wallet: forbid dust altogether in output selection where appropriate

src/wallet/wallet2.cpp

@@ -1515,7 +1515,7 @@ namespace
 // returns:
 //    direct return: amount of money found
 //    modified reference: selected_transfers, a list of iterators/indices of input sources
-uint64_t wallet2::select_transfers(uint64_t needed_money, bool add_dust, uint64_t dust, std::list<transfer_container::iterator>& selected_transfers)
+uint64_t wallet2::select_transfers(uint64_t needed_money, bool add_dust, uint64_t dust, bool hf2_rules, std::list<transfer_container::iterator>& selected_transfers)
 {
   std::vector<size_t> unused_transfers_indices;
   std::vector<size_t> unused_dust_indices;
@@ -1530,7 +1530,15 @@ uint64_t wallet2::select_transfers(uint64_t needed_money, bool add_dust, uint64_
       if (dust < td.amount() && is_valid_decomposed_amount(td.amount()))
         unused_transfers_indices.push_back(i);
       else
-        unused_dust_indices.push_back(i);
+      {
+        // for hf2 rules, we disregard dust, which will be spendable only
+        // via sweep_dust. If we're asked to add dust, though, we still
+        // consider them, as this will be a mixin 0 tx (and thus we may
+        // end up with a tx with one mixable output and N dusty ones).
+        // This should be made better at some point...
+        if (!hf2_rules || add_dust)
+          unused_dust_indices.push_back(i);
+      }
     }
   }
 

src/wallet/wallet2.h

@@ -362,7 +362,7 @@ namespace tools
     void pull_blocks(uint64_t start_height, uint64_t& blocks_start_height, const std::list<crypto::hash> &short_chain_history, std::list<cryptonote::block_complete_entry> &blocks);
     void pull_next_blocks(uint64_t start_height, uint64_t &blocks_start_height, std::list<crypto::hash> &short_chain_history, const std::list<cryptonote::block_complete_entry> &prev_blocks, std::list<cryptonote::block_complete_entry> &blocks, bool &error);
     void process_blocks(uint64_t start_height, const std::list<cryptonote::block_complete_entry> &blocks, uint64_t& blocks_added);
-    uint64_t select_transfers(uint64_t needed_money, bool add_dust, uint64_t dust, std::list<transfer_container::iterator>& selected_transfers);
+    uint64_t select_transfers(uint64_t needed_money, bool add_dust, uint64_t dust, bool hf2_rules, std::list<transfer_container::iterator>& selected_transfers);
     bool prepare_file_names(const std::string& file_path);
     void process_unconfirmed(const cryptonote::transaction& tx, uint64_t height);
     void process_outgoing(const cryptonote::transaction& tx, uint64_t height, uint64_t spent, uint64_t received);
@@ -559,8 +559,9 @@ namespace tools
     // randomly select inputs for transaction
     // throw if requested send amount is greater than amount available to send
     std::list<transfer_container::iterator> selected_transfers;
-    const bool add_dust = (0 == fake_outputs_count) && !use_fork_rules(2); // first fork has version 2
-    uint64_t found_money = select_transfers(needed_money, add_dust, dust_policy.dust_threshold, selected_transfers);
+    bool hf2_rules = use_fork_rules(2); // first fork has version 2
+    const bool add_dust = (0 == fake_outputs_count) && hf2_rules;
+    uint64_t found_money = select_transfers(needed_money, add_dust, dust_policy.dust_threshold, hf2_rules, selected_transfers);
     THROW_WALLET_EXCEPTION_IF(found_money < needed_money, error::not_enough_money, found_money, needed_money - fee, fee);
 
     typedef COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::out_entry out_entry;