Validate outpost client startup configuration

docs/outpost-client-plugins.md

@@ -12,6 +12,14 @@ The Ethereum client plugin is configured via program options as follows:
 ```
 > NOTE:  If you look closely, the reference to `eth-01` in the Ethereum client config, matches the signature provider configured for `Ethereum`.  This mapping is what enables `1..n` clients in a single process
 
+The signer reference is validated during startup. Each
+`--outpost-ethereum-client` must reference the explicit, non-empty name of a
+configured `--signature-provider`; anonymous signature-provider specs cannot be
+referenced by an Ethereum client. When the optional Ethereum chain ID is
+present, startup also calls `eth_chainId` on the configured RPC endpoint and
+fails if the endpoint is unavailable, returns an invalid value, or reports a
+different chain ID.
+
 With the above configuration and the appropriate `app` & `plugin` config, you can access the `outpost-ethereum-client` configured with name/id == `eth-anvil-local` as follows
 
 ```cpp

libraries/libfc-test/include/fc-test/one_shot_http_server.hpp

@@ -0,0 +1,164 @@
+#pragma once
+
+#include <boost/asio.hpp>
+#include <boost/beast/core.hpp>
+#include <boost/beast/http.hpp>
+
+#include <fc/io/json.hpp>
+
+#include <cstdint>
+#include <sstream>
+#include <string>
+#include <thread>
+#include <utility>
+
+namespace fc::test {
+
+/**
+ * Minimal one-request loopback HTTP server for synchronous RPC client tests.
+ *
+ * The caller supplies the complete response body. The server accepts one
+ * request, returns HTTP 200 with that body, and closes the connection. Its
+ * destructor also unblocks an unused accept so tests that fail before making
+ * the expected request do not strand a worker thread.
+ */
+class one_shot_http_server {
+public:
+   explicit one_shot_http_server(std::string response_body, std::string expected_rpc_method = {})
+      : _response_body(std::move(response_body))
+      , _expected_rpc_method(std::move(expected_rpc_method))
+      , _acceptor(_io, tcp::endpoint(boost::asio::ip::make_address("127.0.0.1"), 0))
+      , _port(_acceptor.local_endpoint().port())
+      , _worker([this] { serve(); }) {}
+
+   one_shot_http_server(const one_shot_http_server&) = delete;
+   one_shot_http_server& operator=(const one_shot_http_server&) = delete;
+
+   ~one_shot_http_server() {
+      // Wake a worker blocked in synchronous accept without concurrently
+      // operating on the acceptor from two threads. The temporary socket is
+      // closed immediately, so a worker that accepts it exits its HTTP read.
+      boost::system::error_code error;
+      boost::asio::io_context io;
+      tcp::socket socket(io);
+      socket.connect(tcp::endpoint(boost::asio::ip::make_address("127.0.0.1"), _port), error);
+      socket.close(error);
+      if (_worker.joinable()) {
+         _worker.join();
+      }
+      _acceptor.close(error);
+   }
+
+   /** Return the loopback URL selected for this server. */
+   std::string url() const {
+      return "http://127.0.0.1:" + std::to_string(_port);
+   }
+
+private:
+   using tcp = boost::asio::ip::tcp;
+
+   void serve() {
+      boost::system::error_code error;
+      tcp::socket socket(_io);
+      _acceptor.accept(socket, error);
+      if (error) {
+         return;
+      }
+
+      boost::beast::flat_buffer request_buffer;
+      boost::beast::http::request<boost::beast::http::string_body> request;
+      boost::beast::http::read(socket, request_buffer, request, error);
+      if (error) {
+         return;
+      }
+
+      if (!_expected_rpc_method.empty()) {
+         bool request_matches = false;
+         try {
+            const auto request_object = fc::json::from_string(request.body()).get_object();
+            request_matches =
+               request_object.contains("method") &&
+               request_object["method"].as_string() == _expected_rpc_method &&
+               request_object.contains("params") &&
+               request_object["params"].is_array() &&
+               request_object["params"].get_array().empty();
+         } catch (...) {
+            return;
+         }
+         if (!request_matches) {
+            return;
+         }
+      }
+
+      std::ostringstream response;
+      response << "HTTP/1.1 200 OK\r\n"
+               << "Content-Type: application/json\r\n"
+               << "Content-Length: " << _response_body.size() << "\r\n"
+               << "Connection: close\r\n\r\n"
+               << _response_body;
+      const auto response_text = response.str();
+      boost::asio::write(socket, boost::asio::buffer(response_text), error);
+   }
+
+   std::string             _response_body;
+   std::string             _expected_rpc_method;
+   boost::asio::io_context _io;
+   tcp::acceptor           _acceptor;
+   uint16_t                _port;
+   std::thread             _worker;
+};
+
+/**
+ * Loopback server that deterministically accepts one connection and closes it.
+ *
+ * Unlike selecting and releasing an unused port, this fixture keeps ownership
+ * of the port until the client connects, so another process cannot race the
+ * test and unexpectedly provide a working endpoint.
+ */
+class connection_closing_http_server {
+public:
+   connection_closing_http_server()
+      : _acceptor(_io, tcp::endpoint(boost::asio::ip::make_address("127.0.0.1"), 0))
+      , _port(_acceptor.local_endpoint().port())
+      , _worker([this] { close_connection(); }) {}
+
+   connection_closing_http_server(const connection_closing_http_server&) = delete;
+   connection_closing_http_server& operator=(const connection_closing_http_server&) = delete;
+
+   ~connection_closing_http_server() {
+      boost::system::error_code error;
+      boost::asio::io_context io;
+      tcp::socket socket(io);
+      socket.connect(tcp::endpoint(boost::asio::ip::make_address("127.0.0.1"), _port), error);
+      socket.close(error);
+      if (_worker.joinable()) {
+         _worker.join();
+      }
+      _acceptor.close(error);
+   }
+
+   std::string url() const {
+      return "http://127.0.0.1:" + std::to_string(_port);
+   }
+
+private:
+   using tcp = boost::asio::ip::tcp;
+
+   void close_connection() {
+      boost::system::error_code error;
+      tcp::socket socket(_io);
+      _acceptor.accept(socket, error);
+      if (error) {
+         return;
+      }
+      socket.set_option(boost::asio::socket_base::linger(true, 0), error);
+      socket.close(error);
+   }
+
+   boost::asio::io_context _io;
+   tcp::acceptor           _acceptor;
+   uint16_t                _port;
+   std::thread             _worker;
+};
+
+} // namespace fc::test

plugins/outpost_ethereum_client_plugin/include/sysio/outpost_ethereum_client_plugin.hpp

@@ -19,7 +19,7 @@ struct ethereum_client_entry_t {
    /// batch operator auto-select the client for an outpost row by matching the
    /// row's `external_chain_id`, so multiple EVM outposts never share one
    /// remote endpoint. `nullopt` when the spec omitted the chain id.
-   std::optional<uint64_t>            chain_id;
+   std::optional<uint32_t>            chain_id;
 };
 
 using ethereum_client_entry_ptr = std::shared_ptr<ethereum_client_entry_t>;
@@ -108,7 +108,7 @@ class outpost_ethereum_client_plugin : public appbase::plugin<outpost_ethereum_c
    /// `external_chain_id`; an ambiguous (duplicate chain id) or missing match
    /// yields nullptr so the caller can fail closed rather than relay an
    /// outpost through the wrong endpoint.
-   ethereum_client_entry_ptr get_client_by_chain_id(uint64_t chain_id);
+   ethereum_client_entry_ptr get_client_by_chain_id(uint32_t chain_id);
 
    const std::vector<std::pair<std::filesystem::path, std::vector<fc::network::ethereum::abi::contract>>>& get_abi_files();