refactor: Use NodeClock::duration for m_last_ping_time/m_min_ping_time/m_ping_wait

This refactor does not change any behavior and is needed for a future
commit, to avoid having to add duration casts.

It also improves the docs to better document that this is not a time
point, but a duration.

Also, it uses decltype to explain where the _::max() is coming from.

src/net.h

@@ -210,8 +210,8 @@ public:
     uint64_t nRecvBytes;
     mapMsgTypeSize mapRecvBytesPerMsgType;
     NetPermissionFlags m_permission_flags;
-    std::chrono::microseconds m_last_ping_time;
-    std::chrono::microseconds m_min_ping_time;
+    NodeClock::duration m_last_ping_time;
+    NodeClock::duration m_min_ping_time;
     // Our address, as reported by the peer
     std::string addrLocal;
     // Address of this peer
@@ -890,11 +890,11 @@ public:
     std::atomic<std::chrono::seconds> m_last_tx_time{0s};
 
     /// Last measured round-trip duration. Used only for stats.
-    std::atomic<std::chrono::microseconds> m_last_ping_time{0us};
+    std::atomic<NodeClock::duration> m_last_ping_time{0us};
 
     /// Lowest measured round-trip duration. Used as an inbound peer eviction
     /// criterion in CConnman::AttemptToEvictConnection.
-    std::atomic<std::chrono::microseconds> m_min_ping_time{std::chrono::microseconds::max()};
+    std::atomic<NodeClock::duration> m_min_ping_time{NodeClock::duration::max()};
 
     CNode(NodeId id,
           std::shared_ptr<Sock> sock,
@@ -981,7 +981,8 @@ public:
     std::string DisconnectMsg() const;
 
     /// A ping-pong round trip has completed successfully. Update latest and minimum ping durations.
-    void PongReceived(std::chrono::microseconds ping_time) {
+    void PongReceived(NodeClock::duration ping_time)
+    {
         m_last_ping_time = ping_time;
         m_min_ping_time = std::min(m_min_ping_time.load(), ping_time);
     }

src/net_processing.h

@@ -52,7 +52,7 @@ static const unsigned int MAX_HEADERS_RESULTS = 2000;
 struct CNodeStateStats {
     int nSyncHeight = -1;
     int nCommonHeight = -1;
-    std::chrono::microseconds m_ping_wait;
+    NodeClock::duration m_ping_wait;
     std::vector<int> vHeightInFlight;
     bool m_relay_txs;
     int m_inv_to_send = 0;

src/node/eviction.h

@@ -18,7 +18,7 @@ typedef int64_t NodeId;
 struct NodeEvictionCandidate {
     NodeId id;
     std::chrono::seconds m_connected;
-    std::chrono::microseconds m_min_ping_time;
+    NodeClock::duration m_min_ping_time;
     std::chrono::seconds m_last_block_time;
     std::chrono::seconds m_last_tx_time;
     bool fRelevantServices;

src/qt/guiutil.cpp

@@ -767,9 +767,9 @@ QString formatServicesStr(quint64 mask)
         return QObject::tr("None");
 }
 
-QString formatPingTime(std::chrono::microseconds ping_time)
+QString formatPingTime(NodeClock::duration ping_time)
 {
-    return (ping_time == std::chrono::microseconds::max() || ping_time == 0us) ?
+    return (ping_time == decltype(CNode::m_min_ping_time.load())::max() || ping_time == 0us) ?
         QObject::tr("N/A") :
         QObject::tr("%1 ms").arg(QString::number(Ticks<std::chrono::milliseconds>(ping_time)));
 }

src/qt/guiutil.h

@@ -237,8 +237,8 @@ namespace GUIUtil
     /** Format CNodeStats.nServices bitmask into a user-readable string */
     QString formatServicesStr(quint64 mask);
 
-    /** Format a CNodeStats.m_last_ping_time into a user-readable string or display N/A, if 0 */
-    QString formatPingTime(std::chrono::microseconds ping_time);
+    /// Format a CNodeStats.m_last_ping_time/m_min_ping_time/m_ping_wait into a user-readable string if it exists, or display N/A
+    QString formatPingTime(NodeClock::duration ping_time);
 
     /** Format a CNodeStateStats.time_offset into a user-readable string */
     QString formatTimeOffset(int64_t time_offset);

src/rpc/net.cpp

@@ -253,7 +253,7 @@ static RPCHelpMan getpeerinfo()
         if (stats.m_last_ping_time > 0us) {
             obj.pushKV("pingtime", Ticks<SecondsDouble>(stats.m_last_ping_time));
         }
-        if (stats.m_min_ping_time < std::chrono::microseconds::max()) {
+        if (stats.m_min_ping_time < decltype(CNode::m_min_ping_time.load())::max()) {
             obj.pushKV("minping", Ticks<SecondsDouble>(stats.m_min_ping_time));
         }
         if (statestats.m_ping_wait > 0s) {