There are many places in the shastra where friendship is discussed. Often among people who have their own agendas there is an eagerness to be “friends”. Then on the other side of the coin the term friend is sometimes defined as one who sees one’s faults and corrects them (Siddhanta Saraswati Thakur). However, for most who try to stand in those shoes it is often found that their “friendship” was/is tainted with some other business. Ask me how I know, because I’m honest enough to admit to trying to assume that position on several occasions before understanding that there are indeed different kinds of friends to be found in different stations.

Ultimately Krishna is our only real friend. Having said that we can safely say that His pure devotees who only have Krishna in mind are also friends. Others are to be known as having a mixed agenda.

“We are becoming leaders, the friend of the people. But we are not friend of the people. Krsna is the friend, suhrdam sarva-bhutanam. [Bg 5.29] If I simply say that "I am your friend in this sense, that I deliver the message to you that 'Krsna is your best friend.' I do not... I am friend so far I am giving you this information. But actual friend is Krsna, suhrdam sarva - bhutanam. So this is friendship. If one preaches Krsna consciousness and teaches everyone that Krsna is your best friend... He does not say, "I am your best friend." "I am your best friend in this sense that I am giving you this information." Actually, Krsna is your best friend. What can I do? I am a teeny living entity. What can I do for you? I may become your friend, but when you are in danger, I cannot give you any protection. Krsna can give you protection. This is real friendship. He does not take himself. He always carries the message only. Ya idam paramam guhyam mad-bhaktesv abhidhasyati. [Bg 18.68] Simply our business is to carry the message of Krsna. Then we are friend. Otherwise we are not friend. We may pose to become friend, but we are not friend because we do not know how to benefit the friend. Sometimes we mislead him. Therefore our business is to point that "Krsna is your friend." Suhrdam sarva-bhutanam. (SP lecture on The Nectar of Devotion, Vrindavana, 31 October, 1972.)

...you may know of the four kinds of friends, at least you would know of them by experience, if not by shastric terminology; the mitra is an ordinary friend. You know the kind you happen to be in the same place so you kind of "associate". Chanakya Pandit (Niti shastra 6:8.) says that this kind of friend that is without commitment and without actual caring and love – well-wishing “…is like a bucket of poison with milk on top”. For as soon as there is some friction to the bucket the surface of "friendship" is broken like the surface skin on the bucket of poison is broken and the real nature of the relationship/poison is revealed - "I remember the day when you, you.........!" Not really a friend, eh!!!???( Kiwi colloquialism).
 The next is the madhyastha; he's the middle man, a working friendship, for the sake of the mission we maintain friendly dealings, and so on. But ten or twenty years down the track there's about as much affection to each other as there was after the first year - very little. The commitment is mostly toward the mission - and that's good - at least there's commitment that maintains a relationship unlike the selfish mitra. But often it has been observed that in these working relationships if commitment does not develop with appreciation of the potential of the PERSON, then soon it will revert to that of the mitra.
 The next is the udasina, of which Krishna calls himself in Bhagavad Gita (9:9.; 14:22-25.; SB 6:16:5.) where Sukadev describes it as being indifferent. This was explained to me that as Srila Prabhupad used to say that if one takes one step toward Him, He in return makes 1000 steps toward us. He is there, neutral / indifferent, and so we have to make the first move. But once the friendship is bonded there is commitment. Actually He has been eagerly waiting for us to direct our attention toward Him, and now that we have that commitment becomes steadfast. Krishna is a kind and loving friend, he want us back home more than we want to go/come.
 We’ve been away so long and have gone off track – for those who haven’t gone off track its easy to interact and associate with him, but for us who are so full of our own ideas, desires, etc., like a loving father or friend he tries to encourage us back. Bhagavad Gita is the perfect example of this, where in the 12th chapter (BG 12:8- 15.) He tries to extend himself by showing His inclusive nature to give us options to return according to how far we’ve gone away from him.
 The last we alluded to in the beginning, but in the world, in actual fact it is not so cheaply achieved, in fact it is so rare: Suhrdam sarva bhutanam (BG 5:29.), the suhrt (SB 1:8:49.) really it can only apply to a certain kind of kind of personality, Sri Krishna, Srila Prabhupad, other Vaishnava acaryas in the parampara, possibly a few purified devotees, and senior devotees today....... Suhrt literally means Your Ever Well Wisher. If you’d take a moment to consider what this actually means we come back to the original statement found in the lecture on Nectar of Devotion which states that such a person only has our relationship with Krishna at heart, there’s no question of some secondary, or separate “friendship”.

suhån-miträry-udäséna-
madhyastha-dveñya-bandhuñu
sädhuñv api ca päpeñu
sama-buddhir viçiñyate

“A person is said to be still further advanced when he regards all—the honest well-wisher, friends and enemies, the envious, the pious, the sinner, and those who are indifferent and impartial—with an equal mind.” (Bg. 6.9) This is a sign of real spiritual advancement. In this material world we are considering people friends and enemies on the bodily platform—that is, on the basis of sense gratification. If one gratifies our senses, he is our friend, and if he doesn’t, he is our enemy. However, once we have realized God, or the Absolute Truth, there are no such material considerations.
In this material world, all conditioned souls are under illusion. A doctor treats all patients, and although a patient may be delirious and insult the doctor, the doctor does not refuse to treat him. He still administers the medicine that is required. As Lord Jesus Christ said, we should hate the sin, not the sinner. That is a very nice statement, because the sinner is under illusion. He is mad. If we hate him, how can we deliver him? Therefore, those who are advanced devotees, who are really servants of God, do not hate anyone. When Lord Jesus Christ was being crucified, he said, “My God, forgive them. They know not what they do.” This is the proper attitude of an advanced devotee. He understands that the conditioned souls cannot be hated, because they have become mad due to their materialistic way of thinking. In this Kåñëa consciousness movement, there is no question of hating anyone. Everyone is welcomed to come and chant Hare Kåñëa, take kåñëa-prasäda, listen to the philosophy of Bhagavad-gétä, and try to rectify material, conditioned life. This is the essential program of Kåñëa consciousness.(A.C. Bhaktivedanta Swami Prabhupada. PoP3. Path of Perfection.)

So called friendships of this world may come up to the platform of the mitra, and sometimes even to that of the madhyastha (which is also often tainted with symptoms of the mitra). But it is as “rare as Hen’s teeth” to find a person who is truly Suhrt.
 In the material controlling sense, when someone wants you to do something, or be something, that you might not want, and where the personal relationship is either unconscious or seemingly non-existent, or no longer there, often similar options to that of Bhagavad Gita (12th chapter 8-14.) are given/offered – out-reaches of friendship, conditions and guidelines, options showing favourability, work, charity, thinking kindly – all this at best in the material world brings one to the “working-relationship” of the madhyastha.
 Udasina is always careful, he knows that too much too soon, or forced could also drive one away. So always waiting for our commitment, the udasina waits for us to be ready, then His eagreness is revealed.

We can tell when we are becoming Krishna-ised (purified) when we begin to put the relation to all living beings as being part and parcel of, or in relationship to Krishna – just like Francis of Assisi, and other great devotees who related to Mother Earth, brother tree, cousin, this sister that. Srila Bhaktivinode Thakur in his Sri Chaitanya Shikshamrita spends nearly the entire 4th Chapter going over what he calls “sectarianism” – making distinctions based on sense gratification.
 There was an interesting incident that is depicted in SuMadhwa Vijay (the biography of Madhwacarya life, by Narayan Panditacarya) regarding an incident that happened at Vishnu-mangalam in South India between Sripad Ananda Tirtha (Madhwacarya) and the saintly raj-pandit of the king who returned Madhwa’s books, Trivikram Panditacarya (father of the author of SuMadhwa-vijay).
 Trivikram Panditacarya asked how it is that everything is in relation to the God, and what is that relation? Madhwa called for his trusted aide Hrishikesha Tirtha to bring a full coconut. Madhwa then took the coconut and asked his disciple to break it to reveal its components.
 “What is this?” he asked of Trivikram Pandita. “It is the husk of the coconut” TP replied.
 “…and this?”
 “…it is the coconut kernel” the best of pandits replied.
 “…and this?”
 “…why it is coconut meat” he again answered.
 “…and this?”
 “…it is the milk of the coconut!” Trivikram replied.
 “So what is it that they all have in relation?”
 Trivikram thought for a second and said “…coconut!”
“Yes indeed, without coconut, none of them have any independent existence.” Madhwa stated, “…and so similarly this world and all that we see in it have no separated existence without their creator. Therefore they are all in relation to Him, even though they are individual and separate in their function.” Thus Madhwa preached his philosophy of ‘bimba pratibimbatvada’, which is very close to the later teachings of Sri Chaitanya Mahaprabhu ‘achintya-bhed-abheda tattwa’ – simultaneously one yet difference.
If we can keep the spiritual perspective of who these souls are that we see, in other words if we are actually Krishna conscious, and not just putting on an external show of it, then we will see all living beings in relation to their/our Lord – even those who neglect to acknowledge the fact.
The rebellious son may go away from home, and even reject his father and mother and even tell his new acquaintances that they are dead. But the fact of the matter is that they are in existence, and furthermore would love to see their son reform and come back home to them.