fix: Replaces random endpoint resolution with sequential (#5365)

This change addresses an issue where `rippled` attempts to connect to an IPv6 address, even when the local network lacks IPv6 support, resulting in a "Network is unreachable" error.

The fix replaces the custom endpoint selection logic with `boost::async_connect`, which sequentially attempts to connect to available endpoints until one succeeds or all fail.

src/xrpld/app/misc/detail/ValidatorSite.cpp

@@ -102,7 +102,7 @@ ValidatorSite::ValidatorSite(
 ValidatorSite::~ValidatorSite()
 {
     std::unique_lock<std::mutex> lock{state_mutex_};
-    if (timer_.expires_at() > clock_type::time_point{})
+    if (timer_.expiry() > clock_type::time_point{})
     {
         if (!stopping_)
         {
@@ -168,7 +168,7 @@ ValidatorSite::start()
 {
     std::lock_guard l0{sites_mutex_};
     std::lock_guard l1{state_mutex_};
-    if (timer_.expires_at() == clock_type::time_point{})
+    if (timer_.expiry() == clock_type::time_point{})
         setTimer(l0, l1);
 }
 

src/xrpld/app/misc/detail/WorkBase.h

@@ -96,6 +96,9 @@ public:
     void
     onResolve(error_code const& ec, results_type results);
 
+    void
+    onConnect(error_code const& ec, endpoint_type const& endpoint);
+
     void
     onStart();
 
@@ -195,46 +198,26 @@ WorkBase<Impl>::onResolve(error_code const& ec, results_type results)
     if (ec)
         return fail(ec);
 
-    // Use last endpoint if it is successfully connected
+    boost::asio::async_connect(
-    // and is in the list, otherwise pick a random endpoint
+        socket_,
-    // from the list (excluding last endpoint). If there is
+        results,
-    // only one endpoint and it is the last endpoint then
-    // use the last endpoint.
-    lastEndpoint_ = [&]() -> endpoint_type {
-        int foundIndex = 0;
-        auto const foundIt = std::find_if(
-            results.begin(), results.end(), [&](endpoint_type const& e) {
-                if (e == lastEndpoint_)
-                    return true;
-                foundIndex++;
-                return false;
-            });
-        if (foundIt != results.end() && lastStatus_)
-            return lastEndpoint_;
-        else if (results.size() == 1)
-            return *results.begin();
-        else if (foundIt == results.end())
-            return *std::next(results.begin(), rand_int(results.size() - 1));
-
-        // lastEndpoint_ is part of the collection
-        // Pick a random number from the n-1 valid choices, if we use
-        // this as an index, note the last element will never be chosen
-        // and the `lastEndpoint_` index may be chosen. So when the
-        // `lastEndpoint_` index is chosen, that is treated as if the
-        // last element was chosen.
-        auto randIndex =
-            (results.size() > 2) ? rand_int(results.size() - 2) : 0;
-        if (randIndex == foundIndex)
-            randIndex = results.size() - 1;
-        return *std::next(results.begin(), randIndex);
-    }();
-
-    socket_.async_connect(
-        lastEndpoint_,
         strand_.wrap(std::bind(
-            &Impl::onConnect,
+            &WorkBase::onConnect,
             impl().shared_from_this(),
-            std::placeholders::_1)));
+            std::placeholders::_1,
+            std::placeholders::_2)));
+}
+
+template <class Impl>
+void
+WorkBase<Impl>::onConnect(error_code const& ec, endpoint_type const& endpoint)
+{
+    lastEndpoint_ = endpoint;
+
+    if (ec)
+        return fail(ec);
+
+    impl().onConnect(ec);
 }
 
 template <class Impl>