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Write ACK_EXTENDED frame when supported by peer

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Summary:
Write the new ACK_EXTENDED frame. When any of the ACK_EXTENDED features are enabled locally and supported by the peer, this frame type will take precedence over ACK_ECN and ACK_RECEIVETIMESTAMPS. See first diff in the stack for the features.

Frame format:
```
ACK_EXTENDED Frame {
  Type (i) = 0xB1
  // Fields of the existing ACK (type=0x02) frame:
  Largest Acknowledged (i),
  ACK Delay (i),
  ACK Range Count (i),
  First ACK Range (i),
  ACK Range (..) ...,
  Extended Ack Features (i),
  // Optional ECN counts (if bit 0 is set in Features)
  [ECN Counts (..)],
  // Optional Receive Timestamps (if bit 1 is set in Features)
  [Receive Timestamps (..)]
}
// Fields from the existing ACK_ECN frame
ECN Counts {
  ECT0 Count (i),
  ECT1 Count (i),
  ECN-CE Count (i),
}
// Fields from the existing ACK_RECEIVE_TIMESTAMPS frame
Receive Timestamps {
  Timestamp Range Count (i),
  Timestamp Ranges (..) ...,
}
Timestamp Range {
  Gap (i),
  Timestamp Delta Count (i),
  Timestamp Delta (i) ...,
}
```

Reviewed By: sharmafb

Differential Revision: D68931148

fbshipit-source-id: 0fb4bac23e121f82a11602daabc1ec7084db43dd
This commit is contained in:
Joseph Beshay
2025-02-24 12:32:50 -08:00
committed by Facebook GitHub Bot
parent 31fbb343d1
commit aac108ddc7
8 changed files with 400 additions and 70 deletions
Download Patch File Download Diff File Expand all files Collapse all files

36
quic/api/QuicPacketScheduler.cpp
View File

@ -614,16 +614,38 @@ Optional<PacketNum> AckScheduler::writeNextAcks(
.maxReceiveTimestampsPerAck
: 0;
if (conn_.transportSettings.readEcnOnIngress &&
uint64_t extendedAckSupportedAndEnabled =
conn_.peerAdvertisedExtendedAckFeatures &
conn_.transportSettings.enableExtendedAckFeatures;
// Disable the ECN fields if we are not reading them
if (!conn_.transportSettings.readEcnOnIngress) {
extendedAckSupportedAndEnabled &= ~static_cast<ExtendedAckFeatureMaskType>(
ExtendedAckFeatureMask::ECN_COUNTS);
}
// Disable the receive timestamps fields if we have not regoatiated receive
// timestamps support
if (!isAckReceiveTimestampsSupported || (peerRequestedTimestampsCount == 0)) {
extendedAckSupportedAndEnabled &= ~static_cast<ExtendedAckFeatureMaskType>(
ExtendedAckFeatureMask::RECEIVE_TIMESTAMPS);
}
if (extendedAckSupportedAndEnabled > 0) {
// The peer supports extended ACKs and we have them enabled.
ackWriteResult = writeAckFrame(
meta,
builder,
FrameType::ACK_EXTENDED,
conn_.transportSettings.maybeAckReceiveTimestampsConfigSentToPeer
.value_or(AckReceiveTimestampsConfig()),
peerRequestedTimestampsCount,
extendedAckSupportedAndEnabled);
} else if (
conn_.transportSettings.readEcnOnIngress &&
(meta.ackState.ecnECT0CountReceived ||
meta.ackState.ecnECT1CountReceived ||
meta.ackState.ecnCECountReceived)) {
// If echoing ECN is enabled and we have seen marked packets, this will
// currently take priority over sending receive timestamps. There is
// currently no provision for a frame time that includes both ECN counts and
// receive timestamps.
// TODO: explore design changes for an ACK frame that supports both ECN and
// receive timestamps
// We have to report ECN counts, but we can't use the extended ACK frame. In
// this case, we give ACK_ECN precedence over ACK_RECEIVE_TIMESTAMPS.
ackWriteResult = writeAckFrame(meta, builder, FrameType::ACK_ECN);
} else if (
isAckReceiveTimestampsSupported && (peerRequestedTimestampsCount > 0)) {