Add option `-alerts` to opt out of alert system

Make it possible to opt-out of the centralized alert system by providing
an option `-noalerts` or `-alerts=0`. The default remains unchanged.

This is a gentler form of #6260, in which I went a bit overboard by
removing the alert system completely.

I intend to add this to the GUI options in another pull after this.

Conflicts:
	src/init.cpp
	src/main.cpp

Github-Pull: #6274
Rebased-From: 02a6702a82a5b00e0e0351041dd3267308b7f319

3 files changed, 8 insertions, 2 deletions

diff --git a/src/init.cpp b/src/init.cpp
index ed05c15729..85e4710c39 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -241,6 +241,7 @@ std::string HelpMessage(HelpMessageMode mode)
     string strUsage = _("Options:") + "\n";
     strUsage += "  -?                     " + _("This help message") + "\n";
     strUsage += "  -alertnotify=<cmd>     " + _("Execute command when a relevant alert is received or we see a really long fork (%s in cmd is replaced by message)") + "\n";
+    strUsage += "  -alerts                " + strprintf(_("Receive and display P2P network alerts (default: %u)"), DEFAULT_ALERTS);
     strUsage += "  -blocknotify=<cmd>     " + _("Execute command when the best block changes (%s in cmd is replaced by block hash)") + "\n";
     strUsage += "  -checkblocks=<n>       " + strprintf(_("How many blocks to check at startup (default: %u, 0 = all)"), 288) + "\n";
     strUsage += "  -checklevel=<n>        " + strprintf(_("How thorough the block verification of -checkblocks is (0-4, default: %u)"), 3) + "\n";
@@ -745,6 +746,8 @@ bool AppInit2(boost::thread_group& threadGroup)
     fIsBareMultisigStd = GetArg("-permitbaremultisig", true) != 0;
     nMaxDatacarrierBytes = GetArg("-datacarriersize", nMaxDatacarrierBytes);
 
+    fAlerts = GetBoolArg("-alerts", DEFAULT_ALERTS);
+
     // ********************************************************* Step 4: application initialization: dir lock, daemonize, pidfile, debug log
 
     // Sanity check
diff --git a/src/main.cpp b/src/main.cpp
index c37e1092eb..4d287eec92 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -53,7 +53,7 @@ bool fTxIndex = false;
 bool fIsBareMultisigStd = true;
 bool fCheckBlockIndex = false;
 unsigned int nCoinCacheSize = 5000;
-
+bool fAlerts = DEFAULT_ALERTS;
 
 /** Fees smaller than this (in satoshi) are considered zero fee (for relaying and mining) */
 CFeeRate minRelayTxFee = CFeeRate(1000);
@@ -4265,7 +4265,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
     }
 
 
-    else if (strCommand == "alert")
+    else if (fAlerts && strCommand == "alert")
     {
         CAlert alert;
         vRecv >> alert;
diff --git a/src/main.h b/src/main.h
index 71f21716d0..9a875a0750 100644
--- a/src/main.h
+++ b/src/main.h
@@ -54,6 +54,8 @@ static const unsigned int DEFAULT_BLOCK_MAX_SIZE = 750000;
 static const unsigned int DEFAULT_BLOCK_MIN_SIZE = 0;
 /** Default for -blockprioritysize, maximum space for zero/low-fee transactions **/
 static const unsigned int DEFAULT_BLOCK_PRIORITY_SIZE = 50000;
+/** Default for accepting alerts from the P2P network. */
+static const bool DEFAULT_ALERTS = true;
 /** The maximum size for transactions we're willing to relay/mine */
 static const unsigned int MAX_STANDARD_TX_SIZE = 100000;
 /** The maximum allowed number of signature check operations in a block (network rule) */
@@ -129,6 +131,7 @@ extern bool fIsBareMultisigStd;
 extern bool fCheckBlockIndex;
 extern unsigned int nCoinCacheSize;
 extern CFeeRate minRelayTxFee;
+extern bool fAlerts;
 
 /** Best header we've seen so far (used for getheaders queries' starting points). */
 extern CBlockIndex *pindexBestHeader;