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Add fixed short header padding

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Summary: This adds a knob which puts a fixed amount of padding at the start of short header packets. This is useful to test the consequences of e.g. a larger CID or the impacts of a smaller packet size.

Reviewed By: jbeshay

Differential Revision: D69603113

fbshipit-source-id: b92ba78682eed21b7d75e38c9584a93481e2eb2f
This commit is contained in:
Matt Joras
2025-02-14 09:57:41 -08:00
committed by Facebook GitHub Bot
parent 485e35e787
commit 6a8f9bcb6b
6 changed files with 148 additions and 14 deletions
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23
quic/api/QuicPacketScheduler.cpp
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@ -241,7 +241,19 @@ SchedulingResult FrameScheduler::scheduleFramesForPacket(
PacketBuilderInterface&& builder,
uint32_t writableBytes) {
size_t shortHeaderPadding = 0;
const ShortHeader* shortHeader = builder.getPacketHeader().asShort();
const LongHeader* longHeader = builder.getPacketHeader().asLong();
bool initialPacket =
longHeader && longHeader->getHeaderType() == LongHeader::Types::Initial;
builder.encodePacketHeader();
// Add fixed padding at start of short header packets if configured
if (shortHeader && conn_.transportSettings.fixedShortHeaderPadding > 0) {
for (size_t i = 0; i < conn_.transportSettings.fixedShortHeaderPadding;
i++) {
writeFrame(PaddingFrame(), builder);
}
shortHeaderPadding = conn_.transportSettings.fixedShortHeaderPadding;
}
// We need to keep track of writable bytes after writing header.
writableBytes = writableBytes > builder.getHeaderBytes()
? writableBytes - builder.getHeaderBytes()
@ -307,16 +319,12 @@ SchedulingResult FrameScheduler::scheduleFramesForPacket(
}
if (builder.hasFramesPending()) {
const LongHeader* longHeader = builder.getPacketHeader().asLong();
bool initialPacket =
longHeader && longHeader->getHeaderType() == LongHeader::Types::Initial;
if (initialPacket) {
// This is the initial packet, we need to fill er up.
while (builder.remainingSpaceInPkt() > 0) {
writeFrame(PaddingFrame(), builder);
}
}
const ShortHeader* shortHeader = builder.getPacketHeader().asShort();
if (shortHeader) {
size_t paddingModulo = conn_.transportSettings.paddingModulo;
if (paddingModulo > 0) {
@ -324,7 +332,7 @@ SchedulingResult FrameScheduler::scheduleFramesForPacket(
for (size_t i = 0; i < paddingIncrement; i++) {
writeFrame(PaddingFrame(), builder);
}
shortHeaderPadding = paddingIncrement;
shortHeaderPadding += paddingIncrement;
}
}
}
@ -879,6 +887,9 @@ bool CloningScheduler::hasData() const {
SchedulingResult CloningScheduler::scheduleFramesForPacket(
PacketBuilderInterface&& builder,
uint32_t writableBytes) {
// Store header type information before any moves
auto builderPnSpace = builder.getPacketHeader().getPacketNumberSpace();
auto header = builder.getPacketHeader();
// The writableBytes in this function shouldn't be limited by cwnd, since
// we only use CloningScheduler for the cases that we want to bypass cwnd for
// now.
@ -896,7 +907,6 @@ SchedulingResult CloningScheduler::scheduleFramesForPacket(
}
// TODO: We can avoid the copy & rebuild of the header by creating an
// independent header builder.
auto header = builder.getPacketHeader();
std::move(builder).releaseOutputBuffer();
// Look for an outstanding packet that's no larger than the writableBytes
for (auto& outstandingPacket : conn_.outstandings.packets) {
@ -909,7 +919,6 @@ SchedulingResult CloningScheduler::scheduleFramesForPacket(
// clone packet. So re-create a RegularQuicPacketBuilder every time.
// TODO: We can avoid the copy & rebuild of the header by creating an
// independent header builder.
auto builderPnSpace = builder.getPacketHeader().getPacketNumberSpace();
if (opPnSpace != builderPnSpace) {
continue;
}