Merge #17243: p2p: add PoissonNextSend method that returns mockable time

1a8f0d5a74 [tools] update nNextInvSend to use mockable time (Amiti Uttarwar)
4de630354f [tools] add PoissonNextSend method that returns mockable time (Amiti Uttarwar)

Pull request description:

  Introduce a Poisson helper method that wraps the existing method to return `std::chrono::duration` type, which is mockable.

  Needed for https://github.com/bitcoin/bitcoin/pull/16698.

ACKs for top commit:
  ajtowns:
    ACK 1a8f0d5a74
  MarcoFalke:
    re-ACK 1a8f0d5a74
  naumenkogs:
    ACK 1a8f0d5, and let's merge it and come back to it later.

Tree-SHA512: 7e2325d7c55fc0b4357cb86b83e0c218ba269f678c1786342d8bc380bfd9696373bc24ff124b9ff17a6e761c62b2b44ff5247c3911e2afdc7cc5c20417e8290b

src/net.h

@@ -808,7 +808,7 @@ public:
         bool fSendMempool GUARDED_BY(cs_tx_inventory){false};
         // Last time a "MEMPOOL" request was serviced.
         std::atomic<std::chrono::seconds> m_last_mempool_req{std::chrono::seconds{0}};
-        int64_t nNextInvSend{0};
+        std::chrono::microseconds nNextInvSend{0};
 
         CCriticalSection cs_feeFilter;
         // Minimum fee rate with which to filter inv's to this node
@@ -991,11 +991,13 @@ public:
     void MaybeSetAddrName(const std::string& addrNameIn);
 };
 
-
-
-
-
 /** Return a timestamp in the future (in microseconds) for exponentially distributed events. */
 int64_t PoissonNextSend(int64_t now, int average_interval_seconds);
 
+/** Wrapper to return mockable type */
+inline std::chrono::microseconds PoissonNextSend(std::chrono::microseconds now, std::chrono::seconds average_interval)
+{
+    return std::chrono::microseconds{PoissonNextSend(now.count(), average_interval.count())};
+}
+
 #endif // BITCOIN_NET_H

src/net_processing.cpp

@@ -3575,6 +3575,8 @@ bool PeerLogicValidation::SendMessages(CNode* pto)
 
         // Address refresh broadcast
         int64_t nNow = GetTimeMicros();
+        auto current_time = GetTime<std::chrono::microseconds>();
+
         if (pto->IsAddrRelayPeer() && !::ChainstateActive().IsInitialBlockDownload() && pto->nNextLocalAddrSend < nNow) {
             AdvertiseLocal(pto);
             pto->nNextLocalAddrSend = PoissonNextSend(nNow, AVG_LOCAL_ADDRESS_BROADCAST_INTERVAL);
@@ -3796,13 +3798,13 @@ bool PeerLogicValidation::SendMessages(CNode* pto)
                 LOCK(pto->m_tx_relay->cs_tx_inventory);
                 // Check whether periodic sends should happen
                 bool fSendTrickle = pto->HasPermission(PF_NOBAN);
-                if (pto->m_tx_relay->nNextInvSend < nNow) {
+                if (pto->m_tx_relay->nNextInvSend < current_time) {
                     fSendTrickle = true;
                     if (pto->fInbound) {
-                        pto->m_tx_relay->nNextInvSend = connman->PoissonNextSendInbound(nNow, INVENTORY_BROADCAST_INTERVAL);
+                        pto->m_tx_relay->nNextInvSend = std::chrono::microseconds{connman->PoissonNextSendInbound(nNow, INVENTORY_BROADCAST_INTERVAL)};
                     } else {
                         // Use half the delay for outbound peers, as there is less privacy concern for them.
-                        pto->m_tx_relay->nNextInvSend = PoissonNextSend(nNow, INVENTORY_BROADCAST_INTERVAL >> 1);
+                        pto->m_tx_relay->nNextInvSend = PoissonNextSend(current_time, std::chrono::seconds{INVENTORY_BROADCAST_INTERVAL >> 1});
                     }
                 }
 
@@ -3917,7 +3919,7 @@ bool PeerLogicValidation::SendMessages(CNode* pto)
             connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
 
         // Detect whether we're stalling
-        const auto current_time = GetTime<std::chrono::microseconds>();
+        current_time = GetTime<std::chrono::microseconds>();
         // nNow is the current system time (GetTimeMicros is not mockable) and
         // should be replaced by the mockable current_time eventually
         nNow = GetTimeMicros();

src/test/net_tests.cpp

@@ -301,5 +301,19 @@ BOOST_AUTO_TEST_CASE(LocalAddress_BasicLifecycle)
     BOOST_CHECK_EQUAL(IsLocal(addr), false);
 }
 
+BOOST_AUTO_TEST_CASE(PoissonNextSend)
+{
+    g_mock_deterministic_tests = true;
+
+    int64_t now = 5000;
+    int average_interval_seconds = 600;
+
+    auto poisson = ::PoissonNextSend(now, average_interval_seconds);
+    std::chrono::microseconds poisson_chrono = ::PoissonNextSend(std::chrono::microseconds{now}, std::chrono::seconds{average_interval_seconds});
+
+    BOOST_CHECK_EQUAL(poisson, poisson_chrono.count());
+
+    g_mock_deterministic_tests = false;
+}
 
 BOOST_AUTO_TEST_SUITE_END()