TUN-5299: Send/receive QUIC datagram from edge and proxy to origin as UDP

quic/datagram.go

@@ -0,0 +1,38 @@
+package quic
+
+import (
+	"fmt"
+
+	"github.com/google/uuid"
+)
+
+const (
+	sessionIDLen         = len(uuid.UUID{})
+	MaxDatagramFrameSize = 1220
+)
+
+// Each QUIC datagram should be suffixed with session ID.
+// ExtractSessionID extracts the session ID and a slice with only the payload
+func ExtractSessionID(b []byte) (uuid.UUID, []byte, error) {
+	msgLen := len(b)
+	if msgLen < sessionIDLen {
+		return uuid.Nil, nil, fmt.Errorf("session ID has %d bytes, but data only has %d", sessionIDLen, len(b))
+	}
+	// Parse last 16 bytess as UUID and remove it from slice
+	sessionID, err := uuid.FromBytes(b[len(b)-sessionIDLen:])
+	if err != nil {
+		return uuid.Nil, nil, err
+	}
+	b = b[:len(b)-sessionIDLen]
+	return sessionID, b, nil
+}
+
+// SuffixSessionID appends the session ID at the end of the payload. Suffix is more performant than prefix because
+// the payload slice might already have enough capacity to append the session ID at the end
+func SuffixSessionID(sessionID uuid.UUID, b []byte) ([]byte, error) {
+	if len(b)+len(sessionID) > MaxDatagramFrameSize {
+		return nil, fmt.Errorf("datagram size exceed %d", MaxDatagramFrameSize)
+	}
+	b = append(b, sessionID[:]...)
+	return b, nil
+}