Index: lldb/include/lldb/Host/common/NativeProcessProtocol.h
===================================================================
--- lldb/include/lldb/Host/common/NativeProcessProtocol.h
+++ lldb/include/lldb/Host/common/NativeProcessProtocol.h
@@ -222,6 +222,10 @@
                                      lldb::StateType state) = 0;
 
     virtual void DidExec(NativeProcessProtocol *process) = 0;
+
+    virtual void
+    NewSubprocess(NativeProcessProtocol *parent_process,
+                  std::unique_ptr<NativeProcessProtocol> &child_process) = 0;
   };
 
   /// Register a native delegate.
Index: lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.h
===================================================================
--- lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.h
+++ lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.h
@@ -78,6 +78,10 @@
 
   void DidExec(NativeProcessProtocol *process) override;
 
+  void
+  NewSubprocess(NativeProcessProtocol *parent_process,
+                std::unique_ptr<NativeProcessProtocol> &child_process) override;
+
   Status InitializeConnection(std::unique_ptr<Connection> connection);
 
 protected:
@@ -88,6 +92,8 @@
   lldb::tid_t m_continue_tid = LLDB_INVALID_THREAD_ID;
   std::recursive_mutex m_debugged_process_mutex;
   std::unique_ptr<NativeProcessProtocol> m_debugged_process_up;
+  std::unordered_map<lldb::pid_t, std::unique_ptr<NativeProcessProtocol>>
+      m_additional_processes;
 
   Communication m_stdio_communication;
   MainLoop::ReadHandleUP m_stdio_handle_up;
Index: lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
===================================================================
--- lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
+++ lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
@@ -1030,6 +1030,18 @@
   ClearProcessSpecificData();
 }
 
+void GDBRemoteCommunicationServerLLGS::NewSubprocess(
+    NativeProcessProtocol *parent_process,
+    std::unique_ptr<NativeProcessProtocol> &child_process) {
+  // Apparently the process has been dealt with by another delegate.
+  if (!child_process)
+    return;
+  lldb::pid_t child_pid = child_process->GetID();
+  assert(child_pid != LLDB_INVALID_PROCESS_ID);
+  assert(m_additional_processes.find(child_pid) == m_additional_processes.end());
+  m_additional_processes[child_pid] = std::move(child_process);
+}
+
 void GDBRemoteCommunicationServerLLGS::DataAvailableCallback() {
   Log *log(GetLogIfAnyCategoriesSet(GDBR_LOG_COMM));
 
@@ -3213,19 +3225,43 @@
       return SendIllFormedResponse(packet, "D failed to parse the process id");
   }
 
-  if (pid != LLDB_INVALID_PROCESS_ID && m_debugged_process_up->GetID() != pid) {
-    return SendIllFormedResponse(packet, "Invalid pid");
+  // Detach forked children if their PID was specified *or* no PID was requested
+  // (i.e. detach-all packet).
+  bool detached = false;
+  for (auto it = m_additional_processes.begin(); it != m_additional_processes.end();) {
+    if (pid == LLDB_INVALID_PROCESS_ID || pid == it->first) {
+      const Status error = it->second->Detach();
+      if (error.Fail()) {
+        LLDB_LOGF(log,
+                  "GDBRemoteCommunicationServerLLGS::%s failed to detach from "
+                  "pid %" PRIu64 ": %s\n",
+                  __FUNCTION__, m_debugged_process_up->GetID(), error.AsCString());
+        return SendErrorResponse(0x01);
+      }
+      it = m_additional_processes.erase(it);
+      detached = true;
+    } else
+      ++it;
   }
 
-  const Status error = m_debugged_process_up->Detach();
-  if (error.Fail()) {
-    LLDB_LOGF(log,
-              "GDBRemoteCommunicationServerLLGS::%s failed to detach from "
-              "pid %" PRIu64 ": %s\n",
-              __FUNCTION__, m_debugged_process_up->GetID(), error.AsCString());
-    return SendErrorResponse(0x01);
+  // Detach the main process if PID matches or no PID was requested.
+  if (pid == LLDB_INVALID_PROCESS_ID || m_debugged_process_up->GetID() == pid) {
+    if (!m_additional_processes.empty())
+      return SendErrorResponse(Status("Unable to detach the main process while children are still traced"));
+
+    const Status error = m_debugged_process_up->Detach();
+    if (error.Fail()) {
+      LLDB_LOGF(log,
+                "GDBRemoteCommunicationServerLLGS::%s failed to detach from "
+                "pid %" PRIu64 ": %s\n",
+                __FUNCTION__, m_debugged_process_up->GetID(), error.AsCString());
+      return SendErrorResponse(0x01);
+    }
+    detached = true;
   }
 
+  if (!detached)
+    return SendErrorResponse(Status("PID %" PRIu64 " not traced", pid));
   return SendOKResponse();
 }
 
Index: lldb/source/Utility/StringExtractorGDBRemote.cpp
===================================================================
--- lldb/source/Utility/StringExtractorGDBRemote.cpp
+++ lldb/source/Utility/StringExtractorGDBRemote.cpp
@@ -378,9 +378,7 @@
     return eServerPacketType_C;
 
   case 'D':
-    if (packet_size == 1)
-      return eServerPacketType_D;
-    break;
+    return eServerPacketType_D;
 
   case 'g':
     return eServerPacketType_g;
Index: lldb/unittests/TestingSupport/Host/NativeProcessTestUtils.h
===================================================================
--- lldb/unittests/TestingSupport/Host/NativeProcessTestUtils.h
+++ lldb/unittests/TestingSupport/Host/NativeProcessTestUtils.h
@@ -25,6 +25,9 @@
   MOCK_METHOD2(ProcessStateChanged,
                void(NativeProcessProtocol *Process, StateType State));
   MOCK_METHOD1(DidExec, void(NativeProcessProtocol *Process));
+  MOCK_METHOD2(NewSubprocess,
+               void(NativeProcessProtocol *parent_process,
+                    std::unique_ptr<NativeProcessProtocol> &child_process));
 };
 
 // NB: This class doesn't use the override keyword to avoid