runtime/jdwp/jdwp_adb.cc - platform/art - Gitiles

 /*
  * Copyright (C) 2008 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include <errno.h>
 #include <stdio.h>
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <unistd.h>

 #include "base/logging.h"
 #include "base/stringprintf.h"
 #include "jdwp/jdwp_priv.h"

 #ifdef __ANDROID__
 #include "cutils/sockets.h"
 #endif

 /*
  * The JDWP <-> ADB transport protocol is explained in detail
  * in system/core/adb/jdwp_service.c. Here's a summary.
  *
  * 1/ when the JDWP thread starts, it tries to connect to a Unix
  *    domain stream socket (@jdwp-control) that is opened by the
  *    ADB daemon.
  *
  * 2/ it then sends the current process PID as a string of 4 hexadecimal
  *    chars (no terminating zero)
  *
  * 3/ then, it uses recvmsg to receive file descriptors from the
  *    daemon. each incoming file descriptor is a pass-through to
  *    a given JDWP debugger, that can be used to read the usual
  *    JDWP-handshake, etc...
  */

 #define kJdwpControlName    "\0jdwp-control"
 #define kJdwpControlNameLen (sizeof(kJdwpControlName)-1)

 namespace art {

 namespace JDWP {

 struct JdwpAdbState : public JdwpNetStateBase {
  public:
   explicit JdwpAdbState(JdwpState* state) : JdwpNetStateBase(state) {
     control_sock_ = -1;
     shutting_down_ = false;

     control_addr_.controlAddrUn.sun_family = AF_UNIX;
     control_addr_len_ = sizeof(control_addr_.controlAddrUn.sun_family) + kJdwpControlNameLen;
     memcpy(control_addr_.controlAddrUn.sun_path, kJdwpControlName, kJdwpControlNameLen);
   }

   ~JdwpAdbState() {
     if (clientSock != -1) {
       shutdown(clientSock, SHUT_RDWR);
       close(clientSock);
     }
     if (control_sock_ != -1) {
       shutdown(control_sock_, SHUT_RDWR);
       close(control_sock_);
     }
   }

   virtual bool Accept();

   virtual bool Establish(const JdwpOptions*) {
     return false;
   }

   virtual void Shutdown() {
     shutting_down_ = true;

     int control_sock = this->control_sock_;
     int local_clientSock = this->clientSock;

     /* clear these out so it doesn't wake up and try to reuse them */
     this->control_sock_ = this->clientSock = -1;

     if (local_clientSock != -1) {
       shutdown(local_clientSock, SHUT_RDWR);
     }

     if (control_sock != -1) {
       shutdown(control_sock, SHUT_RDWR);
     }

     WakePipe();
   }

   virtual bool ProcessIncoming();

  private:
   int ReceiveClientFd();

   int control_sock_;
   bool shutting_down_;

   socklen_t control_addr_len_;
   union {
     sockaddr_un controlAddrUn;
     sockaddr controlAddrPlain;
   } control_addr_;
 };

 /*
  * Do initial prep work, e.g. binding to ports and opening files.  This
  * runs in the main thread, before the JDWP thread starts, so it shouldn't
  * do anything that might block forever.
  */
 bool InitAdbTransport(JdwpState* state, const JdwpOptions*) {
   VLOG(jdwp) << "ADB transport startup";
   state->netState = new JdwpAdbState(state);
   return (state->netState != nullptr);
 }

 /*
  * Receive a file descriptor from ADB.  The fd can be used to communicate
  * directly with a debugger or DDMS.
  *
  * Returns the file descriptor on success.  On failure, returns -1 and
  * closes netState->control_sock_.
  */
 int JdwpAdbState::ReceiveClientFd() {
   char dummy = '!';
   union {
     cmsghdr cm;
     char buffer[CMSG_SPACE(sizeof(int))];
   } cm_un;

   iovec iov;
   iov.iov_base       = &dummy;
   iov.iov_len        = 1;

   msghdr msg;
   msg.msg_name       = nullptr;
   msg.msg_namelen    = 0;
   msg.msg_iov        = &iov;
   msg.msg_iovlen     = 1;
   msg.msg_flags      = 0;
   msg.msg_control    = cm_un.buffer;
   msg.msg_controllen = sizeof(cm_un.buffer);

   cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
   cmsg->cmsg_len   = msg.msg_controllen;
   cmsg->cmsg_level = SOL_SOCKET;
   cmsg->cmsg_type  = SCM_RIGHTS;
   (reinterpret_cast<int*>(CMSG_DATA(cmsg)))[0] = -1;

   int rc = TEMP_FAILURE_RETRY(recvmsg(control_sock_, &msg, 0));

   if (rc <= 0) {
     if (rc == -1) {
       PLOG(WARNING) << "Receiving file descriptor from ADB failed (socket " << control_sock_ << ")";
     }
     close(control_sock_);
     control_sock_ = -1;
     return -1;
   }

   return (reinterpret_cast<int*>(CMSG_DATA(cmsg)))[0];
 }

 /*
  * Block forever, waiting for a debugger to connect to us.  Called from the
  * JDWP thread.
  *
  * This needs to un-block and return "false" if the VM is shutting down.  It
  * should return "true" when it successfully accepts a connection.
  */
 bool JdwpAdbState::Accept() {
   int retryCount = 0;

   /* first, ensure that we get a connection to the ADB daemon */

  retry:
   if (shutting_down_) {
     return false;
   }

   if (control_sock_ == -1) {
     int        sleep_ms     = 500;
     const int  sleep_max_ms = 2*1000;
     char       buff[5];

     control_sock_ = socket(PF_UNIX, SOCK_STREAM, 0);
     if (control_sock_ < 0) {
       PLOG(ERROR) << "Could not create ADB control socket";
       return false;
     }

     if (!MakePipe()) {
       return false;
     }

     snprintf(buff, sizeof(buff), "%04x", getpid());
     buff[4] = 0;

     for (;;) {
       /*
        * If adbd isn't running, because USB debugging was disabled or
        * perhaps the system is restarting it for "adb root", the
        * connect() will fail.  We loop here forever waiting for it
        * to come back.
        *
        * Waking up and polling every couple of seconds is generally a
        * bad thing to do, but we only do this if the application is
        * debuggable *and* adbd isn't running.  Still, for the sake
        * of battery life, we should consider timing out and giving
        * up after a few minutes in case somebody ships an app with
        * the debuggable flag set.
        */
       int  ret = connect(control_sock_, &control_addr_.controlAddrPlain, control_addr_len_);
       if (!ret) {
 #ifdef __ANDROID__
         if (!socket_peer_is_trusted(control_sock_)) {
           if (shutdown(control_sock_, SHUT_RDWR)) {
             PLOG(ERROR) << "trouble shutting down socket";
           }
           return false;
         }
 #endif

         /* now try to send our pid to the ADB daemon */
         ret = TEMP_FAILURE_RETRY(send(control_sock_, buff, 4, 0));
         if (ret >= 0) {
           VLOG(jdwp) << StringPrintf("PID sent as '%.*s' to ADB", 4, buff);
           break;
         }

         PLOG(ERROR) << "Weird, can't send JDWP process pid to ADB";
         return false;
       }
       if (VLOG_IS_ON(jdwp)) {
         PLOG(ERROR) << "Can't connect to ADB control socket";
       }

       usleep(sleep_ms * 1000);

       sleep_ms += (sleep_ms >> 1);
       if (sleep_ms > sleep_max_ms) {
         sleep_ms = sleep_max_ms;
       }
       if (shutting_down_) {
         return false;
       }
     }
   }

   VLOG(jdwp) << "trying to receive file descriptor from ADB";
   /* now we can receive a client file descriptor */
   clientSock = ReceiveClientFd();
   if (shutting_down_) {
     return false;       // suppress logs and additional activity
   }
   if (clientSock == -1) {
     if (++retryCount > 5) {
       LOG(ERROR) << "adb connection max retries exceeded";
       return false;
     }
     goto retry;
   } else {
     VLOG(jdwp) << "received file descriptor " << clientSock << " from ADB";
     SetAwaitingHandshake(true);
     input_count_ = 0;
     return true;
   }
 }

 /*
  * Process incoming data.  If no data is available, this will block until
  * some arrives.
  *
  * If we get a full packet, handle it.
  *
  * To take some of the mystery out of life, we want to reject incoming
  * connections if we already have a debugger attached.  If we don't, the
  * debugger will just mysteriously hang until it times out.  We could just
  * close the listen socket, but there's a good chance we won't be able to
  * bind to the same port again, which would confuse utilities.
  *
  * Returns "false" on error (indicating that the connection has been severed),
  * "true" if things are still okay.
  */
 bool JdwpAdbState::ProcessIncoming() {
   int readCount;

   CHECK_NE(clientSock, -1);

   if (!HaveFullPacket()) {
     /* read some more, looping until we have data */
     errno = 0;
     while (1) {
       int selCount;
       fd_set readfds;
       int maxfd = -1;
       int fd;

       FD_ZERO(&readfds);

       /* configure fds; note these may get zapped by another thread */
       fd = control_sock_;
       if (fd >= 0) {
         FD_SET(fd, &readfds);
         if (maxfd < fd) {
           maxfd = fd;
         }
       }
       fd = clientSock;
       if (fd >= 0) {
         FD_SET(fd, &readfds);
         if (maxfd < fd) {
           maxfd = fd;
         }
       }
       fd = wake_pipe_[0];
       if (fd >= 0) {
         FD_SET(fd, &readfds);
         if (maxfd < fd) {
           maxfd = fd;
         }
       } else {
         LOG(INFO) << "NOTE: entering select w/o wakepipe";
       }

       if (maxfd < 0) {
         VLOG(jdwp) << "+++ all fds are closed";
         return false;
       }

       /*
        * Select blocks until it sees activity on the file descriptors.
        * Closing the local file descriptor does not count as activity,
        * so we can't rely on that to wake us up (it works for read()
        * and accept(), but not select()).
        *
        * We can do one of three things: (1) send a signal and catch
        * EINTR, (2) open an additional fd ("wake pipe") and write to
        * it when it's time to exit, or (3) time out periodically and
        * re-issue the select.  We're currently using #2, as it's more
        * reliable than #1 and generally better than #3.  Wastes two fds.
        */
       selCount = select(maxfd + 1, &readfds, nullptr, nullptr, nullptr);
       if (selCount < 0) {
         if (errno == EINTR) {
           continue;
         }
         PLOG(ERROR) << "select failed";
         goto fail;
       }

       if (wake_pipe_[0] >= 0 && FD_ISSET(wake_pipe_[0], &readfds)) {
         VLOG(jdwp) << "Got wake-up signal, bailing out of select";
         goto fail;
       }
       if (control_sock_ >= 0 && FD_ISSET(control_sock_, &readfds)) {
         int  sock = ReceiveClientFd();
         if (sock >= 0) {
           LOG(INFO) << "Ignoring second debugger -- accepting and dropping";
           close(sock);
         } else {
           CHECK_EQ(control_sock_, -1);
           /*
            * Remote side most likely went away, so our next read
            * on clientSock will fail and throw us out of the loop.
            */
         }
       }
       if (clientSock >= 0 && FD_ISSET(clientSock, &readfds)) {
         readCount = read(clientSock, input_buffer_ + input_count_, sizeof(input_buffer_) - input_count_);
         if (readCount < 0) {
           /* read failed */
           if (errno != EINTR) {
             goto fail;
           }
           VLOG(jdwp) << "+++ EINTR hit";
           return true;
         } else if (readCount == 0) {
           /* EOF hit -- far end went away */
           VLOG(jdwp) << "+++ peer disconnected";
           goto fail;
         } else {
           break;
         }
       }
     }

     input_count_ += readCount;
     if (!HaveFullPacket()) {
       return true;        /* still not there yet */
     }
   }

   /*
    * Special-case the initial handshake.  For some bizarre reason we're
    * expected to emulate bad tty settings by echoing the request back
    * exactly as it was sent.  Note the handshake is always initiated by
    * the debugger, no matter who connects to whom.
    *
    * Other than this one case, the protocol [claims to be] stateless.
    */
   if (IsAwaitingHandshake()) {
     if (memcmp(input_buffer_, kMagicHandshake, kMagicHandshakeLen) != 0) {
       LOG(ERROR) << StringPrintf("ERROR: bad handshake '%.14s'", input_buffer_);
       goto fail;
     }

     errno = 0;
     int cc = TEMP_FAILURE_RETRY(write(clientSock, input_buffer_, kMagicHandshakeLen));
     if (cc != kMagicHandshakeLen) {
       PLOG(ERROR) << "Failed writing handshake bytes (" << cc << " of " << kMagicHandshakeLen << ")";
       goto fail;
     }

     ConsumeBytes(kMagicHandshakeLen);
     SetAwaitingHandshake(false);
     VLOG(jdwp) << "+++ handshake complete";
     return true;
   }

   /*
    * Handle this packet.
    */
   return state_->HandlePacket();

  fail:
   Close();
   return false;
 }

 }  // namespace JDWP

 }  // namespace art
	/*
	* Copyright (C) 2008 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include <errno.h>
	#include <stdio.h>
	#include <sys/socket.h>
	#include <sys/un.h>
	#include <unistd.h>

	#include "base/logging.h"
	#include "base/stringprintf.h"
	#include "jdwp/jdwp_priv.h"

	#ifdef __ANDROID__
	#include "cutils/sockets.h"
	#endif

	/*
	* The JDWP <-> ADB transport protocol is explained in detail
	* in system/core/adb/jdwp_service.c. Here's a summary.
	*
	* 1/ when the JDWP thread starts, it tries to connect to a Unix
	* domain stream socket (@jdwp-control) that is opened by the
	* ADB daemon.
	*
	* 2/ it then sends the current process PID as a string of 4 hexadecimal
	* chars (no terminating zero)
	*
	* 3/ then, it uses recvmsg to receive file descriptors from the
	* daemon. each incoming file descriptor is a pass-through to
	* a given JDWP debugger, that can be used to read the usual
	* JDWP-handshake, etc...
	*/

	#define kJdwpControlName "\0jdwp-control"
	#define kJdwpControlNameLen (sizeof(kJdwpControlName)-1)

	namespace art {

	namespace JDWP {

	struct JdwpAdbState : public JdwpNetStateBase {
	public:
	explicit JdwpAdbState(JdwpState* state) : JdwpNetStateBase(state) {
	control_sock_ = -1;
	shutting_down_ = false;

	control_addr_.controlAddrUn.sun_family = AF_UNIX;
	control_addr_len_ = sizeof(control_addr_.controlAddrUn.sun_family) + kJdwpControlNameLen;
	memcpy(control_addr_.controlAddrUn.sun_path, kJdwpControlName, kJdwpControlNameLen);
	}

	~JdwpAdbState() {
	if (clientSock != -1) {
	shutdown(clientSock, SHUT_RDWR);
	close(clientSock);
	}
	if (control_sock_ != -1) {
	shutdown(control_sock_, SHUT_RDWR);
	close(control_sock_);
	}
	}

	virtual bool Accept();

	virtual bool Establish(const JdwpOptions*) {
	return false;
	}

	virtual void Shutdown() {
	shutting_down_ = true;

	int control_sock = this->control_sock_;
	int local_clientSock = this->clientSock;

	/* clear these out so it doesn't wake up and try to reuse them */
	this->control_sock_ = this->clientSock = -1;

	if (local_clientSock != -1) {
	shutdown(local_clientSock, SHUT_RDWR);
	}

	if (control_sock != -1) {
	shutdown(control_sock, SHUT_RDWR);
	}

	WakePipe();
	}

	virtual bool ProcessIncoming();

	private:
	int ReceiveClientFd();

	int control_sock_;
	bool shutting_down_;

	socklen_t control_addr_len_;
	union {
	sockaddr_un controlAddrUn;
	sockaddr controlAddrPlain;
	} control_addr_;
	};

	/*
	* Do initial prep work, e.g. binding to ports and opening files. This
	* runs in the main thread, before the JDWP thread starts, so it shouldn't
	* do anything that might block forever.
	*/
	bool InitAdbTransport(JdwpState* state, const JdwpOptions*) {
	VLOG(jdwp) << "ADB transport startup";
	state->netState = new JdwpAdbState(state);
	return (state->netState != nullptr);
	}

	/*
	* Receive a file descriptor from ADB. The fd can be used to communicate
	* directly with a debugger or DDMS.
	*
	* Returns the file descriptor on success. On failure, returns -1 and
	* closes netState->control_sock_.
	*/
	int JdwpAdbState::ReceiveClientFd() {
	char dummy = '!';
	union {
	cmsghdr cm;
	char buffer[CMSG_SPACE(sizeof(int))];
	} cm_un;

	iovec iov;
	iov.iov_base = &dummy;
	iov.iov_len = 1;

	msghdr msg;
	msg.msg_name = nullptr;
	msg.msg_namelen = 0;
	msg.msg_iov = &iov;
	msg.msg_iovlen = 1;
	msg.msg_flags = 0;
	msg.msg_control = cm_un.buffer;
	msg.msg_controllen = sizeof(cm_un.buffer);

	cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
	cmsg->cmsg_len = msg.msg_controllen;
	cmsg->cmsg_level = SOL_SOCKET;
	cmsg->cmsg_type = SCM_RIGHTS;
	(reinterpret_cast<int*>(CMSG_DATA(cmsg)))[0] = -1;

	int rc = TEMP_FAILURE_RETRY(recvmsg(control_sock_, &msg, 0));

	if (rc <= 0) {
	if (rc == -1) {
	PLOG(WARNING) << "Receiving file descriptor from ADB failed (socket " << control_sock_ << ")";
	}
	close(control_sock_);
	control_sock_ = -1;
	return -1;
	}

	return (reinterpret_cast<int*>(CMSG_DATA(cmsg)))[0];
	}

	/*
	* Block forever, waiting for a debugger to connect to us. Called from the
	* JDWP thread.
	*
	* This needs to un-block and return "false" if the VM is shutting down. It
	* should return "true" when it successfully accepts a connection.
	*/
	bool JdwpAdbState::Accept() {
	int retryCount = 0;

	/* first, ensure that we get a connection to the ADB daemon */

	retry:
	if (shutting_down_) {
	return false;
	}

	if (control_sock_ == -1) {
	int sleep_ms = 500;
	const int sleep_max_ms = 2*1000;
	char buff[5];

	control_sock_ = socket(PF_UNIX, SOCK_STREAM, 0);
	if (control_sock_ < 0) {
	PLOG(ERROR) << "Could not create ADB control socket";
	return false;
	}

	if (!MakePipe()) {
	return false;
	}

	snprintf(buff, sizeof(buff), "%04x", getpid());
	buff[4] = 0;

	for (;;) {
	/*
	* If adbd isn't running, because USB debugging was disabled or
	* perhaps the system is restarting it for "adb root", the
	* connect() will fail. We loop here forever waiting for it
	* to come back.
	*
	* Waking up and polling every couple of seconds is generally a
	* bad thing to do, but we only do this if the application is
	* debuggable and adbd isn't running. Still, for the sake
	* of battery life, we should consider timing out and giving
	* up after a few minutes in case somebody ships an app with
	* the debuggable flag set.
	*/
	int ret = connect(control_sock_, &control_addr_.controlAddrPlain, control_addr_len_);
	if (!ret) {
	#ifdef __ANDROID__
	if (!socket_peer_is_trusted(control_sock_)) {
	if (shutdown(control_sock_, SHUT_RDWR)) {
	PLOG(ERROR) << "trouble shutting down socket";
	}
	return false;
	}
	#endif

	/* now try to send our pid to the ADB daemon */
	ret = TEMP_FAILURE_RETRY(send(control_sock_, buff, 4, 0));
	if (ret >= 0) {
	VLOG(jdwp) << StringPrintf("PID sent as '%.*s' to ADB", 4, buff);
	break;
	}

	PLOG(ERROR) << "Weird, can't send JDWP process pid to ADB";
	return false;
	}
	if (VLOG_IS_ON(jdwp)) {
	PLOG(ERROR) << "Can't connect to ADB control socket";
	}

	usleep(sleep_ms * 1000);

	sleep_ms += (sleep_ms >> 1);
	if (sleep_ms > sleep_max_ms) {
	sleep_ms = sleep_max_ms;
	}
	if (shutting_down_) {
	return false;
	}
	}
	}

	VLOG(jdwp) << "trying to receive file descriptor from ADB";
	/* now we can receive a client file descriptor */
	clientSock = ReceiveClientFd();
	if (shutting_down_) {
	return false; // suppress logs and additional activity
	}
	if (clientSock == -1) {
	if (++retryCount > 5) {
	LOG(ERROR) << "adb connection max retries exceeded";
	return false;
	}
	goto retry;
	} else {
	VLOG(jdwp) << "received file descriptor " << clientSock << " from ADB";
	SetAwaitingHandshake(true);
	input_count_ = 0;
	return true;
	}
	}

	/*
	* Process incoming data. If no data is available, this will block until
	* some arrives.
	*
	* If we get a full packet, handle it.
	*
	* To take some of the mystery out of life, we want to reject incoming
	* connections if we already have a debugger attached. If we don't, the
	* debugger will just mysteriously hang until it times out. We could just
	* close the listen socket, but there's a good chance we won't be able to
	* bind to the same port again, which would confuse utilities.
	*
	* Returns "false" on error (indicating that the connection has been severed),
	* "true" if things are still okay.
	*/
	bool JdwpAdbState::ProcessIncoming() {
	int readCount;

	CHECK_NE(clientSock, -1);

	if (!HaveFullPacket()) {
	/* read some more, looping until we have data */
	errno = 0;
	while (1) {
	int selCount;
	fd_set readfds;
	int maxfd = -1;
	int fd;

	FD_ZERO(&readfds);

	/* configure fds; note these may get zapped by another thread */
	fd = control_sock_;
	if (fd >= 0) {
	FD_SET(fd, &readfds);
	if (maxfd < fd) {
	maxfd = fd;
	}
	}
	fd = clientSock;
	if (fd >= 0) {
	FD_SET(fd, &readfds);
	if (maxfd < fd) {
	maxfd = fd;
	}
	}
	fd = wake_pipe_[0];
	if (fd >= 0) {
	FD_SET(fd, &readfds);
	if (maxfd < fd) {
	maxfd = fd;
	}
	} else {
	LOG(INFO) << "NOTE: entering select w/o wakepipe";
	}

	if (maxfd < 0) {
	VLOG(jdwp) << "+++ all fds are closed";
	return false;
	}

	/*
	* Select blocks until it sees activity on the file descriptors.
	* Closing the local file descriptor does not count as activity,
	* so we can't rely on that to wake us up (it works for read()
	* and accept(), but not select()).
	*
	* We can do one of three things: (1) send a signal and catch
	* EINTR, (2) open an additional fd ("wake pipe") and write to
	* it when it's time to exit, or (3) time out periodically and
	* re-issue the select. We're currently using #2, as it's more
	* reliable than #1 and generally better than #3. Wastes two fds.
	*/
	selCount = select(maxfd + 1, &readfds, nullptr, nullptr, nullptr);
	if (selCount < 0) {
	if (errno == EINTR) {
	continue;
	}
	PLOG(ERROR) << "select failed";
	goto fail;
	}

	if (wake_pipe_[0] >= 0 && FD_ISSET(wake_pipe_[0], &readfds)) {
	VLOG(jdwp) << "Got wake-up signal, bailing out of select";
	goto fail;
	}
	if (control_sock_ >= 0 && FD_ISSET(control_sock_, &readfds)) {
	int sock = ReceiveClientFd();
	if (sock >= 0) {
	LOG(INFO) << "Ignoring second debugger -- accepting and dropping";
	close(sock);
	} else {
	CHECK_EQ(control_sock_, -1);
	/*
	* Remote side most likely went away, so our next read
	* on clientSock will fail and throw us out of the loop.
	*/
	}
	}
	if (clientSock >= 0 && FD_ISSET(clientSock, &readfds)) {
	readCount = read(clientSock, input_buffer_ + input_count_, sizeof(input_buffer_) - input_count_);
	if (readCount < 0) {
	/* read failed */
	if (errno != EINTR) {
	goto fail;
	}
	VLOG(jdwp) << "+++ EINTR hit";
	return true;
	} else if (readCount == 0) {
	/* EOF hit -- far end went away */
	VLOG(jdwp) << "+++ peer disconnected";
	goto fail;
	} else {
	break;
	}
	}
	}

	input_count_ += readCount;
	if (!HaveFullPacket()) {
	return true; /* still not there yet */
	}
	}

	/*
	* Special-case the initial handshake. For some bizarre reason we're
	* expected to emulate bad tty settings by echoing the request back
	* exactly as it was sent. Note the handshake is always initiated by
	* the debugger, no matter who connects to whom.
	*
	* Other than this one case, the protocol [claims to be] stateless.
	*/
	if (IsAwaitingHandshake()) {
	if (memcmp(input_buffer_, kMagicHandshake, kMagicHandshakeLen) != 0) {
	LOG(ERROR) << StringPrintf("ERROR: bad handshake '%.14s'", input_buffer_);
	goto fail;
	}

	errno = 0;
	int cc = TEMP_FAILURE_RETRY(write(clientSock, input_buffer_, kMagicHandshakeLen));
	if (cc != kMagicHandshakeLen) {
	PLOG(ERROR) << "Failed writing handshake bytes (" << cc << " of " << kMagicHandshakeLen << ")";
	goto fail;
	}

	ConsumeBytes(kMagicHandshakeLen);
	SetAwaitingHandshake(false);
	VLOG(jdwp) << "+++ handshake complete";
	return true;
	}

	/*
	* Handle this packet.
	*/
	return state_->HandlePacket();

	fail:
	Close();
	return false;
	}

	} // namespace JDWP

	} // namespace art