[Coll] Implement get host address in libxgboost. (#9644)

- Port `xgboost.tracker.get_host_ip` in C++.

tests/cpp/collective/net_test.h

@@ -0,0 +1,41 @@
+/**
+ * Copyright 2022-2023, XGBoost Contributors
+ */
+#pragma once
+
+#include <gtest/gtest.h>
+#include <xgboost/collective/socket.h>
+
+#include <fstream>  // ifstream
+
+#include "../helpers.h"  // for FileExists
+
+namespace xgboost::collective {
+class SocketTest : public ::testing::Test {
+ protected:
+  std::string skip_msg_{"Skipping IPv6 test"};
+
+  bool SkipTest() {
+    std::string path{"/sys/module/ipv6/parameters/disable"};
+    if (FileExists(path)) {
+      std::ifstream fin(path);
+      if (!fin) {
+        return true;
+      }
+      std::string s_value;
+      fin >> s_value;
+      auto value = std::stoi(s_value);
+      if (value != 0) {
+        return true;
+      }
+    } else {
+      return true;
+    }
+    return false;
+  }
+
+ protected:
+  void SetUp() override { system::SocketStartup(); }
+  void TearDown() override { system::SocketFinalize(); }
+};
+}  // namespace xgboost::collective

tests/cpp/collective/test_socket.cc

@@ -1,19 +1,16 @@
 /**
- * Copyright 2022-2023 by XGBoost Contributors
+ * Copyright 2022-2023, XGBoost Contributors
  */
 #include <gtest/gtest.h>
 #include <xgboost/collective/socket.h>
 
 #include <cerrno>        // EADDRNOTAVAIL
-#include <fstream>       // ifstream
 #include <system_error>  // std::error_code, std::system_category
 
-#include "../helpers.h"
+#include "net_test.h"  // for SocketTest
 
 namespace xgboost::collective {
-TEST(Socket, Basic) {
-  system::SocketStartup();
-
+TEST_F(SocketTest, Basic) {
   SockAddress addr{SockAddrV6::Loopback()};
   ASSERT_TRUE(addr.IsV6());
   addr = SockAddress{SockAddrV4::Loopback()};
@@ -54,34 +51,27 @@ TEST(Socket, Basic) {
 
   run_test(SockDomain::kV4);
 
-  std::string path{"/sys/module/ipv6/parameters/disable"};
-  if (FileExists(path)) {
-    std::ifstream fin(path);
-    if (!fin) {
-      GTEST_SKIP_(msg.c_str());
-    }
-    std::string s_value;
-    fin >> s_value;
-    auto value = std::stoi(s_value);
-    if (value != 0) {
-      GTEST_SKIP_(msg.c_str());
-    }
-  } else {
-    GTEST_SKIP_(msg.c_str());
+  if (SkipTest()) {
+    GTEST_SKIP_(skip_msg_.c_str());
   }
   run_test(SockDomain::kV6);
-
-  system::SocketFinalize();
 }
 
-TEST(Socket, Bind) {
-  system::SocketStartup();
-  auto any = SockAddrV4::InaddrAny().Addr();
-  auto sock = TCPSocket::Create(SockDomain::kV4);
-  std::int32_t port{0};
-  auto rc = sock.Bind(any, &port);
-  ASSERT_TRUE(rc.OK());
-  ASSERT_NE(port, 0);
-  system::SocketFinalize();
+TEST_F(SocketTest, Bind) {
+  auto run = [](SockDomain domain) {
+    auto any =
+        domain == SockDomain::kV4 ? SockAddrV4::InaddrAny().Addr() : SockAddrV6::InaddrAny().Addr();
+    auto sock = TCPSocket::Create(domain);
+    std::int32_t port{0};
+    auto rc = sock.Bind(any, &port);
+    ASSERT_TRUE(rc.OK());
+    ASSERT_NE(port, 0);
+  };
+
+  run(SockDomain::kV4);
+  if (SkipTest()) {
+    GTEST_SKIP_(skip_msg_.c_str());
+  }
+  run(SockDomain::kV6);
 }
 }  // namespace xgboost::collective

tests/cpp/collective/test_tracker.cc

@@ -0,0 +1,18 @@
+/**
+ * Copyright 2023, XGBoost Contributors
+ */
+#include "../../../src/collective/tracker.h"  // for GetHostAddress
+#include "net_test.h"                         // for SocketTest
+
+namespace xgboost::collective {
+namespace {
+class TrackerTest : public SocketTest {};
+}  // namespace
+
+TEST_F(TrackerTest, GetHostAddress) {
+  std::string host;
+  auto rc = GetHostAddress(&host);
+  ASSERT_TRUE(rc.OK());
+  ASSERT_TRUE(host.find("127.") == std::string::npos);
+}
+}  // namespace xgboost::collective