Add functions to construct locators without CChain

This introduces an insignificant performance penalty, as it means locator
construction needs to use the skiplist-based CBlockIndex::GetAncestor()
function instead of the lookup-based CChain, but avoids the need for
callers to have access to a relevant CChain object.

1 files changed, 7 insertions, 6 deletions

diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index b83034463d..cc8d695369 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -2285,7 +2285,7 @@ void PeerManagerImpl::HandleFewUnconnectingHeaders(CNode& pfrom, Peer& peer,
 
     nodestate->nUnconnectingHeaders++;
     // Try to fill in the missing headers.
-    if (MaybeSendGetHeaders(pfrom, m_chainman.ActiveChain().GetLocator(m_chainman.m_best_header), peer)) {
+    if (MaybeSendGetHeaders(pfrom, GetLocator(m_chainman.m_best_header), peer)) {
         LogPrint(BCLog::NET, "received header %s: missing prev block %s, sending getheaders (%d) to end (peer=%d, nUnconnectingHeaders=%d)\n",
             headers[0].GetHash().ToString(),
             headers[0].hashPrevBlock.ToString(),
@@ -2506,11 +2506,12 @@ void PeerManagerImpl::ProcessHeadersMessage(CNode& pfrom, Peer& peer,
             return;
         }
     }
+    Assume(pindexLast);
 
     // Consider fetching more headers.
     if (nCount == MAX_HEADERS_RESULTS) {
         // Headers message had its maximum size; the peer may have more headers.
-        if (MaybeSendGetHeaders(pfrom, WITH_LOCK(m_chainman.GetMutex(), return m_chainman.ActiveChain().GetLocator(pindexLast)), peer)) {
+        if (MaybeSendGetHeaders(pfrom, GetLocator(pindexLast), peer)) {
             LogPrint(BCLog::NET, "more getheaders (%d) to end to peer=%d (startheight:%d)\n",
                     pindexLast->nHeight, pfrom.GetId(), peer.m_starting_height);
         }
@@ -3285,7 +3286,7 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
             // use if we turned on sync with all peers).
             CNodeState& state{*Assert(State(pfrom.GetId()))};
             if (state.fSyncStarted || (!peer->m_inv_triggered_getheaders_before_sync && *best_block != m_last_block_inv_triggering_headers_sync)) {
-                if (MaybeSendGetHeaders(pfrom, m_chainman.ActiveChain().GetLocator(m_chainman.m_best_header), *peer)) {
+                if (MaybeSendGetHeaders(pfrom, GetLocator(m_chainman.m_best_header), *peer)) {
                     LogPrint(BCLog::NET, "getheaders (%d) %s to peer=%d\n",
                             m_chainman.m_best_header->nHeight, best_block->ToString(),
                             pfrom.GetId());
@@ -3752,7 +3753,7 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
         if (!m_chainman.m_blockman.LookupBlockIndex(cmpctblock.header.hashPrevBlock)) {
             // Doesn't connect (or is genesis), instead of DoSing in AcceptBlockHeader, request deeper headers
             if (!m_chainman.ActiveChainstate().IsInitialBlockDownload()) {
-                MaybeSendGetHeaders(pfrom, m_chainman.ActiveChain().GetLocator(m_chainman.m_best_header), *peer);
+                MaybeSendGetHeaders(pfrom, GetLocator(m_chainman.m_best_header), *peer);
             }
             return;
         }
@@ -4502,7 +4503,7 @@ void PeerManagerImpl::ConsiderEviction(CNode& pto, Peer& peer, std::chrono::seco
                 // getheaders in-flight already, in which case the peer should
                 // still respond to us with a sufficiently high work chain tip.
                 MaybeSendGetHeaders(pto,
-                        m_chainman.ActiveChain().GetLocator(state.m_chain_sync.m_work_header->pprev),
+                        GetLocator(state.m_chain_sync.m_work_header->pprev),
                         peer);
                 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());
                 state.m_chain_sync.m_sent_getheaders = true;
@@ -4924,7 +4925,7 @@ bool PeerManagerImpl::SendMessages(CNode* pto)
                    got back an empty response.  */
                 if (pindexStart->pprev)
                     pindexStart = pindexStart->pprev;
-                if (MaybeSendGetHeaders(*pto, m_chainman.ActiveChain().GetLocator(pindexStart), *peer)) {
+                if (MaybeSendGetHeaders(*pto, GetLocator(pindexStart), *peer)) {
                     LogPrint(BCLog::NET, "initial getheaders (%d) to peer=%d (startheight:%d)\n", pindexStart->nHeight, pto->GetId(), peer->m_starting_height);
 
                     state.fSyncStarted = true;