script: reduce OP_RETURN standard relay bytes to 40

Per mailing list discussion.

src/script.cpp

@@ -1298,8 +1298,8 @@ bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, vector<vector<unsi
             }
             else if (opcode2 == OP_SMALLDATA)
             {
-                // small pushdata, <= 80 bytes
-                if (vch1.size() > 80)
+                // small pushdata, <= MAX_OP_RETURN_RELAY bytes
+                if (vch1.size() > MAX_OP_RETURN_RELAY)
                     break;
             }
             else if (opcode1 != opcode2 || vch1 != vch2)

src/script.h

@@ -23,6 +23,7 @@ class CKeyStore;
 class CTransaction;
 
 static const unsigned int MAX_SCRIPT_ELEMENT_SIZE = 520; // bytes
+static const unsigned int MAX_OP_RETURN_RELAY = 40;      // bytes
 
 /** Signature hash types/flags */
 enum

src/test/transaction_tests.cpp

@@ -280,12 +280,12 @@ BOOST_AUTO_TEST_CASE(test_IsStandard)
     t.vout[0].scriptPubKey = CScript() << OP_1;
     BOOST_CHECK(!IsStandardTx(t, reason));
 
-    // 80-byte TX_NULL_DATA (standard)
-    t.vout[0].scriptPubKey = CScript() << OP_RETURN << ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef3804678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38");
+    // 40-byte TX_NULL_DATA (standard)
+    t.vout[0].scriptPubKey = CScript() << OP_RETURN << ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38");
     BOOST_CHECK(IsStandardTx(t, reason));
 
-    // 81-byte TX_NULL_DATA (non-standard)
-    t.vout[0].scriptPubKey = CScript() << OP_RETURN << ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef3804678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef3800");
+    // 41-byte TX_NULL_DATA (non-standard)
+    t.vout[0].scriptPubKey = CScript() << OP_RETURN << ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef3800");
     BOOST_CHECK(!IsStandardTx(t, reason));
 
     // TX_NULL_DATA w/o PUSHDATA
@@ -295,11 +295,11 @@ BOOST_AUTO_TEST_CASE(test_IsStandard)
 
     // Only one TX_NULL_DATA permitted in all cases
     t.vout.resize(2);
-    t.vout[0].scriptPubKey = CScript() << OP_RETURN << ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef3804678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38");
-    t.vout[1].scriptPubKey = CScript() << OP_RETURN << ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef3804678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38");
+    t.vout[0].scriptPubKey = CScript() << OP_RETURN << ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38");
+    t.vout[1].scriptPubKey = CScript() << OP_RETURN << ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38");
     BOOST_CHECK(!IsStandardTx(t, reason));
 
-    t.vout[0].scriptPubKey = CScript() << OP_RETURN << ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef3804678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38");
+    t.vout[0].scriptPubKey = CScript() << OP_RETURN << ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38");
     t.vout[1].scriptPubKey = CScript() << OP_RETURN;
     BOOST_CHECK(!IsStandardTx(t, reason));