rpc: add --rpc-payment-allow-free-loopback

This allows RPC coming from the loopback interface to not have
to pay for service. This makes it possible to run an externally
accessible RPC server for payment while also having a local RPC
server that can be run unrestricted and payment free.

src/rpc/core_rpc_server.cpp

@@ -153,6 +153,7 @@ namespace cryptonote
     command_line::add_arg(desc, arg_rpc_payment_address);
     command_line::add_arg(desc, arg_rpc_payment_difficulty);
     command_line::add_arg(desc, arg_rpc_payment_credits);
+    command_line::add_arg(desc, arg_rpc_payment_allow_free_loopback);
   }
   //------------------------------------------------------------------------------------------------------------------------------
   core_rpc_server::core_rpc_server(
@@ -163,6 +164,7 @@ namespace cryptonote
     , m_p2p(p2p)
     , m_was_bootstrap_ever_used(false)
     , disable_rpc_ban(false)
+    , m_rpc_payment_allow_free_loopback(false)
   {}
   //------------------------------------------------------------------------------------------------------------------------------
   bool core_rpc_server::set_bootstrap_daemon(const std::string &address, const std::string &username_password)
@@ -280,6 +282,7 @@ namespace cryptonote
         MERROR("Payments difficulty and/or payments credits are 0, but a payment address was given");
         return false;
       }
+      m_rpc_payment_allow_free_loopback = command_line::get_arg(vm, arg_rpc_payment_allow_free_loopback);
       m_rpc_payment.reset(new rpc_payment(info.address, diff, credits));
       m_rpc_payment->load(command_line::get_arg(vm, cryptonote::arg_data_dir));
       m_p2p.set_rpc_credits_per_hash(RPC_CREDITS_PER_HASH_SCALE * (credits / (float)diff));
@@ -353,7 +356,7 @@ namespace cryptonote
 #define CHECK_PAYMENT_BASE(req, res, payment, same_ts) do { if (!ctx) break; uint64_t P = (uint64_t)payment; if (P > 0 && !check_payment(req.client, P, tracker.rpc_name(), same_ts, res.status, res.credits, res.top_hash)){return true;} tracker.pay(P); } while(0)
 #define CHECK_PAYMENT(req, res, payment) CHECK_PAYMENT_BASE(req, res, payment, false)
 #define CHECK_PAYMENT_SAME_TS(req, res, payment) CHECK_PAYMENT_BASE(req, res, payment, true)
-#define CHECK_PAYMENT_MIN1(req, res, payment, same_ts) do { if (!ctx) break; uint64_t P = (uint64_t)payment; if (P == 0) P = 1; if(!check_payment(req.client, P, tracker.rpc_name(), same_ts, res.status, res.credits, res.top_hash)){return true;} tracker.pay(P); } while(0)
+#define CHECK_PAYMENT_MIN1(req, res, payment, same_ts) do { if (!ctx || (m_rpc_payment_allow_free_loopback && ctx->m_remote_address.is_loopback())) break; uint64_t P = (uint64_t)payment; if (P == 0) P = 1; if(!check_payment(req.client, P, tracker.rpc_name(), same_ts, res.status, res.credits, res.top_hash)){return true;} tracker.pay(P); } while(0)
   //------------------------------------------------------------------------------------------------------------------------------
   bool core_rpc_server::check_core_ready()
   {
@@ -3255,4 +3258,10 @@ namespace cryptonote
     , "Restrict RPC to clients sending micropayment, yields that many credits per payment"
     , DEFAULT_PAYMENT_CREDITS_PER_HASH
     };
+
+  const command_line::arg_descriptor<bool> core_rpc_server::arg_rpc_payment_allow_free_loopback = {
+      "rpc-payment-allow-free-loopback"
+    , "Allow free access from the loopback address (ie, the local host)"
+    , false
+    };
 }  // namespace cryptonote

src/rpc/core_rpc_server.h

@@ -75,6 +75,7 @@ namespace cryptonote
     static const command_line::arg_descriptor<std::string> arg_rpc_payment_address;
     static const command_line::arg_descriptor<uint64_t> arg_rpc_payment_difficulty;
     static const command_line::arg_descriptor<uint64_t> arg_rpc_payment_credits;
+    static const command_line::arg_descriptor<bool> arg_rpc_payment_allow_free_loopback;
 
     typedef epee::net_utils::connection_context_base connection_context;
 
@@ -287,6 +288,7 @@ private:
     std::map<std::string, uint64_t> m_host_fails_score;
     std::unique_ptr<rpc_payment> m_rpc_payment;
     bool disable_rpc_ban;
+    bool m_rpc_payment_allow_free_loopback;
   };
 }