-const uint32_t kDefaultAckDelayExponent = 3;
+inline constexpr uint32_t kDefaultAckDelayExponent = 3;
// Minimum tail loss probe time in ms.
-static const int64_t kMinTailLossProbeTimeoutMs = 10;
+inline constexpr int64_t kMinTailLossProbeTimeoutMs = 10;
// The timeout before the handshake succeeds.
-const int64_t kInitialIdleTimeoutSecs = 5;
+inline constexpr int64_t kInitialIdleTimeoutSecs = 5;
// The maximum idle timeout that can be negotiated.
-const int64_t kMaximumIdleTimeoutSecs = 60 * 10; // 10 minutes.
+inline constexpr int64_t kMaximumIdleTimeoutSecs = 60 * 10; // 10 minutes.
// The default timeout for a connection until the crypto handshake succeeds.
-const int64_t kMaxTimeForCryptoHandshakeSecs = 10; // 10 secs.
+inline constexpr int64_t kMaxTimeForCryptoHandshakeSecs = 10; // 10 secs.
// Default limit on the number of undecryptable packets the connection buffers
// before the CHLO/SHLO arrive.
-const size_t kDefaultMaxUndecryptablePackets = 10;
+inline constexpr size_t kDefaultMaxUndecryptablePackets = 10;
// Default ping timeout.
-const int64_t kPingTimeoutSecs = 15; // 15 secs.
+inline constexpr int64_t kPingTimeoutSecs = 15; // 15 secs.
// Minimum number of RTTs between Server Config Updates (SCUP) sent to client.
-const int kMinIntervalBetweenServerConfigUpdatesRTTs = 10;
+inline constexpr int kMinIntervalBetweenServerConfigUpdatesRTTs = 10;
// Minimum time between Server Config Updates (SCUP) sent to client.
-const int kMinIntervalBetweenServerConfigUpdatesMs = 1000;
+inline constexpr int kMinIntervalBetweenServerConfigUpdatesMs = 1000;
// Minimum number of packets between Server Config Updates (SCUP).
-const int kMinPacketsBetweenServerConfigUpdates = 100;
+inline constexpr int kMinPacketsBetweenServerConfigUpdates = 100;
// The number of open streams that a server will accept is set to be slightly
// larger than the negotiated limit. Immediately closing the connection if the
@@ -167,31 +175,32 @@
// a FIN that was lost, and simultaneously opened a new stream. The number of
// streams a server accepts is a fixed increment over the negotiated limit, or a
// percentage increase, whichever is larger.
-const float kMaxStreamsMultiplier = 1.1f;
-const int kMaxStreamsMinimumIncrement = 10;
+inline constexpr float kMaxStreamsMultiplier = 1.1f;
+inline constexpr int kMaxStreamsMinimumIncrement = 10;
// Available streams are ones with IDs less than the highest stream that has
// been opened which have neither been opened or reset. The limit on the number
// of available streams is 10 times the limit on the number of open streams.
-const int kMaxAvailableStreamsMultiplier = 10;
+inline constexpr int kMaxAvailableStreamsMultiplier = 10;
// Track the number of promises that are not yet claimed by a
// corresponding get. This must be smaller than
// kMaxAvailableStreamsMultiplier, because RST on a promised stream my
// create available streams entries.
-const int kMaxPromisedStreamsMultiplier = kMaxAvailableStreamsMultiplier - 1;
+inline constexpr int kMaxPromisedStreamsMultiplier =
+ kMaxAvailableStreamsMultiplier - 1;
// The 1st PTO is armed with max of earliest in flight sent time + PTO
// delay and kFirstPtoSrttMultiplier * srtt from last in flight packet.
-const float kFirstPtoSrttMultiplier = 1.5;
+inline constexpr float kFirstPtoSrttMultiplier = 1.5;
// The multiplier of RTT variation when calculating PTO timeout.
-const int kPtoRttvarMultiplier = 2;
+inline constexpr int kPtoRttvarMultiplier = 2;
// TCP RFC calls for 1 second RTO however Linux differs from this default and
// define the minimum RTO to 200ms, we will use the same until we have data to
// support a higher or lower value.
-static const int64_t kMinRetransmissionTimeMs = 200;
+inline constexpr const int64_t kMinRetransmissionTimeMs = 200;
// The delayed ack time must not be greater than half the min RTO.
static_assert(kDefaultDelayedAckTimeMs <= kMinRetransmissionTimeMs / 2,
"Delayed ack time must be less than or equal half the MinRTO");
@@ -205,98 +214,101 @@
// uint64_t value;
// if (exponent == 0) value = mantissa;
// else value = (mantissa | 1 << 11) << (exponent - 1)
-const int kUFloat16ExponentBits = 5;
-const int kUFloat16MaxExponent = (1 << kUFloat16ExponentBits) - 2; // 30
-const int kUFloat16MantissaBits = 16 - kUFloat16ExponentBits; // 11
-const int kUFloat16MantissaEffectiveBits = kUFloat16MantissaBits + 1; // 12
-const uint64_t kUFloat16MaxValue = // 0x3FFC0000000
+inline constexpr int kUFloat16ExponentBits = 5;
+inline constexpr int kUFloat16MaxExponent =
+ (1 << kUFloat16ExponentBits) - 2; // 30
+inline constexpr int kUFloat16MantissaBits = 16 - kUFloat16ExponentBits; // 11
+inline constexpr int kUFloat16MantissaEffectiveBits =
+ kUFloat16MantissaBits + 1; // 12
+inline constexpr uint64_t kUFloat16MaxValue = // 0x3FFC0000000
((UINT64_C(1) << kUFloat16MantissaEffectiveBits) - 1)
<< kUFloat16MaxExponent;
// kDiversificationNonceSize is the size, in bytes, of the nonce that a server
// may set in the packet header to ensure that its INITIAL keys are not
// duplicated.
-const size_t kDiversificationNonceSize = 32;
+inline constexpr size_t kDiversificationNonceSize = 32;
// The largest gap in packets we'll accept without closing the connection.
// This will likely have to be tuned.
-const QuicPacketCount kMaxPacketGap = 5000;
+inline constexpr QuicPacketCount kMaxPacketGap = 5000;
// The max number of sequence number intervals that
// QuicPeerIssuedConnetionIdManager can maintain.
-const size_t kMaxNumConnectionIdSequenceNumberIntervals = 20;
+inline constexpr size_t kMaxNumConnectionIdSequenceNumberIntervals = 20;
// The maximum number of random padding bytes to add.
-const QuicByteCount kMaxNumRandomPaddingBytes = 256;
+inline constexpr QuicByteCount kMaxNumRandomPaddingBytes = 256;
// The size of stream send buffer data slice size in bytes. A data slice is
// piece of stream data stored in contiguous memory, and a stream frame can
// contain data from multiple data slices.
-const QuicByteCount kQuicStreamSendBufferSliceSize = 4 * 1024;
+inline constexpr QuicByteCount kQuicStreamSendBufferSliceSize = 4 * 1024;
// For When using Random Initial Packet Numbers, they can start
// anyplace in the range 1...((2^31)-1) or 0x7fffffff
QUIC_EXPORT_PRIVATE QuicPacketNumber MaxRandomInitialPacketNumber();
// Used to represent an invalid or no control frame id.
-const QuicControlFrameId kInvalidControlFrameId = 0;
+inline constexpr QuicControlFrameId kInvalidControlFrameId = 0;
// The max length a stream can have.
-const QuicByteCount kMaxStreamLength = (UINT64_C(1) << 62) - 1;
+inline constexpr QuicByteCount kMaxStreamLength = (UINT64_C(1) << 62) - 1;
// The max value that can be encoded using IETF Var Ints.
-const uint64_t kMaxIetfVarInt = UINT64_C(0x3fffffffffffffff);
+inline constexpr uint64_t kMaxIetfVarInt = UINT64_C(0x3fffffffffffffff);
// The maximum stream id value that is supported - (2^32)-1
-const QuicStreamId kMaxQuicStreamId = 0xffffffff;
+inline constexpr QuicStreamId kMaxQuicStreamId = 0xffffffff;
// The maximum value that can be stored in a 32-bit QuicStreamCount.
-const QuicStreamCount kMaxQuicStreamCount = 0xffffffff;
+inline constexpr QuicStreamCount kMaxQuicStreamCount = 0xffffffff;
// Number of bytes reserved for packet header type.
-const size_t kPacketHeaderTypeSize = 1;
+inline constexpr size_t kPacketHeaderTypeSize = 1;
// Number of bytes reserved for connection ID length.
-const size_t kConnectionIdLengthSize = 1;
+inline constexpr size_t kConnectionIdLengthSize = 1;
// Minimum length of random bytes in IETF stateless reset packet.
-const size_t kMinRandomBytesLengthInStatelessReset = 24;
+inline constexpr size_t kMinRandomBytesLengthInStatelessReset = 24;
// Maximum length allowed for the token in a NEW_TOKEN frame.
-const size_t kMaxNewTokenTokenLength = 0xffff;
+inline constexpr size_t kMaxNewTokenTokenLength = 0xffff;
// The prefix used by a source address token in a NEW_TOKEN frame.
-const uint8_t kAddressTokenPrefix = 0;
+inline constexpr uint8_t kAddressTokenPrefix = 0;
// Default initial rtt used before any samples are received.
-const int kInitialRttMs = 100;
+inline constexpr int kInitialRttMs = 100;
// Default threshold of packet reordering before a packet is declared lost.
-static const QuicPacketCount kDefaultPacketReorderingThreshold = 3;
+inline constexpr QuicPacketCount kDefaultPacketReorderingThreshold = 3;
// Default fraction (1/4) of an RTT the algorithm waits before determining a
// packet is lost due to early retransmission by time based loss detection.
-static const int kDefaultLossDelayShift = 2;
+inline constexpr int kDefaultLossDelayShift = 2;
// Default fraction (1/8) of an RTT when doing IETF loss detection.
-static const int kDefaultIetfLossDelayShift = 3;
+inline constexpr int kDefaultIetfLossDelayShift = 3;
// Maximum number of retransmittable packets received before sending an ack.
-const QuicPacketCount kDefaultRetransmittablePacketsBeforeAck = 2;
+inline constexpr QuicPacketCount kDefaultRetransmittablePacketsBeforeAck = 2;
// Wait for up to 10 retransmittable packets before sending an ack.
-const QuicPacketCount kMaxRetransmittablePacketsBeforeAck = 10;
+inline constexpr QuicPacketCount kMaxRetransmittablePacketsBeforeAck = 10;
// Minimum number of packets received before ack decimation is enabled.
// This intends to avoid the beginning of slow start, when CWNDs may be
// rapidly increasing.
-const QuicPacketCount kMinReceivedBeforeAckDecimation = 100;
+inline constexpr QuicPacketCount kMinReceivedBeforeAckDecimation = 100;
// One quarter RTT delay when doing ack decimation.
-const float kAckDecimationDelay = 0.25;
+inline constexpr float kAckDecimationDelay = 0.25;
// The default alarm granularity assumed by QUIC code.
-const QuicTime::Delta kAlarmGranularity = QuicTime::Delta::FromMilliseconds(1);
+inline constexpr QuicTime::Delta kAlarmGranularity =
+ QuicTime::Delta::FromMilliseconds(1);
// Maximum number of unretired connection IDs a connection can have.
-const size_t kMaxNumConnectonIdsInUse = 10u;
+inline constexpr size_t kMaxNumConnectonIdsInUse = 10u;
// Packet number of first sending packet of a connection. Please note, this
// cannot be used as first received packet because peer can choose its starting
@@ -307,9 +319,7 @@
QUIC_EXPORT_PRIVATE extern const char* const kEPIDGoogleFrontEnd;
QUIC_EXPORT_PRIVATE extern const char* const kEPIDGoogleFrontEnd0;
-enum : uint64_t {
- kHttpDatagramStreamIdDivisor = 4,
-};
+inline constexpr uint64_t kHttpDatagramStreamIdDivisor = 4;
} // namespace quic
