P2P: add maxtimeadjustment command line option

src/init.cpp

@@ -27,6 +27,7 @@
 #include "script/standard.h"
 #include "script/sigcache.h"
 #include "scheduler.h"
+#include "timedata.h"
 #include "txdb.h"
 #include "txmempool.h"
 #include "torcontrol.h"
@@ -365,6 +366,7 @@ std::string HelpMessage(HelpMessageMode mode)
     strUsage += HelpMessageOpt("-maxconnections=<n>", strprintf(_("Maintain at most <n> connections to peers (default: %u)"), DEFAULT_MAX_PEER_CONNECTIONS));
     strUsage += HelpMessageOpt("-maxreceivebuffer=<n>", strprintf(_("Maximum per-connection receive buffer, <n>*1000 bytes (default: %u)"), DEFAULT_MAXRECEIVEBUFFER));
     strUsage += HelpMessageOpt("-maxsendbuffer=<n>", strprintf(_("Maximum per-connection send buffer, <n>*1000 bytes (default: %u)"), DEFAULT_MAXSENDBUFFER));
+    strUsage += HelpMessageOpt("-maxtimeadjustment", strprintf(_("Maximum allowed median peer time offset adjustment. Local perspective of time may be influenced by peers forward or backward by this amount. (default: %u seconds)"), DEFAULT_MAX_TIME_ADJUSTMENT));
     strUsage += HelpMessageOpt("-onion=<ip:port>", strprintf(_("Use separate SOCKS5 proxy to reach peers via Tor hidden services (default: %s)"), "-proxy"));
     strUsage += HelpMessageOpt("-onlynet=<net>", _("Only connect to nodes in network <net> (ipv4, ipv6 or onion)"));
     strUsage += HelpMessageOpt("-permitbaremultisig", strprintf(_("Relay non-P2SH multisig (default: %u)"), DEFAULT_PERMIT_BAREMULTISIG));

src/timedata.cpp

@@ -83,7 +83,7 @@ void AddTimeData(const CNetAddr& ip, int64_t nOffsetSample)
         int64_t nMedian = vTimeOffsets.median();
         std::vector<int64_t> vSorted = vTimeOffsets.sorted();
         // Only let other nodes change our time by so much
-        if (abs64(nMedian) < 70 * 60)
+        if (abs64(nMedian) <= std::max<int64_t>(0, GetArg("-maxtimeadjustment", DEFAULT_MAX_TIME_ADJUSTMENT)))
         {
             nTimeOffset = nMedian;
         }

src/timedata.h

@@ -10,6 +10,8 @@
 #include <stdint.h>
 #include <vector>
 
+static const int64_t DEFAULT_MAX_TIME_ADJUSTMENT = 70 * 60;
+
 class CNetAddr;
 
 /**