fix peer picking algorithm
The old code was always picking the first to_pick peers from the set.
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c75b243490
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@ -214,18 +214,15 @@ namespace
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else
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else
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{
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{
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tcp const protocol = requester.is_v4() ? tcp::v4() : tcp::v6();
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tcp const protocol = requester.is_v4() ? tcp::v4() : tcp::v6();
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int max = m_settings.max_peers_reply;
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int to_pick = m_settings.max_peers_reply;
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// if these are IPv6 peers their addresses are 4x the size of IPv4
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// if these are IPv6 peers their addresses are 4x the size of IPv4
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// so reduce the max peers 4 fold to compensate
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// so reduce the max peers 4 fold to compensate
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// max_peers_reply should probably be specified in bytes
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// max_peers_reply should probably be specified in bytes
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if (!v.peers.empty() && protocol == tcp::v6())
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if (!v.peers.empty() && protocol == tcp::v6())
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max /= 4;
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to_pick /= 4;
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// we're picking "to_pick" from a list of "num" at random.
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int const to_pick = std::min(int(v.peers.size()), max);
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std::set<peer_entry>::const_iterator iter = v.peers.begin();
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entry::list_type& pe = peers["values"].list();
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entry::list_type& pe = peers["values"].list();
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for (int t = 0, m = 0; m < to_pick && iter != v.peers.end(); ++iter)
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for (auto iter = v.peers.begin(); to_pick > 0 && iter != v.peers.end(); ++iter)
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{
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{
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// if the node asking for peers is a seed, skip seeds from the
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// if the node asking for peers is a seed, skip seeds from the
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// peer list
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// peer list
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@ -235,26 +232,20 @@ namespace
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if (iter->addr.protocol() != protocol)
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if (iter->addr.protocol() != protocol)
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continue;
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continue;
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++t;
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// pick this peer with probability
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std::string* str;
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// <peers left to pick> / <peers left in the set>
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if (t <= to_pick)
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if (random(uint32_t(std::distance(iter, v.peers.end()))) > to_pick)
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{
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continue;
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pe.push_back(entry());
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str = &pe.back().string();
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}
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else
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{
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// maybe replace an item we've already picked
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if (random(t - 1) >= to_pick) continue;
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str = &pe[random(to_pick - 1)].string();
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}
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str->resize(18);
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pe.push_back(entry());
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std::string::iterator out = str->begin();
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std::string& str = pe.back().string();
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str.resize(18);
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std::string::iterator out = str.begin();
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detail::write_endpoint(iter->addr, out);
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detail::write_endpoint(iter->addr, out);
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str->resize(out - str->begin());
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str.resize(out - str.begin());
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++m;
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--to_pick;
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}
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}
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}
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}
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@ -339,6 +339,41 @@ TORRENT_TEST(mutable_item_limit)
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TEST_EQUAL(cnt.mutable_data, 42);
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TEST_EQUAL(cnt.mutable_data, 42);
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}
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}
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TORRENT_TEST(get_peers_dist)
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{
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// test that get_peers returns reasonably disjoint sets of peers with each call
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// take two samples of 100 peers from 1000 and make sure there aren't too many
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// peers found in both lists
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dht_settings sett = test_settings();
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sett.max_peers = 1000;
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sett.max_peers_reply = 100;
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std::unique_ptr<dht_storage_interface> s(create_default_dht_storage(sett));
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address addr = rand_v4();
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for (int i = 0; i < 1000; ++i)
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{
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s->announce_peer(n1, tcp::endpoint(addr, uint16_t(i))
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, "torrent_name", false);
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}
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std::set<int> peer_set;
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int duplicates = 0;
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for (int i = 0; i < 2; ++i)
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{
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entry peers;
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s->get_peers(n1, false, false, address(), peers);
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TEST_EQUAL(peers["values"].list().size(), 100);
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for (auto const& p : peers["values"].list())
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{
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int port = detail::read_v4_endpoint<tcp::endpoint>(p.string().begin()).port();
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if (!peer_set.insert(port).second)
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++duplicates;
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}
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}
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std::printf("duplicate peers found: %d\n", duplicates);
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TEST_CHECK(duplicates < 20);
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}
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TORRENT_TEST(update_node_ids)
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TORRENT_TEST(update_node_ids)
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{
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{
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dht_settings sett = test_settings();
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dht_settings sett = test_settings();
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