problem with the up-to-date versions of BitTorrent client

[anvoebugz@gmail.com]

It looks like the last releases of BitTorrent clients violate their own specification.

The reason why I think so: the client replies on random non-existence info-hash that they know about (but really they don't know) with 50% probability.

What is a necessity to do so?

[Harold Feit]

The reason why I think so: the client replies on random non-existence info-hash that they know about (but really they don't know) with 50% probability.

Replies to what and how?

[anvoebugz@gmail.com]

Replies to what and how?

For the DHT query get_peers with non-existence info_hash uTorrent returns 'Response with peers' instead of 'Response with closest nodes'.

[Harold Feit]

That's not misbehaving. That's normal behavior for DHT traffic.

[anvoebugz@gmail.com]

That's not misbehaving. That's normal behavior for DHT traffic.

According to the specification:

get_peers
<...>
If the queried node has no peers for the infohash, a key "nodes" is returned containing the K nodes 
in the queried nodes routing table closest to the infohash supplied in the query. 
In either case a "token" key is also included in the return value.
<...>
Example Packets:
<...>
Response with peers = {"t":"aa", "y":"r", "r": {"id":"abcdefghij0123456789", "token":"aoeusnth", "values": ["axje.u", "idhtnm"]}}
bencoded = d1:rd2:id20:abcdefghij01234567895:token8:aoeusnth6:valuesl6:axje.u6:idhtnmee1:t2:aa1:y1:re

Response with closest nodes = {"t":"aa", "y":"r", "r": {"id":"abcdefghij0123456789", "token":"aoeusnth", "nodes": "def456..."}}
bencoded = d1:rd2:id20:abcdefghij01234567895:nodes9:def456...5:token8:aoeusnthe1:t2:aa1:y1:re

There are two different answers (peers/closest nodes) for two the different cases (exactly know that we can get info-hash from nodes/otherwise).

[Harold Feit]

Just because a specific torrent's infohash isn't in your active torrent list, it doesn't mean your DHT table doesn't have peers for it.

Sorry, nothing misbehaving.

[anvoebugz@gmail.com]

Just because a specific torrent's infohash isn't in your active torrent list, it doesn't mean your DHT table doesn't have peers for it.

Sorry, nothing misbehaving.

OK. It sounds good, but it is strange that for almost any sequence of random info-hashes (each of which has probability current_number_of_torrents_in_DHT_network/2^160 ~ 0)

we got 'Response with peers' and the retrieved peers know nothing about requested info-hash.