opendht/src/node_cache.cpp

// Copyright (c) 2014-2026 Savoir-faire Linux Inc.
// SPDX-License-Identifier: MIT

#include "node_cache.h"

namespace dht {

constexpr size_t CLEANUP_MAX_NODES {4 * 1024};
constexpr size_t CLEANUP_FREQ {4 * 1024};

NodeCache::~NodeCache()
{
    clear();
}

void
NodeCache::clear()
{
    cache_4.setExpired();
    cache_6.setExpired();
}

Sp<Node>
NodeCache::getNode(const InfoHash& id, sa_family_t family)
{
    return cache(family).getNode(id);
}

Sp<Node>
NodeCache::getNode(const InfoHash& id, const SockAddr& addr, time_point now, bool confirm, bool client)
{
    if (not id)
        return std::make_shared<Node>(id, addr, rd, client);
    return cache(addr.getFamily()).getNode(id, addr, now, confirm, client, rd);
}

std::vector<Sp<Node>>
NodeCache::getCachedNodes(const InfoHash& id, sa_family_t sa_f, size_t count) const
{
    return cache(sa_f).getCachedNodes(id, count);
}

std::vector<Sp<Node>>
NodeCache::NodeMap::getCachedNodes(const InfoHash& id, size_t count) const
{
    std::vector<Sp<Node>> nodes;
    nodes.reserve(std::min(size(), count));
    const_iterator it;
    auto dec_it = [this](const_iterator& it) {
        auto ret = it;
        it = (it == cbegin()) ? cend() : std::prev(it);
        return ret;
    };

    auto it_p = lower_bound(id), it_n = it_p;
    if (not empty())
        dec_it(it_p); /* Create 2 separate iterator if we could */

    while (nodes.size() < count and (it_n != cend() or it_p != cend())) {
        /* If one of the iterator is at the end, then take the other one
           If they are both in middle of somewhere comapre both and take
           the closest to the id. */
        if (it_p == cend())
            it = it_n++;
        else if (it_n == cend())
            it = dec_it(it_p);
        else
            it = id.xorCmp(it_p->first, it_n->first) < 0 ? dec_it(it_p) : it_n++;

        if (auto n = it->second.lock())
            if (not n->isExpired() and not n->isClient())
                nodes.emplace_back(std::move(n));
    }

    return nodes;
}

void
NodeCache::clearBadNodes(sa_family_t family)
{
    if (family == 0) {
        clearBadNodes(AF_INET);
        clearBadNodes(AF_INET6);
    } else {
        cache(family).clearBadNodes();
    }
}

Sp<Node>
NodeCache::NodeMap::getNode(const InfoHash& id)
{
    auto wn = find(id);
    if (wn == end())
        return {};
    if (auto n = wn->second.lock())
        return n;
    erase(wn);
    return {};
}

Sp<Node>
NodeCache::NodeMap::getNode(
    const InfoHash& id, const SockAddr& addr, time_point now, bool confirm, bool client, std::mt19937_64& rd)
{
    auto& nref = (*this)[id];
    auto node = nref.lock();
    if (not node) {
        node = std::make_shared<Node>(id, addr, rd, client);
        nref = node;
        if (cleanup_counter++ == CLEANUP_FREQ) {
            cleanup();
            cleanup_counter = 0;
        }
    } else if (confirm or node->isOld(now)) {
        node->update(addr);
    }
    return node;
}

void
NodeCache::NodeMap::clearBadNodes()
{
    for (auto it = cbegin(); it != cend();) {
        if (auto n = it->second.lock()) {
            n->reset();
            ++it;
        } else {
            erase(it++);
        }
    }
    cleanup_counter = 0;
}

void
NodeCache::NodeMap::setExpired()
{
    for (auto& wn : *this)
        if (auto n = wn.second.lock())
            n->setExpired();
    clear();
    cleanup_counter = 0;
}

void
NodeCache::NodeMap::cleanup()
{
    auto it = lower_bound(InfoHash::getRandom());
    for (size_t n = 0, maxNodes = std::min(size(), CLEANUP_MAX_NODES); n != maxNodes; n++) {
        if (it == end())
            it = begin();
        if (it->second.expired())
            erase(it++);
        else
            ++it;
    }
}

} // namespace dht