evo: prohibit overwriting entry in MnNetInfo

Author: kwvg

src/evo/deterministicmns.cpp

@@ -1255,6 +1255,7 @@ static bool CheckService(const ProTx& proTx, TxValidationState& state)
         return true;
     // Shouldn't be possible during self-checks
     case NetInfoStatus::BadInput:
+    case NetInfoStatus::MaxLimit:
         assert(false);
     } // no default case, so the compiler can warn about missing cases
     assert(false);

src/evo/netinfo.cpp

@@ -172,6 +172,9 @@ NetInfoStatus MnNetInfo::ValidateService(const CService& service)
 
 NetInfoStatus MnNetInfo::AddEntry(const std::string& input)
 {
+    if (!IsEmpty()) {
+        return NetInfoStatus::MaxLimit;
+    }
     if (auto service_opt{Lookup(input, /*portDefault=*/Params().GetDefaultPort(), /*fAllowLookup=*/false)}) {
         const auto ret{ValidateService(*service_opt)};
         if (ret == NetInfoStatus::Success) {

src/evo/netinfo.h

@@ -16,6 +16,7 @@ class CService;
 enum class NetInfoStatus : uint8_t {
     // Managing entries
     BadInput,
+    MaxLimit,
 
     // Validation
     BadAddress,
@@ -42,6 +43,8 @@ constexpr std::string_view NISToString(const NetInfoStatus code)
         return "unroutable address";
     case NetInfoStatus::Malformed:
         return "malformed";
+    case NetInfoStatus::MaxLimit:
+        return "too many entries";
     case NetInfoStatus::Success:
         return "success";
     } // no default case, so the compiler can warn about missing cases

src/test/evo_netinfo_tests.cpp

@@ -60,6 +60,14 @@ BOOST_AUTO_TEST_CASE(mnnetinfo_rules)
             ValidateGetEntries(netInfo.GetEntries(), /*expected_size=*/1);
         }
     }
+
+    {
+        // MnNetInfo only stores one value, overwriting prohibited
+        MnNetInfo netInfo;
+        BOOST_CHECK_EQUAL(netInfo.AddEntry("1.1.1.1:9999"), NetInfoStatus::Success);
+        BOOST_CHECK_EQUAL(netInfo.AddEntry("1.1.1.2:9999"), NetInfoStatus::MaxLimit);
+        ValidateGetEntries(netInfo.GetEntries(), /*expected_size=*/1);
+    }
 }
 
 BOOST_AUTO_TEST_CASE(netinfo_ser)