Fix connecting via abstract socket

lldb/include/lldb/Host/linux/AbstractSocket.h

@@ -15,6 +15,7 @@ namespace lldb_private {
 class AbstractSocket : public DomainSocket {
 public:
   AbstractSocket();
+  AbstractSocket(NativeSocket socket, bool should_close);
 
 protected:
   size_t GetNameOffset() const override;

lldb/include/lldb/Host/posix/DomainSocket.h

@@ -31,8 +31,11 @@ class DomainSocket : public Socket {
 
   std::vector<std::string> GetListeningConnectionURI() const override;
 
+  static Socket *Create(NativeSocket sockfd, bool should_close, Status &error);
+
 protected:
   DomainSocket(SocketProtocol protocol);
+  DomainSocket(SocketProtocol protocol, NativeSocket socket, bool should_close);
 
   virtual size_t GetNameOffset() const;
   virtual void DeleteSocketFile(llvm::StringRef name);

lldb/source/Host/linux/AbstractSocket.cpp

@@ -15,6 +15,9 @@ using namespace lldb_private;
 
 AbstractSocket::AbstractSocket() : DomainSocket(ProtocolUnixAbstract) {}
 
+AbstractSocket::AbstractSocket(NativeSocket socket, bool should_close)
+    : DomainSocket(ProtocolUnixAbstract, socket, should_close) {}
+
 size_t AbstractSocket::GetNameOffset() const { return 1; }
 
 void AbstractSocket::DeleteSocketFile(llvm::StringRef name) {}

lldb/source/Host/posix/DomainSocket.cpp

@@ -8,6 +8,9 @@
 
 #include "lldb/Host/posix/DomainSocket.h"
 #include "lldb/Utility/LLDBLog.h"
+#ifdef __linux__
+#include <lldb/Host/linux/AbstractSocket.h>
+#endif
 
 #include "llvm/Support/Errno.h"
 #include "llvm/Support/FileSystem.h"
@@ -67,6 +70,12 @@ DomainSocket::DomainSocket(NativeSocket socket,
   m_socket = socket;
 }
 
+DomainSocket::DomainSocket(SocketProtocol protocol, NativeSocket socket,
+                           bool should_close)
+    : Socket(protocol, should_close) {
+  m_socket = socket;
+}
+
 Status DomainSocket::Connect(llvm::StringRef name) {
   sockaddr_un saddr_un;
   socklen_t saddr_un_len;
@@ -182,3 +191,22 @@ std::vector<std::string> DomainSocket::GetListeningConnectionURI() const {
 
   return {llvm::formatv("unix-connect://{0}", addr.sun_path)};
 }
+
+Socket *DomainSocket::Create(NativeSocket sockfd, bool should_close,
+                             Status &error) {
+#ifdef __linux__
+  // Check if fd represents domain socket or abstract socket.
+  struct sockaddr_un addr;
+  socklen_t addr_len = sizeof(addr);
+  if (getsockname(sockfd, (struct sockaddr *)&addr, &addr_len) == -1) {
+    error = Status::FromErrorString(
+        "lldb-platform child: not a socket or error occurred");
+    return nullptr;
+  }
+
+  if (addr.sun_family == AF_UNIX && addr.sun_path[0] == '\0') {
+    return new AbstractSocket(sockfd, should_close);
+  }
+#endif
+  return new DomainSocket(sockfd, should_close);
+}

lldb/tools/lldb-server/lldb-platform.cpp

@@ -455,35 +455,29 @@ int main_platform(int argc, char *argv[]) {
   lldb_private::Args inferior_arguments;
   inferior_arguments.SetArguments(argc, const_cast<const char **>(argv));
 
-  Socket::SocketProtocol protocol = Socket::ProtocolUnixDomain;
-
+  Log *log = GetLog(LLDBLog::Platform);
   if (fd != SharedSocket::kInvalidFD) {
     // Child process will handle the connection and exit.
-    if (gdbserver_port)
-      protocol = Socket::ProtocolTcp;
-
-    Log *log = GetLog(LLDBLog::Platform);
-
     NativeSocket sockfd;
     error = SharedSocket::GetNativeSocket(fd, sockfd);
     if (error.Fail()) {
       LLDB_LOGF(log, "lldb-platform child: %s", error.AsCString());
       return socket_error;
     }
 
-    GDBRemoteCommunicationServerPlatform platform(protocol, gdbserver_port);
     Socket *socket;
-    if (protocol == Socket::ProtocolTcp)
+    if (gdbserver_port) {
       socket = new TCPSocket(sockfd, /*should_close=*/true);
-    else {
-#if LLDB_ENABLE_POSIX
-      socket = new DomainSocket(sockfd, /*should_close=*/true);
-#else
-      WithColor::error() << "lldb-platform child: Unix domain sockets are not "
-                            "supported on this platform.";
-      return socket_error;
-#endif
+    } else {
+      socket = DomainSocket::Create(sockfd, /*should_close=*/true, error);
+      if (error.Fail()) {
+        LLDB_LOGF(log, "Failed to create socket: %s\n", error.AsCString());
+        return socket_error;
+      }
     }
+
+    Socket::SocketProtocol protocol = socket->GetSocketProtocol();
+    GDBRemoteCommunicationServerPlatform platform(protocol, gdbserver_port);
     platform.SetConnection(
         std::unique_ptr<Connection>(new ConnectionFileDescriptor(socket)));
     client_handle(platform, inferior_arguments);
@@ -498,6 +492,7 @@ int main_platform(int argc, char *argv[]) {
     return 1;
   }
 
+  Socket::SocketProtocol protocol;
   std::string address;
   std::string gdb_address;
   uint16_t platform_port = 0;