opendht/src/dht.cpp

/*
Copyright (C) 2009-2014 Juliusz Chroboczek
Copyright (C) 2014-2016 Savoir-faire Linux Inc.

Author(s) : Adrien Béraud <adrien.beraud@savoirfairelinux.com>,
            Juliusz Chroboczek <jch@pps.univ–paris–diderot.fr>
            Simon Désaulniers <sim.desaulniers@gmail.com>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/

#include "dht.h"
#include "rng.h"

#include <msgpack.hpp>
extern "C" {
#include <gnutls/gnutls.h>
}

#ifndef _WIN32
#include <arpa/inet.h>
#else
#include <ws2tcpip.h>
#endif

#include <algorithm>
#include <random>
#include <sstream>

#include <unistd.h>
#include <fcntl.h>
#include <cstring>

#ifdef _WIN32

static bool
set_nonblocking(int fd, int nonblocking)
{
    unsigned long mode = !!nonblocking;
    int rc = ioctlsocket(fd, FIONBIO, &mode);
    return rc == 0;
}

extern const char *inet_ntop(int, const void *, char *, socklen_t);

#else

static bool
set_nonblocking(int fd, int nonblocking)
{
    int rc = fcntl(fd, F_GETFL, 0);
    if (rc < 0)
        return false;
    rc = fcntl(fd, F_SETFL, nonblocking?(rc | O_NONBLOCK):(rc & ~O_NONBLOCK));
    return rc >= 0;
}

#endif

static std::mt19937 rd {dht::crypto::random_device{}()};
static std::uniform_int_distribution<uint8_t> rand_byte;

static const uint8_t v4prefix[16] = {
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF, 0, 0, 0, 0
};

static std::string
to_hex(const uint8_t *buf, size_t buflen)
{
    std::stringstream s;
    s << std::hex;
    for (size_t i = 0; i < buflen; i++)
        s << std::setfill('0') << std::setw(2) << (unsigned)buf[i];
    s << std::dec;
    return s.str();
}

template <class DT>
static double
print_dt(DT d) {
    return std::chrono::duration_cast<std::chrono::duration<double>>(d).count();
}

namespace dht {

constexpr std::chrono::seconds Dht::SEARCH_GET_STEP;
constexpr std::chrono::minutes Dht::MAX_STORAGE_MAINTENANCE_EXPIRE_TIME;
constexpr std::chrono::minutes Dht::SEARCH_EXPIRE_TIME;
constexpr std::chrono::seconds Dht::LISTEN_EXPIRE_TIME;
constexpr std::chrono::seconds Dht::REANNOUNCE_MARGIN;

void
Dht::setLoggers(LogMethod&& error, LogMethod&& warn, LogMethod&& debug)
{
    DHT_LOG.DEBUG = std::move(debug);
    DHT_LOG.WARN = std::move(warn);
    DHT_LOG.ERROR = std::move(error);
}

Dht::Status
Dht::getStatus(sa_family_t af) const
{
    unsigned good = 0, dubious = 0, cached = 0, incoming = 0;
    int tot = getNodesStats(af, &good, &dubious, &cached, &incoming);
    if (tot < 1)
        return Status::Disconnected;
    else if (good < 1)
        return Status::Connecting;
    return Status::Connected;
}

void
Dht::shutdown(ShutdownCallback cb) {
    /****************************
     *  Last store maintenance  *
     ****************************/

    auto remaining = std::make_shared<int>(0);
    auto str_donecb = [=](bool, const std::vector<std::shared_ptr<Node>>&) {
        --*remaining;
        if (!*remaining && cb) { cb(); }
        else DHT_LOG.WARN("Shuting down node: %u ops remaining.", *remaining);
    };

    for (const auto& str : store) {
        *remaining += maintainStorage(str.id, true, str_donecb);
    }
    DHT_LOG.WARN("Shuting down node: %u ops remaining.", *remaining);
    if (!*remaining && cb) { cb(); }
}

bool
Dht::isRunning(sa_family_t af) const
{
    switch (af) {
    case 0:
        return dht_socket  >= 0 ||  dht_socket6 >= 0;
    case AF_INET:
        return dht_socket  >= 0;
    case AF_INET6:
        return dht_socket6 >= 0;
    default:
        return false;
    }
}

bool
Dht::isMartian(const sockaddr *sa, socklen_t len)
{
    // Check that sa_family can be accessed safely
    if (!sa || len < sizeof(sockaddr_in))
        return true;

    switch(sa->sa_family) {
    case AF_INET: {
        sockaddr_in *sin = (sockaddr_in*)sa;
        const uint8_t *address = (const uint8_t*)&sin->sin_addr;
        return sin->sin_port == 0 ||
            (address[0] == 0) ||
            (address[0] == 127) ||
            ((address[0] & 0xE0) == 0xE0);
    }
    case AF_INET6: {
        if (len < sizeof(sockaddr_in6))
            return true;
        sockaddr_in6 *sin6 = (sockaddr_in6*)sa;
        const uint8_t *address = (const uint8_t*)&sin6->sin6_addr;
        return sin6->sin6_port == 0 ||
            (address[0] == 0xFF) ||
            (address[0] == 0xFE && (address[1] & 0xC0) == 0x80) ||
            (memcmp(address, zeroes.data(), 15) == 0 &&
             (address[15] == 0 || address[15] == 1)) ||
            (memcmp(address, v4prefix, 12) == 0);
    }

    default:
        return true;
    }
}

std::shared_ptr<Node>
Dht::Bucket::randomNode()
{
    if (nodes.empty())
        return nullptr;
    std::uniform_int_distribution<unsigned> rand_node(0, nodes.size()-1);
    unsigned nn = rand_node(rd);
    for (auto& n : nodes)
        if (not nn--) return n;
    return nodes.back();
}

InfoHash
Dht::RoutingTable::randomId(const Dht::RoutingTable::const_iterator& it) const
{
    int bit1 = it->first.lowbit();
    int bit2 = std::next(it) != end() ? std::next(it)->first.lowbit() : -1;
    int bit = std::max(bit1, bit2) + 1;

    if (bit >= 8*(int)HASH_LEN)
        return it->first;

    int b = bit/8;
    InfoHash id_return;
    std::copy_n(it->first.begin(), b, id_return.begin());
    id_return[b] = it->first[b] & (0xFF00 >> (bit % 8));
    id_return[b] |= rand_byte(rd) >> (bit % 8);
    for (unsigned i = b + 1; i < HASH_LEN; i++)
        id_return[i] = rand_byte(rd);
    return id_return;
}

InfoHash
Dht::RoutingTable::middle(const RoutingTable::const_iterator& it) const
{
    unsigned bit = depth(it);
    if (bit >= 8*HASH_LEN)
        throw std::out_of_range("End of table");

    InfoHash id = it->first;
    id.setBit(bit, 1);
    return id;
}

unsigned
Dht::RoutingTable::depth(const RoutingTable::const_iterator& it) const
{
    int bit1 = it->first.lowbit();
    int bit2 = std::next(it) != end() ? std::next(it)->first.lowbit() : -1;
    return std::max(bit1, bit2)+1;
}

std::vector<std::shared_ptr<Node>>
Dht::RoutingTable::findClosestNodes(const InfoHash id, time_point now, size_t count) const
{
    std::vector<std::shared_ptr<Node>> nodes {};
    auto bucket = findBucket(id);

    if (bucket == end()) { return nodes; }

    auto sortedBucketInsert = [&](const Bucket &b) {
        for (auto n : b.nodes) {
            if (not n->isGood(now))
                continue;

            auto here = std::find_if(nodes.begin(), nodes.end(),
                [&id,&n](std::shared_ptr<Node> &node) {
                    return id.xorCmp(n->id, node->id) < 0;
                }
            );
            nodes.insert(here, n);
        }
    };

    auto itn = bucket;
    auto itp = std::prev(bucket);
    while (nodes.size() < count && (itn != end() || itp != end())) {
        if (itn != end()) {
            sortedBucketInsert(*itn);
            itn = std::next(itn);
        }
        if (itp != end()) {
            sortedBucketInsert(*itp);
            if (itp == begin()) {
                itp = end();
                continue;
            }
            itp = std::prev(itp);
        }
    }

    // shrink to the count closest nodes.
    if (nodes.size() > count) {
        nodes.resize(count);
    }
    return nodes;
}

Dht::RoutingTable::iterator
Dht::RoutingTable::findBucket(const InfoHash& id)
{
    if (empty())
        return end();
    auto b = begin();
    while (true) {
        auto next = std::next(b);
        if (next == end())
            return b;
        if (InfoHash::cmp(id, next->first) < 0)
            return b;
        b = next;
    }
}

Dht::RoutingTable::const_iterator
Dht::RoutingTable::findBucket(const InfoHash& id) const
{
    /* Avoid code duplication for the const version */
    const_iterator it = const_cast<RoutingTable*>(this)->findBucket(id);
    return it;
}

/* Every bucket contains an unordered list of nodes. */
std::shared_ptr<Node>
Dht::findNode(const InfoHash& id, sa_family_t af)
{
    Bucket* b = findBucket(id, af);
    if (!b)
        return {};
    for (auto& n : b->nodes)
        if (n->id == id) return n;
    return {};
}

const std::shared_ptr<Node>
Dht::findNode(const InfoHash& id, sa_family_t af) const
{
    const Bucket* b = findBucket(id, af);
    if (!b)
        return {};
    for (const auto& n : b->nodes)
        if (n->id == id) return n;
    return {};
}

std::shared_ptr<Node>
Dht::NodeCache::getNode(const InfoHash& id, sa_family_t family) {
    auto& list = family == AF_INET ? cache_4 : cache_6;
    for (auto n = list.begin(); n != list.end();) {
        if (auto ln = n->lock()) {
            if (ln->id == id)
                return ln;
            ++n;
        } else {
            n = list.erase(n);
        }
    }
    return nullptr;
}

std::shared_ptr<Node>
Dht::NodeCache::getNode(const InfoHash& id, const sockaddr* sa, socklen_t sa_len, time_point now, int confirm) {
    auto node = getNode(id, sa->sa_family);
    if (not node) {
        node = std::make_shared<Node>(id, sa, sa_len);
        putNode(node);
    } else if (confirm || node->time < now - Node::NODE_EXPIRE_TIME) {
        node->update(sa, sa_len);
    }
    if (confirm)
        node->received(now, confirm >= 2);
    return node;
}

void
Dht::NodeCache::putNode(std::shared_ptr<Node> n) {
    if (not n) return;
    auto& list = n->ss.ss_family == AF_INET ? cache_4 : cache_6;
    list.push_back(n);
}

void
Dht::NodeCache::clearBadNodes(sa_family_t family)
{
    if (family == 0) {
        clearBadNodes(AF_INET);
        clearBadNodes(AF_INET6);
    } else {
        auto& list = family == AF_INET ? cache_4 : cache_6;
        for (auto n = list.begin(); n != list.end();) {
            if (auto ln = n->lock()) {
                ln->pinged = 0;
                ++n;
            } else {
                n = list.erase(n);
            }
        }
    }
}

/* Every bucket caches the address of a likely node.  Ping it. */
int
Dht::sendCachedPing(Bucket& b)
{
    /* We set family to 0 when there's no cached node. */
    if (b.cached.ss_family == 0)
        return 0;

    DHT_LOG.DEBUG("Sending ping to cached node.");
    network_engine->sendPing((sockaddr*)&b.cached, b.cachedlen, nullptr, nullptr);
    b.cached.ss_family = 0;
    b.cachedlen = 0;
    return 0;
}

/* Called whenever we send a request to a node, increases the ping count
   and, if that reaches 3, sends a ping to a new candidate. */
void
Dht::pinged(Node& n, Bucket* b)
{

    if (not n.isExpired(now)) {
        n.requested(now);
        if (n.pinged >= 3) {
            if (not b)
                b = findBucket(n.id, n.ss.ss_family);
            if (b) sendCachedPing(*b);
        }
    }
}

/* The internal blacklist is an LRU cache of nodes that have sent
   incorrect messages. */
void
Dht::blacklistNode(const InfoHash* id, const sockaddr *sa, socklen_t salen)
{
    DHT_LOG.WARN("Blacklisting broken node.");

    if (id) {
        /* Make the node easy to discard. */
        auto n = findNode(*id, sa->sa_family);
        if (n) {
            n->pinged = 3;
            pinged(*n);
        }
        /* Discard it from any searches in progress. */
        auto black_list_in = [&](std::map<InfoHash, Search> srs) {
            for (auto& srp : srs) {
                auto& sr = srp.second;
                sr.nodes.erase(std::partition(sr.nodes.begin(), sr.nodes.end(), [&](SearchNode& sn) {
                    return sn.node != n;
                }), sr.nodes.end());
            }
        };
        black_list_in(searches4);
        black_list_in(searches6);
    }
    /* And make sure we don't hear from it again. */
    memcpy(&blacklist[next_blacklisted], sa, salen);
    next_blacklisted = (next_blacklisted + 1) % BLACKLISTED_MAX;
}

bool
Dht::isNodeBlacklisted(const sockaddr *sa, socklen_t salen) const
{
    if (salen > sizeof(sockaddr_storage))
        return true;

    if (isBlacklisted(sa, salen))
        return true;

    for (unsigned i = 0; i < BLACKLISTED_MAX; i++) {
        if (memcmp(&blacklist[i], sa, salen) == 0)
            return true;
    }

    return false;
}

std::vector<Address>
Dht::getPublicAddress(sa_family_t family)
{
    std::sort(reported_addr.begin(), reported_addr.end(), [](const ReportedAddr& a, const ReportedAddr& b) {
        return a.first < b.first;
    });
    std::vector<Address> ret;
    for (const auto& addr : reported_addr)
        if (!family || family == addr.second.first.ss_family)
            ret.emplace_back(addr.second);
    return ret;
}

/* Split a bucket into two equal parts. */
bool
Dht::RoutingTable::split(const RoutingTable::iterator& b)
{
    InfoHash new_id;
    try {
        new_id = middle(b);
    } catch (const std::out_of_range& e) {
        return false;
    }

    // Insert new bucket
    insert(std::next(b), Bucket {b->af, new_id, b->time});

    // Re-assign nodes
    std::list<std::shared_ptr<Node>> nodes {};
    nodes.splice(nodes.begin(), b->nodes);
    while (!nodes.empty()) {
        auto n = nodes.begin();
        auto b = findBucket((*n)->id);
        if (b == end())
            nodes.erase(n);
        else
            b->nodes.splice(b->nodes.begin(), nodes, n);
    }
    return true;
}

bool
Dht::trySearchInsert(const std::shared_ptr<Node>& node)
{
    if (not node) return false;

    bool inserted = false;
    auto family = node->getFamily();
    auto srs = family == AF_INET ? searches4 : searches6;
    for (auto& srp : srs) {
        auto& s = srp.second;
        if (s.insertNode(node, now)) {
            inserted = true;
            search_time = std::min(search_time, s.getNextStepTime(types, now));
        }
    }
    return inserted;
}

void
Dht::reportedAddr(const sockaddr *sa, socklen_t sa_len)
{
    auto it = std::find_if(reported_addr.begin(), reported_addr.end(), [=](const ReportedAddr& addr){
        return (addr.second.second == sa_len) &&
            std::equal((uint8_t*)&addr.second.first, (uint8_t*)&addr.second.first + addr.second.second, (uint8_t*)sa);
    });
    if (it == reported_addr.end()) {
        if (reported_addr.size() < 32)
            reported_addr.emplace_back(1, std::make_pair(*((sockaddr_storage*)sa), sa_len));
    } else
        it->first++;
}

/* We just learnt about a node, not necessarily a new one.  Confirm is 1 if
   the node sent a message, 2 if it sent us a reply. */
std::shared_ptr<Node>
Dht::newNode(const InfoHash& id, const sockaddr *sa, socklen_t salen, int confirm)
{
    if (id == myid || isMartian(sa, salen) || isNodeBlacklisted(sa, salen))
        return nullptr;

    auto& list = sa->sa_family == AF_INET ? buckets : buckets6;
    auto b = list.findBucket(id);
    if (b == list.end())
        return nullptr;

    bool mybucket = list.contains(b, myid);

    for (auto& n : b->nodes) {
        if (n->id != id) continue;
        /* Known node.  Update stuff. */

        if (confirm || n->time + Node::NODE_EXPIRE_TIME < now) {
            n->update(sa, salen);
            if (confirm) {
                n->received(now, confirm >= 2);
                /* If this node existed in searches but was expired, give it another chance. */
                trySearchInsert(n);
            }
        }
        return n;
    }

    /* New node. */

    if (mybucket) {
        if (sa->sa_family == AF_INET)
            mybucket_grow_time = now;
        else
            mybucket6_grow_time = now;
    }

    /* First, try to get rid of a known-bad node. */
    for (auto& n : b->nodes) {
        if (not n->isExpired(now))
            continue;
        n = cache.getNode(id, sa, salen, now, confirm);

        /* Try adding the node to searches */
        trySearchInsert(n);
        return n;
    }

    if (b->nodes.size() >= TARGET_NODES) {
        /* Bucket full.  Ping a dubious node */
        bool dubious = false;
        for (auto& n : b->nodes) {
            /* Pick the first dubious node that we haven't pinged in the
               last 9 seconds.  This gives nodes the time to reply, but
               tends to concentrate on the same nodes, so that we get rid
               of bad nodes fast. */
            if (not n->isGood(now)) {
                dubious = true;
                if (n->pinged_time + Node::MAX_RESPONSE_TIME < now) {
                    DHT_LOG.DEBUG("Sending ping to dubious node.");
                    network_engine->sendPing(n, nullptr, nullptr);
                    n->pinged++;
                    n->pinged_time = now;
                    //pinged(n, b);
                    break;
                }
            }
        }

        if ((mybucket || (is_bootstrap and list.depth(b) < 6)) && (!dubious || list.size() == 1)) {
            DHT_LOG.DEBUG("Splitting from depth %u", list.depth(b));
            sendCachedPing(*b);
            list.split(b);
            return newNode(id, sa, salen, confirm);
        }

        /* No space for this node.  Cache it away for later. */
        if (confirm || b->cached.ss_family == 0) {
            memcpy(&b->cached, sa, salen);
            b->cachedlen = salen;
        }
        auto cn = cache.getNode(id, sa, salen, now, confirm);
        trySearchInsert(cn);
        return cn;
    }

    /* Create a new node. */
    auto cn = cache.getNode(id, sa, salen, now, confirm);
    b->nodes.emplace_front(cn);
    trySearchInsert(cn);
    return cn;
}

/* Called periodically to purge known-bad nodes.  Note that we're very
   conservative here: broken nodes in the table don't do much harm, we'll
   recover as soon as we find better ones. */
void
Dht::expireBuckets(RoutingTable& list)
{
    for (auto& b : list) {
        bool changed = false;
        b.nodes.remove_if([&changed](const std::shared_ptr<Node>& n) {
            if (n->pinged >= 4) {
                changed = true;
                return true;
            }
            return false;
        });
        if (changed)
            sendCachedPing(b);
    }
    uniform_duration_distribution<> time_dis(std::chrono::minutes(2), std::chrono::minutes(6));
    expire_stuff_time = now + duration(time_dis(rd));
}

bool
Dht::Search::removeExpiredNode(time_point now)
{
    auto e = nodes.end();
    while (e != nodes.cbegin()) {
        e = std::prev(e);
        const Node& n = *e->node;
        if (n.isExpired(now) and n.time + Node::NODE_EXPIRE_TIME < now) {
            //std::cout << "Removing expired node " << n.id << " from IPv" << (af==AF_INET?'4':'6') << " search " << id << std::endl;
            nodes.erase(e);
            return true;
        }
    }
    return false;
}

/* A search contains a list of nodes, sorted by decreasing distance to the
   target.  We just got a new candidate, insert it at the right spot or
   discard it. */
bool
Dht::Search::insertNode(std::shared_ptr<Node> node, time_point now, const Blob& token)
{
    if (node->ss.ss_family != af) {
        //DHT_LOG.DEBUG("Attempted to insert node in the wrong family.");
        return false;
    }

    const auto& nid = node->id;

    // Fast track for the case where the node is not relevant for this search
    if (nodes.size() >= SEARCH_NODES && id.xorCmp(nid, nodes.back().node->id) > 0 && node->isExpired(now))
        return false;

    bool found = false;
    unsigned num_bad_nodes = getNumberOfBadNodes(now);
    auto n = std::find_if(nodes.begin(), nodes.end(), [&](const SearchNode& sn) {
        if (sn.node == node) {
            found = true;
            return true;
        }
        return id.xorCmp(nid, sn.node->id) < 0;
    });

    bool new_search_node = false;
    if (!found) {
        if (nodes.size()-num_bad_nodes >= SEARCH_NODES) {
            if (node->isExpired(now))
                return false;
            if (n == nodes.end())
                return false;
        }

        // Reset search timer if the search is empty
        if (nodes.empty()) {
            step_time = TIME_INVALID;
            get_step_time = TIME_INVALID;
        }

        //bool synced = isSynced(now);
        n = nodes.insert(n, SearchNode(node));
        node->time = now;
        new_search_node = true;
        /*if (synced) {
            n->candidate = true;
            //std::cout << "Adding candidate node " << node->id << " to IPv" << (af==AF_INET?'4':'6') << " synced search " << id << std::endl;
        }*//* else {
            std::cout << "Adding real node " << node->id << " to IPv" << (af==AF_INET?'4':'6') << " synced search " << id << std::endl;
        }*/
        while (nodes.size()-num_bad_nodes > SEARCH_NODES) {
            if (removeExpiredNode(now))
                num_bad_nodes--;

            auto farthest_not_bad_node = std::find_if(nodes.rbegin(), nodes.rend(),
                [&](const SearchNode& n) { return not n.isBad(now); }
            );
            if (farthest_not_bad_node != nodes.rend()) {
                nodes.erase(std::prev(farthest_not_bad_node.base()));
            } // else, all nodes are expired.
        }
        expired = false;
    }
    if (not token.empty()) {
        n->getStatus->reply_time = now;
        n->getStatus->last_try = TIME_INVALID;
        n->candidate = false;
        if (token.size() <= 64)
            n->token = token;
        expired = false;
    }
    return new_search_node;
}

std::vector<std::shared_ptr<Node>>
Dht::Search::getNodes() const
{
    std::vector<std::shared_ptr<Node>> ret {};
    ret.reserve(nodes.size());
    for (const auto& sn : nodes)
        ret.emplace_back(sn.node);
    return ret;
}

void
Dht::expireSearches()
{
    auto t = now - SEARCH_EXPIRE_TIME;
    auto expired = [t](std::pair<const InfoHash, Search>& srp) {
        auto& sr = srp.second;
        return sr.callbacks.empty() && sr.announce.empty() && sr.listeners.empty() && sr.step_time < t;
    };
    erase_if(searches4, expired);
    erase_if(searches6, expired);
}

Dht::SearchNode*
Dht::searchSendGetValues(Search& sr, SearchNode* pn, bool update)
{
    const time_point up = update ? sr.getLastGetTime() : time_point::min();
    SearchNode* n = nullptr;
    if (pn) {
        if (not pn->canGet(now, up))
            return nullptr;
        n = pn;
    } else {
        for (auto& sn : sr.nodes) {
            if (sn.canGet(now, up)) {
                n = &sn;
                break;
            }
        }
        if (not n)
            return nullptr;
    }

    DHT_LOG.DEBUG("[search %s IPv%c] [node %s %s] sending 'get' (p %d last get %lf)",
        sr.id.toString().c_str(), sr.af == AF_INET ? '4' : '6',
        n->node->id.toString().c_str(),
        print_addr(n->node->ss, n->node->sslen).c_str(),
        n->node->pinged, print_dt(now-n->getStatus->last_try));

    auto srp = &sr;
    auto onDone =
        [=](std::shared_ptr<NetworkEngine::RequestStatus> status, NetworkEngine::RequestAnswer&& answer) mutable {
            if (srp) {
                onGetValuesDone(status, answer, srp);
                searchStep(*srp);
            }
        };
    auto onExpired =
        [=](std::shared_ptr<NetworkEngine::RequestStatus>, NetworkEngine::RequestAnswer&&) mutable {
            if (srp) {
                searchStep(*srp);
            }
        };
    if (sr.callbacks.empty() and sr.listeners.empty())
        network_engine->sendFindNode(n->node, sr.id, -1, onDone, onExpired);
    else
        network_engine->sendGetValues(n->node, sr.id, -1, onDone, onExpired);
    n->getStatus->last_try = now;
    pinged(*n->node);
    if (n->node->pinged > 1 and not n->candidate) {
        n->candidate = true;
    }

    return n;
}

/* When a search is in progress, we periodically call search_step to send
   further requests. */
void
Dht::searchStep(Search& sr)
{
    DHT_LOG.DEBUG("[search %s IPv%c] step", sr.id.toString().c_str(), sr.af == AF_INET ? '4' : '6');
    sr.step_time = now;

    /*
     * The accurate delay between two refills has not been strongly determined.
     * TODO: Emprical analysis over refill timeout.
     */
    if (sr.refill_time + Node::NODE_EXPIRE_TIME < now and sr.nodes.size()-sr.getNumberOfBadNodes(now) < SEARCH_NODES) {
        auto added = sr.refill(sr.af == AF_INET ? buckets : buckets6, now);
        if (added)
            sr.refill_time = now;
        DHT_LOG.WARN("[search %s IPv%c] refilled with %u nodes", sr.id.toString().c_str(), (sr.af == AF_INET) ? '4' : '6', added);
    }

    /* Check if the first TARGET_NODES (8) live nodes have replied. */
    if (sr.isSynced(now)) {

        if (not sr.callbacks.empty()) {
            // search is synced but some (newer) get operations are not complete
            // Call callbacks when done
            for (auto b = sr.callbacks.begin(); b != sr.callbacks.end();) {
                if (sr.isDone(*b, now)) {
                    if (b->done_cb)
                        b->done_cb(true, sr.getNodes());
                    b = sr.callbacks.erase(b);
                }
                else
                    ++b;
            }
            if (sr.callbacks.empty() && sr.announce.empty() && sr.listeners.empty())
                sr.done = true;
        }

        // true if this node is part of the target nodes cluter.
        bool in = sr.id.xorCmp(myid, sr.nodes.back().node->id) < 0;

        DHT_LOG.DEBUG("[search %s IPv%c] synced%s", sr.id.toString().c_str(), sr.af == AF_INET ? '4' : '6', in ? ", in" : "");

        if (not sr.listeners.empty()) {
            unsigned i = 0, t = 0;
            for (auto& n : sr.nodes) {
                if (not n.isSynced(now) or (n.candidate and t >= LISTEN_NODES))
                    continue;
                if (n.getListenTime() <= now) {
                    DHT_LOG.WARN("[search %s IPv%c] [node %s %s] sending 'listen'",
                        sr.id.toString().c_str(), sr.af == AF_INET ? '4' : '6',
                        n.node->id.toString().c_str(),
                        print_addr(n.node->ss, n.node->sslen).c_str());
                    //std::cout << "Sending listen to " << n.node->id << " " << print_addr(n.node->ss, n.node->sslen) << std::endl;

                    {
                        auto srp = &sr;
                        network_engine->sendListen(n.node, sr.id, n.token,
                            [=](std::shared_ptr<NetworkEngine::RequestStatus> status,
                                    NetworkEngine::RequestAnswer&& answer) mutable
                            { /* on done */
                                if (srp) {
                                    onListenDone(status, answer, srp);
                                    searchStep(*srp);
                                }
                            },
                            [=](std::shared_ptr<NetworkEngine::RequestStatus>, NetworkEngine::RequestAnswer&&) mutable
                            { /* on expired */
                                if (srp) {
                                    searchStep(*srp);
                                }
                            }
                        );
                    }
                    n.pending = true;
                    n.listenStatus->last_try = now;
                }
                t++;
                if (not n.candidate and ++i == LISTEN_NODES)
                    break;
            }
        }

        // Announce requests
        for (auto& a : sr.announce) {
            if (!a.value) continue;
            unsigned i = 0, t = 0;
            auto vid = a.value->id;
            const auto& type = getType(a.value->type);
            if (in) {
                DHT_LOG.WARN("[search %s IPv%c] [value %lu] storing locally",
                    sr.id.toString().c_str(), sr.af == AF_INET ? '4' : '6', vid);
                storageStore(sr.id, a.value, a.created);
            }
            for (auto& n : sr.nodes) {
                if (not n.isSynced(now) or (n.candidate and t >= TARGET_NODES))
                    continue;
                auto a_status = n.acked.find(vid);
                auto at = n.getAnnounceTime(a_status, type);
                if ( at <= now ) {
                    DHT_LOG.WARN("[search %s IPv%c] [node %s %s] sending 'put'",
                        sr.id.toString().c_str(), sr.af == AF_INET ? '4' : '6',
                        n.node->id.toString().c_str(),
                        print_addr(n.node->ss, n.node->sslen).c_str());
                    //std::cout << "Sending announce_value to " << n.node->id << " " << print_addr(n.node->ss, n.node->sslen) << std::endl;

                    {
                        auto srp = &sr;
                        network_engine->sendAnnounceValue(n.node, sr.id, *a.value, a.created, n.token,
                            [=](std::shared_ptr<NetworkEngine::RequestStatus>, NetworkEngine::RequestAnswer&&) mutable
                            { /* on done */
                                if (srp) {
                                    searchStep(*srp);
                                }
                            },
                            [=](std::shared_ptr<NetworkEngine::RequestStatus>, NetworkEngine::RequestAnswer&&) mutable
                            { /* on expired */
                                if (srp) {
                                    searchStep(*srp);
                                }
                            }
                        );
                    }
                    if (a_status == n.acked.end()) {
                        n.acked[vid] = std::make_shared<NetworkEngine::RequestStatus>(now);
                    } else {
                        a_status->second->last_try = now;
                    }
                    // use the "pending" flag so we update the "pinged"
                    // fields after sending the announce requests for every value to announce
                    n.pending = true;
                }
                t++;
                if (not n.candidate and ++i == TARGET_NODES)
                    break;
            }
        }
        if (sr.callbacks.empty() && sr.announce.empty() && sr.listeners.empty())
            sr.done = true;
    }

    if (sr.get_step_time + SEARCH_GET_STEP <= now) {
        unsigned i = 0;
        SearchNode* sent;
        do {
            sent = searchSendGetValues(sr);
            if (sent) {
                sent->pending = false;
                if (not sent->candidate)
                    i++;
            }
        }
        while (sent and i < 3);
        DHT_LOG.DEBUG("[search %s IPv%c] step: sent %u requests.",
            sr.id.toString().c_str(), sr.af == AF_INET ? '4' : '6', i);

        if (i > 0)
            sr.get_step_time = now;
        else if ((size_t)std::count_if(sr.nodes.begin(), sr.nodes.end(), [&](const SearchNode& sn) {
                    return sn.candidate or sn.node->isExpired(now);
                }) == sr.nodes.size())
        {
            DHT_LOG.ERROR("[search %s IPv%c] expired", sr.id.toString().c_str(), sr.af == AF_INET ? '4' : '6');
            // no nodes or all expired nodes
            sr.expired = true;
            if (sr.announce.empty() && sr.listeners.empty()) {
                // Listening or announcing requires keeping the cluster up to date.
                sr.done = true;
            }
            {
                auto get_cbs = std::move(sr.callbacks);
                for (const auto& g : get_cbs) {
                    if (g.done_cb)
                        g.done_cb(false, {});
                }
            }
            {
                std::vector<DoneCallback> a_cbs;
                a_cbs.reserve(sr.announce.size());
                for (const auto& a : sr.announce)
                    if (a.callback)
                        a_cbs.emplace_back(std::move(a.callback));
                for (const auto& a : a_cbs)
                    a(false, {});
            }
        }
    }

    for (auto& n : sr.nodes) {
        if (n.pending) {
            n.pending = false;
            pinged(*n.node);
        }
    }

}


Dht::Search*
Dht::newSearch(InfoHash id, sa_family_t af)
{
    auto srs = af == AF_INET ? searches4 : searches6;
    auto o = std::min_element(srs.begin(), srs.end(),
        [](std::pair<const InfoHash, Search>& lsr, std::pair<const InfoHash, Search>& rsr) {
            return lsr.second.done && rsr.second.step_time > lsr.second.step_time;
        });
    Search* oldest = o != srs.end() ? &(o->second) : nullptr;

    /* The oldest slot is expired. */
    if (oldest && oldest->announce.empty() && oldest->listeners.empty() && oldest->step_time < now - SEARCH_EXPIRE_TIME) {
        DHT_LOG.WARN("Reusing expired search %s", oldest->id.toString().c_str());
        return oldest;
    }

    /* Allocate a new slot. */
    if (searches4.size() + searches6.size() < MAX_SEARCHES) {
        srs[id] = Search {};
        return &srs[id];
    }

    /* Oh, well, never mind.  Reuse the oldest slot. */
    return oldest;
}

/* Insert the contents of a bucket into a search structure. */
unsigned
Dht::Search::insertBucket(const Bucket& b, time_point now)
{
    unsigned inserted = 0;
    for (auto& n : b.nodes) {
        if (not n->isExpired(now) and insertNode(n, now))
            inserted++;
    }
    return inserted;
}

bool
Dht::Search::isSynced(time_point now) const
{
    unsigned i = 0;
    for (const auto& n : nodes) {
        if (n.node->isExpired(now) or n.candidate)
            continue;
        if (not n.isSynced(now))
            return false;
        if (++i == TARGET_NODES)
            break;
    }
    return i > 0;
}

unsigned Dht::Search::getNumberOfBadNodes(time_point now) {
    return std::count_if(nodes.begin(), nodes.end(),
            [=](const SearchNode& sn) {
                return sn.isBad(now);
            });
}

time_point
Dht::Search::getLastGetTime() const
{
    time_point last = time_point::min();
    for (const auto& g : callbacks)
        last = std::max(last, g.start);
    return last;
}

bool
Dht::Search::isDone(const Get& get, time_point now) const
{
    unsigned i = 0;
    const auto limit = std::max(get.start, now - Node::NODE_EXPIRE_TIME);
    for (const auto& sn : nodes) {
        if (sn.node->isExpired(now) or sn.candidate)
            continue;
        if (sn.getStatus->reply_time < limit)
            return false;
        if (++i == TARGET_NODES)
            break;
    }
    return true;
}

time_point
Dht::Search::getUpdateTime(time_point now) const
{
    time_point ut = time_point::max();
    const auto last_get = getLastGetTime();
    unsigned i = 0, t = 0, d = 0;
    for (const auto& sn : nodes) {
        if (sn.node->isExpired(now) or (sn.candidate and t >= TARGET_NODES))
            continue;
        if (sn.getStatus->reply_time < std::max(now - Node::NODE_EXPIRE_TIME, last_get)) {
            // not isSynced
            ut = std::min(ut, std::max(
                sn.getStatus->last_try + Node::MAX_RESPONSE_TIME,
                get_step_time + SEARCH_GET_STEP));
            if (not sn.candidate)
                d++;
        } else {
            ut = std::min(ut, std::max(
                sn.getStatus->last_try + Node::MAX_RESPONSE_TIME,
                sn.getStatus->reply_time + Node::NODE_EXPIRE_TIME));
        }
        t++;
        if (not sn.candidate and ++i == TARGET_NODES)
            break;
    }
    if ((not callbacks.empty() or not announce.empty()) and d == 0) {
        // If all synced/updated but some callbacks remain, step now to clear them
        return now;
    }
    return ut;
}

bool
Dht::Search::isAnnounced(Value::Id id, const ValueType& type, time_point now) const
{
    if (nodes.empty())
        return false;
    unsigned i = 0;
    for (const auto& n : nodes) {
        if (n.candidate or n.node->isExpired(now))
            continue;
        if (not n.isAnnounced(id, type, now))
            return false;
        if (++i == TARGET_NODES)
            break;
    }
    return i;
}

bool
Dht::Search::isListening(time_point now) const
{
    if (nodes.empty() or listeners.empty())
        return false;
    unsigned i = 0;
    for (const auto& n : nodes) {
        if (n.candidate or n.node->isExpired(now))
            continue;
        if (!n.isListening(now))
            return false;
        if (++i == LISTEN_NODES)
            break;
    }
    return i;
}

time_point
Dht::Search::getAnnounceTime(const std::map<ValueType::Id, ValueType>& types, time_point now) const
{
    if (nodes.empty())
        return time_point::max();
    time_point ret {time_point::max()};
    for (const auto& a : announce) {
        if (!a.value) continue;
        auto type_it = types.find(a.value->type);
        const ValueType& type = (type_it == types.end()) ? ValueType::USER_DATA : type_it->second;
        unsigned i = 0, t = 0;
        for (const auto& n : nodes) {
            if (not n.isSynced(now) or (n.candidate and t >= TARGET_NODES))
                continue;
            ret = std::min(ret, n.getAnnounceTime(a.value->id, type));
            t++;
            if (not n.candidate and ++i == TARGET_NODES)
                break;
        }
    }
    return ret;
}

time_point
Dht::Search::getListenTime(time_point now) const
{
    if (listeners.empty())
        return time_point::max();
    time_point listen_time {time_point::max()};
    unsigned i = 0, t = 0;
    for (const auto& sn : nodes) {
        if (not sn.isSynced(now) or (sn.candidate and t >= LISTEN_NODES))
            continue;
        auto lt = sn.getListenTime();
        listen_time = std::min(listen_time, lt);
        t++;
        if (not sn.candidate and ++i == LISTEN_NODES)
            break;
    }
    return listen_time;
}

time_point
Dht::Search::getNextStepTime(const std::map<ValueType::Id, ValueType>& types, time_point now) const
{
    auto next_step = time_point::max();
    if (expired or done)
        return next_step;

    auto ut = getUpdateTime(now);
    if (ut != time_point::max()) {
        //std::cout << id.toString() << " IPv" << (af==AF_INET?"4":"6") << " update time in " << print_dt(ut - now) << " s" << std::endl;
        next_step = std::min(next_step, ut);
    }

    if (isSynced(now))
    {
        auto at = getAnnounceTime(types, now);
        if (at != time_point::max()) {
            //std::cout << id.toString() << " IPv" << (af==AF_INET?"4":"6") << " announce time in " << print_dt(at - now) << " s" << std::endl;
            next_step = std::min(next_step, at);
        }

        auto lt = getListenTime(now);
        if (lt != time_point::max()) {
            //std::cout << id.toString() << " IPv" << (af==AF_INET?"4":"6") << " listen time in " << print_dt(lt - now) << " s" << std::endl;
            next_step = std::min(next_step, lt);
        }
    }


    return next_step;
}

void
Dht::bootstrapSearch(Dht::Search& sr)
{
    auto& list = (sr.af == AF_INET) ? buckets : buckets6;
    if (list.empty() || (list.size() == 1 && list.front().nodes.empty()))
        return;
    auto b = list.findBucket(sr.id);
    if (b == list.end()) {
        DHT_LOG.ERROR("No bucket");
        return;
    }

    sr.insertBucket(*b, now);
    if (sr.nodes.size() < SEARCH_NODES) {
        if (std::next(b) != list.end())
            sr.insertBucket(*std::next(b), now);
        if (b != list.begin())
            sr.insertBucket(*std::prev(b), now);
    }
    if (sr.nodes.size() < SEARCH_NODES)
        sr.insertBucket(*list.findBucket(myid), now);
    sr.refill_time = now;
}

unsigned
Dht::Search::refill(const RoutingTable& r, time_point now) {
    if (r.isEmpty() or r.front().af != af)
        return 0;
    unsigned added = 0;
    auto num_bad_nodes = getNumberOfBadNodes(now);
    auto b = r.findBucket(id);
    auto n = b;
    while (nodes.size()-num_bad_nodes < SEARCH_NODES && (std::next(n) != r.end() || b != r.begin())) {
        if (std::next(n) != r.end()) {
            added += insertBucket(*std::next(n), now);
            n = std::next(n);
        }
        if (b != r.begin()) {
            added += insertBucket(*std::prev(b), now);
            b = std::prev(b);
        }
    }

    return added;
}

/* Start a search. */
Dht::Search*
Dht::search(const InfoHash& id, sa_family_t af, GetCallback callback, DoneCallback done_callback, Value::Filter filter)
{
    if (!isRunning(af)) {
        DHT_LOG.ERROR("[search %s IPv%c] unsupported protocol", id.toString().c_str(), (af == AF_INET) ? '4' : '6');
        if (done_callback)
            done_callback(false, {});
        return nullptr;
    }

    auto srs = (af == AF_INET ? searches4 : searches6);
    auto srp = srs.find(id);
    Search* sr = nullptr;

    if (srp != srs.end()) {
        sr = &srp->second;
        sr->done = false;
        sr->expired = false;
    } else {
        sr = newSearch(id, af);
        if (not sr)
            return nullptr;
        sr->af = af;
        sr->tid = search_id++;
        sr->step_time = TIME_INVALID;
        sr->get_step_time = TIME_INVALID;
        sr->id = id;
        sr->done = false;
        sr->expired = false;
        sr->nodes.clear();
        sr->nodes.reserve(SEARCH_NODES+1);
        DHT_LOG.WARN("[search %s IPv%c] new search", id.toString().c_str(), (af == AF_INET) ? '4' : '6');
        if (search_id == 0)
            search_id++;
    }

    if (callback)
        sr->callbacks.push_back({.start=now, .filter=filter, .get_cb=callback, .done_cb=done_callback});

    bootstrapSearch(*sr);
    searchStep(*sr);
    search_time = now;
    return &(*sr);
}

void
Dht::announce(const InfoHash& id, sa_family_t af, std::shared_ptr<Value> value, DoneCallback callback, time_point created)
{
    if (!value) {
        if (callback)
            callback(false, {});
        return;
    }
    auto srs = (af == AF_INET ? searches4 : searches6);
    auto srp = srs.find(id);
    Search* sr = (srp == srs.end()) ? search(id, af, nullptr, nullptr) : &srp->second;
    if (!sr) {
        if (callback)
            callback(false, {});
        return;
    }
    sr->done = false;
    sr->expired = false;
    auto a_sr = std::find_if(sr->announce.begin(), sr->announce.end(), [&](const Announce& a){
        return a.value->id == value->id;
    });
    if (a_sr == sr->announce.end()) {
        sr->announce.emplace_back(Announce {value, std::min(now, created), callback});
        for (auto& n : sr->nodes)
            n.acked[value->id] = {};
    }
    else {
        if (a_sr->value != value) {
            a_sr->value = value;
            for (auto& n : sr->nodes)
                n.acked[value->id] = {};
        }
        if (sr->isAnnounced(value->id, getType(value->type), now)) {
            if (a_sr->callback)
                a_sr->callback(true, {});
            a_sr->callback = {};
            if (callback) {
                callback(true, {});
            }
            return;
        } else {
            if (a_sr->callback)
                a_sr->callback(false, {});
            a_sr->callback = callback;
        }
    }
    auto tm = sr->getNextStepTime(types, now);
    if (tm < search_time) {
        DHT_LOG.ERROR("[search %s IPv%c] search_time is now in %lfs", sr->id.toString().c_str(), (sr->af == AF_INET) ? '4' : '6', print_dt(tm-clock::now()));
        search_time = tm;
    }
}

size_t
Dht::listenTo(const InfoHash& id, sa_family_t af, GetCallback cb, Value::Filter f)
{
    if (!isRunning(af))
        return 0;
       // DHT_LOG.ERROR("[search %s IPv%c] search_time is now in %lfs", sr->id.toString().c_str(), (sr->af == AF_INET) ? '4' : '6', print_dt(tm-clock::now()));

    //DHT_LOG.WARN("listenTo %s", id.toString().c_str());
    auto srs = af == AF_INET ? searches4 : searches6;
    auto srp = srs.find(id);
    Search* sr = (srp == srs.end()) ? search(id, af, nullptr, nullptr) : &srp->second;
    if (!sr)
        throw DhtException("Can't create search");
    DHT_LOG.ERROR("[search %s IPv%c] listen", id.toString().c_str(), (af == AF_INET) ? '4' : '6');
    sr->done = false;
    auto token = ++sr->listener_token;
    sr->listeners.emplace(token, LocalListener{f, cb});
    search_time = std::min(search_time, sr->getNextStepTime(types, now));
    return token;
}

size_t
Dht::listen(const InfoHash& id, GetCallback cb, Value::Filter f)
{
    now = clock::now();

    auto vals = std::make_shared<std::map<Value::Id, std::shared_ptr<Value>>>();
    auto token = ++listener_token;

    auto gcb = [=](const std::vector<std::shared_ptr<Value>>& values) {
        std::vector<std::shared_ptr<Value>> newvals {};
        for (const auto& v : values) {
            auto it = vals->find(v->id);
            if (it == vals->cend() || !(*it->second == *v))
                newvals.push_back(v);
        }
        if (!newvals.empty()) {
            if (!cb(newvals)) {
                cancelListen(id, token);
                return false;
            }
            for (const auto& v : newvals) {
                auto it = vals->emplace(v->id, v);
                if (not it.second)
                    it.first->second = v;
            }
        }
        return true;
    };

    auto st = findStorage(id);
    size_t tokenlocal = 0;
    if (st == store.end() && store.size() < MAX_HASHES) {
        store.emplace_back(id, now);
        st = std::prev(store.end());
    }
    if (st != store.end()) {
        if (not st->empty()) {
            std::vector<std::shared_ptr<Value>> newvals = st->get(f);
            if (not newvals.empty()) {
                if (!cb(newvals))
                    return 0;
                for (const auto& v : newvals) {
                    auto it = vals->emplace(v->id, v);
                    if (not it.second)
                        it.first->second = v;
                }
            }
        }
        tokenlocal = ++st->listener_token;
        st->local_listeners.emplace(tokenlocal, LocalListener{f, gcb});
    }

    auto token4 = Dht::listenTo(id, AF_INET, gcb, f);
    auto token6 = Dht::listenTo(id, AF_INET6, gcb, f);

    DHT_LOG.DEBUG("Added listen : %d -> %d %d %d", token, tokenlocal, token4, token6);
    listeners.emplace(token, std::make_tuple(tokenlocal, token4, token6));
    return token;
}

bool
Dht::cancelListen(const InfoHash& id, size_t token)
{
    now = clock::now();

    auto it = listeners.find(token);
    if (it == listeners.end()) {
        DHT_LOG.WARN("Listen token not found: %d", token);
        return false;
    }
    DHT_LOG.DEBUG("cancelListen %s with token %d", id.toString().c_str(), token);
    auto st = findStorage(id);
    auto tokenlocal = std::get<0>(it->second);
    if (st != store.end() && tokenlocal)
        st->local_listeners.erase(tokenlocal);

    auto searches_cancel_listen = [&](std::map<InfoHash, Search> srs) {
        for (auto& sp : srs) {
            auto& s = sp.second;
            if (s.id != id) continue;
            auto af_token = s.af == AF_INET ? std::get<1>(it->second) : std::get<2>(it->second);
            if (af_token == 0)
                continue;
            s.listeners.erase(af_token);
        }
    };
    searches_cancel_listen(searches4);
    searches_cancel_listen(searches6);
    listeners.erase(it);
    return true;
}

void
Dht::put(const InfoHash& id, std::shared_ptr<Value> val, DoneCallback callback, time_point created)
{
    now = clock::now();

    if (val->id == Value::INVALID_ID) {
        crypto::random_device rdev;
        std::uniform_int_distribution<Value::Id> rand_id {};
        val->id = rand_id(rdev);
    }

    DHT_LOG.DEBUG("put: adding %s -> %s", id.toString().c_str(), val->toString().c_str());

    auto ok = std::make_shared<bool>(false);
    auto done = std::make_shared<bool>(false);
    auto done4 = std::make_shared<bool>(false);
    auto done6 = std::make_shared<bool>(false);
    auto donecb = [=](const std::vector<std::shared_ptr<Node>>& nodes) {
        // Callback as soon as the value is announced on one of the available networks
        if (callback && !*done && (*ok || (*done4 && *done6))) {
            callback(*ok, nodes);
            *done = true;
        }
    };
    announce(id, AF_INET, val, [=](bool ok4, const std::vector<std::shared_ptr<Node>>& nodes) {
        DHT_LOG.DEBUG("Announce done IPv4 %d", ok4);
        *done4 = true;
        *ok |= ok4;
        donecb(nodes);
    }, created);
    announce(id, AF_INET6, val, [=](bool ok6, const std::vector<std::shared_ptr<Node>>& nodes) {
        DHT_LOG.DEBUG("Announce done IPv6 %d", ok6);
        *done6 = true;
        *ok |= ok6;
        donecb(nodes);
    }, created);
}

struct OpStatus {
    bool done {false};
    bool ok {false};
};

void
Dht::get(const InfoHash& id, GetCallback getcb, DoneCallback donecb, Value::Filter filter)
{
    now = clock::now();

    auto status = std::make_shared<OpStatus>();
    auto status4 = std::make_shared<OpStatus>();
    auto status6 = std::make_shared<OpStatus>();
    auto vals = std::make_shared<std::vector<std::shared_ptr<Value>>>();
    auto all_nodes = std::make_shared<std::vector<std::shared_ptr<Node>>>();

    auto done_l = [=](const std::vector<std::shared_ptr<Node>>& nodes) {
        if (status->done)
            return;
        all_nodes->insert(all_nodes->end(), nodes.begin(), nodes.end());
        if (status->ok || (status4->done && status6->done)) {
            bool ok = status->ok || status4->ok || status6->ok;
            status->done = true;
            if (donecb)
                donecb(ok, *all_nodes);
        }
    };
    auto cb = [=](const std::vector<std::shared_ptr<Value>>& values) {
        if (status->done)
            return false;
        std::vector<std::shared_ptr<Value>> newvals {};
        for (const auto& v : values) {
            auto it = std::find_if(vals->cbegin(), vals->cend(), [&](const std::shared_ptr<Value>& sv) {
                return sv == v || *sv == *v;
            });
            if (it == vals->cend()) {
                if (!filter || filter(*v))
                    newvals.push_back(v);
            }
        }
        if (!newvals.empty()) {
            status->ok = !getcb(newvals);
            vals->insert(vals->end(), newvals.begin(), newvals.end());
        }
        done_l({});
        return !status->ok;
    };

    /* Try to answer this search locally. */
    cb(getLocal(id, filter));

    Dht::search(id, AF_INET, cb, [=](bool ok, const std::vector<std::shared_ptr<Node>>& nodes) {
        //DHT_LOG.WARN("DHT done IPv4");
        status4->done = true;
        status4->ok = ok;
        done_l(nodes);
    });
    Dht::search(id, AF_INET6, cb, [=](bool ok, const std::vector<std::shared_ptr<Node>>& nodes) {
        //DHT_LOG.WARN("DHT done IPv6");
        status6->done = true;
        status6->ok = ok;
        done_l(nodes);
    });
}

std::vector<std::shared_ptr<Value>>
Dht::getLocal(const InfoHash& id, Value::Filter f) const
{
    auto s = findStorage(id);
    if (s == store.end()) return {};
    return s->get(f);
}

std::shared_ptr<Value>
Dht::getLocalById(const InfoHash& id, Value::Id vid) const
{
    auto s = findStorage(id);
    if (s != store.end())
        return s->getById(vid);
    return {};
}

std::vector<std::shared_ptr<Value>>
Dht::getPut(const InfoHash& id)
{
    std::vector<std::shared_ptr<Value>> ret;
    auto find_values = [&](std::map<InfoHash, Search> srs) {
        auto srp = srs.find(id);
        if (srp == srs.end())
            return;
        auto& search = srp->second;
        ret.reserve(ret.size() + search.announce.size());
        for (const auto& a : search.announce)
            ret.push_back(a.value);
    };
    find_values(searches4);
    find_values(searches6);
    return ret;
}

std::shared_ptr<Value>
Dht::getPut(const InfoHash& id, const Value::Id& vid)
{
    auto find_value = [&](std::map<InfoHash, Search> srs) {
        auto srp = srs.find(id);
        if (srp == srs.end())
            return std::shared_ptr<Value> {};
        auto& search = srp->second;
        for (const auto& a : search.announce) {
            if (a.value->id == vid)
                return a.value;
        }
        return std::shared_ptr<Value> {};
    };
    auto v4 = find_value(searches4);
    if (v4) return v4;
    auto v6 = find_value(searches6);
    if (v6) return v6;
    return {};
}

bool
Dht::cancelPut(const InfoHash& id, const Value::Id& vid)
{
    bool canceled {false};
    auto sr_cancel_put = [&](std::map<InfoHash, Search> srs) {
        auto srp = srs.find(id);
        if (srp == srs.end())
            return;

        auto& sr = srp->second;
        for (auto it = sr.announce.begin(); it != sr.announce.end();) {
            if (it->value->id == vid) {
                canceled = true;
                it = sr.announce.erase(it);
            }
            else
                ++it;
        }
    };
    sr_cancel_put(searches4);
    sr_cancel_put(searches6);
    return canceled;
}

void
Dht::storageChanged(Storage& st, ValueStorage& v)
{
    {
        std::vector<std::pair<GetCallback, std::vector<std::shared_ptr<Value>>>> cbs;
        for (const auto& l : st.local_listeners) {
            std::vector<std::shared_ptr<Value>> vals;
            if (not l.second.filter or l.second.filter(*v.data))
                vals.push_back(v.data);
            if (not vals.empty())
                cbs.emplace_back(l.second.get_cb, std::move(vals));
        }
        // listeners are copied: they may be deleted by the callback
        for (auto& cb : cbs)
            cb.first(cb.second);
    }

    for (const auto& l : st.listeners) {
        DHT_LOG.WARN("Storage changed. Sending update to %s %s.",
                l.id.toString().c_str(), print_addr((sockaddr*)&l.ss, l.sslen).c_str());
        std::vector<std::shared_ptr<Value>> vals;
        vals.push_back(v.data);
        Blob ntoken = makeToken((const sockaddr*)&l.ss, false);
        network_engine->tellListener((const sockaddr*)&l.ss, l.sslen, l.rid, st.id, WANT4 | WANT6, ntoken,
                buckets.findClosestNodes(st.id, now, TARGET_NODES), buckets6.findClosestNodes(st.id, now, TARGET_NODES),
                vals);
    }
}

bool
Dht::storageStore(const InfoHash& id, const std::shared_ptr<Value>& value, time_point created)
{
    created = std::min(created, now);
    auto st = findStorage(id);
    if (st == store.end()) {
        if (store.size() >= MAX_HASHES)
            return false;
        store.emplace_back(id, now);
        st = std::prev(store.end());
    }

    auto store = st->store(value, created, max_store_size - total_store_size);
    if (std::get<0>(store)) {
        total_store_size += std::get<1>(store);
        total_values += std::get<2>(store);
        storageChanged(*st, *std::get<0>(store));
    }
    return std::get<0>(store);
}

std::tuple<Dht::ValueStorage*, ssize_t, ssize_t>
Dht::Storage::store(const std::shared_ptr<Value>& value, time_point created, ssize_t size_left) {

    auto it = std::find_if (values.begin(), values.end(), [&](const ValueStorage& vr) {
        return vr.data == value || vr.data->id == value->id;
    });
    if (it != values.end()) {
        /* Already there, only need to refresh */
        it->time = created;
        ssize_t size_diff = value->size() - it->data->size();
        if (size_diff <= size_left and it->data != value) {
            //DHT_LOG.DEBUG("Updating %s -> %s", id.toString().c_str(), value->toString().c_str());
            it->data = value;
            total_size += size_diff;
            return std::make_tuple(&(*it), size_diff, 0);
        }
        return std::make_tuple(nullptr, 0, 0);
    } else {
        //DHT_LOG.DEBUG("Storing %s -> %s", id.toString().c_str(), value->toString().c_str());
        ssize_t size = value->size();
        if (size <= size_left and values.size() < MAX_VALUES) {
            total_size += size;
            values.emplace_back(value, created);
            return std::make_tuple(&values.back(), size, 1);
        }
        return std::make_tuple(nullptr, 0, 0);
    }
}

void
Dht::Storage::clear()
{
    values.clear();
    total_size = 0;
}

void
Dht::storageAddListener(const InfoHash& id, const InfoHash& node, const sockaddr *from, socklen_t fromlen, size_t rid)
{
    auto st = findStorage(id);
    if (st == store.end()) {
        if (store.size() >= MAX_HASHES)
            return;
        store.emplace_back(id, now);
        st = std::prev(store.end());
    }
    sa_family_t af = from->sa_family;
    auto l = std::find_if(st->listeners.begin(), st->listeners.end(), [&](const Listener& l){
        return l.ss.ss_family == af && l.id == node;
    });
    if (l == st->listeners.end()) {
        auto stvalues = st->getValues();
        std::vector<std::shared_ptr<Value>> values(stvalues.size());
        std::transform(stvalues.begin(), stvalues.end(), values.begin(), [=](ValueStorage& vs) { return vs.data; });

        network_engine->tellListener(from, fromlen, rid, id, WANT4 | WANT6, makeToken(from, false),
                buckets.findClosestNodes(id, now, TARGET_NODES), buckets6.findClosestNodes(id, now, TARGET_NODES),
                values);
        st->listeners.emplace_back(node, from, fromlen, rid, now);
    }
    else
        l->refresh(from, fromlen, rid, now);
}

void
Dht::expireStorage()
{
    auto i = store.begin();
    while (i != store.end()) {
        // put elements to remove at the end with std::partition,
        // and then remove them with std::vector::erase.
        i->listeners.erase(
            std::partition(i->listeners.begin(), i->listeners.end(),
                [&](const Listener& l)
                {
                    bool expired = l.time + Node::NODE_EXPIRE_TIME < now;
                    if (expired)
                        DHT_LOG.DEBUG("Discarding expired listener %s", l.id.toString().c_str());
                    // return false if the element should be removed
                    return !expired;
                }),
            i->listeners.end());

        auto stats = i->expire(types, now);
        total_store_size += stats.first;
        total_values += stats.second;

        if (i->empty() && i->listeners.empty()) {
            DHT_LOG.DEBUG("Discarding expired value %s", i->id.toString().c_str());
            i = store.erase(i);
        }
        else
            ++i;
    }
}

std::pair<ssize_t, ssize_t>
Dht::Storage::expire(const std::map<ValueType::Id, ValueType>& types, time_point now)
{
    auto r = std::partition(values.begin(), values.end(), [&](const ValueStorage& v) {
        if (!v.data) return false; // should not happen
        auto type_it = types.find(v.data->type);
        const ValueType& type = (type_it == types.end()) ? ValueType::USER_DATA : type_it->second;
        bool expired = v.time + type.expiration < now;
        //if (expired)
        //    DHT_LOG.DEBUG("Discarding expired value %s", v.data->toString().c_str());
        return !expired;
    });
    ssize_t del_num = std::distance(r, values.end());
    ssize_t size_diff {};
    std::for_each(r, values.end(), [&](const ValueStorage& v){
        size_diff -= v.data->size();
    });
    total_size += size_diff;
    values.erase(r, values.end());
    return {size_diff, -del_num};
}

void
Dht::connectivityChanged()
{
    confirm_nodes_time = now;
    mybucket_grow_time = now;
    mybucket6_grow_time = now;
    reported_addr.clear();
    cache.clearBadNodes();
    auto stop_listen = [&](std::map<InfoHash, Search> srs) {
        for (auto& sp : srs)
            for (auto& sn : sp.second.nodes)
                sn.listenStatus = {};
    };
    stop_listen(searches4);
    stop_listen(searches6);
}

void
Dht::rotateSecrets()
{
    uniform_duration_distribution<> time_dist(std::chrono::minutes(15), std::chrono::minutes(45));
    rotate_secrets_time = now + time_dist(rd);

    oldsecret = secret;
    {
        crypto::random_device rdev;
        std::generate_n(secret.begin(), secret.size(), std::bind(rand_byte, std::ref(rdev)));
    }
}

Blob
Dht::makeToken(const sockaddr *sa, bool old) const
{
    void *ip;
    size_t iplen;
    in_port_t port;

    if (sa->sa_family == AF_INET) {
        sockaddr_in *sin = (sockaddr_in*)sa;
        ip = &sin->sin_addr;
        iplen = 4;
        port = htons(sin->sin_port);
    } else if (sa->sa_family == AF_INET6) {
        sockaddr_in6 *sin6 = (sockaddr_in6*)sa;
        ip = &sin6->sin6_addr;
        iplen = 16;
        port = htons(sin6->sin6_port);
    } else {
        return {};
    }

    const auto& c1 = old ? oldsecret : secret;
    Blob data;
    data.reserve(sizeof(secret)+2+iplen);
    data.insert(data.end(), c1.begin(), c1.end());
    data.insert(data.end(), (uint8_t*)ip, (uint8_t*)ip+iplen);
    data.insert(data.end(), (uint8_t*)&port, ((uint8_t*)&port)+2);

    size_t sz = TOKEN_SIZE;
    Blob ret {};
    ret.resize(sz);
    gnutls_datum_t gnudata = {data.data(), (unsigned int)data.size()};
    if (gnutls_fingerprint(GNUTLS_DIG_SHA512, &gnudata, ret.data(), &sz) != GNUTLS_E_SUCCESS)
        throw DhtException("Can't compute SHA512");
    ret.resize(sz);
    return ret;
}

bool
Dht::tokenMatch(const Blob& token, const sockaddr *sa) const
{
    if (!sa || token.size() != TOKEN_SIZE)
        return false;
    if (token == makeToken(sa, false))
        return true;
    if (token == makeToken(sa, true))
        return true;
    return false;
}

int
Dht::getNodesStats(sa_family_t af, unsigned *good_return, unsigned *dubious_return, unsigned *cached_return, unsigned *incoming_return) const
{
    unsigned good = 0, dubious = 0, cached = 0, incoming = 0;
    auto& list = (af == AF_INET) ? buckets : buckets6;

    for (const auto& b : list) {
        for (auto& n : b.nodes) {
            if (n->isGood(now)) {
                good++;
                if (n->time > n->reply_time)
                    incoming++;
            } else {
                dubious++;
            }
        }
        if (b.cached.ss_family > 0)
            cached++;
    }
    if (good_return)
        *good_return = good;
    if (dubious_return)
        *dubious_return = dubious;
    if (cached_return)
        *cached_return = cached;
    if (incoming_return)
        *incoming_return = incoming;
    return good + dubious;
}

void
Dht::dumpBucket(const Bucket& b, std::ostream& out) const
{
    using namespace std::chrono;
    out << b.first << " count " << b.nodes.size() << " age " << duration_cast<seconds>(now - b.time).count() << " sec";
    if (b.cached.ss_family)
        out << " (cached)";
    out  << std::endl;
    for (auto& n : b.nodes) {
        out << "    Node " << n->id << " " << print_addr((sockaddr*)&n->ss, n->sslen);
        if (n->time != n->reply_time)
            out << " age " << duration_cast<seconds>(now - n->time).count() << ", reply: " << duration_cast<seconds>(now - n->reply_time).count();
        else
            out << " age " << duration_cast<seconds>(now - n->time).count();
        if (n->pinged)
            out << " [p " << n->pinged << "]";
        if (n->isExpired(now))
            out << " [expired]";
        else if (n->isGood(now))
            out << " [good]";
        out << std::endl;
    }
}

void
Dht::dumpSearch(const Search& sr, std::ostream& out) const
{
    using namespace std::chrono;
    out << std::endl << "Search IPv" << (sr.af == AF_INET6 ? '6' : '4') << ' ' << sr.id << " G" << sr.callbacks.size();
    out << " age " << duration_cast<seconds>(now - sr.step_time).count() << " s tid " << sr.tid;
    if (sr.done)
        out << " [done]";
    bool synced = sr.isSynced(now);
    out << (synced ? " [synced]" : " [not synced]");
    if (synced && sr.isListening(now)) {
        auto lt = sr.getListenTime(now);
        out << " [listening, next in " << duration_cast<minutes>(lt-now).count() << " min]";
    }
    out << std::endl;

    for (const auto& n : sr.announce) {
        bool announced = sr.isAnnounced(n.value->id, getType(n.value->type), now);
        out << "Announcement: " << *n.value << (announced ? " [announced]" : "") << std::endl;
    }

    out << " Common bits    InfoHash                          Conn. Get   Put IP" << std::endl;
    unsigned i = 0;
    auto last_get = sr.getLastGetTime();
    for (const auto& n : sr.nodes) {
        i++;
        out << std::setfill (' ') << std::setw(3) << InfoHash::commonBits(sr.id, n.node->id) << ' ' << n.node->id;
        out << ' ' << (findNode(n.node->id, AF_INET) || findNode(n.node->id, AF_INET6) ? '*' : ' ');
        out << ' ' << (n.candidate ? 'c' : ' ');
        out << " ["
            << (n.node->isMessagePending(now) ? 'f':' ');
        if (n.node->pinged)
            out << n.node->pinged;
        else
            out << ' ';
        out << (n.node->isExpired(now) ? 'x' : ' ') << "]";

        out << " ["
            << (n.getStatus->pending(now) ? 'f' : (n.getStatus->expired(now) ? 'x' : ' '))
            << (n.isSynced(now) ? 's' : '-')
            << ((n.getStatus->reply_time > last_get) ? 'u' : '-') << "] ";

        if (not sr.listeners.empty()) {
            if (n.listenStatus->last_try == time_point::min())
                out << "     ";
            else
                out << "["
                    << (n.listenStatus->pending(now) ? 'f' : (n.listenStatus->expired(now) ? 'x' : ' '))
                    << (n.isListening(now) ? 'l' : '-') << "] ";
        }

        if (not sr.announce.empty()) {
            if (n.acked.empty()) {
                out << "   ";
                for (size_t a=0; a < sr.announce.size(); a++)
                    out << ' ';
            } else {
                out << "[";
                for (const auto& a : sr.announce) {
                    auto ack = n.acked.find(a.value->id);
                    if (ack == n.acked.end()) {
                        out << ' ';
                    } else {
                        auto& astatus = ack->second;
                        if (astatus->reply_time + getType(a.value->type).expiration > now)
                            out << 'a';
                        else if (astatus->pending(now))
                            out << 'f';
                        else if (astatus->expired(now))
                            out << 'x';
                        else
                            out << ' ';
                    }
                }
                out << "] ";
            }
        }
        out << print_addr(n.node->ss, n.node->sslen);
        out << std::endl;
    }
}

void
Dht::dumpTables() const
{
    std::stringstream out;
    out << "My id " << myid << std::endl;

    out << "Buckets IPv4 :" << std::endl;
    for (const auto& b : buckets)
        dumpBucket(b, out);
    out << "Buckets IPv6 :" << std::endl;
    for (const auto& b : buckets6)
        dumpBucket(b, out);

    auto dump_searches = [&](std::map<InfoHash, Search> srs) {
        for (auto& srp : srs)
            dumpSearch(srp.second, out);
    };
    dump_searches(searches4);
    dump_searches(searches6);
    out << std::endl;

    out << getStorageLog() << std::endl;

    DHT_LOG.DEBUG("%s", out.str().c_str());
}

std::string
Dht::getStorageLog() const
{
    using namespace std::chrono;
    std::stringstream out;
    for (const auto& st : store) {
        out << "Storage " << st.id << " " << st.listeners.size() << " list., " << st.valueCount() << " values (" << st.totalSize() << " bytes)" << std::endl;
        for (const auto& l : st.listeners) {
            out << "   " << "Listener " << l.id << " " << print_addr((sockaddr*)&l.ss, l.sslen);
            auto since = duration_cast<seconds>(now - l.time);
            auto expires = duration_cast<seconds>(l.time + Node::NODE_EXPIRE_TIME - now);
            out << " (since " << since.count() << "s, exp in " << expires.count() << "s)" << std::endl;
        }
    }
    out << "Total " << store.size() << " storages, " << total_values << " values (" << (total_store_size/1024) << " ĶB)" << std::endl;
    return out.str();
}

std::string
Dht::getRoutingTablesLog(sa_family_t af) const
{
    auto& list = (af == AF_INET) ? buckets : buckets6;
    std::stringstream out;
    for (const auto& b : list)
        dumpBucket(b, out);
    return out.str();
}

std::string
Dht::getSearchesLog(sa_family_t af) const
{
    std::stringstream out;
    out << "s:synched, u:updated, a:announced, c:candidate, f:cur req, x:expired, *:known" << std::endl;
    auto srs = af == AF_INET ? searches4 : searches6;
    for (const auto& srp : srs) {
        auto& sr = srp.second;
        if (af == 0 or sr.af == af)
            dumpSearch(sr, out);
    }
    return out.str();
}

Dht::Dht(int s, int s6, Config config)
 : dht_socket(s), dht_socket6(s6), myid(config.node_id), is_bootstrap(config.is_bootstrap),
   now(clock::now()), mybucket_grow_time(now), mybucket6_grow_time(now)
{
    if (s < 0 && s6 < 0)
        return;

    if (s >= 0) {
        buckets = {Bucket {AF_INET}};
        if (!set_nonblocking(s, 1))
            throw DhtException("Can't set socket to non-blocking mode");
    }

    if (s6 >= 0) {
        buckets6 = {Bucket {AF_INET6}};
        if (!set_nonblocking(s6, 1))
            throw DhtException("Can't set socket to non-blocking mode");
    }

    search_id = std::uniform_int_distribution<decltype(search_id)>{}(rd);

    uniform_duration_distribution<> time_dis {std::chrono::seconds(0), std::chrono::seconds(3)};
    confirm_nodes_time = now + time_dis(rd);

    // Fill old secret
    {
        crypto::random_device rdev;
        std::generate_n(secret.begin(), secret.size(), std::bind(rand_byte, std::ref(rdev)));
    }
    rotateSecrets();

    expireBuckets(buckets);
    expireBuckets(buckets6);


    using namespace std::placeholders;
    network_engine = std::unique_ptr<NetworkEngine>(
          new NetworkEngine {
              NetworkEngine::DhtInfo {myid, dht_socket, dht_socket6, DHT_LOG}, scheduler,
              std::bind(&Dht::onError, this, _1, _2),
              std::bind(&Dht::newNode, this, _1, _2, _3, _4),
              std::bind(&Dht::onReportedAddr, this, _1, _2, _3),
              std::bind(&Dht::onPing, this, _1),
              std::bind(&Dht::onFindNode, this, _1, _2, _3),
              std::bind(&Dht::onGetValues, this, _1, _2, _3),
              std::bind(&Dht::onListen, this, _1, _2, _3, _4),
              std::bind(&Dht::onAnnounce, this, _1, _2, _3, _4, _5)
          }
    );
    DHT_LOG.DEBUG("DHT initialised with node ID %s", myid.toString().c_str());
}


bool
Dht::neighbourhoodMaintenance(RoutingTable& list)
{
    //DHT_LOG.DEBUG("neighbourhoodMaintenance");
    auto b = list.findBucket(myid);
    if (b == list.end())
        return false;

    InfoHash id = myid;
    id[HASH_LEN-1] = rand_byte(rd);

    std::bernoulli_distribution rand_trial(1./8.);
    auto q = b;
    if (std::next(q) != list.end() && (q->nodes.empty() || rand_trial(rd)))
        q = std::next(q);
    if (b != list.begin() && (q->nodes.empty() || rand_trial(rd))) {
        auto r = std::prev(b);
        if (!r->nodes.empty())
            q = r;
    }

    /* Since our node-id is the same in both DHTs, it's probably
       profitable to query both families. */
    want_t want = dht_socket >= 0 && dht_socket6 >= 0 ? (WANT4 | WANT6) : -1;
    auto n = q->randomNode();
    if (n) {
        DHT_LOG.DEBUG("[find %s IPv%c] sending find for neighborhood maintenance.", id.toString().c_str(), q->af == AF_INET6 ? '6' : '4');
        auto sr = q->af == AF_INET ? searches4.find(id) : searches6.find(id);
        auto srp = &sr->second;
        network_engine->sendFindNode(n, id, want,
          [=](std::shared_ptr<NetworkEngine::RequestStatus> status,
              NetworkEngine::RequestAnswer&& answer) mutable
          { /* on done */
              onGetValuesDone(status, answer, srp);
          },
          [=](std::shared_ptr<NetworkEngine::RequestStatus>, NetworkEngine::RequestAnswer&&) mutable
          { /* on expired */
              searchStep(*srp);
          }
        );
        pinged(*n, &(*q));
    }

    return true;
}

bool
Dht::bucketMaintenance(RoutingTable& list)
{
    std::bernoulli_distribution rand_trial(1./8.);
    std::bernoulli_distribution rand_trial_38(1./38.);

    for (auto b = list.begin(); b != list.end(); ++b) {
        if (b->time < now - std::chrono::minutes(10) || b->nodes.empty()) {
            /* This bucket hasn't seen any positive confirmation for a long
               time.  Pick a random id in this bucket's range, and send
               a request to a random node. */
            InfoHash id = list.randomId(b);
            auto q = b;
            /* If the bucket is empty, we try to fill it from a neighbour.
               We also sometimes do it gratuitiously to recover from
               buckets full of broken nodes. */
            if (std::next(b) != list.end() && (q->nodes.empty() || rand_trial(rd)))
                q = std::next(b);
            if (b != list.begin() && (q->nodes.empty() || rand_trial(rd))) {
                auto r = std::prev(b);
                if (!r->nodes.empty())
                    q = r;
            }

            auto n = q->randomNode();
            if (n) {
                want_t want = -1;

                if (dht_socket >= 0 && dht_socket6 >= 0) {
                    auto otherbucket = findBucket(id, q->af == AF_INET ? AF_INET6 : AF_INET);
                    if (otherbucket && otherbucket->nodes.size() < TARGET_NODES)
                        /* The corresponding bucket in the other family
                           is emptyish -- querying both is useful. */
                        want = WANT4 | WANT6;
                    else if (rand_trial_38(rd))
                        /* Most of the time, this just adds overhead.
                           However, it might help stitch back one of
                           the DHTs after a network collapse, so query
                           both, but only very occasionally. */
                        want = WANT4 | WANT6;
                }

                DHT_LOG.DEBUG("[find %s IPv%c] sending for bucket maintenance.", id.toString().c_str(), q->af == AF_INET6 ? '6' : '4');
                auto sr = q->af == AF_INET ? searches4.find(id) : searches6.find(id);
                auto srp = &sr->second;
                network_engine->sendFindNode(n, id, want,
                    [=](std::shared_ptr<NetworkEngine::RequestStatus> status,
                        NetworkEngine::RequestAnswer&& answer) mutable
                    { /* on done */
                        onGetValuesDone(status, answer, srp);
                    },
                    [=](std::shared_ptr<NetworkEngine::RequestStatus>, NetworkEngine::RequestAnswer&&) mutable
                    { /* on expired */
                        searchStep(*srp);
                    }
                );
                pinged(*n, &(*q));
                /* In order to avoid sending queries back-to-back,
                   give up for now and reschedule us soon. */
                return true;
            }
        }
    }
    return false;
}

size_t
Dht::maintainStorage(InfoHash id, bool force, DoneCallback donecb) {
    size_t announce_per_af = 0;
    auto local_storage = findStorage(id);
    if (local_storage == store.end()) { return 0; }

    bool want4 = true, want6 = true;

    auto nodes = buckets.findClosestNodes(id, now);
    if (!nodes.empty()) {
        if (force || id.xorCmp(nodes.back()->id, myid) < 0) {
            for (auto &value : local_storage->getValues()) {
                const auto& vt = getType(value.data->type);
                if (force || value.time + vt.expiration > now + MAX_STORAGE_MAINTENANCE_EXPIRE_TIME) {
                    // gotta put that value there
                    announce(id, AF_INET, value.data, donecb, value.time);
                    ++announce_per_af;
                }
            }
            want4 = false;
        }
    }
    else { want4 = false; }

    auto nodes6 = buckets6.findClosestNodes(id, now);
    if (!nodes6.empty()) {
        if (force || id.xorCmp(nodes6.back()->id, myid) < 0) {
            for (auto &value : local_storage->getValues()) {
                const auto& vt = getType(value.data->type);
                if (force || value.time + vt.expiration > now + MAX_STORAGE_MAINTENANCE_EXPIRE_TIME) {
                    // gotta put that value there
                    announce(id, AF_INET6, value.data, donecb, value.time);
                    ++announce_per_af;
                }
            }
            want6 = false;
        }
    }
    else { want6 = false; }

    if (not want4 and not want6) {
        DHT_LOG.DEBUG("Discarding storage values %s", id.toString().c_str());
        local_storage->clear();
    }

    return announce_per_af;
}

void
Dht::processMessage(const uint8_t *buf, size_t buflen, const sockaddr *from, socklen_t fromlen) {
    if (buflen == 0)
        return;

    if (isMartian(from, fromlen))
        return;

    if (isNodeBlacklisted(from, fromlen)) {
        DHT_LOG.DEBUG("Received packet from blacklisted node.");
        return;
    }

    try {
        network_engine->processMessage(buf, buflen, from, fromlen, now);
    } catch (DhtProtocolException& e) {
        auto code = e.getCode();
        if (code == DhtProtocolException::INVALID_REPLY_TID
                or code == DhtProtocolException::WRONG_NODE_INFO_BUF_LEN) {
            /* This is really annoying, as it means that we will
               time-out all our searches that go through this node.
               Kill it. */
            const auto& id = e.getNodeId();
            blacklistNode(&id, from, fromlen);
        }
    }
}

time_point
Dht::periodic(const uint8_t *buf, size_t buflen, const sockaddr *from, socklen_t fromlen)
{
    using namespace std::chrono;
    now = clock::now();

    processMessage(buf, buflen, from, fromlen);
}

std::vector<Dht::ValuesExport>
Dht::exportValues() const
{
    std::vector<ValuesExport> e {};
    e.reserve(store.size());
    for (const auto& h : store) {
        ValuesExport ve;
        ve.first = h.id;

        msgpack::sbuffer buffer;
        msgpack::packer<msgpack::sbuffer> pk(&buffer);
        pk.pack_array(h.getValues().size());
        for (const auto& v : h.getValues()) {
            pk.pack_array(2);
            pk.pack(v.time.time_since_epoch().count());
            v.data->msgpack_pack(pk);
        }
        ve.second = {buffer.data(), buffer.data()+buffer.size()};
        e.push_back(std::move(ve));
    }
    return e;
}

void
Dht::importValues(const std::vector<ValuesExport>& import)
{
    for (const auto& h : import) {
        if (h.second.empty())
            continue;

        try {
            msgpack::unpacked msg;
            msgpack::unpack(msg, (const char*)h.second.data(), h.second.size());
            auto valarr = msg.get();
            if (valarr.type != msgpack::type::ARRAY)
                throw msgpack::type_error();
            for (unsigned i = 0; i < valarr.via.array.size; i++) {
                auto& valel = valarr.via.array.ptr[i];
                if (valel.via.array.size < 2)
                    throw msgpack::type_error();
                time_point val_time;
                Value tmp_val;
                try {
                    val_time = time_point{time_point::duration{valel.via.array.ptr[0].as<time_point::duration::rep>()}};
                    tmp_val.msgpack_unpack(valel.via.array.ptr[1]);
                } catch (const std::exception&) {
                    DHT_LOG.ERROR("Error reading value at %s", h.first.toString().c_str());
                    continue;
                }
                if (val_time + getType(tmp_val.type).expiration < now) {
                    DHT_LOG.DEBUG("Discarding expired value at %s", h.first.toString().c_str());
                    continue;
                }
                storageStore(h.first, std::make_shared<Value>(std::move(tmp_val)), val_time);
            }
        } catch (const std::exception&) {
            DHT_LOG.ERROR("Error reading values at %s", h.first.toString().c_str());
            continue;
        }
    }
}


std::vector<NodeExport>
Dht::exportNodes()
{
    std::vector<NodeExport> nodes;
    const auto b4 = buckets.findBucket(myid);
    if (b4 != buckets.end()) {
        for (auto& n : b4->nodes)
            if (n->isGood(now))
                nodes.push_back(n->exportNode());
    }
    const auto b6 = buckets6.findBucket(myid);
    if (b6 != buckets6.end()) {
        for (auto& n : b6->nodes)
            if (n->isGood(now))
                nodes.push_back(n->exportNode());
    }
    for (auto b = buckets.begin(); b != buckets.end(); ++b) {
        if (b == b4) continue;
        for (auto& n : b->nodes)
            if (n->isGood(now))
                nodes.push_back(n->exportNode());
    }
    for (auto b = buckets6.begin(); b != buckets6.end(); ++b) {
        if (b == b6) continue;
        for (auto& n : b->nodes)
            if (n->isGood(now))
                nodes.push_back(n->exportNode());
    }
    return nodes;
}

bool
Dht::insertNode(const InfoHash& id, const sockaddr *sa, socklen_t salen)
{
    if (sa->sa_family != AF_INET && sa->sa_family != AF_INET6)
        return false;
    now = clock::now();
    auto n = newNode(id, sa, salen, 0);
    return !!n;
}

int
Dht::pingNode(const sockaddr *sa, socklen_t salen)
{
    DHT_LOG.DEBUG("Sending ping to %s", print_addr(sa, salen).c_str());
    //return sendPing(sa, salen, TransId {TransPrefix::PING});
    return -1;
}

void
Dht::onError(std::shared_ptr<NetworkEngine::RequestStatus> status, DhtProtocolException e) {
    if (e.getCode() == DhtProtocolException::UNAUTHORIZED) {
        //TODO: utiliser map de search
        /*auto esr = findSearch(ttid, from->sa_family);*/
        //if (!esr) return;
        unsigned cleared = 0;
        for (auto& srp : status->node->ss.ss_family == AF_INET ? searches4 : searches6) {
            auto sr = srp.second;
            for (auto& n : sr.nodes) {
                if (n.node != status->node) continue;
                cleared++;
                n.getStatus->last_try = TIME_INVALID;
                n.getStatus->reply_time = TIME_INVALID;
                if (searchSendGetValues(sr))
                    sr.get_step_time = now;
                break;
            }
        }
        DHT_LOG.WARN("[node %s %s] token flush (%d searches affected)",
                status->node->id.toString().c_str(), print_addr((sockaddr*)&status->node->ss, status->node->sslen).c_str(), cleared);
    }
}

void
Dht::onReportedAddr(const InfoHash& id, sockaddr* addr , socklen_t addr_length)
{
    const auto& b = (addr->sa_family == AF_INET ? buckets : buckets6).findBucket(id);
    b->time = now;
    if (addr and addr_length)
        reportedAddr(addr, addr_length);
}

NetworkEngine::RequestAnswer
Dht::onPing(std::shared_ptr<Node>)
{
    return {};
}

NetworkEngine::RequestAnswer
Dht::onFindNode(std::shared_ptr<Node> node, InfoHash& hash, want_t want)
{
    Blob ntoken = makeToken((sockaddr*)&node->ss, false);
    std::vector<std::shared_ptr<Node>> nodes, nodes6;
    if ((want & WANT4)) {
        auto tmp = buckets.findClosestNodes(hash, now, TARGET_NODES);
        nodes.insert(nodes.begin(), tmp.begin(), tmp.end());
    }
    if ((want & WANT6)) {
        auto tmp = buckets6.findClosestNodes(hash, now, TARGET_NODES);
        nodes6.insert(nodes6.begin(), tmp.begin(), tmp.end());
    }
    NetworkEngine::RequestAnswer answer {ntoken, {}, std::move(nodes), std::move(nodes6)};
    return std::move(answer);
}

NetworkEngine::RequestAnswer
Dht::onGetValues(std::shared_ptr<Node> node, InfoHash& hash, want_t)
{
    NetworkEngine::RequestAnswer* answer;
    DHT_LOG.DEBUG("[node %s %s] got 'get' request for %s.",
            node->id.toString().c_str(), print_addr(node->ss, node->sslen).c_str(), hash.toString().c_str());
    if (hash == zeroes) {
        DHT_LOG.WARN("[node %s %s] Eek! Got get_values with no info_hash.",
                node->id.toString().c_str(), print_addr(node->ss, node->sslen).c_str());
        throw DhtProtocolException {DhtProtocolException::NON_AUTHORITATIVE_INFORMATION, DhtProtocolException::GET_NO_INFOHASH};
    } else {
        auto st = findStorage(hash);
        Blob ntoken = makeToken((sockaddr*)&node->ss, false);
        answer = new NetworkEngine::RequestAnswer {
            ntoken,
            {},
            buckets.findClosestNodes(hash, now, TARGET_NODES),
            buckets6.findClosestNodes(hash, now, TARGET_NODES)
        };
        if (st != store.end() && not st->empty()) {
            DHT_LOG.DEBUG("[node %s %s] sending %u values.",
                    node->id.toString().c_str(), print_addr(node->ss, node->sslen).c_str(), st->valueCount());
            auto values = st->getValues();
            answer->values.resize(values.size());
            std::transform(values.begin(), values.end(), answer->values.begin(), [](const ValueStorage& vs) {
                return std::move(vs.data);
            });
        } else {
            DHT_LOG.DEBUG("[node %s %s] sending nodes.",
                    node->id.toString().c_str(), print_addr(node->ss, node->sslen).c_str());
        }
    }
    return std::move(*answer);
}

void
Dht::onGetValuesDone(std::shared_ptr<NetworkEngine::RequestStatus> status, NetworkEngine::RequestAnswer& a, Search* sr)
{
    if (not sr)
        return;

    auto now = scheduler->time();
    if (sr == nullptr)
        return;
    sr->insertNode(status->node, now, a.ntoken);
    if (!a.values.empty()) {
        DHT_LOG.DEBUG("[search %s IPv%c] found %u values",
                sr->id.toString().c_str(), sr->af == AF_INET ? '4' : '6',
                a.values.size());
        for (auto& cb : sr->callbacks) {
            if (!cb.get_cb) continue;
            std::vector<std::shared_ptr<Value>> tmp;
            std::copy_if(a.values.begin(), a.values.end(), std::back_inserter(tmp), [&](const std::shared_ptr<Value>& v) {
                    return not static_cast<bool>(cb.filter) or cb.filter(*v);
                    });
            if (not tmp.empty())
                cb.get_cb(tmp);
        }
        std::vector<std::pair<GetCallback, std::vector<std::shared_ptr<Value>>>> tmp_lists;
        for (auto& l : sr->listeners) {
            if (!l.second.get_cb) continue;
            std::vector<std::shared_ptr<Value>> tmp;
            std::copy_if(a.values.begin(), a.values.end(), std::back_inserter(tmp), [&](const std::shared_ptr<Value>& v) {
                    return not static_cast<bool>(l.second.filter) or l.second.filter(*v);
                    });
            if (not tmp.empty())
                tmp_lists.emplace_back(l.second.get_cb, tmp);
        }
        for (auto& l : tmp_lists)
            l.first(l.second);
    }
    // Force to recompute the next step time
    if (sr->isSynced(now))
        search_time = now;
    searchStep(*sr); /* trigger a searchstep after a response. */
}

NetworkEngine::RequestAnswer
Dht::onListen(std::shared_ptr<Node> node, InfoHash& hash, Blob& token, size_t rid)
{
    DHT_LOG.DEBUG("[node %s %s] got 'listen' request for %s.",
            node->id.toString().c_str(), print_addr(node->ss, node->sslen).c_str(), hash.toString().c_str());
    if (hash == zeroes) {
        DHT_LOG.WARN("Listen with no info_hash.");
        throw DhtProtocolException {
            DhtProtocolException::NON_AUTHORITATIVE_INFORMATION,
            DhtProtocolException::LISTEN_NO_INFOHASH
        };
    }
    if (!tokenMatch(token, (sockaddr*)&node->ss)) {
        DHT_LOG.WARN("[node %s %s] incorrect token %s for 'listen'.",
            node->id.toString().c_str(), print_addr(node->ss, node->sslen).c_str(),
            hash.toString().c_str(), to_hex(token.data(), token.size()).c_str());
        throw DhtProtocolException {DhtProtocolException::UNAUTHORIZED, DhtProtocolException::LISTEN_WRONG_TOKEN};
    }
    storageAddListener(hash, node->id, (sockaddr*)&node->ss, node->sslen, rid);
    return {};
}

void
Dht::onListenDone(std::shared_ptr<NetworkEngine::RequestStatus> status, NetworkEngine::RequestAnswer&, Search* sr)
{
   DHT_LOG.DEBUG("Got reply to listen.");
   if (sr) {
       for (auto& sn : sr->nodes)
           if (sn.node == status->node) {
               sn.listenStatus->reply_time = now;
               break;
           }
       /* See comment for gp above. */
       if (searchSendGetValues(*sr))
           sr->get_step_time = now;
   }
}

NetworkEngine::RequestAnswer
Dht::onAnnounce(std::shared_ptr<Node> node, InfoHash& hash, Blob& token, std::vector<std::shared_ptr<Value>> values,
        time_point created)
{
    DHT_LOG.DEBUG("[node %s %s] got 'put' request for %s.",
        node->id.toString().c_str(), print_addr(node->ss, node->sslen).c_str(),
        hash.toString().c_str());
    if (hash == zeroes) {
        DHT_LOG.WARN("Put with no info_hash.");
        throw DhtProtocolException {
            DhtProtocolException::NON_AUTHORITATIVE_INFORMATION,
            DhtProtocolException::PUT_NO_INFOHASH
        };
    }
    if (!tokenMatch(token, (sockaddr*)&node->ss)) {
        DHT_LOG.WARN("[node %s %s] incorrect token %s for 'put'.",
            node->id.toString().c_str(), print_addr(node->ss, node->sslen).c_str(),
            hash.toString().c_str(), to_hex(token.data(), token.size()).c_str());
        throw DhtProtocolException {DhtProtocolException::UNAUTHORIZED, DhtProtocolException::PUT_WRONG_TOKEN};
    }
    {
        // We store a value only if we think we're part of the
        // SEARCH_NODES nodes around the target id.
        auto closest_nodes = (
                ((sockaddr*)&node->ss)->sa_family == AF_INET ? buckets : buckets6
            ).findClosestNodes(hash, now, SEARCH_NODES);
        if (hash.xorCmp(closest_nodes.back()->id, myid) < 0) {
            DHT_LOG.WARN("[node %s %s] announce too far from the target id. Dropping value.",
                    node->id.toString().c_str(), print_addr(node->ss, node->sslen).c_str());
            return {};
        }
    }

    for (const auto& v : values) {
        if (v->id == Value::INVALID_ID) {
            DHT_LOG.WARN("[value %s %s] incorrect value id", hash.toString().c_str(), v->id);
            throw DhtProtocolException {
                DhtProtocolException::NON_AUTHORITATIVE_INFORMATION,
                DhtProtocolException::PUT_INVALID_ID
            };
        }
        auto lv = getLocalById(hash, v->id);
        std::shared_ptr<Value> vc = v;
        if (lv) {
            if (*lv == *vc) {
                DHT_LOG.WARN("[value %s %lu] nothing to do.", hash.toString().c_str(), lv->id);
            } else {
                const auto& type = getType(lv->type);
                if (type.editPolicy(hash, lv, vc, node->id, (sockaddr*)&node->ss, node->sslen)) {
                    DHT_LOG.DEBUG("[value %s %lu] editing %s.",
                            hash.toString().c_str(), lv->id, vc->toString().c_str());
                    storageStore(hash, vc, created);
                } else {
                    DHT_LOG.DEBUG("[value %s %lu] rejecting edition of %s because of storage policy.",
                            hash.toString().c_str(), lv->id, vc->toString().c_str());
                }
            }
        } else {
            // Allow the value to be edited by the storage policy
            const auto& type = getType(vc->type);
            if (type.storePolicy(hash, vc, node->id, (sockaddr*)&node->ss, node->sslen)) {
                DHT_LOG.DEBUG("[value %s %lu] storing %s.", hash.toString().c_str(), vc->id, vc->toString().c_str());
                storageStore(hash, vc, created);
            } else {
                DHT_LOG.DEBUG("[value %s %lu] rejecting storage of %s.",
                        hash.toString().c_str(), vc->id, vc->toString().c_str());
            }
        }
    }
    return {};
}

void
Dht::onAnnounceDone(std::shared_ptr<NetworkEngine::RequestStatus> status, NetworkEngine::RequestAnswer& answer, Search* sr)
{
    DHT_LOG.DEBUG("[search %s IPv%c] got reply to put!",
            sr->id.toString().c_str(), sr->af == AF_INET ? '4' : '6',
            answer.values.size());

    auto& v = answer.values.front();
    for (auto& sn : sr->nodes)
        if (sn.node == status->node) {
            auto it = sn.acked[v->id] = status;
            break;
        }
    /* See comment for gp above. */
    if (searchSendGetValues(*sr))
        sr->get_step_time = now;

    // If the value was just successfully announced, call the callback
    sr->announce.erase(std::remove_if(sr->announce.begin(), sr->announce.end(),
        [&](Announce& a) {
            if (!a.value || a.value->id != v->id)
                return false;
            auto type = getType(a.value->type);
            if (sr->isAnnounced(v->id, type, now)) {
                if (a.callback) {
                    a.callback(true, sr->getNodes());
                    a.callback = nullptr;
                }
                return true;
            }
            return false;
    }), sr->announce.end());
}

}