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package protocol
import (
"crypto/rand"
"encoding/binary"
"fmt"
"math"
)
// VersionNumber is a version number as int
type VersionNumber uint32
// gQUIC version range as defined in the wiki: https://github.com/quicwg/base-drafts/wiki/QUIC-Versions
const (
gquicVersion0 = 0x51303030
maxGquicVersion = 0x51303439
)
// The version numbers, making grepping easier
const (
VersionTLS VersionNumber = 0x51474fff
VersionWhatever VersionNumber = 1 // for when the version doesn't matter
VersionUnknown VersionNumber = math.MaxUint32
)
// SupportedVersions lists the versions that the server supports
// must be in sorted descending order
var SupportedVersions = []VersionNumber{VersionTLS}
// IsValidVersion says if the version is known to quic-go
func IsValidVersion(v VersionNumber) bool {
return v == VersionTLS || IsSupportedVersion(SupportedVersions, v)
}
func (vn VersionNumber) String() string {
switch vn {
case VersionWhatever:
return "whatever"
case VersionUnknown:
return "unknown"
case VersionTLS:
return "TLS dev version (WIP)"
default:
if vn.isGQUIC() {
return fmt.Sprintf("gQUIC %d", vn.toGQUICVersion())
}
return fmt.Sprintf("%#x", uint32(vn))
}
}
func (vn VersionNumber) isGQUIC() bool {
return vn > gquicVersion0 && vn <= maxGquicVersion
}
func (vn VersionNumber) toGQUICVersion() int {
return int(10*(vn-gquicVersion0)/0x100) + int(vn%0x10)
}
// IsSupportedVersion returns true if the server supports this version
func IsSupportedVersion(supported []VersionNumber, v VersionNumber) bool {
for _, t := range supported {
if t == v {
return true
}
}
return false
}
// ChooseSupportedVersion finds the best version in the overlap of ours and theirs
// ours is a slice of versions that we support, sorted by our preference (descending)
// theirs is a slice of versions offered by the peer. The order does not matter.
// The bool returned indicates if a matching version was found.
func ChooseSupportedVersion(ours, theirs []VersionNumber) (VersionNumber, bool) {
for _, ourVer := range ours {
for _, theirVer := range theirs {
if ourVer == theirVer {
return ourVer, true
}
}
}
return 0, false
}
// generateReservedVersion generates a reserved version number (v & 0x0f0f0f0f == 0x0a0a0a0a)
func generateReservedVersion() VersionNumber {
b := make([]byte, 4)
_, _ = rand.Read(b) // ignore the error here. Failure to read random data doesn't break anything
return VersionNumber((binary.BigEndian.Uint32(b) | 0x0a0a0a0a) & 0xfafafafa)
}
// GetGreasedVersions adds one reserved version number to a slice of version numbers, at a random position
func GetGreasedVersions(supported []VersionNumber) []VersionNumber {
b := make([]byte, 1)
_, _ = rand.Read(b) // ignore the error here. Failure to read random data doesn't break anything
randPos := int(b[0]) % (len(supported) + 1)
greased := make([]VersionNumber, len(supported)+1)
copy(greased, supported[:randPos])
greased[randPos] = generateReservedVersion()
copy(greased[randPos+1:], supported[randPos:])
return greased
}
// StripGreasedVersions strips all greased versions from a slice of versions
func StripGreasedVersions(versions []VersionNumber) []VersionNumber {
realVersions := make([]VersionNumber, 0, len(versions))
for _, v := range versions {
if v&0x0f0f0f0f != 0x0a0a0a0a {
realVersions = append(realVersions, v)
}
}
return realVersions
}
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