Guru Padmasambhava or Yungdrung Tongdrol. In the Bon Tradition he received Dzogchen Teaching from Jetapihritsa (believed to be one and the same as Garab Dorje) and his father Drenpa Namkha, whose transmissions came both directly from Kunto Zangbo (Samantabhadra) and from various masters who have achieved rainbow bodies.
The name Drenpa Namkha is not to be confused with Drenpa Namkha of a later period. The latter one is also called Drenpa Yeshe Dragpa.
There is so much to be learned about these great masters. A large number of Tibetan texts have not been translated and thus are inaccessible to us. The problem we face today is that our knowledge comes mainly from limited sources. In addition, Tibetan lamas do not usually study and practice other traditions. Hence, many of them have limited knowledge concerning other traditions. This is why being a rimed or non-sectarian practitioner is extremely important. Besides, there are many confusing names. For example, there are two Drenpa Namkhas who are different persons. Garab Dorje and Jetapihritsa are believed to be the same person, though they have different names.
I can use my own name as an example. In Tibet I am called Kesang Dawa. In Thailand my name is Krisadawan. This is one and the same person with different labels. Suppose 100 years from now there’s another person named Kesang Dawa and she is not the same person as I. We cannot say that the later Kesang Dawa and the present-day Kesang Dawa are one and the same. If we understand this fact, there is not so much confusion. The key is that we have to be broad-minded and do a lot of investigation before we come to a conclusion and make any assessment.