feat: fabric-bridge auto-fetch target_info from remote target node

Initiator can now auto-discover target_info by polling the target's
HTTP control server. Just set target_host and target_port in config:
  --config '{"mode":"initiator",...,"target_host":"10.10.100.1","target_port":9100}'

No more manual copy-paste of target_info JSON between hosts.

nodes/fabric-bridge/src/fabric_bridge_node.cpp

@@ -4,6 +4,14 @@
 
 #include <spdlog/spdlog.h>
 
+#ifndef _WIN32
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <unistd.h>
+#include <netdb.h>
+#endif
+
 namespace dmf_node {
 
 FabricBridgeNode::~FabricBridgeNode() {
@@ -49,6 +57,12 @@ void FabricBridgeNode::configure(const nlohmann::json& params) {
             spdlog::info("Fabric-bridge: target_info set, signaling startup");
         }
     }
+
+    if (params.contains("target_host")) {
+        target_host_ = params["target_host"].get<std::string>();
+        target_port_ = params.value("target_port", 9100);
+        spdlog::info("Fabric-bridge: will fetch target_info from {}:{}", target_host_, target_port_);
+    }
 }
 
 void FabricBridgeNode::on_add_writer(const std::string& port_id, mxlFlowWriter writer) {
@@ -85,14 +99,106 @@ void FabricBridgeNode::on_remove_reader(const std::string& port_id) {
     }
 }
 
+void FabricBridgeNode::fetch_target_info() {
+    if (target_host_.empty()) return;
+
+    spdlog::info("Fabric-bridge: fetching target_info from {}:{}", target_host_, target_port_);
+
+    std::string request = "POST /cmd HTTP/1.1\r\n"
+                           "Host: " + target_host_ + "\r\n"
+                           "Content-Type: application/json\r\n"
+                           "Connection: close\r\n"
+                           "Content-Length: 20\r\n"
+                           "\r\n"
+                           "{\"cmd\":\"status\"}";
+
+    for (int attempt = 0; attempt < 30 && running_ && target_info_str_.empty(); ++attempt) {
+        int sock = socket(AF_INET, SOCK_STREAM, 0);
+        if (sock < 0) {
+            spdlog::warn("Fabric-bridge: socket() failed, retry {}...", attempt + 1);
+            std::this_thread::sleep_for(std::chrono::milliseconds(1000));
+            continue;
+        }
+
+        struct hostent* he = gethostbyname(target_host_.c_str());
+        if (!he) {
+            spdlog::warn("Fabric-bridge: cannot resolve {}, retry {}...", target_host_, attempt + 1);
+            close(sock);
+            std::this_thread::sleep_for(std::chrono::milliseconds(1000));
+            continue;
+        }
+
+        struct sockaddr_in addr{};
+        addr.sin_family = AF_INET;
+        addr.sin_port = htons(target_port_);
+        std::memcpy(&addr.sin_addr, he->h_addr_list[0], he->h_length);
+
+        if (connect(sock, reinterpret_cast<struct sockaddr*>(&addr), sizeof(addr)) < 0) {
+            spdlog::warn("Fabric-bridge: connect to {}:{} failed, retry {}...", target_host_, target_port_, attempt + 1);
+            close(sock);
+            std::this_thread::sleep_for(std::chrono::milliseconds(1000));
+            continue;
+        }
+
+        if (send(sock, request.c_str(), request.size(), 0) < 0) {
+            spdlog::warn("Fabric-bridge: send failed, retry {}...", attempt + 1);
+            close(sock);
+            std::this_thread::sleep_for(std::chrono::milliseconds(1000));
+            continue;
+        }
+
+        std::string response;
+        char buf[4096];
+        ssize_t n;
+        while ((n = recv(sock, buf, sizeof(buf), 0)) > 0) {
+            response.append(buf, n);
+        }
+        close(sock);
+
+        auto body_pos = response.find("\r\n\r\n");
+        if (body_pos == std::string::npos) {
+            spdlog::warn("Fabric-bridge: no HTTP body in response, retry {}...", attempt + 1);
+            std::this_thread::sleep_for(std::chrono::milliseconds(500));
+            continue;
+        }
+
+        try {
+            auto json = nlohmann::json::parse(response.substr(body_pos + 4));
+            if (json.contains("data") && json["data"].contains("target_info")) {
+                auto ti = json["data"]["target_info"].get<std::string>();
+                if (!ti.empty()) {
+                    target_info_str_ = ti;
+                    start_requested_.store(true);
+                    spdlog::info("Fabric-bridge: fetched target_info ({} bytes)", target_info_str_.size());
+                    return;
+                }
+            }
+        } catch (const nlohmann::json::exception& e) {
+            spdlog::warn("Fabric-bridge: JSON parse error: {}", e.what());
+        }
+
+        spdlog::info("Fabric-bridge: target_info not ready yet, retry {}...", attempt + 1);
+        std::this_thread::sleep_for(std::chrono::milliseconds(500));
+    }
+
+    if (target_info_str_.empty()) {
+        spdlog::error("Fabric-bridge: failed to fetch target_info after 30 attempts");
+    }
+}
+
 void FabricBridgeNode::process() {
     if (!worker_thread_.has_value() && start_requested_.load()) {
-        running_ = true;
-        spdlog::info("Fabric-bridge: starting worker thread (mode={})", mode_ == FabricMode::Initiator ? "initiator" : "target");
-        if (mode_ == FabricMode::Initiator) {
-            worker_thread_ = std::thread(&FabricBridgeNode::run_initiator, this);
-        } else {
-            worker_thread_ = std::thread(&FabricBridgeNode::run_target, this);
+        if (mode_ == FabricMode::Initiator && !target_host_.empty() && target_info_str_.empty()) {
+            fetch_target_info();
+        }
+        if (start_requested_.load()) {
+            running_ = true;
+            spdlog::info("Fabric-bridge: starting worker thread (mode={})", mode_ == FabricMode::Initiator ? "initiator" : "target");
+            if (mode_ == FabricMode::Initiator) {
+                worker_thread_ = std::thread(&FabricBridgeNode::run_initiator, this);
+            } else {
+                worker_thread_ = std::thread(&FabricBridgeNode::run_target, this);
+            }
         }
     }
     std::this_thread::sleep_for(std::chrono::milliseconds(100));

nodes/fabric-bridge/src/fabric_bridge_node.hpp

@@ -51,6 +51,11 @@ private:
 
     std::string target_info_str_;
 
+    std::string target_host_;
+    uint16_t target_port_ = 9100;
+
+    void fetch_target_info();
+
     mxlFabricsInstance fabrics_instance_ = nullptr;
     mxlFabricsInitiator initiator_ = nullptr;
     mxlFabricsTarget target_ = nullptr;