[test] Use either `127.0.0.1` or `[::1]` to run in ipv6-only environments.

[rupprecht]

Summary

Test for both IPv4 and IPv6 support to determine if either 127.0.0.1 or [::1] are appropriate IP addresses to attempt to connect to. In an IPv6-only environment, 127.0.0.1 is not available.

Using localhost is problematic because we might not be able to get the same port on each IP flavor, and later try to connect to the wrong thing.

[rupprecht]

I previously converted some tests to support running in ipv6-only environments in D87333, but we weren't running these tests so I missed them. Looking at history, I see D58131 specifically changed this from localhost to 127.0.0.1. Do the reasons there still apply today? I could make this more complicated and probe to see if 127.0.0.1 is supported, and fallback to ::1 if that doesn't work, like I did in parts of D87333, although this would be preferred IMO.

[labath]

I believe the reasons are still relevant. Basically the problem is that listening on localhost:x creates two sockets (one for 127.0.0.1, one for ::1), and there's no way to guarantee that we'll be able to grab the same port for both (one could be taken by some other application). Our listening code will succeed if it opens at least one socket, but then if we again try to connect using the localhost name, we may end up connecting to the wrong thing. I think the correct fix is to take the address (ip+port) that we've *actually* started listening on, and then pass *that* as the argument to the connect command, but I'm not sure if our current Socket APIs allow you to get that information.

[rupprecht]

• Add a GetLocalhostIp helper to socket host utilities

[rupprecht]

In D133393#3773793, @labath wrote:

I believe the reasons are still relevant. Basically the problem is that listening on localhost:x creates two sockets (one for 127.0.0.1, one for ::1), and there's no way to guarantee that we'll be able to grab the same port for both (one could be taken by some other application). Our listening code will succeed if it opens at least one socket, but then if we again try to connect using the localhost name, we may end up connecting to the wrong thing. I think the correct fix is to take the address (ip+port) that we've *actually* started listening on, and then pass *that* as the argument to the connect command, but I'm not sure if our current Socket APIs allow you to get that information.

There's listen_socket.GetLocalIPAddress(), but that returns an empty string here.

Anyway, I just changed to use the HostSupportsIPv4()/HostSupportsIPv6() helper methods and pick an appropriate scheme. PTAL.

[JDevlieghere]

lldb/unittests/TestingSupport/Host/SocketTestUtilities.h

50

nit

[rupprecht]

• Ip -> IP casing

[labath]

In D133393#3775995, @rupprecht wrote:

In D133393#3773793, @labath wrote:

I believe the reasons are still relevant. Basically the problem is that listening on localhost:x creates two sockets (one for 127.0.0.1, one for ::1), and there's no way to guarantee that we'll be able to grab the same port for both (one could be taken by some other application). Our listening code will succeed if it opens at least one socket, but then if we again try to connect using the localhost name, we may end up connecting to the wrong thing. I think the correct fix is to take the address (ip+port) that we've *actually* started listening on, and then pass *that* as the argument to the connect command, but I'm not sure if our current Socket APIs allow you to get that information.

There's listen_socket.GetLocalIPAddress(), but that returns an empty string here.

Yeah, that probably only works on connected sockets.

lldb/unittests/TestingSupport/Host/SocketTestUtilities.h

 #if LLDB_ENABLE_POSIX
 void CreateDomainConnectedSockets(llvm::StringRef path,
                                   std::unique_ptr<DomainSocket> *a_up,
                                   std::unique_ptr<DomainSocket> *b_up);
 #endif
 
 bool HostSupportsIPv6();
 bool HostSupportsIPv4();
+
+/// Return an IP for localhost based on host support.
+///
+/// This will return either "127.0.0.1" if IPv4 is detected, or "[::1]" if IPv6
+/// is detected. If neither are detected, return an error.
+llvm::Expected<std::string> GetLocalhostIP();
+
 } // namespace lldb_private
 
 #endif

lldb/unittests/TestingSupport/Host/SocketTestUtilities.cpp

 
 bool lldb_private::HostSupportsIPv4() {
   return CheckIPSupport("IPv4", "127.0.0.1:0");
 }
 
 bool lldb_private::HostSupportsIPv6() {
   return CheckIPSupport("IPv6", "[::1]:0");
 }
+
+llvm::Expected<std::string> lldb_private::GetLocalhostIP() {
+  if (HostSupportsIPv4())
+    return "127.0.0.1";
+  if (HostSupportsIPv6())
+    return "[::1]";
+  return llvm::make_error<llvm::StringError>(
+      "Neither IPv4 nor IPv6 appear to be supported",
+      llvm::inconvertibleErrorCode());
+}

lldb/unittests/tools/lldb-server/tests/CMakeLists.txt

 add_lldb_unittest(LLDBServerTests
   LLGSTest.cpp
   MessageObjects.cpp
   TestBase.cpp
   TestClient.cpp
 
   LINK_LIBS
     lldbHost
     lldbCore
+    lldbHostHelpers
     lldbInterpreter
     lldbTarget
     lldbPluginPlatformLinux
     lldbPluginProcessGDBRemote
 
     LLVMTestingSupport
   LINK_COMPONENTS
     Support
   )
 
 add_dependencies(LLDBServerTests lldb-server ${ALL_LLDB_TEST_EXECUTABLES})

lldb/unittests/tools/lldb-server/tests/TestClient.cpp

 //===-- TestClient.cpp ----------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "TestClient.h"
+#include "TestingSupport/Host/SocketTestUtilities.h"
 #include "lldb/Host/HostInfo.h"
 #include "lldb/Host/common/TCPSocket.h"
 #include "lldb/Host/posix/ConnectionFileDescriptorPosix.h"
 #include "lldb/Utility/Args.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Testing/Support/Error.h"
 #include "gtest/gtest.h"
Expected<std::unique_ptr<TestClient>> TestClient::launchCustom(StringRef Log, ArrayRef<StringRef> ServerArgs, ArrayRef<StringRef> InferiorArgs) {
   if (!Log.empty()) {
     args.AppendArgument(("--log-file=" + Log).str());
     if (IsLldbServer())
       args.AppendArgument("--log-channels=gdb-remote packets");
     else
       args.AppendArgument("--log-flags=0x800000");
   }
 
+  auto LocalhostIPOrErr = GetLocalhostIP();
+  if (!LocalhostIPOrErr)
+    return LocalhostIPOrErr.takeError();
+  const std::string &LocalhostIP = *LocalhostIPOrErr;
+
   Status status;
   TCPSocket listen_socket(true, false);
-  status = listen_socket.Listen("127.0.0.1:0", 5);
+  status = listen_socket.Listen(LocalhostIP + ":0", 5);
   if (status.Fail())
     return status.ToError();
 
   args.AppendArgument(
-      ("127.0.0.1:" + Twine(listen_socket.GetLocalPortNumber())).str());
+      formatv("{0}:{1}", LocalhostIP, listen_socket.GetLocalPortNumber())
+          .str());
 
   for (StringRef arg : ServerArgs)
     args.AppendArgument(arg);
 
   if (!InferiorArgs.empty()) {
     args.AppendArgument("--");
     for (StringRef arg : InferiorArgs)
       args.AppendArgument(arg);