gr1ffon/quic-go
1
0
Fork 0
forked from quic-go/quic-go
Code Pull Requests Activity

protocol: use the packet number decoding / encoding logic from the RFC (#4661)

Browse Source
This commit is contained in:
Marten Seemann
2024-09-06 00:54:44 +08:00
committed by GitHub
parent 135b8c0e75
commit 4be70e0146
3 changed files with 56 additions and 234 deletions
Download Patch File Download Diff File Expand all files Collapse all files

68
internal/protocol/packet_number.go
View File

@@ -21,58 +21,36 @@ const (
PacketNumberLen4 PacketNumberLen = 4
)
// DecodePacketNumber calculates the packet number based on the received packet number, its length and the last seen packet number
func DecodePacketNumber(
packetNumberLength PacketNumberLen,
lastPacketNumber PacketNumber,
wirePacketNumber PacketNumber,
) PacketNumber {
var epochDelta PacketNumber
switch packetNumberLength {
case PacketNumberLen1:
epochDelta = PacketNumber(1) << 8
case PacketNumberLen2:
epochDelta = PacketNumber(1) << 16
case PacketNumberLen3:
epochDelta = PacketNumber(1) << 24
case PacketNumberLen4:
epochDelta = PacketNumber(1) << 32
// DecodePacketNumber calculates the packet number based its length and the last seen packet number
// This function is taken from https://www.rfc-editor.org/rfc/rfc9000.html#section-a.3.
func DecodePacketNumber(length PacketNumberLen, largest PacketNumber, truncated PacketNumber) PacketNumber {
expected := largest + 1
win := PacketNumber(1 << (length * 8))
hwin := win / 2
mask := win - 1
candidate := (expected & ^mask) | truncated
if candidate <= expected-hwin && candidate < 1<<62-win {
return candidate + win
}
epoch := lastPacketNumber & ^(epochDelta - 1)
var prevEpochBegin PacketNumber
if epoch > epochDelta {
prevEpochBegin = epoch - epochDelta
if candidate > expected+hwin && candidate >= win {
return candidate - win
}
nextEpochBegin := epoch + epochDelta
return closestTo(
lastPacketNumber+1,
epoch+wirePacketNumber,
closestTo(lastPacketNumber+1, prevEpochBegin+wirePacketNumber, nextEpochBegin+wirePacketNumber),
)
return candidate
}
func closestTo(target, a, b PacketNumber) PacketNumber {
if delta(target, a) < delta(target, b) {
return a
}
return b
}
func delta(a, b PacketNumber) PacketNumber {
if a < b {
return b - a
}
return a - b
}
// GetPacketNumberLengthForHeader gets the length of the packet number for the public header
// PacketNumberLengthForHeader gets the length of the packet number for the public header
// it never chooses a PacketNumberLen of 1 byte, since this is too short under certain circumstances
func GetPacketNumberLengthForHeader(packetNumber, leastUnacked PacketNumber) PacketNumberLen {
diff := uint64(packetNumber - leastUnacked)
if diff < (1 << (16 - 1)) {
func PacketNumberLengthForHeader(pn, largestAcked PacketNumber) PacketNumberLen {
var numUnacked PacketNumber
if largestAcked == InvalidPacketNumber {
numUnacked = pn + 1
} else {
numUnacked = pn - largestAcked
}
if numUnacked < 1<<(16-1) {
return PacketNumberLen2
}
if diff < (1 << (24 - 1)) {
if numUnacked < 1<<(24-1) {
return PacketNumberLen3
}
return PacketNumberLen4