set max block size for gbt

src/cryptonote_config.h

@@ -6,6 +6,7 @@
 
 #define CRYPTONOTE_MAX_BLOCK_NUMBER                     500000000
 #define CRYPTONOTE_MAX_BLOCK_SIZE                       500000000  // block header blob limit, never used!
+#define CRYPTONOTE_GETBLOCKTEMPLATE_MAX_BLOCK_SIZE	196608 //size of block (bytes) that is the maximum that miners will produce
 #define CRYPTONOTE_MAX_TX_SIZE                          1000000000
 #define CRYPTONOTE_PUBLIC_ADDRESS_TEXTBLOB_VER          0
 #define CRYPTONOTE_PUBLIC_ADDRESS_BASE58_PREFIX         18 // addresses start with "4"

src/cryptonote_core/tx_pool.cpp

@@ -424,6 +424,14 @@ namespace cryptonote
       if (tx.second.blob_size > upper_transaction_size_limit)
         continue;
 
+      // If adding this tx will make the block size
+      // greater than CRYPTONOTE_GETBLOCKTEMPLATE_MAX
+      // _BLOCK_SIZE bytes, reject the tx; this will 
+      // keep block sizes from becoming too unwieldly
+      // to propagate at 60s block times.
+      if ( (total_size + tx.second.blob_size) > CRYPTONOTE_GETBLOCKTEMPLATE_MAX_BLOCK_SIZE )
+        continue;
+
       // If adding this tx will make the block size
       // greater than 130% of the median, reject the
       // tx; this will keep down largely punitive tx