[all-commits] [llvm/llvm-project] 926a7e: [lldb] Fix TCPSocket::Connect when getaddrinfo ret...

[Pavel Labath via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 926a7ecdc8b21f01b06a1db78bdd81f1dacaad61
      https://github.com/llvm/llvm-project/commit/926a7ecdc8b21f01b06a1db78bdd81f1dacaad61
  Author: Pavel Labath <pavel at labath.sk>
  Date:   2022-06-14 (Tue, 14 Jun 2022)

  Changed paths:
    M lldb/source/Host/common/TCPSocket.cpp

  Log Message:
  -----------
  [lldb] Fix TCPSocket::Connect when getaddrinfo returns multiple addrs

TCPSocket::Connect() calls SocketAddress::GetAddressInfo() and tries to
connect any of them (in a for loop).

This used to work before commit 4f6d3a376c9f("[LLDB] Fix setting of
success in Socket::Close()") https://reviews.llvm.org/D116768.

As a side effect of that commit, TCPSocket can only connect to the first
address returned by SocketAddress::GetAddressInfo().

1. If the attempt to connect to the first address fails,
   TCPSocket::Connect(), calls CLOSE_SOCKET(GetNativeSocket()), which
   closes the fd, but DOES NOT set m_socket to kInvalidSocketValue.
2. On the second attempt, TCPSocket::CreateSocket() calls
   Socket::Close().
3. Socket::Close() proceeds, because IsValid() is true (m_socket was not
   reset on step 1).
4. Socket::Close() calls ::close(m_socket), which fails
5. Since commit 4f6d3a376c9f("[LLDB] Fix setting of success in
   Socket::Close()"), this is error is detected. Socket::Close() returns
   an error.
6. TCPSocket::CreateSocket() therefore returns an error.
7. TCPSocket::Connect() detects the error and continues, skipping the
   second (and the third, fourth...) address.

This commit fixes the problem by changing step 1: by calling
Socket::Close, instead of directly calling close(m_socket), m_socket is
also se to kInvalidSocketValue. On step 3, Socket::Close() is going to
return immediately and, on step 6, TCPSocket::CreateSocket() does not
fail.

How to reproduce this problem:

On my system, getaddrinfo() resolves "localhost" to "::1" (first) and to
"127.0.0.1" (second).

Start a gdbserver that only listens on 127.0.0.1:

```
gdbserver 127.0.0.1:2159 /bin/cat
Process /bin/cat created; pid = 2146709
Listening on port 2159
```

Start lldb and make it connect to "localhost:2159"

```
./bin/lldb
(lldb) gdb-remote localhost:2159
```

Before 4f6d3a376c9f("[LLDB] Fix setting of success in Socket::Close()"),
this used to work. After that commit, it stopped working. This commit
fixes the problem.

Reviewed By: labath

Differential Revision: https://reviews.llvm.org/D126702