For software that interfaces with Bitcoin Core via RPC, it can be useful to know whether the fRelayTxes flag is set. It could be added to `getnetworkinfo`.

mempool.check(pcoinsTip);
    
    if (fInvalidFound)
        CheckForkWarningConditionsOnNewFork(vpindexToConnect.back());
    else
        CheckForkWarningConditions();
    return true;
}
/**
 * Make the best chain active, in multiple steps. The result is either failure
 * or an activated best chain. pblock is either NULL or a pointer to a block
 * that is already loaded (to avoid loading it again from disk).
 */
bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams, const CBlock *pblock) {
    CBlockIndex *pindexMostWork = NULL;
    do {
        boost::this_thread::interruption_point();
        if (ShutdownRequested())
            break;
        CBlockIndex *pindexNewTip = NULL;
        const CBlockIndex *pindexFork;
        bool fInitialDownload;
        {
            LOCK(cs_main);
            CBlockIndex *pindexOldTip = chainActive.Tip();
            pindexMostWork = FindMostWorkChain();
            
            if (pindexMostWork == NULL || pindexMostWork == chainActive.Tip())
                return true;
            if (!ActivateBestChainStep(state, chainparams, pindexMostWork, pblock && pblock->GetHash() == pindexMostWork->GetBlockHash() ? pblock : NULL))