pool: refuse jobs when no peer has reported a height for 20 minutes

The peer-height gate replaced a tip-age check that was wrong in both
directions. It is a strict improvement and it is still blind in the one
case that matters most.

When the node goes deaf -- peers still in vNodes, nothing arriving -- no
peer announces anything, GetPeerMedianHeight() returns -1, and the
fallback mines our best chain. That fallback is right for a node that has
not been told yet and wrong for a node that has stopped being able to
hear, and a height nobody sent cannot tell those apart. A wedged node is
exactly a node with no peer height information, so the gate was silent
for the whole of heights 3966-4085: 120 blocks, 5890.50 BTF voided.

Time can tell them apart. GetPeerHeightAgeSecs() measures how long since
any peer reported a height, counting from first use rather than the epoch
so a starting node does not refuse jobs before its first handshake. Past
20 minutes the pool stops issuing jobs and says so unconditionally in the
log. /poolmineblind overrides it: without an escape hatch a genuinely
isolated pool that is 90% of the hashrate could never restart its own
chain, which is the deadlock the tip-age check used to cause.

Also stop nStartingHeight from going stale. It was a snapshot taken once
during the version handshake and never touched again, so on a long-lived
connection the median is built from heights the peers had hours ago, and
the behind-the-network check drifts toward 'everyone is behind us' and
quietly stops firing. A peer that hands us a block is demonstrably at
least at that block's height.

(cherry picked from commit 0800c18faf703b4acde1b131d0b742d37a86d92b)

1 files changed, 1 insertions, 0 deletions

diff --git a/src/main.h b/src/main.h
index 6b1ff0a..f5409e9 100644
--- a/src/main.h
+++ b/src/main.h
@@ -93,6 +93,7 @@ extern string strParticipantPool; // participant: pool .btf address
 extern string strPayoutAddress;   // participant: /payoutaddr override (mine without a wallet)
 extern string strPayoutFile;      // participant: /payoutfile address list, rotated per reconnect
 extern bool   fPoolNoAnnounce;      // /noannounce: suppress pool announcements
+extern bool   fPoolMineBlind;       // /poolmineblind: mine on even when deaf to every peer
 extern int    nHashThreads;       // participant: /hashthreads override (0 = cores-1)
 extern string strPoolName;        // operator: announced pool name
 extern string strPoolDashboardUrl; // operator: optional dashboard URL