Initial support for IPv6 (#8225)

- Merge rabit socket into XGBoost.
- Dask interface support.
- Add test to the socket.

tests/cpp/collective/test_socket.cc

@@ -0,0 +1,77 @@
+/*!
+ * Copyright (c) 2022 by 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"
+
+namespace xgboost {
+namespace collective {
+TEST(Socket, Basic) {
+  system::SocketStartup();
+
+  SockAddress addr{SockAddrV6::Loopback()};
+  ASSERT_TRUE(addr.IsV6());
+  addr = SockAddress{SockAddrV4::Loopback()};
+  ASSERT_TRUE(addr.IsV4());
+
+  std::string msg{"Skipping IPv6 test"};
+
+  auto run_test = [msg](SockDomain domain) {
+    auto server = TCPSocket::Create(domain);
+    ASSERT_EQ(server.Domain(), domain);
+    auto port = server.BindHost();
+    server.Listen();
+
+    TCPSocket client;
+    if (domain == SockDomain::kV4) {
+      auto const& addr = SockAddrV4::Loopback().Addr();
+      ASSERT_EQ(Connect(MakeSockAddress(StringView{addr}, port), &client), std::errc{});
+    } else {
+      auto const& addr = SockAddrV6::Loopback().Addr();
+      auto rc = Connect(MakeSockAddress(StringView{addr}, port), &client);
+      // some environment (docker) has restricted network configuration.
+      if (rc == std::error_code{EADDRNOTAVAIL, std::system_category()}) {
+        GTEST_SKIP_(msg.c_str());
+      }
+      ASSERT_EQ(rc, std::errc{});
+    }
+    ASSERT_EQ(client.Domain(), domain);
+
+    auto accepted = server.Accept();
+    StringView msg{"Hello world."};
+    accepted.Send(msg);
+
+    std::string str;
+    client.Recv(&str);
+    ASSERT_EQ(StringView{str}, msg);
+  };
+
+  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());
+  }
+  run_test(SockDomain::kV6);
+
+  system::SocketFinalize();
+}
+}  // namespace collective
+}  // namespace xgboost

tests/cpp/filesystem.h

@@ -1,7 +1,6 @@
 /*!
  * Copyright (c) 2022 by XGBoost Contributors
  */
-
 #ifndef XGBOOST_TESTS_CPP_FILESYSTEM_H
 #define XGBOOST_TESTS_CPP_FILESYSTEM_H
 

tests/cpp/tree/test_partitioner.h

@@ -1,8 +1,12 @@
 /*!
  * Copyright 2021-2022, XGBoost contributors.
  */
+#ifndef XGBOOST_TESTS_CPP_TREE_TEST_PARTITIONER_H_
+#define XGBOOST_TESTS_CPP_TREE_TEST_PARTITIONER_H_
 #include <xgboost/tree_model.h>
+
 #include <vector>
+
 #include "../../../src/tree/hist/expand_entry.h"
 
 namespace xgboost {
@@ -19,3 +23,4 @@ inline void GetSplit(RegTree *tree, float split_value, std::vector<CPUExpandEntr
 }
 }  // namespace tree
 }  // namespace xgboost
+#endif  // XGBOOST_TESTS_CPP_TREE_TEST_PARTITIONER_H_