DHT Vote

[FLYBYME]

Does anyone know how utorrent implements the "vote" system over the DHT?

I looked online but there is next to nothing about it.

Some information:
http://lists.ibiblio.org/pipermail/bittorrent/2011-January/002413.html

http://arxiv.org/ftp/arxiv/papers/1305/1305.0711.pdf

You get a message something like this:

{ a:
   { id: '907050177fb05376db71ce066663819503eb0a9a',
     target: '546d6d0e5aacfae66299f26a300a428c497b23b5',
     token: '5b3f3de3d4f5ba42721dac14b2076dc64bc829da',
     vote: 0 },
  q: 'vote',
  t: '+=\u0000\u0000',
  v: 'UT??',
  y: 'q' }

The only thing I dont get it the target They say its sha1(info-hash + "rating") but i dont know. So the rating 1-5 and 0 been the query for votes. So if a infohash has 5 votes ranging from 1 to 5 would you receive 5 responses?

Has anyone played around with this?

[pldubouilh]

It seems that the peers can cast their vote at sha1(info# + {1,2,3,4,5}). Although, it's not been bep'd so I think only utorrent would handle these requests.

And an user willing to check the ratings for a given infohash would DHT.get at sha1(info# + 1), sha1(info# + 2), sha1(info# + 3), sha1(info# + 4) and sha1(info# + 5). So 5 DHT.get, to receive the number of votes received for each rating.

That paper states that 1% of the total DHT traffic is related to votes (mostly 0 stars), and that seems to be like an awful lot. I'll try to hack something around bittorent-dht to see if I can reproduce that figure.

[mastilver]

@pldubouilh Thank you, that is really helpful 👍

[FLYBYME]

So I played around with the idea.

Here is the code:

var DHT = require('bittorrent-dht');
var crypto = require('crypto');
function sha1(str) {
    return crypto.createHash('sha1').update(str).digest('hex')
}

var dht = new DHT();

dht.listen(8000, function() {
    console.log('now listening');
});

function lookup(infoHash) {
    console.log('lookup(' + infoHash + ')');

    function cb(err, result) {
        if (result)
            console.log(err, result);
    }

    for (var i = 0,
        j = 5; i < j; i++) {
        dht.get(sha1(infoHash + i), cb);
    };
}

dht.on('ready', function() {
    console.log('now ready');
});
dht.on('error', function(err) {
    console.log(err);
});
dht.on('warning', function(warning) {
    console.log(warning);
});
dht.on('vote', function(query, peer) {
    var infoHash = query.a.target.toString('hex');
    lookup(infoHash);
});

dht.on('announce', function(peer, infoHash) {
    lookup(infoHash.toString('hex'));
});

It is interesting that nodes send out a vote query. I dont think they use the get query but the vote. From what I understand the vote: 0 is the query for the votes from 1-5 so then vote: 1 would be a vote of one and so on.

Using the put method to keep track of how many votes would not work. The number of votes would keep getting overwritten.

[mastilver]

I think they are only using the vote even to broadcast the fact that their is new vote to query
So you are not querying the i+1 hash all the time

[pldubouilh]

Right, so I did some tests as well - the query is, indeed, vote and not get, so you'll have to change a few lines in client.js otherwise the message is considered as unexpected.

Also, for the record, it seems that the paper's correct. I receive a good amount of votes, and they are mostly 0...

[FLYBYME]

@pldubouilh would you mind sharing your code?

[pldubouilh]

There you go. It's nothing really fancy, I just added a case: 'vote', so I can see what's happening instead of treating it as unexpected.