Method FetchBlock

src/net_processing.cpp:1985–2023

}

util::Expected<void, std::string> PeerManagerImpl::FetchBlock(NodeId peer_id, const CBlockIndex& block_index)
{
    if (m_chainman.m_blockman.LoadingBlocks()) return util::Unexpected{"Loading blocks ..."};

    // The lock must be taken here before fetching Peer so another thread does
    // not delete the CNodeState from under the current thread, causing an
    // assertion failure in BlockRequested. This lock can be replaced with a
    // net-specific lock when more of CNodeState is moved into Peer.
    LOCK(cs_main);

    // Ensure this peer exists and hasn't been disconnected
    PeerRef peer = GetPeerRef(peer_id);
    if (peer == nullptr) return util::Unexpected{"Peer does not exist"};

    // Ignore pre-segwit peers
    if (!CanServeWitnesses(*peer)) return util::Unexpected{"Pre-SegWit peer"};

    // Forget about all prior requests
    RemoveBlockRequest(block_index.GetBlockHash(), std::nullopt);

    // Mark block as in-flight
    if (!BlockRequested(peer_id, block_index)) return util::Unexpected{"Already requested from this peer"};

    // Construct message to request the block
    const uint256& hash{block_index.GetBlockHash()};
    std::vector<CInv> invs{CInv(MSG_BLOCK | MSG_WITNESS_FLAG, hash)};

    // Send block request message to the peer
    bool success = m_connman.ForNode(peer_id, [this, &invs](CNode* node) {
        this->MakeAndPushMessage(*node, NetMsgType::GETDATA, invs);
        return true;
    });

    if (!success) return util::Unexpected{"Peer not fully connected"};

    LogDebug(BCLog::NET, "Requesting block %s from peer=%d\n",
                 hash.ToString(), peer_id);
    return {};
}

std::unique_ptr<PeerManager> PeerManager::make(CConnman& connman, AddrMan& addrman,
                                               BanMan* banman, ChainstateManager& chainman,