static ring size 22 from v9

src/cryptonote_config.h

@@ -138,12 +138,12 @@
 
 #define THREAD_STACK_SIZE                       5 * 1024 * 1024
 
-#define DEFAULT_MIXIN                           9 // ring size 10
+#define DEFAULT_MIXIN                           21 // ring size 22
 
 #define HF_VERSION_DYNAMIC_FEE                  4
 #define HF_VERSION_MIN_MIXIN_4                  6
 #define HF_VERSION_MIN_MIXIN_7                  7
-#define HF_VERSION_MIN_MIXIN_9                  9
+#define HF_VERSION_MIN_MIXIN_21                 9
 #define HF_VERSION_ENFORCE_RCT                  6
 
 #define PER_KB_FEE_QUANTIZATION_DECIMALS        8

src/cryptonote_core/blockchain.cpp

@@ -2623,7 +2623,7 @@ bool Blockchain::check_tx_inputs(transaction& tx, tx_verification_context &tvc,
   {
     size_t n_unmixable = 0, n_mixable = 0;
     size_t mixin = std::numeric_limits<size_t>::max();
-    const size_t min_mixin = hf_version >= HF_VERSION_MIN_MIXIN_9 ? 9 : hf_version >= HF_VERSION_MIN_MIXIN_7 ? 7 : hf_version >= HF_VERSION_MIN_MIXIN_4 ? 4 : 2;
+    const size_t min_mixin = hf_version >= HF_VERSION_MIN_MIXIN_21 ? 21 : hf_version >= HF_VERSION_MIN_MIXIN_7 ? 7 : hf_version >= HF_VERSION_MIN_MIXIN_4 ? 4 : 2;
     for (const auto& txin : tx.vin)
     {
       // non txin_to_key inputs will be rejected below
@@ -2669,7 +2669,7 @@ bool Blockchain::check_tx_inputs(transaction& tx, tx_verification_context &tvc,
     }
 
     // from v9, all transactions must have the same ring size
-    if (hf_version >= HF_VERSION_MIN_MIXIN_9)
+    if (hf_version >= HF_VERSION_MIN_MIXIN_21)
     {
       if (mixin != min_mixin)
       {