The `Broadcast`/`ResendWalletTransactions` interface is strange:

- it's the node saying to the wallet "Try to submit your unconfirmed transactions to the mempool again"
- it's called in one place by the node, in `SendMessages()` here: https://github.com/bitcoin/bitcoin/blob/c033c4b5cef89a654e4d9d5c5f9bd823871b068b/src/net_processing.cpp#L3515. `SendMessages()` is called on the message handling thread on a loop.
- the actual scheduling of when the wallet sends messages is handled in the `ResendWalletTransactions()` function itself, using the `nNextResend` and `nLastResend` wallet globals (which could as easily be static variables in `ResendWalletTransactions()`).

Therefore the only use of `Broadcast()` is to periodically prod the wallet. The wallet itself decides whether it's time to resend transactions. This could be done by scheduling regular calls to `ResendWalletTransactions()`, in the same way that we schedule regular wallet flushes here: https://github.com/bitcoin/bitcoin/blob/c033c4b5cef89a654e4d9d5c5f9bd823871b068b/src/wallet/init.cpp#L215.

A couple of minor implementation details:

- the call to `Broadcast()` in `SendMessages()` is protected by an if statement `if (!fReindex && !fImporting && !IsInitialBlockDownload()) {`. Those tests could be moved into `ResendWalletTransactions()` (through the `Chain` interface).
- The `Broadcast` notification passes in the `nTimeBestReceived` time of the best block. That could be fetched by `ResendWalletTransactions()` through the `Chain` interface.
state.m_chain_sync.m_timeout = time_in_seconds + CHAIN_SYNC_TIMEOUT;
            state.m_chain_sync.m_work_header = chainActive.Tip();
            state.m_chain_sync.m_sent_getheaders = false;
        } else if (state.m_chain_sync.m_timeout > 0 && time_in_seconds > state.m_chain_sync.m_timeout) {
            
            
            
            if (state.m_chain_sync.m_sent_getheaders) {
                
                LogPrintf("Disconnecting outbound peer %d for old chain, best known block = %s\n", pto->GetId(), state.pindexBestKnownBlock != nullptr ? state.pindexBestKnownBlock->GetBlockHash().ToString() : "<none>");
                pto->fDisconnect = true;
            } else {
                assert(state.m_chain_sync.m_work_header);
                LogPrint(BCLog::NET, "sending getheaders to outbound peer=%d to verify chain work (current best known block:%s, benchmark blockhash: %s)\n", pto->GetId(), state.pindexBestKnownBlock != nullptr ? state.pindexBestKnownBlock->GetBlockHash().ToString() : "<none>", state.m_chain_sync.m_work_header->GetBlockHash().ToString());
                connman->PushMessage(pto, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(state.m_chain_sync.m_work_header->pprev), uint256()));
                state.m_chain_sync.m_sent_getheaders = true;
                constexpr int64_t HEADERS_RESPONSE_TIME = 120; 
                
                
                
                
                
                state.m_chain_sync.m_timeout = time_in_seconds + HEADERS_RESPONSE_TIME;
            }
        }
    }
}
void PeerLogicValidation::EvictExtraOutboundPeers(int64_t time_in_seconds)