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/connection_id.go

@@ -0,0 +1,69 @@
+package protocol
+
+import (
+	"bytes"
+	"crypto/rand"
+	"fmt"
+	"io"
+)
+
+// A ConnectionID in QUIC
+type ConnectionID []byte
+
+const maxConnectionIDLen = 20
+
+// GenerateConnectionID generates a connection ID using cryptographic random
+func GenerateConnectionID(len int) (ConnectionID, error) {
+	b := make([]byte, len)
+	if _, err := rand.Read(b); err != nil {
+		return nil, err
+	}
+	return ConnectionID(b), nil
+}
+
+// GenerateConnectionIDForInitial generates a connection ID for the Initial packet.
+// It uses a length randomly chosen between 8 and 20 bytes.
+func GenerateConnectionIDForInitial() (ConnectionID, error) {
+	r := make([]byte, 1)
+	if _, err := rand.Read(r); err != nil {
+		return nil, err
+	}
+	len := MinConnectionIDLenInitial + int(r[0])%(maxConnectionIDLen-MinConnectionIDLenInitial+1)
+	return GenerateConnectionID(len)
+}
+
+// ReadConnectionID reads a connection ID of length len from the given io.Reader.
+// It returns io.EOF if there are not enough bytes to read.
+func ReadConnectionID(r io.Reader, len int) (ConnectionID, error) {
+	if len == 0 {
+		return nil, nil
+	}
+	c := make(ConnectionID, len)
+	_, err := io.ReadFull(r, c)
+	if err == io.ErrUnexpectedEOF {
+		return nil, io.EOF
+	}
+	return c, err
+}
+
+// Equal says if two connection IDs are equal
+func (c ConnectionID) Equal(other ConnectionID) bool {
+	return bytes.Equal(c, other)
+}
+
+// Len returns the length of the connection ID in bytes
+func (c ConnectionID) Len() int {
+	return len(c)
+}
+
+// Bytes returns the byte representation
+func (c ConnectionID) Bytes() []byte {
+	return []byte(c)
+}
+
+func (c ConnectionID) String() string {
+	if c.Len() == 0 {
+		return "(empty)"
+	}
+	return fmt.Sprintf("%x", c.Bytes())
+}