TUN-4597: Add a QUIC server skeleton

- Added a QUIC server to accept streams
- Unit test for this server also tests ALPN
- Temporary echo capability for HTTP ConnectionType

vendor/github.com/lucas-clemente/quic-go/internal/protocol/version.go

@@ -0,0 +1,134 @@
+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 = 0x1
+	VersionWhatever VersionNumber = math.MaxUint32 - 1 // for when the version doesn't matter
+	VersionUnknown  VersionNumber = math.MaxUint32
+	VersionDraft29  VersionNumber = 0xff00001d
+	VersionDraft32  VersionNumber = 0xff000020
+	VersionDraft34  VersionNumber = 0xff000022
+	Version1        VersionNumber = 0x1
+)
+
+// SupportedVersions lists the versions that the server supports
+// must be in sorted descending order
+var SupportedVersions = []VersionNumber{Version1, VersionDraft34, VersionDraft32, VersionDraft29}
+
+// 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 {
+	// For releases, VersionTLS will be set to a draft version.
+	// A switch statement can't contain duplicate cases.
+	if vn == VersionTLS && VersionTLS != VersionDraft29 && VersionTLS != VersionDraft32 && VersionTLS != Version1 {
+		return "TLS dev version (WIP)"
+	}
+	//nolint:exhaustive
+	switch vn {
+	case VersionWhatever:
+		return "whatever"
+	case VersionUnknown:
+		return "unknown"
+	case VersionDraft29:
+		return "draft-29"
+	case VersionDraft32:
+		return "draft-32"
+	case VersionDraft34:
+		return "draft-34"
+	case Version1:
+		return "v1"
+	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)
+}
+
+// UseRetireBugBackwardsCompatibilityMode says if it is necessary to use the backwards compatilibity mode.
+// This is only the case if it 1. is enabled and 2. draft-29 is used.
+func UseRetireBugBackwardsCompatibilityMode(enabled bool, v VersionNumber) bool {
+	return enabled && v == VersionDraft29
+}
+
+// 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
+}