Validations.h

//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2012-2017 Ripple Labs Inc.
 
    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.
 
    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================
 
#ifndef RIPPLE_CONSENSUS_VALIDATIONS_H_INCLUDED
#define RIPPLE_CONSENSUS_VALIDATIONS_H_INCLUDED
 
#include <ripple/basics/Log.h>
#include <ripple/basics/UnorderedContainers.h>
#include <ripple/basics/chrono.h>
#include <ripple/beast/container/aged_container_utility.h>
#include <ripple/beast/container/aged_unordered_map.h>
#include <ripple/consensus/LedgerTrie.h>
#include <ripple/protocol/PublicKey.h>
#include <boost/optional.hpp>
#include <mutex>
#include <utility>
#include <vector>
 
namespace ripple {
 
struct ValidationParms
{
    explicit ValidationParms() = default;
 
    std::chrono::seconds validationCURRENT_WALL = std::chrono::minutes{5};
 
    std::chrono::seconds validationCURRENT_LOCAL = std::chrono::minutes{3};
 
    std::chrono::seconds validationCURRENT_EARLY = std::chrono::minutes{3};
 
    std::chrono::seconds validationSET_EXPIRES = std::chrono::minutes{10};
 
    std::chrono::seconds validationFRESHNESS = std::chrono::seconds{20};
};
 
template <class Seq>
class SeqEnforcer
{
    using time_point = std::chrono::steady_clock::time_point;
    Seq seq_{0};
    time_point when_;
 
public:
    bool
    operator()(time_point now, Seq s, ValidationParms const& p)
    {
        if (now > (when_ + p.validationSET_EXPIRES))
            seq_ = Seq{0};
        if (s <= seq_)
            return false;
        seq_ = s;
        when_ = now;
        return true;
    }
 
    Seq
    largest() const
    {
        return seq_;
    }
};
inline bool
isCurrent(
    ValidationParms const& p,
    NetClock::time_point now,
    NetClock::time_point signTime,
    NetClock::time_point seenTime)
{
    // Because this can be called on untrusted, possibly
    // malicious validations, we do our math in a way
    // that avoids any chance of overflowing or underflowing
    // the signing time.
 
    return (signTime > (now - p.validationCURRENT_EARLY)) &&
        (signTime < (now + p.validationCURRENT_WALL)) &&
        ((seenTime == NetClock::time_point{}) ||
         (seenTime < (now + p.validationCURRENT_LOCAL)));
}
 
enum class ValStatus {
    current,
    stale,
    badSeq,
    multiple,
    conflicting
};
 
inline std::string
to_string(ValStatus m)
{
    switch (m)
    {
        case ValStatus::current:
            return "current";
        case ValStatus::stale:
            return "stale";
        case ValStatus::badSeq:
            return "badSeq";
        case ValStatus::multiple:
            return "multiple";
        case ValStatus::conflicting:
            return "conflicting";
        default:
            return "unknown";
    }
}
 
template <class Adaptor>
class Validations
{
    using Mutex = typename Adaptor::Mutex;
    using Validation = typename Adaptor::Validation;
    using Ledger = typename Adaptor::Ledger;
    using ID = typename Ledger::ID;
    using Seq = typename Ledger::Seq;
    using NodeID = typename Validation::NodeID;
    using NodeKey = typename Validation::NodeKey;
 
    using WrappedValidationType = std::decay_t<
        std::result_of_t<decltype (&Validation::unwrap)(Validation)>>;
 
    // Manages concurrent access to members
    mutable Mutex mutex_;
 
    // Validations from currently listed and trusted nodes (partial and full)
    hash_map<NodeID, Validation> current_;
 
    // Used to enforce the largest validation invariant for the local node
    SeqEnforcer<Seq> localSeqEnforcer_;
 
    // Sequence of the largest validation received from each node
    hash_map<NodeID, SeqEnforcer<Seq>> seqEnforcers_;
 
    beast::aged_unordered_map<
        ID,
        hash_map<NodeID, Validation>,
        std::chrono::steady_clock,
        beast::uhash<>>
        byLedger_;
 
    // Partial and full validations indexed by sequence
    beast::aged_unordered_map<
        Seq,
        hash_map<NodeID, Validation>,
        std::chrono::steady_clock,
        beast::uhash<>>
        bySequence_;
 
    // Sequence of the earliest validation to keep from expire
    boost::optional<Seq> toKeep_;
 
    // Represents the ancestry of validated ledgers
    LedgerTrie<Ledger> trie_;
 
    // Last (validated) ledger successfully acquired. If in this map, it is
    // accounted for in the trie.
    hash_map<NodeID, Ledger> lastLedger_;
 
    // Set of ledgers being acquired from the network
    hash_map<std::pair<Seq, ID>, hash_set<NodeID>> acquiring_;
 
    // Parameters to determine validation staleness
    ValidationParms const parms_;
 
    // Adaptor instance
    // Is NOT managed by the mutex_ above
    Adaptor adaptor_;
 
private:
    // Remove support of a validated ledger
    void
    removeTrie(
        std::lock_guard<Mutex> const&,
        NodeID const& nodeID,
        Validation const& val)
    {
        {
            auto it =
                acquiring_.find(std::make_pair(val.seq(), val.ledgerID()));
            if (it != acquiring_.end())
            {
                it->second.erase(nodeID);
                if (it->second.empty())
                    acquiring_.erase(it);
            }
        }
        {
            auto it = lastLedger_.find(nodeID);
            if (it != lastLedger_.end() && it->second.id() == val.ledgerID())
            {
                trie_.remove(it->second);
                lastLedger_.erase(nodeID);
            }
        }
    }
 
    // Check if any pending acquire ledger requests are complete
    void
    checkAcquired(std::lock_guard<Mutex> const& lock)
    {
        for (auto it = acquiring_.begin(); it != acquiring_.end();)
        {
            if (boost::optional<Ledger> ledger =
                    adaptor_.acquire(it->first.second))
            {
                for (NodeID const& nodeID : it->second)
                    updateTrie(lock, nodeID, *ledger);
 
                it = acquiring_.erase(it);
            }
            else
                ++it;
        }
    }
 
    // Update the trie to reflect a new validated ledger
    void
    updateTrie(
        std::lock_guard<Mutex> const&,
        NodeID const& nodeID,
        Ledger ledger)
    {
        auto const [it, inserted] = lastLedger_.emplace(nodeID, ledger);
        if (!inserted)
        {
            trie_.remove(it->second);
            it->second = ledger;
        }
        trie_.insert(ledger);
    }
 
    void
    updateTrie(
        std::lock_guard<Mutex> const& lock,
        NodeID const& nodeID,
        Validation const& val,
        boost::optional<std::pair<Seq, ID>> prior)
    {
        assert(val.trusted());
 
        // Clear any prior acquiring ledger for this node
        if (prior)
        {
            auto it = acquiring_.find(*prior);
            if (it != acquiring_.end())
            {
                it->second.erase(nodeID);
                if (it->second.empty())
                    acquiring_.erase(it);
            }
        }
 
        checkAcquired(lock);
 
        std::pair<Seq, ID> valPair{val.seq(), val.ledgerID()};
        auto it = acquiring_.find(valPair);
        if (it != acquiring_.end())
        {
            it->second.insert(nodeID);
        }
        else
        {
            if (boost::optional<Ledger> ledger =
                    adaptor_.acquire(val.ledgerID()))
                updateTrie(lock, nodeID, *ledger);
            else
                acquiring_[valPair].insert(nodeID);
        }
    }
 
    template <class F>
    auto
    withTrie(std::lock_guard<Mutex> const& lock, F&& f)
    {
        // Call current to flush any stale validations
        current(
            lock, [](auto) {}, [](auto, auto) {});
        checkAcquired(lock);
        return f(trie_);
    }
 
    template <class Pre, class F>
    void
    current(std::lock_guard<Mutex> const& lock, Pre&& pre, F&& f)
    {
        NetClock::time_point t = adaptor_.now();
        pre(current_.size());
        auto it = current_.begin();
        while (it != current_.end())
        {
            // Check for staleness
            if (!isCurrent(
                    parms_, t, it->second.signTime(), it->second.seenTime()))
            {
                removeTrie(lock, it->first, it->second);
                it = current_.erase(it);
            }
            else
            {
                auto cit = typename decltype(current_)::const_iterator{it};
                // contains a live record
                f(cit->first, cit->second);
                ++it;
            }
        }
    }
 
    template <class Pre, class F>
    void
    byLedger(
        std::lock_guard<Mutex> const&,
        ID const& ledgerID,
        Pre&& pre,
        F&& f)
    {
        auto it = byLedger_.find(ledgerID);
        if (it != byLedger_.end())
        {
            // Update set time since it is being used
            byLedger_.touch(it);
            pre(it->second.size());
            for (auto const& [key, val] : it->second)
                f(key, val);
        }
    }
 
public:
    template <class... Ts>
    Validations(
        ValidationParms const& p,
        beast::abstract_clock<std::chrono::steady_clock>& c,
        Ts&&... ts)
        : byLedger_(c)
        , bySequence_(c)
        , parms_(p)
        , adaptor_(std::forward<Ts>(ts)...)
    {
    }
 
    Adaptor const&
    adaptor() const
    {
        return adaptor_;
    }
 
    ValidationParms const&
    parms() const
    {
        return parms_;
    }
 
    bool
    canValidateSeq(Seq const s)
    {
        std::lock_guard lock{mutex_};
        return localSeqEnforcer_(byLedger_.clock().now(), s, parms_);
    }
 
    ValStatus
    add(NodeID const& nodeID, Validation const& val)
    {
        if (!isCurrent(parms_, adaptor_.now(), val.signTime(), val.seenTime()))
            return ValStatus::stale;
 
        {
            std::lock_guard lock{mutex_};
 
            // Check that validation sequence is greater than any non-expired
            // validations sequence from that validator; if it's not, perform
            // additional work to detect Byzantine validations
            auto const now = byLedger_.clock().now();
 
            auto const [seqit, seqinserted] =
                bySequence_[val.seq()].emplace(nodeID, val);
 
            if (!seqinserted)
            {
                // Check if the entry we're already tracking was signed
                // long enough ago that we can disregard it.
                auto const diff =
                    std::max(seqit->second.signTime(), val.signTime()) -
                    std::min(seqit->second.signTime(), val.signTime());
 
                if (diff > parms_.validationCURRENT_WALL &&
                    val.signTime() > seqit->second.signTime())
                    seqit->second = val;
            }
 
            // Enforce monotonically increasing sequences for validations
            // by a given node:
            if (auto& enf = seqEnforcers_[nodeID]; !enf(now, val.seq(), parms_))
            {
                // If the validation is for the same sequence as one we are
                // tracking, check it closely:
                if (seqit->second.seq() == val.seq())
                {
                    // Two validations for the same sequence but for different
                    // ledgers. This could be the result of misconfiguration
                    // but it can also mean a Byzantine validator.
                    if (seqit->second.ledgerID() != val.ledgerID())
                        return ValStatus::conflicting;
 
                    // Two validations for the same sequence but with different
                    // cookies. This is probably accidental misconfiguration.
                    if (seqit->second.cookie() != val.cookie())
                        return ValStatus::multiple;
                }
 
                return ValStatus::badSeq;
            }
 
            byLedger_[val.ledgerID()].insert_or_assign(nodeID, val);
 
            auto const [it, inserted] = current_.emplace(nodeID, val);
            if (!inserted)
            {
                // Replace existing only if this one is newer
                Validation& oldVal = it->second;
                if (val.signTime() > oldVal.signTime())
                {
                    std::pair<Seq, ID> old(oldVal.seq(), oldVal.ledgerID());
                    it->second = val;
                    if (val.trusted())
                        updateTrie(lock, nodeID, val, old);
                }
                else
                    return ValStatus::stale;
            }
            else if (val.trusted())
            {
                updateTrie(lock, nodeID, val, boost::none);
            }
        }
 
        return ValStatus::current;
    }
 
    void
    setSeqToKeep(Seq const& s)
    {
        std::lock_guard lock{mutex_};
        toKeep_ = s;
    }
 
    void
    expire()
    {
        std::lock_guard lock{mutex_};
        if (toKeep_)
        {
            for (auto i = byLedger_.begin(); i != byLedger_.end(); ++i)
            {
                auto const& validationMap = i->second;
                if (!validationMap.empty() &&
                    validationMap.begin()->second.seq() >= toKeep_)
                {
                    byLedger_.touch(i);
                }
            }
 
            for (auto i = bySequence_.begin(); i != bySequence_.end(); ++i)
            {
                if (i->first >= toKeep_)
                {
                    bySequence_.touch(i);
                }
            }
        }
 
        beast::expire(byLedger_, parms_.validationSET_EXPIRES);
        beast::expire(bySequence_, parms_.validationSET_EXPIRES);
    }
 
    void
    trustChanged(hash_set<NodeID> const& added, hash_set<NodeID> const& removed)
    {
        std::lock_guard lock{mutex_};
 
        for (auto& [nodeId, validation] : current_)
        {
            if (added.find(nodeId) != added.end())
            {
                validation.setTrusted();
                updateTrie(lock, nodeId, validation, boost::none);
            }
            else if (removed.find(nodeId) != removed.end())
            {
                validation.setUntrusted();
                removeTrie(lock, nodeId, validation);
            }
        }
 
        for (auto& [_, validationMap] : byLedger_)
        {
            (void)_;
            for (auto& [nodeId, validation] : validationMap)
            {
                if (added.find(nodeId) != added.end())
                {
                    validation.setTrusted();
                }
                else if (removed.find(nodeId) != removed.end())
                {
                    validation.setUntrusted();
                }
            }
        }
    }
 
    Json::Value
    getJsonTrie() const
    {
        std::lock_guard lock{mutex_};
        return trie_.getJson();
    }
 
    boost::optional<std::pair<Seq, ID>>
    getPreferred(Ledger const& curr)
    {
        std::lock_guard lock{mutex_};
        boost::optional<SpanTip<Ledger>> preferred =
            withTrie(lock, [this](LedgerTrie<Ledger>& trie) {
                return trie.getPreferred(localSeqEnforcer_.largest());
            });
        // No trusted validations to determine branch
        if (!preferred)
        {
            // fall back to majority over acquiring ledgers
            auto it = std::max_element(
                acquiring_.begin(),
                acquiring_.end(),
                [](auto const& a, auto const& b) {
                    std::pair<Seq, ID> const& aKey = a.first;
                    typename hash_set<NodeID>::size_type const& aSize =
                        a.second.size();
                    std::pair<Seq, ID> const& bKey = b.first;
                    typename hash_set<NodeID>::size_type const& bSize =
                        b.second.size();
                    // order by number of trusted peers validating that ledger
                    // break ties with ledger ID
                    return std::tie(aSize, aKey.second) <
                        std::tie(bSize, bKey.second);
                });
            if (it != acquiring_.end())
                return it->first;
            return boost::none;
        }
 
        // If we are the parent of the preferred ledger, stick with our
        // current ledger since we might be about to generate it
        if (preferred->seq == curr.seq() + Seq{1} &&
            preferred->ancestor(curr.seq()) == curr.id())
            return std::make_pair(curr.seq(), curr.id());
 
        // A ledger ahead of us is preferred regardless of whether it is
        // a descendant of our working ledger or it is on a different chain
        if (preferred->seq > curr.seq())
            return std::make_pair(preferred->seq, preferred->id);
 
        // Only switch to earlier or same sequence number
        // if it is a different chain.
        if (curr[preferred->seq] != preferred->id)
            return std::make_pair(preferred->seq, preferred->id);
 
        // Stick with current ledger
        return std::make_pair(curr.seq(), curr.id());
    }
 
    ID
    getPreferred(Ledger const& curr, Seq minValidSeq)
    {
        boost::optional<std::pair<Seq, ID>> preferred = getPreferred(curr);
        if (preferred && preferred->first >= minValidSeq)
            return preferred->second;
        return curr.id();
    }
 
    ID
    getPreferredLCL(
        Ledger const& lcl,
        Seq minSeq,
        hash_map<ID, std::uint32_t> const& peerCounts)
    {
        boost::optional<std::pair<Seq, ID>> preferred = getPreferred(lcl);
 
        // Trusted validations exist, but stick with local preferred ledger if
        // preferred is in the past
        if (preferred)
            return (preferred->first >= minSeq) ? preferred->second : lcl.id();
 
        // Otherwise, rely on peer ledgers
        auto it = std::max_element(
            peerCounts.begin(), peerCounts.end(), [](auto& a, auto& b) {
                // Prefer larger counts, then larger ids on ties
                // (max_element expects this to return true if a < b)
                return std::tie(a.second, a.first) <
                    std::tie(b.second, b.first);
            });
 
        if (it != peerCounts.end())
            return it->first;
        return lcl.id();
    }
 
    std::size_t
    getNodesAfter(Ledger const& ledger, ID const& ledgerID)
    {
        std::lock_guard lock{mutex_};
 
        // Use trie if ledger is the right one
        if (ledger.id() == ledgerID)
            return withTrie(lock, [&ledger](LedgerTrie<Ledger>& trie) {
                return trie.branchSupport(ledger) - trie.tipSupport(ledger);
            });
 
        // Count parent ledgers as fallback
        return std::count_if(
            lastLedger_.begin(),
            lastLedger_.end(),
            [&ledgerID](auto const& it) {
                auto const& curr = it.second;
                return curr.seq() > Seq{0} &&
                    curr[curr.seq() - Seq{1}] == ledgerID;
            });
    }
 
    std::vector<WrappedValidationType>
    currentTrusted()
    {
        std::vector<WrappedValidationType> ret;
        std::lock_guard lock{mutex_};
        current(
            lock,
            [&](std::size_t numValidations) { ret.reserve(numValidations); },
            [&](NodeID const&, Validation const& v) {
                if (v.trusted() && v.full())
                    ret.push_back(v.unwrap());
            });
        return ret;
    }
 
    auto
    getCurrentNodeIDs() -> hash_set<NodeID>
    {
        hash_set<NodeID> ret;
        std::lock_guard lock{mutex_};
        current(
            lock,
            [&](std::size_t numValidations) { ret.reserve(numValidations); },
            [&](NodeID const& nid, Validation const&) { ret.insert(nid); });
 
        return ret;
    }
 
    std::size_t
    numTrustedForLedger(ID const& ledgerID)
    {
        std::size_t count = 0;
        std::lock_guard lock{mutex_};
        byLedger(
            lock,
            ledgerID,
            [&](std::size_t) {},  // nothing to reserve
            [&](NodeID const&, Validation const& v) {
                if (v.trusted() && v.full())
                    ++count;
            });
        return count;
    }
 
    std::vector<WrappedValidationType>
    getTrustedForLedger(ID const& ledgerID)
    {
        std::vector<WrappedValidationType> res;
        std::lock_guard lock{mutex_};
        byLedger(
            lock,
            ledgerID,
            [&](std::size_t numValidations) { res.reserve(numValidations); },
            [&](NodeID const&, Validation const& v) {
                if (v.trusted() && v.full())
                    res.emplace_back(v.unwrap());
            });
 
        return res;
    }
 
    std::vector<std::uint32_t>
    fees(ID const& ledgerID, std::uint32_t baseFee)
    {
        std::vector<std::uint32_t> res;
        std::lock_guard lock{mutex_};
        byLedger(
            lock,
            ledgerID,
            [&](std::size_t numValidations) { res.reserve(numValidations); },
            [&](NodeID const&, Validation const& v) {
                if (v.trusted() && v.full())
                {
                    boost::optional<std::uint32_t> loadFee = v.loadFee();
                    if (loadFee)
                        res.push_back(*loadFee);
                    else
                        res.push_back(baseFee);
                }
            });
        return res;
    }
 
    void
    flush()
    {
        std::lock_guard lock{mutex_};
        current_.clear();
    }
 
    std::size_t
    laggards(Seq const seq, hash_set<NodeKey>& trustedKeys)
    {
        std::size_t laggards = 0;
 
        current(
            std::lock_guard{mutex_},
            [](std::size_t) {},
            [&](NodeID const&, Validation const& v) {
                if (adaptor_.now() <
                        v.seenTime() + parms_.validationFRESHNESS &&
                    trustedKeys.find(v.key()) != trustedKeys.end())
                {
                    trustedKeys.erase(v.key());
                    if (seq > v.seq())
                        ++laggards;
                }
            });
 
        return laggards;
    }
};
 
}  // namespace ripple
#endif