BRPeerManager.c

//
//  BRPeerManager.c
//
//  Created by Aaron Voisine on 9/2/15.
//  Copyright (c) 2015 breadwallet LLC.
//
//  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 "BRPeerManager.h"
#include "BRBloomFilter.h"
#include "BRSet.h"
#include "BRArray.h"
#include "BRInt.h"
#include <stdlib.h>
#include <stdio.h>
#include <inttypes.h>
#include <limits.h>
#include <time.h>
#include <assert.h>
#include <pthread.h>
#include <errno.h>
#include <netdb.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define PROTOCOL_TIMEOUT      20.0
#define MAX_CONNECT_FAILURES  20 // notify user of network problems after this many connect failures in a row
#define PEER_FLAG_SYNCED      0x01
#define PEER_FLAG_NEEDSUPDATE 0x02

#define genesis_block_hash(params) UInt256Reverse((params)->checkpoints[0].hash)

typedef struct {
    BRPeerManager *manager;
    const char *hostname;
    uint64_t services;
} BRFindPeersInfo;

typedef struct {
    BRPeer *peer;
    BRPeerManager *manager;
    UInt256 hash;
} BRPeerCallbackInfo;

typedef struct {
    BRTransaction *tx;
    void *info;
    void (*callback)(void *info, int error);
} BRPublishedTx;

typedef struct {
    UInt256 txHash;
    BRPeer *peers;
} BRTxPeerList;

// true if peer is contained in the list of peers associated with txHash
static int _BRTxPeerListHasPeer(const BRTxPeerList *list, UInt256 txHash, const BRPeer *peer)
{
    for (size_t i = array_count(list); i > 0; i--) {
        if (! UInt256Eq(list[i - 1].txHash, txHash)) continue;

        for (size_t j = array_count(list[i - 1].peers); j > 0; j--) {
            if (BRPeerEq(&list[i - 1].peers[j - 1], peer)) return 1;
        }
        
        break;
    }
    
    return 0;
}

// number of peers associated with txHash
static size_t _BRTxPeerListCount(const BRTxPeerList *list, UInt256 txHash)
{
    for (size_t i = array_count(list); i > 0; i--) {
        if (UInt256Eq(list[i - 1].txHash, txHash)) return array_count(list[i - 1].peers);
    }
    
    return 0;
}

// adds peer to the list of peers associated with txHash and returns the new total number of peers
static size_t _BRTxPeerListAddPeer(BRTxPeerList **list, UInt256 txHash, const BRPeer *peer)
{
    for (size_t i = array_count(*list); i > 0; i--) {
        if (! UInt256Eq((*list)[i - 1].txHash, txHash)) continue;
        
        for (size_t j = array_count((*list)[i - 1].peers); j > 0; j--) {
            if (BRPeerEq(&(*list)[i - 1].peers[j - 1], peer)) return array_count((*list)[i - 1].peers);
        }
        
        array_add((*list)[i - 1].peers, *peer);
        return array_count((*list)[i - 1].peers);
    }

    array_add(*list, ((BRTxPeerList) { txHash, NULL }));
    array_new((*list)[array_count(*list) - 1].peers, PEER_MAX_CONNECTIONS);
    array_add((*list)[array_count(*list) - 1].peers, *peer);
    return 1;
}

// removes peer from the list of peers associated with txHash, returns true if peer was found
static int _BRTxPeerListRemovePeer(BRTxPeerList *list, UInt256 txHash, const BRPeer *peer)
{
    for (size_t i = array_count(list); i > 0; i--) {
        if (! UInt256Eq(list[i - 1].txHash, txHash)) continue;
        
        for (size_t j = array_count(list[i - 1].peers); j > 0; j--) {
            if (! BRPeerEq(&list[i - 1].peers[j - 1], peer)) continue;
            array_rm(list[i - 1].peers, j - 1);
            return 1;
        }
        
        break;
    }
    
    return 0;
}

// comparator for sorting peers by timestamp, most recent first
inline static int _peerTimestampCompare(const void *peer, const void *otherPeer)
{
    if (((const BRPeer *)peer)->timestamp < ((const BRPeer *)otherPeer)->timestamp) return 1;
    if (((const BRPeer *)peer)->timestamp > ((const BRPeer *)otherPeer)->timestamp) return -1;
    return 0;
}

// returns a hash value for a block's prevBlock value suitable for use in a hashtable
inline static size_t _BRPrevBlockHash(const void *block)
{
    return (size_t)((const BRMerkleBlock *)block)->prevBlock.u32[0];
}

// true if block and otherBlock have equal prevBlock values
inline static int _BRPrevBlockEq(const void *block, const void *otherBlock)
{
    return UInt256Eq(((const BRMerkleBlock *)block)->prevBlock, ((const BRMerkleBlock *)otherBlock)->prevBlock);
}

// returns a hash value for a block's height value suitable for use in a hashtable
inline static size_t _BRBlockHeightHash(const void *block)
{
    // (FNV_OFFSET xor height)*FNV_PRIME
    return (size_t)((0x811C9dc5 ^ ((const BRMerkleBlock *)block)->height)*0x01000193);
}

// true if block and otherBlock have equal height values
inline static int _BRBlockHeightEq(const void *block, const void *otherBlock)
{
    return (((const BRMerkleBlock *)block)->height == ((const BRMerkleBlock *)otherBlock)->height);
}

struct BRPeerManagerStruct {
    const BRChainParams *params;
    BRWallet *wallet;
    int isConnected, connectFailureCount, misbehavinCount, dnsThreadCount, maxConnectCount;
    BRPeer *peers, *downloadPeer, fixedPeer, **connectedPeers;
    char downloadPeerName[INET6_ADDRSTRLEN + 6];
    uint32_t earliestKeyTime, syncStartHeight, filterUpdateHeight, estimatedHeight;
    BRBloomFilter *bloomFilter;
    double fpRate, averageTxPerBlock;
    BRSet *blocks, *orphans, *checkpoints;
    BRMerkleBlock *lastBlock, *lastOrphan;
    BRTxPeerList *txRelays, *txRequests;
    BRPublishedTx *publishedTx;
    UInt256 *publishedTxHashes;
    void *info;
    void (*syncStarted)(void *info);
    void (*syncStopped)(void *info, int error);
    void (*txStatusUpdate)(void *info);
    void (*saveBlocks)(void *info, int replace, BRMerkleBlock *blocks[], size_t blocksCount);
    void (*savePeers)(void *info, int replace, const BRPeer peers[], size_t peersCount);
    int (*networkIsReachable)(void *info);
    void (*threadCleanup)(void *info);
    pthread_mutex_t lock;
};

static void _BRPeerManagerPeerMisbehavin(BRPeerManager *manager, BRPeer *peer)
{
    for (size_t i = array_count(manager->peers); i > 0; i--) {
        if (BRPeerEq(&manager->peers[i - 1], peer)) array_rm(manager->peers, i - 1);
    }

    if (++manager->misbehavinCount >= 10) { // clear out stored peers so we get a fresh list from DNS for next connect
        manager->misbehavinCount = 0;
        array_clear(manager->peers);
    }

    BRPeerDisconnect(peer);
}

static void _BRPeerManagerSyncStopped(BRPeerManager *manager)
{
    manager->syncStartHeight = 0;

    if (manager->downloadPeer) {
        // don't cancel timeout if there's a pending tx publish callback
        for (size_t i = array_count(manager->publishedTx); i > 0; i--) {
            if (manager->publishedTx[i - 1].callback != NULL) return;
        }
    
        BRPeerScheduleDisconnect(manager->downloadPeer, -1); // cancel sync timeout
    }
}

// adds transaction to list of tx to be published, along with any unconfirmed inputs
static void _BRPeerManagerAddTxToPublishList(BRPeerManager *manager, BRTransaction *tx, void *info,
                                             void (*callback)(void *, int))
{
    if (tx && tx->blockHeight == TX_UNCONFIRMED) {
        for (size_t i = array_count(manager->publishedTx); i > 0; i--) {
            if (BRTransactionEq(manager->publishedTx[i - 1].tx, tx)) return;
        }
        
        array_add(manager->publishedTx, ((BRPublishedTx) { tx, info, callback }));
        array_add(manager->publishedTxHashes, tx->txHash);

        for (size_t i = 0; i < tx->inCount; i++) {
            _BRPeerManagerAddTxToPublishList(manager, BRWalletTransactionForHash(manager->wallet, tx->inputs[i].txHash),
                                             NULL, NULL);
        }
    }
}

static size_t _BRPeerManagerBlockLocators(BRPeerManager *manager, UInt256 locators[], size_t locatorsCount)
{
    // append 10 most recent block hashes, decending, then continue appending, doubling the step back each time,
    // finishing with the genesis block (top, -1, -2, -3, -4, -5, -6, -7, -8, -9, -11, -15, -23, -39, -71, -135, ..., 0)
    BRMerkleBlock *block = manager->lastBlock;
    int32_t step = 1, i = 0, j;
    
    while (block && block->height > 0) {
        if (locators && i < locatorsCount) locators[i] = block->blockHash;
        if (++i >= 10) step *= 2;
        
        for (j = 0; block && j < step; j++) {
            block = BRSetGet(manager->blocks, &block->prevBlock);
        }
    }
    
    if (locators && i < locatorsCount) locators[i] = genesis_block_hash(manager->params);
    return ++i;
}

static void _setApplyFreeBlock(void *info, void *block)
{
    BRMerkleBlockFree(block);
}

static void _BRPeerManagerLoadBloomFilter(BRPeerManager *manager, BRPeer *peer)
{
    // every time a new wallet address is added, the bloom filter has to be rebuilt, and each address is only used
    // for one transaction, so here we generate some spare addresses to avoid rebuilding the filter each time a
    // wallet transaction is encountered during the chain sync
    BRWalletUnusedAddrs(manager->wallet, NULL, SEQUENCE_GAP_LIMIT_EXTERNAL + 100, 0);
    BRWalletUnusedAddrs(manager->wallet, NULL, SEQUENCE_GAP_LIMIT_INTERNAL + 100, 1);

    BRSetApply(manager->orphans, NULL, _setApplyFreeBlock);
    BRSetClear(manager->orphans); // clear out orphans that may have been received on an old filter
    manager->lastOrphan = NULL;
    manager->filterUpdateHeight = manager->lastBlock->height;
    manager->fpRate = BLOOM_REDUCED_FALSEPOSITIVE_RATE;
    
    size_t addrsCount = BRWalletAllAddrs(manager->wallet, NULL, 0);
    BRAddress *addrs = malloc(addrsCount*sizeof(*addrs));
    size_t utxosCount = BRWalletUTXOs(manager->wallet, NULL, 0);
    BRUTXO *utxos = malloc(utxosCount*sizeof(*utxos));
    uint32_t blockHeight = (manager->lastBlock->height > 100) ? manager->lastBlock->height - 100 : 0;
    size_t txCount = BRWalletTxUnconfirmedBefore(manager->wallet, NULL, 0, blockHeight);
    BRTransaction **transactions = malloc(txCount*sizeof(*transactions));
    BRBloomFilter *filter;
    
    assert(addrs != NULL);
    assert(utxos != NULL);
    assert(transactions != NULL);
    addrsCount = BRWalletAllAddrs(manager->wallet, addrs, addrsCount);
    utxosCount = BRWalletUTXOs(manager->wallet, utxos, utxosCount);
    txCount = BRWalletTxUnconfirmedBefore(manager->wallet, transactions, txCount, blockHeight);
    filter = BRBloomFilterNew(manager->fpRate, addrsCount + utxosCount + txCount + 100, (uint32_t)BRPeerHash(peer),
                              BLOOM_UPDATE_ALL); // BUG: XXX txCount not the same as number of spent wallet outputs
    
    for (size_t i = 0; i < addrsCount; i++) { // add addresses to watch for tx receiveing money to the wallet
        UInt160 hash = UINT160_ZERO;
        
        BRAddressHash160(&hash, addrs[i].s);
        
        if (! UInt160IsZero(hash) && ! BRBloomFilterContainsData(filter, hash.u8, sizeof(hash))) {
            BRBloomFilterInsertData(filter, hash.u8, sizeof(hash));
        }
    }

    free(addrs);
        
    for (size_t i = 0; i < utxosCount; i++) { // add UTXOs to watch for tx sending money from the wallet
        uint8_t o[sizeof(UInt256) + sizeof(uint32_t)];
        
        UInt256Set(o, utxos[i].hash);
        UInt32SetLE(&o[sizeof(UInt256)], utxos[i].n);
        if (! BRBloomFilterContainsData(filter, o, sizeof(o))) BRBloomFilterInsertData(filter, o, sizeof(o));
    }
    
    free(utxos);
        
    for (size_t i = 0; i < txCount; i++) { // also add TXOs spent within the last 100 blocks
        for (size_t j = 0; j < transactions[i]->inCount; j++) {
            BRTxInput *input = &transactions[i]->inputs[j];
            BRTransaction *tx = BRWalletTransactionForHash(manager->wallet, input->txHash);
            uint8_t o[sizeof(UInt256) + sizeof(uint32_t)];
            
            if (tx && input->index < tx->outCount &&
                BRWalletContainsAddress(manager->wallet, tx->outputs[input->index].address)) {
                UInt256Set(o, input->txHash);
                UInt32SetLE(&o[sizeof(UInt256)], input->index);
                if (! BRBloomFilterContainsData(filter, o, sizeof(o))) BRBloomFilterInsertData(filter, o,sizeof(o));
            }
        }
    }
    
    free(transactions);
    if (manager->bloomFilter) BRBloomFilterFree(manager->bloomFilter);
    manager->bloomFilter = filter;
    // TODO: XXX if already synced, recursively add inputs of unconfirmed receives

    uint8_t data[BRBloomFilterSerialize(filter, NULL, 0)];
    size_t len = BRBloomFilterSerialize(filter, data, sizeof(data));
    
    BRPeerSendFilterload(peer, data, len);
}

static void _updateFilterRerequestDone(void *info, int success)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    
    free(info);
    
    if (success) {
        pthread_mutex_lock(&manager->lock);

        if ((peer->flags & PEER_FLAG_NEEDSUPDATE) == 0) {
            UInt256 locators[_BRPeerManagerBlockLocators(manager, NULL, 0)];
            size_t count = _BRPeerManagerBlockLocators(manager, locators, sizeof(locators)/sizeof(*locators));
            
            BRPeerSendGetblocks(peer, locators, count, UINT256_ZERO);
        }

        pthread_mutex_unlock(&manager->lock);
    }
}

static void _updateFilterLoadDone(void *info, int success)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    BRPeerCallbackInfo *peerInfo;

    free(info);
    
    if (success) {
        pthread_mutex_lock(&manager->lock);
        BRPeerSetNeedsFilterUpdate(peer, 0);
        peer->flags &= ~PEER_FLAG_NEEDSUPDATE;
        
        if (manager->lastBlock->height < manager->estimatedHeight) { // if syncing, rerequest blocks
            peerInfo = calloc(1, sizeof(*peerInfo));
            assert(peerInfo != NULL);
            peerInfo->peer = peer;
            peerInfo->manager = manager;
            BRPeerRerequestBlocks(manager->downloadPeer, manager->lastBlock->blockHash);
            BRPeerSendPing(manager->downloadPeer, peerInfo, _updateFilterRerequestDone);
        }
        else BRPeerSendMempool(peer, NULL, 0, NULL, NULL); // if not syncing, request mempool
        
        pthread_mutex_unlock(&manager->lock);
    }
}

static void _updateFilterPingDone(void *info, int success)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    BRPeerCallbackInfo *peerInfo;
    
    if (success) {
        pthread_mutex_lock(&manager->lock);
        peer_log(peer, "updating filter with newly created wallet addresses");
        if (manager->bloomFilter) BRBloomFilterFree(manager->bloomFilter);
        manager->bloomFilter = NULL;

        if (manager->lastBlock->height < manager->estimatedHeight) { // if we're syncing, only update download peer
            if (manager->downloadPeer) {
                _BRPeerManagerLoadBloomFilter(manager, manager->downloadPeer);
                BRPeerSendPing(manager->downloadPeer, info, _updateFilterLoadDone); // wait for pong so filter is loaded
            }
            else free(info);
        }
        else {
            free(info);
            
            for (size_t i = array_count(manager->connectedPeers); i > 0; i--) {
                if (BRPeerConnectStatus(manager->connectedPeers[i - 1]) != BRPeerStatusConnected) continue;
                peerInfo = calloc(1, sizeof(*peerInfo));
                assert(peerInfo != NULL);
                peerInfo->peer = manager->connectedPeers[i - 1];
                peerInfo->manager = manager;
                _BRPeerManagerLoadBloomFilter(manager, peerInfo->peer);
                BRPeerSendPing(peerInfo->peer, peerInfo, _updateFilterLoadDone); // wait for pong so filter is loaded
            }
        }

         pthread_mutex_unlock(&manager->lock);
    }
    else free(info);
}

static void _BRPeerManagerUpdateFilter(BRPeerManager *manager)
{
    BRPeerCallbackInfo *info;

    if (manager->downloadPeer && (manager->downloadPeer->flags & PEER_FLAG_NEEDSUPDATE) == 0) {
        BRPeerSetNeedsFilterUpdate(manager->downloadPeer, 1);
        manager->downloadPeer->flags |= PEER_FLAG_NEEDSUPDATE;
        peer_log(manager->downloadPeer, "filter update needed, waiting for pong");
        info = calloc(1, sizeof(*info));
        assert(info != NULL);
        info->peer = manager->downloadPeer;
        info->manager = manager;
        // wait for pong so we're sure to include any tx already sent by the peer in the updated filter
        BRPeerSendPing(manager->downloadPeer, info, _updateFilterPingDone);
    }
}

// unconfirmed transactions that aren't in the mempools of any of connected peers have likely dropped off the network
static void _requestUnrelayedTxGetdataDone(void *info, int success)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    int isPublishing;
    size_t count = 0;

    free(info);
    pthread_mutex_lock(&manager->lock);
    if (success) peer->flags |= PEER_FLAG_SYNCED;
    
    for (size_t i = array_count(manager->connectedPeers); i > 0; i--) {
        peer = manager->connectedPeers[i - 1];
        if (BRPeerConnectStatus(peer) == BRPeerStatusConnected) count++;
        if ((peer->flags & PEER_FLAG_SYNCED) != 0) continue;
        count = 0;
        break;
    }

    // don't remove transactions until we're connected to maxConnectCount peers, and all peers have finished
    // relaying their mempools
    if (count >= manager->maxConnectCount) {
        UInt256 hash;
        size_t txCount = BRWalletTxUnconfirmedBefore(manager->wallet, NULL, 0, TX_UNCONFIRMED);
        BRTransaction *tx[(txCount*sizeof(BRTransaction *) <= 0x1000) ? txCount : 0x1000/sizeof(BRTransaction *)];
        
        txCount = BRWalletTxUnconfirmedBefore(manager->wallet, tx, sizeof(tx)/sizeof(*tx), TX_UNCONFIRMED);

        for (size_t i = txCount; i > 0; i--) {
            hash = tx[i - 1]->txHash;
            isPublishing = 0;
            
            for (size_t j = array_count(manager->publishedTx); ! isPublishing && j > 0; j--) {
                if (BRTransactionEq(manager->publishedTx[j - 1].tx, tx[i - 1]) &&
                    manager->publishedTx[j - 1].callback != NULL) isPublishing = 1;
            }
            
            if (! isPublishing && _BRTxPeerListCount(manager->txRelays, hash) == 0 &&
                _BRTxPeerListCount(manager->txRequests, hash) == 0) {
                peer_log(peer, "removing tx unconfirmed at: %d, txHash: %s", manager->lastBlock->height, u256hex(hash));
                assert(tx[i - 1]->blockHeight == TX_UNCONFIRMED);
                BRWalletRemoveTransaction(manager->wallet, hash);
            }
            else if (! isPublishing && _BRTxPeerListCount(manager->txRelays, hash) < manager->maxConnectCount) {
                // set timestamp 0 to mark as unverified
                BRWalletUpdateTransactions(manager->wallet, &hash, 1, TX_UNCONFIRMED, 0);
            }
        }
    }

    pthread_mutex_unlock(&manager->lock);
}

static void _BRPeerManagerRequestUnrelayedTx(BRPeerManager *manager, BRPeer *peer)
{
    BRPeerCallbackInfo *info;
    size_t hashCount = 0, txCount = BRWalletTxUnconfirmedBefore(manager->wallet, NULL, 0, TX_UNCONFIRMED);
    BRTransaction *tx[txCount];
    UInt256 txHashes[txCount];
    
    txCount = BRWalletTxUnconfirmedBefore(manager->wallet, tx, txCount, TX_UNCONFIRMED);
    
    for (size_t i = 0; i < txCount; i++) {
        if (! _BRTxPeerListHasPeer(manager->txRelays, tx[i]->txHash, peer) &&
            ! _BRTxPeerListHasPeer(manager->txRequests, tx[i]->txHash, peer)) {
            txHashes[hashCount++] = tx[i]->txHash;
            _BRTxPeerListAddPeer(&manager->txRequests, tx[i]->txHash, peer);
        }
    }

    if (hashCount > 0) {
        BRPeerSendGetdata(peer, txHashes, hashCount, NULL, 0);
    
        if ((peer->flags & PEER_FLAG_SYNCED) == 0) {
            info = calloc(1, sizeof(*info));
            assert(info != NULL);
            info->peer = peer;
            info->manager = manager;
            BRPeerSendPing(peer, info, _requestUnrelayedTxGetdataDone);
        }
    }
    else peer->flags |= PEER_FLAG_SYNCED;
}

static void _BRPeerManagerPublishPendingTx(BRPeerManager *manager, BRPeer *peer)
{
    for (size_t i = array_count(manager->publishedTx); i > 0; i--) {
        if (manager->publishedTx[i - 1].callback == NULL) continue;
        BRPeerScheduleDisconnect(peer, PROTOCOL_TIMEOUT); // schedule publish timeout
        break;
    }
    
    BRPeerSendInv(peer, manager->publishedTxHashes, array_count(manager->publishedTxHashes));
}

static void _mempoolDone(void *info, int success)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    int syncFinished = 0;
    
    free(info);
    
    if (success) {
        peer_log(peer, "mempool request finished");
        pthread_mutex_lock(&manager->lock);
        if (manager->syncStartHeight > 0) {
            peer_log(peer, "sync succeeded");
            syncFinished = 1;
            _BRPeerManagerSyncStopped(manager);
        }

        _BRPeerManagerRequestUnrelayedTx(manager, peer);
        BRPeerSendGetaddr(peer); // request a list of other bitcoin peers
        pthread_mutex_unlock(&manager->lock);
        if (manager->txStatusUpdate) manager->txStatusUpdate(manager->info);
        if (syncFinished && manager->syncStopped) manager->syncStopped(manager->info, 0);
    }
    else peer_log(peer, "mempool request failed");
}

static void _loadBloomFilterDone(void *info, int success)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;

    pthread_mutex_lock(&manager->lock);
    
    if (success) {
        BRPeerSendMempool(peer, manager->publishedTxHashes, array_count(manager->publishedTxHashes), info,
                          _mempoolDone);
        pthread_mutex_unlock(&manager->lock);
    }
    else {
        free(info);
        
        if (peer == manager->downloadPeer) {
            peer_log(peer, "sync succeeded");
            _BRPeerManagerSyncStopped(manager);
            pthread_mutex_unlock(&manager->lock);
            if (manager->syncStopped) manager->syncStopped(manager->info, 0);
        }
        else pthread_mutex_unlock(&manager->lock);
    }
}

static void _BRPeerManagerLoadMempools(BRPeerManager *manager)
{
    // after syncing, load filters and get mempools from other peers
    for (size_t i = array_count(manager->connectedPeers); i > 0; i--) {
        BRPeer *peer = manager->connectedPeers[i - 1];
        BRPeerCallbackInfo *info;

        if (BRPeerConnectStatus(peer) != BRPeerStatusConnected) continue;
        info = calloc(1, sizeof(*info));
        assert(info != NULL);
        info->peer = peer;
        info->manager = manager;
        
        if (peer != manager->downloadPeer || manager->fpRate > BLOOM_REDUCED_FALSEPOSITIVE_RATE*5.0) {
            _BRPeerManagerLoadBloomFilter(manager, peer);
            _BRPeerManagerPublishPendingTx(manager, peer);
            BRPeerSendPing(peer, info, _loadBloomFilterDone); // load mempool after updating bloomfilter
        }
        else BRPeerSendMempool(peer, manager->publishedTxHashes, array_count(manager->publishedTxHashes), info,
                               _mempoolDone);
    }
}

// returns a UINT128_ZERO terminated array of addresses for hostname that must be freed, or NULL if lookup failed
static UInt128 *_addressLookup(const char *hostname)
{
    struct addrinfo *servinfo, *p;
    UInt128 *addrList = NULL;
    size_t count = 0, i = 0;
    
    if (getaddrinfo(hostname, NULL, NULL, &servinfo) == 0) {
        for (p = servinfo; p != NULL; p = p->ai_next) count++;
        if (count > 0) addrList = calloc(count + 1, sizeof(*addrList));
        assert(addrList != NULL || count == 0);
        
        for (p = servinfo; p != NULL; p = p->ai_next) {
            if (p->ai_family == AF_INET) {
                addrList[i].u16[5] = 0xffff;
                addrList[i].u32[3] = ((struct sockaddr_in *)p->ai_addr)->sin_addr.s_addr;
                i++;
            }
            else if (p->ai_family == AF_INET6) {
                addrList[i++] = *(UInt128 *)&((struct sockaddr_in6 *)p->ai_addr)->sin6_addr;
            }
        }
        
        freeaddrinfo(servinfo);
    }
    
    return addrList;
}

static void *_findPeersThreadRoutine(void *arg)
{
    BRPeerManager *manager = ((BRFindPeersInfo *)arg)->manager;
    uint64_t services = ((BRFindPeersInfo *)arg)->services;
    UInt128 *addrList, *addr;
    time_t now = time(NULL), age;
    
    pthread_cleanup_push(manager->threadCleanup, manager->info);
    addrList = _addressLookup(((BRFindPeersInfo *)arg)->hostname);
    free(arg);
    pthread_mutex_lock(&manager->lock);
    
    for (addr = addrList; addr && ! UInt128IsZero(*addr); addr++) {
        age = 24*60*60 + BRRand(2*24*60*60); // add between 1 and 3 days
        array_add(manager->peers, ((BRPeer) { *addr, manager->params->standardPort, services, now - age, 0 }));
    }

    manager->dnsThreadCount--;
    pthread_mutex_unlock(&manager->lock);
    if (addrList) free(addrList);
    pthread_cleanup_pop(1);
    return NULL;
}

// DNS peer discovery
static void _BRPeerManagerFindPeers(BRPeerManager *manager)
{
    uint64_t services = SERVICES_NODE_NETWORK | SERVICES_NODE_BLOOM | manager->params->services;
    time_t now = time(NULL);
    struct timespec ts;
    pthread_t thread;
    pthread_attr_t attr;
    UInt128 *addr, *addrList;
    BRFindPeersInfo *info;
    
    if (! UInt128IsZero(manager->fixedPeer.address)) {
        array_set_count(manager->peers, 1);
        manager->peers[0] = manager->fixedPeer;
        manager->peers[0].services = services;
        manager->peers[0].timestamp = now;
    }
    else {
        for (size_t i = 1; manager->params->dnsSeeds[i]; i++) {
            info = calloc(1, sizeof(BRFindPeersInfo));
            assert(info != NULL);
            info->manager = manager;
            info->hostname = manager->params->dnsSeeds[i];
            info->services = services;
            if (pthread_attr_init(&attr) == 0 && pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED) == 0 &&
                pthread_create(&thread, &attr, _findPeersThreadRoutine, info) == 0) manager->dnsThreadCount++;
        }

        for (addr = addrList = _addressLookup(manager->params->dnsSeeds[0]); addr && ! UInt128IsZero(*addr); addr++) {
            array_add(manager->peers, ((BRPeer) { *addr, manager->params->standardPort, services, now, 0 }));
        }

        if (addrList) free(addrList);
        ts.tv_sec = 0;
        ts.tv_nsec = 1;

        do {
            pthread_mutex_unlock(&manager->lock);
            nanosleep(&ts, NULL); // pthread_yield() isn't POSIX standard :(
            pthread_mutex_lock(&manager->lock);
        } while (manager->dnsThreadCount > 0 && array_count(manager->peers) < PEER_MAX_CONNECTIONS);
    
        qsort(manager->peers, array_count(manager->peers), sizeof(*manager->peers), _peerTimestampCompare);
    }
}

static void _peerConnected(void *info)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    BRPeerCallbackInfo *peerInfo;
    time_t now = time(NULL);
    
    pthread_mutex_lock(&manager->lock);
    if (peer->timestamp > now + 2*60*60 || peer->timestamp < now - 2*60*60) peer->timestamp = now; // sanity check
    
    // TODO: XXX does this work with 0.11 pruned nodes?
    if ((peer->services & manager->params->services) != manager->params->services) {
        peer_log(peer, "unsupported node type");
        BRPeerDisconnect(peer);
    }
    else if ((peer->services & SERVICES_NODE_NETWORK) != SERVICES_NODE_NETWORK) {
        peer_log(peer, "node doesn't carry full blocks");
        BRPeerDisconnect(peer);
    }
    else if (BRPeerLastBlock(peer) + 10 < manager->lastBlock->height) {
        peer_log(peer, "node isn't synced");
        BRPeerDisconnect(peer);
    }
    else if (BRPeerVersion(peer) >= 70011 && (peer->services & SERVICES_NODE_BLOOM) != SERVICES_NODE_BLOOM) {
        peer_log(peer, "node doesn't support SPV mode");
        BRPeerDisconnect(peer);
    }
    else if (manager->downloadPeer && // check if we should stick with the existing download peer
             (BRPeerLastBlock(manager->downloadPeer) >= BRPeerLastBlock(peer) ||
              manager->lastBlock->height >= BRPeerLastBlock(peer))) {
        if (manager->lastBlock->height >= BRPeerLastBlock(peer)) { // only load bloom filter if we're done syncing
            manager->connectFailureCount = 0; // also reset connect failure count if we're already synced
            _BRPeerManagerLoadBloomFilter(manager, peer);
            _BRPeerManagerPublishPendingTx(manager, peer);
            peerInfo = calloc(1, sizeof(*peerInfo));
            assert(peerInfo != NULL);
            peerInfo->peer = peer;
            peerInfo->manager = manager;
            BRPeerSendPing(peer, peerInfo, _loadBloomFilterDone);
        }
    }
    else { // select the peer with the lowest ping time to download the chain from if we're behind
        // BUG: XXX a malicious peer can report a higher lastblock to make us select them as the download peer, if
        // two peers agree on lastblock, use one of those two instead
        for (size_t i = array_count(manager->connectedPeers); i > 0; i--) {
            BRPeer *p = manager->connectedPeers[i - 1];
            
            if (BRPeerConnectStatus(p) != BRPeerStatusConnected) continue;
            if ((BRPeerPingTime(p) < BRPeerPingTime(peer) && BRPeerLastBlock(p) >= BRPeerLastBlock(peer)) ||
                BRPeerLastBlock(p) > BRPeerLastBlock(peer)) peer = p;
        }
        
        if (manager->downloadPeer) {
            peer_log(peer, "selecting new download peer with higher reported lastblock");
            BRPeerDisconnect(manager->downloadPeer);
        }
        
        manager->downloadPeer = peer;
        manager->isConnected = 1;
        manager->estimatedHeight = BRPeerLastBlock(peer);
        _BRPeerManagerLoadBloomFilter(manager, peer);
        BRPeerSetCurrentBlockHeight(peer, manager->lastBlock->height);
        _BRPeerManagerPublishPendingTx(manager, peer);
            
        if (manager->lastBlock->height < BRPeerLastBlock(peer)) { // start blockchain sync
            UInt256 locators[_BRPeerManagerBlockLocators(manager, NULL, 0)];
            size_t count = _BRPeerManagerBlockLocators(manager, locators, sizeof(locators)/sizeof(*locators));
            
            BRPeerScheduleDisconnect(peer, PROTOCOL_TIMEOUT); // schedule sync timeout

            // request just block headers up to a week before earliestKeyTime, and then merkleblocks after that
            // we do not reset connect failure count yet incase this request times out
            if (manager->lastBlock->timestamp + 7*24*60*60 >= manager->earliestKeyTime) {
                BRPeerSendGetblocks(peer, locators, count, UINT256_ZERO);
            }
            else BRPeerSendGetheaders(peer, locators, count, UINT256_ZERO);
        }
        else { // we're already synced
            manager->connectFailureCount = 0; // reset connect failure count
            _BRPeerManagerLoadMempools(manager);
        }
    }

    pthread_mutex_unlock(&manager->lock);
}

static void _peerDisconnected(void *info, int error)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    BRTxPeerList *peerList;
    int willSave = 0, willReconnect = 0, txError = 0;
    size_t txCount = 0;
    
    //free(info);
    pthread_mutex_lock(&manager->lock);

    BRPublishedTx pubTx[array_count(manager->publishedTx)];
    
    if (error == EPROTO) { // if it's protocol error, the peer isn't following standard policy
        _BRPeerManagerPeerMisbehavin(manager, peer);
    }
    else if (error) { // timeout or some non-protocol related network error
        for (size_t i = array_count(manager->peers); i > 0; i--) {
            if (BRPeerEq(&manager->peers[i - 1], peer)) array_rm(manager->peers, i - 1);
        }
        
        manager->connectFailureCount++;
        
        // if it's a timeout and there's pending tx publish callbacks, the tx publish timed out
        // BUG: XXX what if it's a connect timeout and not a publish timeout?
        if (error == ETIMEDOUT && (peer != manager->downloadPeer || manager->syncStartHeight == 0 ||
                                   array_count(manager->connectedPeers) == 1)) txError = ETIMEDOUT;
    }
    
    for (size_t i = array_count(manager->txRelays); i > 0; i--) {
        peerList = &manager->txRelays[i - 1];

        for (size_t j = array_count(peerList->peers); j > 0; j--) {
            if (BRPeerEq(&peerList->peers[j - 1], peer)) array_rm(peerList->peers, j - 1);
        }
    }

    if (peer == manager->downloadPeer) { // download peer disconnected
        manager->isConnected = 0;
        manager->downloadPeer = NULL;
        if (manager->connectFailureCount > MAX_CONNECT_FAILURES) manager->connectFailureCount = MAX_CONNECT_FAILURES;
    }

    if (! manager->isConnected && manager->connectFailureCount == MAX_CONNECT_FAILURES) {
        _BRPeerManagerSyncStopped(manager);
        
        // clear out stored peers so we get a fresh list from DNS on next connect attempt
        array_clear(manager->peers);
        txError = ENOTCONN; // trigger any pending tx publish callbacks
        willSave = 1;
        peer_log(peer, "sync failed");
    }
    else if (manager->connectFailureCount < MAX_CONNECT_FAILURES) willReconnect = 1;
    
    if (txError) {
        for (size_t i = array_count(manager->publishedTx); i > 0; i--) {
            if (manager->publishedTx[i - 1].callback == NULL) continue;
            peer_log(peer, "transaction canceled: %s", strerror(txError));
            pubTx[txCount++] = manager->publishedTx[i - 1];
            manager->publishedTx[i - 1].callback = NULL;
            manager->publishedTx[i - 1].info = NULL;
        }
    }
    
    for (size_t i = array_count(manager->connectedPeers); i > 0; i--) {
        if (manager->connectedPeers[i - 1] != peer) continue;
        array_rm(manager->connectedPeers, i - 1);
        break;
    }

    BRPeerFree(peer);
    pthread_mutex_unlock(&manager->lock);
    
    for (size_t i = 0; i < txCount; i++) {
        pubTx[i].callback(pubTx[i].info, txError);
    }
    
    if (willSave && manager->savePeers) manager->savePeers(manager->info, 1, NULL, 0);
    if (willSave && manager->syncStopped) manager->syncStopped(manager->info, error);
    if (willReconnect) BRPeerManagerConnect(manager); // try connecting to another peer
    if (manager->txStatusUpdate) manager->txStatusUpdate(manager->info);
}

static void _peerRelayedPeers(void *info, const BRPeer peers[], size_t peersCount)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    time_t now = time(NULL);

    pthread_mutex_lock(&manager->lock);
    peer_log(peer, "relayed %zu peer(s)", peersCount);

    array_add_array(manager->peers, peers, peersCount);
    qsort(manager->peers, array_count(manager->peers), sizeof(*manager->peers), _peerTimestampCompare);

    // limit total to 2500 peers
    if (array_count(manager->peers) > 2500) array_set_count(manager->peers, 2500);
    peersCount = array_count(manager->peers);
    
    // remove peers more than 3 hours old, or until there are only 1000 left
    while (peersCount > 1000 && manager->peers[peersCount - 1].timestamp + 3*60*60 < now) peersCount--;
    array_set_count(manager->peers, peersCount);
    
    BRPeer save[peersCount];

    for (size_t i = 0; i < peersCount; i++) save[i] = manager->peers[i];
    pthread_mutex_unlock(&manager->lock);
    
    // peer relaying is complete when we receive <1000
    if (peersCount > 1 && peersCount < 1000 &&
        manager->savePeers) manager->savePeers(manager->info, 1, save, peersCount);
}

static void _peerRelayedTx(void *info, BRTransaction *tx)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    void *txInfo = NULL;
    void (*txCallback)(void *, int) = NULL;
    int isWalletTx = 0, hasPendingCallbacks = 0;
    size_t relayCount = 0;
    
    pthread_mutex_lock(&manager->lock);
    peer_log(peer, "relayed tx: %s", u256hex(tx->txHash));
    
    for (size_t i = array_count(manager->publishedTx); i > 0; i--) { // see if tx is in list of published tx
        if (UInt256Eq(manager->publishedTxHashes[i - 1], tx->txHash)) {
            txInfo = manager->publishedTx[i - 1].info;
            txCallback = manager->publishedTx[i - 1].callback;
            manager->publishedTx[i - 1].info = NULL;
            manager->publishedTx[i - 1].callback = NULL;
            relayCount = _BRTxPeerListAddPeer(&manager->txRelays, tx->txHash, peer);
        }
        else if (manager->publishedTx[i - 1].callback != NULL) hasPendingCallbacks = 1;
    }

    // cancel tx publish timeout if no publish callbacks are pending, and syncing is done or this is not downloadPeer
    if (! hasPendingCallbacks && (manager->syncStartHeight == 0 || peer != manager->downloadPeer)) {
        BRPeerScheduleDisconnect(peer, -1); // cancel publish tx timeout
    }

    if (manager->syncStartHeight == 0 || BRWalletContainsTransaction(manager->wallet, tx)) {
        isWalletTx = BRWalletRegisterTransaction(manager->wallet, tx);
        if (isWalletTx) tx = BRWalletTransactionForHash(manager->wallet, tx->txHash);
    }
    else {
        BRTransactionFree(tx);
        tx = NULL;
    }
    
    if (tx && isWalletTx) {
        // reschedule sync timeout
        if (manager->syncStartHeight > 0 && peer == manager->downloadPeer) {
            BRPeerScheduleDisconnect(peer, PROTOCOL_TIMEOUT);
        }
        
        if (BRWalletAmountSentByTx(manager->wallet, tx) > 0 && BRWalletTransactionIsValid(manager->wallet, tx)) {
            _BRPeerManagerAddTxToPublishList(manager, tx, NULL, NULL); // add valid send tx to mempool
        }

        // keep track of how many peers have or relay a tx, this indicates how likely the tx is to confirm
        // (we only need to track this after syncing is complete)
        if (manager->syncStartHeight == 0) relayCount = _BRTxPeerListAddPeer(&manager->txRelays, tx->txHash, peer);
        
        _BRTxPeerListRemovePeer(manager->txRequests, tx->txHash, peer);
        
        if (manager->bloomFilter != NULL) { // check if bloom filter is already being updated
            BRAddress addrs[SEQUENCE_GAP_LIMIT_EXTERNAL + SEQUENCE_GAP_LIMIT_INTERNAL];
            UInt160 hash;

            // the transaction likely consumed one or more wallet addresses, so check that at least the next <gap limit>
            // unused addresses are still matched by the bloom filter
            BRWalletUnusedAddrs(manager->wallet, addrs, SEQUENCE_GAP_LIMIT_EXTERNAL, 0);
            BRWalletUnusedAddrs(manager->wallet, addrs + SEQUENCE_GAP_LIMIT_EXTERNAL, SEQUENCE_GAP_LIMIT_INTERNAL, 1);

            for (size_t i = 0; i < SEQUENCE_GAP_LIMIT_EXTERNAL + SEQUENCE_GAP_LIMIT_INTERNAL; i++) {
                if (! BRAddressHash160(&hash, addrs[i].s) ||
                    BRBloomFilterContainsData(manager->bloomFilter, hash.u8, sizeof(hash))) continue;
                if (manager->bloomFilter) BRBloomFilterFree(manager->bloomFilter);
                manager->bloomFilter = NULL; // reset bloom filter so it's recreated with new wallet addresses
                _BRPeerManagerUpdateFilter(manager);
                break;
            }
        }
    }
    
    // set timestamp when tx is verified
    if (tx && relayCount >= manager->maxConnectCount && tx->blockHeight == TX_UNCONFIRMED && tx->timestamp == 0) {
        BRWalletUpdateTransactions(manager->wallet, &tx->txHash, 1, TX_UNCONFIRMED, (uint32_t)time(NULL));
    }
    
    pthread_mutex_unlock(&manager->lock);
    if (txCallback) txCallback(txInfo, 0);
}

static void _peerHasTx(void *info, UInt256 txHash)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    BRTransaction *tx;
    BRPublishedTx pubTx = { NULL, NULL, NULL };
    int isWalletTx = 0, hasPendingCallbacks = 0;
    size_t relayCount = 0;
    
    pthread_mutex_lock(&manager->lock);
    tx = BRWalletTransactionForHash(manager->wallet, txHash);
    peer_log(peer, "has tx: %s", u256hex(txHash));

    for (size_t i = array_count(manager->publishedTx); i > 0; i--) { // see if tx is in list of published tx
        if (UInt256Eq(manager->publishedTxHashes[i - 1], txHash)) {
            pubTx = manager->publishedTx[i - 1];
            if (! tx) tx = pubTx.tx;
            manager->publishedTx[i - 1].callback = NULL;
            manager->publishedTx[i - 1].info = NULL;
            relayCount = _BRTxPeerListAddPeer(&manager->txRelays, txHash, peer);
        }
        else if (manager->publishedTx[i - 1].callback != NULL) hasPendingCallbacks = 1;
    }
    
    // cancel tx publish timeout if no publish callbacks are pending, and syncing is done or this is not downloadPeer
    if (! hasPendingCallbacks && (manager->syncStartHeight == 0 || peer != manager->downloadPeer)) {
        BRPeerScheduleDisconnect(peer, -1); // cancel publish tx timeout
    }

    if (tx) {
        isWalletTx = BRWalletRegisterTransaction(manager->wallet, tx);
        if (isWalletTx) tx = BRWalletTransactionForHash(manager->wallet, tx->txHash);

        // reschedule sync timeout
        if (manager->syncStartHeight > 0 && peer == manager->downloadPeer && isWalletTx) {
            BRPeerScheduleDisconnect(peer, PROTOCOL_TIMEOUT);
        }
        
        // keep track of how many peers have or relay a tx, this indicates how likely the tx is to confirm
        // (we only need to track this after syncing is complete)
        if (manager->syncStartHeight == 0) relayCount = _BRTxPeerListAddPeer(&manager->txRelays, txHash, peer);

        // set timestamp when tx is verified
        if (relayCount >= manager->maxConnectCount && tx && tx->blockHeight == TX_UNCONFIRMED && tx->timestamp == 0) {
            BRWalletUpdateTransactions(manager->wallet, &txHash, 1, TX_UNCONFIRMED, (uint32_t)time(NULL));
        }

        _BRTxPeerListRemovePeer(manager->txRequests, txHash, peer);
    }
    
    pthread_mutex_unlock(&manager->lock);
    if (pubTx.callback) pubTx.callback(pubTx.info, 0);
}

static void _peerRejectedTx(void *info, UInt256 txHash, uint8_t code)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    BRTransaction *tx, *t;

    pthread_mutex_lock(&manager->lock);
    peer_log(peer, "rejected tx: %s", u256hex(txHash));
    tx = BRWalletTransactionForHash(manager->wallet, txHash);
    _BRTxPeerListRemovePeer(manager->txRequests, txHash, peer);

    if (tx) {
        if (_BRTxPeerListRemovePeer(manager->txRelays, txHash, peer) && tx->blockHeight == TX_UNCONFIRMED) {
            // set timestamp 0 to mark tx as unverified
            BRWalletUpdateTransactions(manager->wallet, &txHash, 1, TX_UNCONFIRMED, 0);
        }

        // if we get rejected for any reason other than double-spend, the peer is likely misconfigured
        if (code != REJECT_SPENT && BRWalletAmountSentByTx(manager->wallet, tx) > 0) {
            for (size_t i = 0; i < tx->inCount; i++) { // check that all inputs are confirmed before dropping peer
                t = BRWalletTransactionForHash(manager->wallet, tx->inputs[i].txHash);
                if (! t || t->blockHeight != TX_UNCONFIRMED) continue;
                tx = NULL;
                break;
            }
            
            if (tx) _BRPeerManagerPeerMisbehavin(manager, peer);
        }
    }

    pthread_mutex_unlock(&manager->lock);
    if (manager->txStatusUpdate) manager->txStatusUpdate(manager->info);
}

static int _BRPeerManagerVerifyBlock(BRPeerManager *manager, BRMerkleBlock *block, BRMerkleBlock *prev, BRPeer *peer)
{
    int r = 1;

    if (! prev || ! UInt256Eq(block->prevBlock, prev->blockHash) || block->height != prev->height + 1) r = 0;

    // check if we hit a difficulty transition, and find previous transition time
    if (r && (block->height % BLOCK_DIFFICULTY_INTERVAL) == 0) {
        BRMerkleBlock *b = block;
        UInt256 prevBlock;

        for (uint32_t i = 0; b && i < BLOCK_DIFFICULTY_INTERVAL; i++) {
            b = BRSetGet(manager->blocks, &b->prevBlock);
        }

        if (! b) {
            peer_log(peer, "missing previous difficulty tansition, can't verify block: %s", u256hex(block->blockHash));
            r = 0;
        }
        else prevBlock = b->prevBlock;

        while (b) { // free up some memory
            b = BRSetGet(manager->blocks, &prevBlock);
            if (b) prevBlock = b->prevBlock;

            if (b && (b->height % BLOCK_DIFFICULTY_INTERVAL) != 0) {
                BRSetRemove(manager->blocks, b);
                BRMerkleBlockFree(b);
            }
        }
    }

    // verify block difficulty
    if (r && ! manager->params->verifyDifficulty(block, manager->blocks)) {
        peer_log(peer, "relayed block with invalid difficulty target %x, blockHash: %s", block->target,
                 u256hex(block->blockHash));
        r = 0;
    }
    
    if (r) {
        BRMerkleBlock *checkpoint = BRSetGet(manager->checkpoints, block);

        // verify blockchain checkpoints
        if (checkpoint && ! BRMerkleBlockEq(block, checkpoint)) {
            peer_log(peer, "relayed a block that differs from the checkpoint at height %"PRIu32", blockHash: %s, "
                     "expected: %s", block->height, u256hex(block->blockHash), u256hex(checkpoint->blockHash));
            r = 0;
        }
    }

    return r;
}

static void _peerRelayedBlock(void *info, BRMerkleBlock *block)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    size_t txCount = BRMerkleBlockTxHashes(block, NULL, 0);
    UInt256 _txHashes[(sizeof(UInt256)*txCount <= 0x1000) ? txCount : 0],
            *txHashes = (sizeof(UInt256)*txCount <= 0x1000) ? _txHashes : malloc(txCount*sizeof(*txHashes));
    size_t i, j, fpCount = 0, saveCount = 0;
    BRMerkleBlock orphan, *b, *b2, *prev, *next = NULL;
    uint32_t txTime = 0;
    
    assert(txHashes != NULL);
    txCount = BRMerkleBlockTxHashes(block, txHashes, txCount);
    pthread_mutex_lock(&manager->lock);
    prev = BRSetGet(manager->blocks, &block->prevBlock);

    if (prev) {
        txTime = block->timestamp/2 + prev->timestamp/2;
        block->height = prev->height + 1;
    }
    
    // track the observed bloom filter false positive rate using a low pass filter to smooth out variance
    if (peer == manager->downloadPeer && block->totalTx > 0) {
        for (i = 0; i < txCount; i++) { // wallet tx are not false-positives
            if (! BRWalletTransactionForHash(manager->wallet, txHashes[i])) fpCount++;
        }
        
        // moving average number of tx-per-block
        manager->averageTxPerBlock = manager->averageTxPerBlock*0.999 + block->totalTx*0.001;
        
        // 1% low pass filter, also weights each block by total transactions, compared to the avarage
        manager->fpRate = manager->fpRate*(1.0 - 0.01*block->totalTx/manager->averageTxPerBlock) +
                          0.01*fpCount/manager->averageTxPerBlock;
        
        // false positive rate sanity check
        if (BRPeerConnectStatus(peer) == BRPeerStatusConnected &&
            manager->fpRate > BLOOM_DEFAULT_FALSEPOSITIVE_RATE*10.0) {
            peer_log(peer, "bloom filter false positive rate %f too high after %"PRIu32" blocks, disconnecting...",
                     manager->fpRate, manager->lastBlock->height + 1 - manager->filterUpdateHeight);
            BRPeerDisconnect(peer);
        }
        else if (manager->lastBlock->height + 500 < BRPeerLastBlock(peer) &&
                 manager->fpRate > BLOOM_REDUCED_FALSEPOSITIVE_RATE*10.0) {
            _BRPeerManagerUpdateFilter(manager); // rebuild bloom filter when it starts to degrade
        }
    }

    // ignore block headers that are newer than one week before earliestKeyTime (it's a header if it has 0 totalTx)
    if (block->totalTx == 0 && block->timestamp + 7*24*60*60 > manager->earliestKeyTime + 2*60*60) {
        BRMerkleBlockFree(block);
        block = NULL;
    }
    else if (manager->bloomFilter == NULL) { // ingore potentially incomplete blocks when a filter update is pending
        BRMerkleBlockFree(block);
        block = NULL;

        if (peer == manager->downloadPeer && manager->lastBlock->height < manager->estimatedHeight) {
            BRPeerScheduleDisconnect(peer, PROTOCOL_TIMEOUT); // reschedule sync timeout
            manager->connectFailureCount = 0; // reset failure count once we know our initial request didn't timeout
        }
    }
    else if (! prev) { // block is an orphan
        peer_log(peer, "relayed orphan block %s, previous %s, last block is %s, height %"PRIu32,
                 u256hex(block->blockHash), u256hex(block->prevBlock), u256hex(manager->lastBlock->blockHash),
                 manager->lastBlock->height);
        
        if (block->timestamp + 7*24*60*60 < time(NULL)) { // ignore orphans older than one week ago
            BRMerkleBlockFree(block);
            block = NULL;
        }
        else {
            // call getblocks, unless we already did with the previous block, or we're still syncing
            if (manager->lastBlock->height >= BRPeerLastBlock(peer) &&
                (! manager->lastOrphan || ! UInt256Eq(manager->lastOrphan->blockHash, block->prevBlock))) {
                UInt256 locators[_BRPeerManagerBlockLocators(manager, NULL, 0)];
                size_t locatorsCount = _BRPeerManagerBlockLocators(manager, locators,
                                                                   sizeof(locators)/sizeof(*locators));
                
                peer_log(peer, "calling getblocks");
                BRPeerSendGetblocks(peer, locators, locatorsCount, UINT256_ZERO);
            }
            
            BRSetAdd(manager->orphans, block); // BUG: limit total orphans to avoid memory exhaustion attack
            manager->lastOrphan = block;
        }
    }
    else if (! _BRPeerManagerVerifyBlock(manager, block, prev, peer)) { // block is invalid
        peer_log(peer, "relayed invalid block");
        BRMerkleBlockFree(block);
        block = NULL;
        _BRPeerManagerPeerMisbehavin(manager, peer);
    }
    else if (UInt256Eq(block->prevBlock, manager->lastBlock->blockHash)) { // new block extends main chain
        if ((block->height % 500) == 0 || txCount > 0 || block->height >= BRPeerLastBlock(peer)) {
            peer_log(peer, "adding block #%"PRIu32", false positive rate: %f", block->height, manager->fpRate);
        }
        
        BRSetAdd(manager->blocks, block);
        manager->lastBlock = block;
        if (txCount > 0) BRWalletUpdateTransactions(manager->wallet, txHashes, txCount, block->height, txTime);
        if (manager->downloadPeer) BRPeerSetCurrentBlockHeight(manager->downloadPeer, block->height);
            
        if (block->height < manager->estimatedHeight && peer == manager->downloadPeer) {
            BRPeerScheduleDisconnect(peer, PROTOCOL_TIMEOUT); // reschedule sync timeout
            manager->connectFailureCount = 0; // reset failure count once we know our initial request didn't timeout
        }
        
        if ((block->height % BLOCK_DIFFICULTY_INTERVAL) == 0) saveCount = 1; // save transition block immediately
        
        if (block->height == manager->estimatedHeight) { // chain download is complete
            saveCount = (block->height % BLOCK_DIFFICULTY_INTERVAL) + BLOCK_DIFFICULTY_INTERVAL + 1;
            _BRPeerManagerLoadMempools(manager);
        }
    }
    else if (BRSetContains(manager->blocks, block)) { // we already have the block (or at least the header)
        if ((block->height % 500) == 0 || txCount > 0 || block->height >= BRPeerLastBlock(peer)) {
            peer_log(peer, "relayed existing block #%"PRIu32, block->height);
        }
        
        b = manager->lastBlock;
        while (b && b->height > block->height) b = BRSetGet(manager->blocks, &b->prevBlock); // is block in main chain?
        
        if (BRMerkleBlockEq(b, block)) { // if it's not on a fork, set block heights for its transactions
            if (txCount > 0) BRWalletUpdateTransactions(manager->wallet, txHashes, txCount, block->height, txTime);
            if (block->height == manager->lastBlock->height) manager->lastBlock = block;
        }
        
        b = BRSetAdd(manager->blocks, block);

        if (b != block) {
            if (BRSetGet(manager->orphans, b) == b) BRSetRemove(manager->orphans, b);
            if (manager->lastOrphan == b) manager->lastOrphan = NULL;
            BRMerkleBlockFree(b);
        }
    }
    else if (manager->lastBlock->height < BRPeerLastBlock(peer) &&
             block->height > manager->lastBlock->height + 1) { // special case, new block mined durring rescan
        peer_log(peer, "marking new block #%"PRIu32" as orphan until rescan completes", block->height);
        BRSetAdd(manager->orphans, block); // mark as orphan til we're caught up
        manager->lastOrphan = block;
    }
    else if (block->height <= manager->params->checkpoints[manager->params->checkpointsCount - 1].height) { // old fork
        peer_log(peer, "ignoring block on fork older than most recent checkpoint, block #%"PRIu32", hash: %s",
                 block->height, u256hex(block->blockHash));
        BRMerkleBlockFree(block);
        block = NULL;
    }
    else { // new block is on a fork
        peer_log(peer, "chain fork reached height %"PRIu32, block->height);
        BRSetAdd(manager->blocks, block);

        // TODO: calculate chain work and use that instead of block height to determine longest chain
        if (block->height > manager->lastBlock->height) { // check if fork is now longer than main chain
            b = block;
            b2 = manager->lastBlock;
            
            while (b && b2 && ! BRMerkleBlockEq(b, b2)) { // walk back to where the fork joins the main chain
                b = BRSetGet(manager->blocks, &b->prevBlock);
                if (b && b->height < b2->height) b2 = BRSetGet(manager->blocks, &b2->prevBlock);
            }
            
            peer_log(peer, "reorganizing chain from height %"PRIu32", new height is %"PRIu32, b->height, block->height);
        
            BRWalletSetTxUnconfirmedAfter(manager->wallet, b->height); // mark tx after the join point as unconfirmed

            b = block;
        
            while (b && b2 && b->height > b2->height) { // set transaction heights for new main chain
                size_t count = BRMerkleBlockTxHashes(b, NULL, 0);
                uint32_t height = b->height, timestamp = b->timestamp;
                
                if (count > txCount) {
                    txHashes = (txHashes != _txHashes) ? realloc(txHashes, count*sizeof(*txHashes)) :
                               malloc(count*sizeof(*txHashes));
                    assert(txHashes != NULL);
                    txCount = count;
                }
                
                count = BRMerkleBlockTxHashes(b, txHashes, count);
                b = BRSetGet(manager->blocks, &b->prevBlock);
                if (b) timestamp = timestamp/2 + b->timestamp/2;
                if (count > 0) BRWalletUpdateTransactions(manager->wallet, txHashes, count, height, timestamp);
            }
        
            manager->lastBlock = block;
            
            if (block->height == manager->estimatedHeight) { // chain download is complete
                saveCount = (block->height % BLOCK_DIFFICULTY_INTERVAL) + BLOCK_DIFFICULTY_INTERVAL + 1;
                _BRPeerManagerLoadMempools(manager);
            }
        }
    }
   
    if (txHashes != _txHashes) free(txHashes);
   
    if (block && block->height != BLOCK_UNKNOWN_HEIGHT) {
        if (block->height > manager->estimatedHeight) manager->estimatedHeight = block->height;
        
        // check if the next block was received as an orphan
        orphan.prevBlock = block->blockHash;
        next = BRSetRemove(manager->orphans, &orphan);
    }
    
    BRMerkleBlock *saveBlocks[saveCount];
    
    for (i = 0, b = block; b && i < saveCount; i++) {
        assert(b->height != BLOCK_UNKNOWN_HEIGHT); // verify all blocks to be saved are in the chain
        saveBlocks[i] = b;
        b = BRSetGet(manager->blocks, &b->prevBlock);
    }
    
    // make sure the set of blocks to be saved starts at a difficulty interval
    j = (i > 0) ? saveBlocks[i - 1]->height % BLOCK_DIFFICULTY_INTERVAL : 0;
    if (j > 0) i -= (i > BLOCK_DIFFICULTY_INTERVAL - j) ? BLOCK_DIFFICULTY_INTERVAL - j : i;
    assert(i == 0 || (saveBlocks[i - 1]->height % BLOCK_DIFFICULTY_INTERVAL) == 0);
    if (i > 0 && manager->saveBlocks) manager->saveBlocks(manager->info, (i > 1 ? 1 : 0), saveBlocks, i);
    pthread_mutex_unlock(&manager->lock);
    
    if (block && block->height != BLOCK_UNKNOWN_HEIGHT && block->height >= BRPeerLastBlock(peer) &&
        manager->txStatusUpdate) {
        manager->txStatusUpdate(manager->info); // notify that transaction confirmations may have changed
    }
    
    if (next) _peerRelayedBlock(info, next);
}

static void _peerDataNotfound(void *info, const UInt256 txHashes[], size_t txCount,
                             const UInt256 blockHashes[], size_t blockCount)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;

    pthread_mutex_lock(&manager->lock);

    for (size_t i = 0; i < txCount; i++) {
        _BRTxPeerListRemovePeer(manager->txRelays, txHashes[i], peer);
        _BRTxPeerListRemovePeer(manager->txRequests, txHashes[i], peer);
    }

    pthread_mutex_unlock(&manager->lock);
}

static void _peerSetFeePerKb(void *info, uint64_t feePerKb)
{
    BRPeer *p, *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    uint64_t maxFeePerKb = 0, secondFeePerKb = 0;
    
    pthread_mutex_lock(&manager->lock);
    
    for (size_t i = array_count(manager->connectedPeers); i > 0; i--) { // find second highest fee rate
        p = manager->connectedPeers[i - 1];
        if (BRPeerConnectStatus(p) != BRPeerStatusConnected) continue;
        if (BRPeerFeePerKb(p) > maxFeePerKb) secondFeePerKb = maxFeePerKb, maxFeePerKb = BRPeerFeePerKb(p);
    }
    
    if (secondFeePerKb*3/2 > DEFAULT_FEE_PER_KB && secondFeePerKb*3/2 <= MAX_FEE_PER_KB &&
        secondFeePerKb*3/2 > BRWalletFeePerKb(manager->wallet)) {
        peer_log(peer, "increasing feePerKb to %"PRIu64" based on feefilter messages from peers", secondFeePerKb*3/2);
        BRWalletSetFeePerKb(manager->wallet, secondFeePerKb*3/2);
    }

    pthread_mutex_unlock(&manager->lock);
}

static BRTransaction *_peerRequestedTx(void *info, UInt256 txHash)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    BRPublishedTx pubTx = { NULL, NULL, NULL };
    int hasPendingCallbacks = 0, error = 0;

    pthread_mutex_lock(&manager->lock);

    for (size_t i = array_count(manager->publishedTx); i > 0; i--) {
        if (UInt256Eq(manager->publishedTxHashes[i - 1], txHash)) {
            pubTx = manager->publishedTx[i - 1];
            manager->publishedTx[i - 1].callback = NULL;
            manager->publishedTx[i - 1].info = NULL;
        }
        else if (manager->publishedTx[i - 1].callback != NULL) hasPendingCallbacks = 1;
    }

    // cancel tx publish timeout if no publish callbacks are pending, and syncing is done or this is not downloadPeer
    if (! hasPendingCallbacks && (manager->syncStartHeight == 0 || peer != manager->downloadPeer)) {
        BRPeerScheduleDisconnect(peer, -1); // cancel publish tx timeout
    }

    _BRTxPeerListAddPeer(&manager->txRelays, txHash, peer);
    if (pubTx.tx) BRWalletRegisterTransaction(manager->wallet, pubTx.tx);
    if (pubTx.tx && ! BRWalletTransactionIsValid(manager->wallet, pubTx.tx)) error = EINVAL;
    pthread_mutex_unlock(&manager->lock);
    if (pubTx.callback) pubTx.callback(pubTx.info, error);
    return pubTx.tx;
}

static int _peerNetworkIsReachable(void *info)
{
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;

    return (manager->networkIsReachable) ? manager->networkIsReachable(manager->info) : 1;
}

static void _peerThreadCleanup(void *info)
{
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;

    free(info);
    if (manager->threadCleanup) manager->threadCleanup(manager->info);
}

static void _dummyThreadCleanup(void *info)
{
}

// returns a newly allocated BRPeerManager struct that must be freed by calling BRPeerManagerFree()
BRPeerManager *BRPeerManagerNew(const BRChainParams *params, BRWallet *wallet, uint32_t earliestKeyTime,
                                BRMerkleBlock *blocks[], size_t blocksCount, const BRPeer peers[], size_t peersCount)
{
    BRPeerManager *manager = calloc(1, sizeof(*manager));
    BRMerkleBlock orphan, *block = NULL;
    
    assert(manager != NULL);
    assert(params != NULL);
    assert(params->standardPort != 0);
    assert(wallet != NULL);
    assert(blocks != NULL || blocksCount == 0);
    assert(peers != NULL || peersCount == 0);
    manager->params = params;
    manager->wallet = wallet;
    manager->earliestKeyTime = earliestKeyTime;
    manager->averageTxPerBlock = 1400;
    manager->maxConnectCount = PEER_MAX_CONNECTIONS;
    array_new(manager->peers, peersCount);
    if (peers) array_add_array(manager->peers, peers, peersCount);
    qsort(manager->peers, array_count(manager->peers), sizeof(*manager->peers), _peerTimestampCompare);
    array_new(manager->connectedPeers, PEER_MAX_CONNECTIONS);
    manager->blocks = BRSetNew(BRMerkleBlockHash, BRMerkleBlockEq, blocksCount);
    manager->orphans = BRSetNew(_BRPrevBlockHash, _BRPrevBlockEq, blocksCount); // orphans are indexed by prevBlock
    manager->checkpoints = BRSetNew(_BRBlockHeightHash, _BRBlockHeightEq, 100); // checkpoints are indexed by height

    for (size_t i = 0; i < manager->params->checkpointsCount; i++) {
        block = BRMerkleBlockNew();
        block->height = manager->params->checkpoints[i].height;
        block->blockHash = UInt256Reverse(manager->params->checkpoints[i].hash);
        block->timestamp = manager->params->checkpoints[i].timestamp;
        block->target = manager->params->checkpoints[i].target;
        BRSetAdd(manager->checkpoints, block);
        BRSetAdd(manager->blocks, block);
        if (i == 0 || block->timestamp + 7*24*60*60 < manager->earliestKeyTime) manager->lastBlock = block;
    }

    block = NULL;
    
    for (size_t i = 0; blocks && i < blocksCount; i++) {
        assert(blocks[i]->height != BLOCK_UNKNOWN_HEIGHT); // height must be saved/restored along with serialized block
        BRSetAdd(manager->orphans, blocks[i]);

        if ((blocks[i]->height % BLOCK_DIFFICULTY_INTERVAL) == 0 &&
            (! block || blocks[i]->height > block->height)) block = blocks[i]; // find last transition block
    }
    
    while (block) {
        BRSetAdd(manager->blocks, block);
        manager->lastBlock = block;
        orphan.prevBlock = block->prevBlock;
        BRSetRemove(manager->orphans, &orphan);
        orphan.prevBlock = block->blockHash;
        block = BRSetGet(manager->orphans, &orphan);
    }
    
    array_new(manager->txRelays, 10);
    array_new(manager->txRequests, 10);
    array_new(manager->publishedTx, 10);
    array_new(manager->publishedTxHashes, 10);
    pthread_mutex_init(&manager->lock, NULL);
    manager->threadCleanup = _dummyThreadCleanup;
    return manager;
}

// not thread-safe, set callbacks once before calling BRPeerManagerConnect()
// info is a void pointer that will be passed along with each callback call
// void syncStarted(void *) - called when blockchain syncing starts
// void syncStopped(void *, int) - called when blockchain syncing stops, error is an errno.h code
// void txStatusUpdate(void *) - called when transaction status may have changed such as when a new block arrives
// void saveBlocks(void *, int, BRMerkleBlock *[], size_t) - called when blocks should be saved to the persistent store
// - if replace is true, remove any previously saved blocks first
// void savePeers(void *, int, const BRPeer[], size_t) - called when peers should be saved to the persistent store
// - if replace is true, remove any previously saved peers first
// int networkIsReachable(void *) - must return true when networking is available, false otherwise
// void threadCleanup(void *) - called before a thread terminates to faciliate any needed cleanup
void BRPeerManagerSetCallbacks(BRPeerManager *manager, void *info,
                               void (*syncStarted)(void *info),
                               void (*syncStopped)(void *info, int error),
                               void (*txStatusUpdate)(void *info),
                               void (*saveBlocks)(void *info, int replace, BRMerkleBlock *blocks[], size_t blocksCount),
                               void (*savePeers)(void *info, int replace, const BRPeer peers[], size_t peersCount),
                               int (*networkIsReachable)(void *info),
                               void (*threadCleanup)(void *info))
{
    assert(manager != NULL);
    manager->info = info;
    manager->syncStarted = syncStarted;
    manager->syncStopped = syncStopped;
    manager->txStatusUpdate = txStatusUpdate;
    manager->saveBlocks = saveBlocks;
    manager->savePeers = savePeers;
    manager->networkIsReachable = networkIsReachable;
    manager->threadCleanup = (threadCleanup) ? threadCleanup : _dummyThreadCleanup;
}

// specifies a single fixed peer to use when connecting to the bitcoin network
// set address to UINT128_ZERO to revert to default behavior
void BRPeerManagerSetFixedPeer(BRPeerManager *manager, UInt128 address, uint16_t port)
{
    assert(manager != NULL);
    BRPeerManagerDisconnect(manager);
    pthread_mutex_lock(&manager->lock);
    manager->maxConnectCount = UInt128IsZero(address) ? PEER_MAX_CONNECTIONS : 1;
    manager->fixedPeer = ((BRPeer) { address, port, 0, 0, 0 });
    array_clear(manager->peers);
    pthread_mutex_unlock(&manager->lock);
}

// current connect status
BRPeerStatus BRPeerManagerConnectStatus(BRPeerManager *manager)
{
    BRPeerStatus status = BRPeerStatusDisconnected;
    
    assert(manager != NULL);
    pthread_mutex_lock(&manager->lock);
    if (manager->isConnected != 0) status = BRPeerStatusConnected;

    for (size_t i = array_count(manager->connectedPeers); i > 0 && status == BRPeerStatusDisconnected; i--) {
        if (BRPeerConnectStatus(manager->connectedPeers[i - 1]) == BRPeerStatusDisconnected) continue;
        status = BRPeerStatusConnecting;
    }

    pthread_mutex_unlock(&manager->lock);
    return status;
}

// connect to bitcoin peer-to-peer network (also call this whenever networkIsReachable() status changes)
void BRPeerManagerConnect(BRPeerManager *manager)
{
    assert(manager != NULL);
    pthread_mutex_lock(&manager->lock);
    if (manager->connectFailureCount >= MAX_CONNECT_FAILURES) manager->connectFailureCount = 0; //this is a manual retry
    
    if ((! manager->downloadPeer || manager->lastBlock->height < manager->estimatedHeight) &&
        manager->syncStartHeight == 0) {
        manager->syncStartHeight = manager->lastBlock->height + 1;
        pthread_mutex_unlock(&manager->lock);
        if (manager->syncStarted) manager->syncStarted(manager->info);
        pthread_mutex_lock(&manager->lock);
    }
    
    for (size_t i = array_count(manager->connectedPeers); i > 0; i--) {
        BRPeer *p = manager->connectedPeers[i - 1];

        if (BRPeerConnectStatus(p) == BRPeerStatusConnecting) BRPeerConnect(p);
    }
    
    if (array_count(manager->connectedPeers) < manager->maxConnectCount) {
        time_t now = time(NULL);
        BRPeer *peers;

        if (array_count(manager->peers) < manager->maxConnectCount ||
            manager->peers[manager->maxConnectCount - 1].timestamp + 3*24*60*60 < now) {
            _BRPeerManagerFindPeers(manager);
        }
        
        array_new(peers, 100);
        array_add_array(peers, manager->peers,
                        (array_count(manager->peers) < 100) ? array_count(manager->peers) : 100);

        while (array_count(peers) > 0 && array_count(manager->connectedPeers) < manager->maxConnectCount) {
            size_t i = BRRand((uint32_t)array_count(peers)); // index of random peer
            BRPeerCallbackInfo *info;
            
            i = i*i/array_count(peers); // bias random peer selection toward peers with more recent timestamp
        
            for (size_t j = array_count(manager->connectedPeers); i != SIZE_MAX && j > 0; j--) {
                if (! BRPeerEq(&peers[i], manager->connectedPeers[j - 1])) continue;
                array_rm(peers, i); // already in connectedPeers
                i = SIZE_MAX;
            }
            
            if (i != SIZE_MAX) {
                info = calloc(1, sizeof(*info));
                assert(info != NULL);
                info->manager = manager;
                info->peer = BRPeerNew(manager->params->magicNumber);
                *info->peer = peers[i];
                array_rm(peers, i);
                array_add(manager->connectedPeers, info->peer);
                BRPeerSetCallbacks(info->peer, info, _peerConnected, _peerDisconnected, _peerRelayedPeers,
                                   _peerRelayedTx, _peerHasTx, _peerRejectedTx, _peerRelayedBlock, _peerDataNotfound,
                                   _peerSetFeePerKb, _peerRequestedTx, _peerNetworkIsReachable, _peerThreadCleanup);
                BRPeerSetEarliestKeyTime(info->peer, manager->earliestKeyTime);
                BRPeerConnect(info->peer);
            }
        }

        array_free(peers);
    }
    
    if (array_count(manager->connectedPeers) == 0) {
        peer_log(&BR_PEER_NONE, "sync failed");
        _BRPeerManagerSyncStopped(manager);
        pthread_mutex_unlock(&manager->lock);
        if (manager->syncStopped) manager->syncStopped(manager->info, ENETUNREACH);
    }
    else pthread_mutex_unlock(&manager->lock);
}

void BRPeerManagerDisconnect(BRPeerManager *manager)
{
    struct timespec ts;
    size_t peerCount, dnsThreadCount;
    
    assert(manager != NULL);
    pthread_mutex_lock(&manager->lock);
    peerCount = array_count(manager->connectedPeers);
    dnsThreadCount = manager->dnsThreadCount;
    
    for (size_t i = peerCount; i > 0; i--) {
        manager->connectFailureCount = MAX_CONNECT_FAILURES; // prevent futher automatic reconnect attempts
        BRPeerDisconnect(manager->connectedPeers[i - 1]);
    }
    
    pthread_mutex_unlock(&manager->lock);
    ts.tv_sec = 0;
    ts.tv_nsec = 1;
    
    while (peerCount > 0 || dnsThreadCount > 0) {
        nanosleep(&ts, NULL); // pthread_yield() isn't POSIX standard :(
        pthread_mutex_lock(&manager->lock);
        peerCount = array_count(manager->connectedPeers);
        dnsThreadCount = manager->dnsThreadCount;
        pthread_mutex_unlock(&manager->lock);
    }
}

static int _BRPeerManagerRescan (BRPeerManager *manager, BRMerkleBlock *newLastBlock) {
    if (NULL == newLastBlock) return 0;

    manager->lastBlock = newLastBlock;

    if (manager->downloadPeer) { // disconnect the current download peer so a new random one will be selected
        for (size_t i = array_count(manager->peers); i > 0; i--) {
            if (BRPeerEq(&manager->peers[i - 1], manager->downloadPeer)) array_rm(manager->peers, i - 1);
        }

        BRPeerDisconnect(manager->downloadPeer);
    }

    manager->syncStartHeight = 0; // a syncStartHeight of 0 indicates that syncing hasn't started yet
    return 1;
}

// rescans blocks and transactions after earliestKeyTime (a new random download peer is also selected due to the
// possibility that a malicious node might lie by omitting transactions that match the bloom filter)
void BRPeerManagerRescan(BRPeerManager *manager)
{
    assert(manager != NULL);
    pthread_mutex_lock(&manager->lock);
    
    int needConnect = 0;
    if (manager->isConnected) {
        BRMerkleBlock *newLastBlock = NULL;

        // start the chain download from the most recent checkpoint that's at least a week older than earliestKeyTime
        for (size_t i = manager->params->checkpointsCount; i > 0; i--) {
            if (i - 1 == 0 || manager->params->checkpoints[i - 1].timestamp + 7*24*60*60 < manager->earliestKeyTime) {
                UInt256 hash = UInt256Reverse(manager->params->checkpoints[i - 1].hash);

                newLastBlock = BRSetGet(manager->blocks, &hash);
                break;
            }
        }

        needConnect = _BRPeerManagerRescan(manager, newLastBlock);
    }
    pthread_mutex_unlock(&manager->lock);
    if (needConnect) BRPeerManagerConnect(manager);
}

// rescans blocks and transactions after the last hardcoded checkpoint
void BRPeerManagerRescanFromLastHardcodedCheckpoint(BRPeerManager *manager)
{
    assert(manager != NULL);
    pthread_mutex_lock(&manager->lock);

    int needConnect = 0;
    if (manager->isConnected) {
        size_t i = manager->params->checkpointsCount;
        if (i > 0) {
            UInt256 hash = UInt256Reverse(manager->params->checkpoints[i - 1].hash);
            needConnect = _BRPeerManagerRescan(manager, BRSetGet (manager->blocks, &hash));
        }
    }
    pthread_mutex_unlock(&manager->lock);
    if (needConnect) BRPeerManagerConnect(manager);
}

static BRMerkleBlock *_BRPeerManagerLookupBlockFromBlockNumber (BRPeerManager *manager, uint32_t blockNumber)
{
    BRMerkleBlock *block = manager->lastBlock;

    // walk the chain, looking for blockNumber
    while (block) {
        if (block->height == blockNumber) return block;
        block = BRSetGet (manager->blocks, &block->prevBlock);
    }

    // blockNumber not in the (abbreviated) chain - look through checkpoints
    for (int i = 0; i < manager->params->checkpointsCount; i++)
        if (manager->params->checkpoints[i].height == blockNumber) {
            UInt256 hash = UInt256Reverse(manager->params->checkpoints[i].hash);
            return BRSetGet(manager->blocks, &hash);
        }

    return NULL;
}

// rescans blocks and transactions from after the blockNumber.  If blockNumber is not known, then
// rescan from the just prior checkpoint.
void BRPeerManagerRescanFromBlockNumber(BRPeerManager *manager, uint32_t blockNumber)
{
    assert(manager != NULL);
    pthread_mutex_lock(&manager->lock);

    int needConnect = 0;
    if (manager->isConnected) {
        BRMerkleBlock *block = _BRPeerManagerLookupBlockFromBlockNumber(manager, blockNumber);

        // If there was no block, find the preceeding hardcoded checkpoint.
        if (NULL == block) {
            for (size_t i = manager->params->checkpointsCount; i > 0; i--) {
                if (i - 1 == 0 || manager->params->checkpoints[i - 1].height < blockNumber) {
                    UInt256 hash = UInt256Reverse(manager->params->checkpoints[i - 1].hash);
                    block = BRSetGet(manager->blocks, &hash);
                    break;
                }
            }
        }

        needConnect = _BRPeerManagerRescan(manager, block);
    }
    pthread_mutex_unlock(&manager->lock);
    if (needConnect) BRPeerManagerConnect(manager);
}

// the (unverified) best block height reported by connected peers
uint32_t BRPeerManagerEstimatedBlockHeight(BRPeerManager *manager)
{
    uint32_t height;
    
    assert(manager != NULL);
    pthread_mutex_lock(&manager->lock);
    height = (manager->lastBlock->height < manager->estimatedHeight) ? manager->estimatedHeight :
             manager->lastBlock->height;
    pthread_mutex_unlock(&manager->lock);
    return height;
}

// current proof-of-work verified best block height
uint32_t BRPeerManagerLastBlockHeight(BRPeerManager *manager)
{
    uint32_t height;
    
    assert(manager != NULL);
    pthread_mutex_lock(&manager->lock);
    height = manager->lastBlock->height;
    pthread_mutex_unlock(&manager->lock);
    return height;
}

// current proof-of-work verified best block timestamp (time interval since unix epoch)
uint32_t BRPeerManagerLastBlockTimestamp(BRPeerManager *manager)
{
    uint32_t timestamp;
    
    assert(manager != NULL);
    pthread_mutex_lock(&manager->lock);
    timestamp = manager->lastBlock->timestamp;
    pthread_mutex_unlock(&manager->lock);
    return timestamp;
}

// current network sync progress from 0 to 1
// startHeight is the block height of the most recent fully completed sync
double BRPeerManagerSyncProgress(BRPeerManager *manager, uint32_t startHeight)
{
    double progress;
    
    assert(manager != NULL);
    pthread_mutex_lock(&manager->lock);
    if (startHeight == 0) startHeight = manager->syncStartHeight;
    
    if (! manager->downloadPeer && manager->syncStartHeight == 0) {
        progress = 0.0;
    }
    else if (! manager->downloadPeer || manager->lastBlock->height < manager->estimatedHeight) {
        if (manager->lastBlock->height > startHeight && manager->estimatedHeight > startHeight) {
            progress = 0.1 + 0.9*(manager->lastBlock->height - startHeight)/(manager->estimatedHeight - startHeight);
        }
        else progress = 0.05;
    }
    else progress = 1.0;

    pthread_mutex_unlock(&manager->lock);
    return progress;
}

// returns the number of currently connected peers
size_t BRPeerManagerPeerCount(BRPeerManager *manager)
{
    size_t count = 0;
    
    assert(manager != NULL);
    pthread_mutex_lock(&manager->lock);
    
    for (size_t i = array_count(manager->connectedPeers); i > 0; i--) {
        if (BRPeerConnectStatus(manager->connectedPeers[i - 1]) != BRPeerStatusDisconnected) count++;
    }
    
    pthread_mutex_unlock(&manager->lock);
    return count;
}

// description of the peer most recently used to sync blockchain data
const char *BRPeerManagerDownloadPeerName(BRPeerManager *manager)
{
    assert(manager != NULL);
    pthread_mutex_lock(&manager->lock);

    if (manager->downloadPeer) {
        sprintf(manager->downloadPeerName, "%s:%d", BRPeerHost(manager->downloadPeer), manager->downloadPeer->port);
    }
    else manager->downloadPeerName[0] = '\0';
    
    pthread_mutex_unlock(&manager->lock);
    return manager->downloadPeerName;
}

static void _publishTxInvDone(void *info, int success)
{
    BRPeer *peer = ((BRPeerCallbackInfo *)info)->peer;
    BRPeerManager *manager = ((BRPeerCallbackInfo *)info)->manager;
    
    free(info);
    pthread_mutex_lock(&manager->lock);
    _BRPeerManagerRequestUnrelayedTx(manager, peer);
    pthread_mutex_unlock(&manager->lock);
}

// publishes tx to bitcoin network (do not call BRTransactionFree() on tx afterward)
void BRPeerManagerPublishTx(BRPeerManager *manager, BRTransaction *tx, void *info,
                            void (*callback)(void *info, int error))
{
    assert(manager != NULL);
    assert(tx != NULL && BRTransactionIsSigned(tx));
    if (tx) pthread_mutex_lock(&manager->lock);
    
    if (tx && ! BRTransactionIsSigned(tx)) {
        pthread_mutex_unlock(&manager->lock);
        if (callback) callback(info, EINVAL); // transaction not signed
        tx = NULL;
    }
    else if (tx && ! manager->isConnected) {
        int connectFailureCount = manager->connectFailureCount;

        pthread_mutex_unlock(&manager->lock);

        if (connectFailureCount >= MAX_CONNECT_FAILURES ||
            (manager->networkIsReachable && ! manager->networkIsReachable(manager->info))) {
            if (callback) callback(info, ENOTCONN); // not connected to bitcoin network
            tx = NULL;
        }
        else pthread_mutex_lock(&manager->lock);
    }
    
    if (tx) {
        size_t i, count = 0;
        
        tx->timestamp = (uint32_t)time(NULL); // set timestamp to publish time
        _BRPeerManagerAddTxToPublishList(manager, tx, info, callback);

        for (i = array_count(manager->connectedPeers); i > 0; i--) {
            if (BRPeerConnectStatus(manager->connectedPeers[i - 1]) == BRPeerStatusConnected) count++;
        }

        for (i = array_count(manager->connectedPeers); i > 0; i--) {
            BRPeer *peer = manager->connectedPeers[i - 1];
            BRPeerCallbackInfo *peerInfo;

            if (BRPeerConnectStatus(peer) != BRPeerStatusConnected) continue;
            
            // instead of publishing to all peers, leave out downloadPeer to see if tx propogates/gets relayed back
            // TODO: XXX connect to a random peer with an empty or fake bloom filter just for publishing
            if (peer != manager->downloadPeer || count == 1) {
                _BRPeerManagerPublishPendingTx(manager, peer);
                peerInfo = calloc(1, sizeof(*peerInfo));
                assert(peerInfo != NULL);
                peerInfo->peer = peer;
                peerInfo->manager = manager;
                BRPeerSendPing(peer, peerInfo, _publishTxInvDone);
            }
        }

        pthread_mutex_unlock(&manager->lock);
    }
}

// number of connected peers that have relayed the given unconfirmed transaction
size_t BRPeerManagerRelayCount(BRPeerManager *manager, UInt256 txHash)
{
    size_t count = 0;

    assert(manager != NULL);
    assert(! UInt256IsZero(txHash));
    pthread_mutex_lock(&manager->lock);
    
    for (size_t i = array_count(manager->txRelays); i > 0; i--) {
        if (! UInt256Eq(manager->txRelays[i - 1].txHash, txHash)) continue;
        count = array_count(manager->txRelays[i - 1].peers);
        break;
    }
    
    pthread_mutex_unlock(&manager->lock);
    return count;
}

const BRChainParams *BRPeerManagerChainParams (BRPeerManager *manager) {
    return manager->params;
}

// frees memory allocated for manager
void BRPeerManagerFree(BRPeerManager *manager)
{
    BRTransaction *tx;
    
    assert(manager != NULL);
    pthread_mutex_lock(&manager->lock);
    array_free(manager->peers);
    for (size_t i = array_count(manager->connectedPeers); i > 0; i--) BRPeerFree(manager->connectedPeers[i - 1]);
    array_free(manager->connectedPeers);
    BRSetApply(manager->blocks, NULL, _setApplyFreeBlock);
    BRSetFree(manager->blocks);
    BRSetApply(manager->orphans, NULL, _setApplyFreeBlock);
    BRSetFree(manager->orphans);
    BRSetFree(manager->checkpoints);
    for (size_t i = array_count(manager->txRelays); i > 0; i--) free(manager->txRelays[i - 1].peers);
    array_free(manager->txRelays);
    for (size_t i = array_count(manager->txRequests); i > 0; i--) free(manager->txRequests[i - 1].peers);
    array_free(manager->txRequests);

    for (size_t i = array_count(manager->publishedTx); i > 0; i--) {
        tx = manager->publishedTx[i - 1].tx;
        if (tx && tx != BRWalletTransactionForHash(manager->wallet, tx->txHash)) BRTransactionFree(tx);
    }

    array_free(manager->publishedTx);
    array_free(manager->publishedTxHashes);
    pthread_mutex_unlock(&manager->lock);
    pthread_mutex_destroy(&manager->lock);
    free(manager);
}