src/core/lib/iomgr/tcp_client_posix.cc - platform/external/grpc-grpc - Git at Google

 /*
  *
  * Copyright 2015 gRPC authors.
  *
  * 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 <grpc/support/port_platform.h>

 #include "src/core/lib/iomgr/port.h"

 #ifdef GRPC_POSIX_SOCKET_TCP_CLIENT

 #include "src/core/lib/iomgr/tcp_client_posix.h"

 #include <errno.h>
 #include <netinet/in.h>
 #include <string.h>
 #include <unistd.h>
 #include <sys/un.h>

 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 #include <grpc/support/time.h>

 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/iomgr/ev_posix.h"
 #include "src/core/lib/iomgr/iomgr_posix.h"
 #include "src/core/lib/iomgr/sockaddr.h"
 #include "src/core/lib/iomgr/sockaddr_utils.h"
 #include "src/core/lib/iomgr/socket_mutator.h"
 #include "src/core/lib/iomgr/socket_utils_posix.h"
 #include "src/core/lib/iomgr/tcp_posix.h"
 #include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/iomgr/unix_sockets_posix.h"
 #include "src/core/lib/slice/slice_internal.h"

 extern grpc_core::TraceFlag grpc_tcp_trace;

 typedef struct {
   gpr_mu mu;
   grpc_fd* fd;
   grpc_timer alarm;
   grpc_closure on_alarm;
   int refs;
   grpc_closure write_closure;
   grpc_pollset_set* interested_parties;
   char* addr_str;
   grpc_endpoint** ep;
   grpc_closure* closure;
   grpc_channel_args* channel_args;
 } async_connect;

 static grpc_error* prepare_socket(const grpc_resolved_address* addr, int fd,
                                   const grpc_channel_args* channel_args) {
   grpc_error* err = GRPC_ERROR_NONE;

   GPR_ASSERT(fd >= 0);

   err = grpc_set_socket_nonblocking(fd, 1);
   if (err != GRPC_ERROR_NONE) goto error;
   err = grpc_set_socket_cloexec(fd, 1);
   if (err != GRPC_ERROR_NONE) goto error;
   if (!grpc_is_unix_socket(addr)) {
     err = grpc_set_socket_low_latency(fd, 1);
     if (err != GRPC_ERROR_NONE) goto error;
     err = grpc_set_socket_reuse_addr(fd, 1);
     if (err != GRPC_ERROR_NONE) goto error;
     err = grpc_set_socket_tcp_user_timeout(fd, channel_args,
                                            true /* is_client */);
     if (err != GRPC_ERROR_NONE) goto error;
   }
   err = grpc_set_socket_no_sigpipe_if_possible(fd);
   if (err != GRPC_ERROR_NONE) goto error;
   if (channel_args) {
     for (size_t i = 0; i < channel_args->num_args; i++) {
       if (0 == strcmp(channel_args->args[i].key, GRPC_ARG_SOCKET_MUTATOR)) {
         GPR_ASSERT(channel_args->args[i].type == GRPC_ARG_POINTER);
         grpc_socket_mutator* mutator = static_cast<grpc_socket_mutator*>(
             channel_args->args[i].value.pointer.p);
         err = grpc_set_socket_with_mutator(fd, mutator);
         if (err != GRPC_ERROR_NONE) goto error;
       }
     }
   }
   goto done;

 error:
   if (fd >= 0) {
     close(fd);
   }
 done:
   return err;
 }

 static void tc_on_alarm(void* acp, grpc_error* error) {
   int done;
   async_connect* ac = static_cast<async_connect*>(acp);
   if (GRPC_TRACE_FLAG_ENABLED(grpc_tcp_trace)) {
     const char* str = grpc_error_string(error);
     gpr_log(GPR_INFO, "CLIENT_CONNECT: %s: on_alarm: error=%s", ac->addr_str,
             str);
   }
   gpr_mu_lock(&ac->mu);
   if (ac->fd != nullptr) {
     grpc_fd_shutdown(
         ac->fd, GRPC_ERROR_CREATE_FROM_STATIC_STRING("connect() timed out"));
   }
   done = (--ac->refs == 0);
   gpr_mu_unlock(&ac->mu);
   if (done) {
     gpr_mu_destroy(&ac->mu);
     gpr_free(ac->addr_str);
     grpc_channel_args_destroy(ac->channel_args);
     gpr_free(ac);
   }
 }

 grpc_endpoint* grpc_tcp_client_create_from_fd(
     grpc_fd* fd, const grpc_channel_args* channel_args, const char* addr_str) {
   return grpc_tcp_create(fd, channel_args, addr_str);
 }

 static void on_writable(void* acp, grpc_error* error) {
   async_connect* ac = static_cast<async_connect*>(acp);
   int so_error = 0;
   socklen_t so_error_size;
   int err;
   int done;
   grpc_endpoint** ep = ac->ep;
   grpc_closure* closure = ac->closure;
   grpc_fd* fd;

   GRPC_ERROR_REF(error);

   if (GRPC_TRACE_FLAG_ENABLED(grpc_tcp_trace)) {
     const char* str = grpc_error_string(error);
     gpr_log(GPR_INFO, "CLIENT_CONNECT: %s: on_writable: error=%s", ac->addr_str,
             str);
   }

   gpr_mu_lock(&ac->mu);
   GPR_ASSERT(ac->fd);
   fd = ac->fd;
   ac->fd = nullptr;
   gpr_mu_unlock(&ac->mu);

   grpc_timer_cancel(&ac->alarm);

   gpr_mu_lock(&ac->mu);
   if (error != GRPC_ERROR_NONE) {
     error =
         grpc_error_set_str(error, GRPC_ERROR_STR_OS_ERROR,
                            grpc_slice_from_static_string("Timeout occurred"));
     goto finish;
   }

   do {
     so_error_size = sizeof(so_error);
     err = getsockopt(grpc_fd_wrapped_fd(fd), SOL_SOCKET, SO_ERROR, &so_error,
                      &so_error_size);
   } while (err < 0 && errno == EINTR);
   if (err < 0) {
     error = GRPC_OS_ERROR(errno, "getsockopt");
     goto finish;
   }

   switch (so_error) {
     case 0:
       grpc_pollset_set_del_fd(ac->interested_parties, fd);
       *ep = grpc_tcp_client_create_from_fd(fd, ac->channel_args, ac->addr_str);
       fd = nullptr;
       break;
     case ENOBUFS:
       /* We will get one of these errors if we have run out of
          memory in the kernel for the data structures allocated
          when you connect a socket.  If this happens it is very
          likely that if we wait a little bit then try again the
          connection will work (since other programs or this
          program will close their network connections and free up
          memory).  This does _not_ indicate that there is anything
          wrong with the server we are connecting to, this is a
          local problem.

          If you are looking at this code, then chances are that
          your program or another program on the same computer
          opened too many network connections.  The "easy" fix:
          don't do that! */
       gpr_log(GPR_ERROR, "kernel out of buffers");
       gpr_mu_unlock(&ac->mu);
       grpc_fd_notify_on_write(fd, &ac->write_closure);
       return;
     case ECONNREFUSED:
       /* This error shouldn't happen for anything other than connect(). */
       error = GRPC_OS_ERROR(so_error, "connect");
       break;
     default:
       /* We don't really know which syscall triggered the problem here,
          so punt by reporting getsockopt(). */
       error = GRPC_OS_ERROR(so_error, "getsockopt(SO_ERROR)");
       break;
   }

 finish:
   if (fd != nullptr) {
     grpc_pollset_set_del_fd(ac->interested_parties, fd);
     grpc_fd_orphan(fd, nullptr, nullptr, "tcp_client_orphan");
     fd = nullptr;
   }
   done = (--ac->refs == 0);
   // Create a copy of the data from "ac" to be accessed after the unlock, as
   // "ac" and its contents may be deallocated by the time they are read.
   const grpc_slice addr_str_slice = grpc_slice_from_copied_string(ac->addr_str);
   gpr_mu_unlock(&ac->mu);
   if (error != GRPC_ERROR_NONE) {
     char* error_descr;
     grpc_slice str;
     bool ret = grpc_error_get_str(error, GRPC_ERROR_STR_DESCRIPTION, &str);
     GPR_ASSERT(ret);
     char* desc = grpc_slice_to_c_string(str);
     gpr_asprintf(&error_descr, "Failed to connect to remote host: %s", desc);
     error = grpc_error_set_str(error, GRPC_ERROR_STR_DESCRIPTION,
                                grpc_slice_from_copied_string(error_descr));
     gpr_free(error_descr);
     gpr_free(desc);
     error = grpc_error_set_str(error, GRPC_ERROR_STR_TARGET_ADDRESS,
                                addr_str_slice /* takes ownership */);
   } else {
     grpc_slice_unref_internal(addr_str_slice);
   }
   if (done) {
     // This is safe even outside the lock, because "done", the sentinel, is
     // populated *inside* the lock.
     gpr_mu_destroy(&ac->mu);
     gpr_free(ac->addr_str);
     grpc_channel_args_destroy(ac->channel_args);
     gpr_free(ac);
   }
   GRPC_CLOSURE_SCHED(closure, error);
 }

 grpc_error* grpc_tcp_client_prepare_fd(const grpc_channel_args* channel_args,
                                        const grpc_resolved_address* addr,
                                        grpc_resolved_address* mapped_addr,
                                        grpc_fd** fdobj) {
   grpc_dualstack_mode dsmode;
   int fd;
   grpc_error* error;
   char* name;
   char* addr_str;
   *fdobj = nullptr;
   /* Use dualstack sockets where available. Set mapped to v6 or v4 mapped to
      v6. */
   if (!grpc_sockaddr_to_v4mapped(addr, mapped_addr)) {
     /* addr is v4 mapped to v6 or v6. */
     memcpy(mapped_addr, addr, sizeof(*mapped_addr));
   }
   error =
       grpc_create_dualstack_socket(mapped_addr, SOCK_STREAM, 0, &dsmode, &fd);
   if (error != GRPC_ERROR_NONE) {
     return error;
   }
   if (dsmode == GRPC_DSMODE_IPV4) {
     /* Original addr is either v4 or v4 mapped to v6. Set mapped_addr to v4. */
     if (!grpc_sockaddr_is_v4mapped(addr, mapped_addr)) {
       memcpy(mapped_addr, addr, sizeof(*mapped_addr));
     }
   }
   if ((error = prepare_socket(mapped_addr, fd, channel_args)) !=
       GRPC_ERROR_NONE) {
     return error;
   }
   addr_str = grpc_sockaddr_to_uri(mapped_addr);
   gpr_asprintf(&name, "tcp-client:%s", addr_str);
   *fdobj = grpc_fd_create(fd, name, true);
   gpr_free(name);
   gpr_free(addr_str);
   return GRPC_ERROR_NONE;
 }

 void grpc_tcp_client_create_from_prepared_fd(
     grpc_pollset_set* interested_parties, grpc_closure* closure, grpc_fd* fdobj,
     const grpc_channel_args* channel_args, const grpc_resolved_address* addr,
     grpc_millis deadline, grpc_endpoint** ep) {
   const int fd = grpc_fd_wrapped_fd(fdobj);
   int err = 0;
   async_connect* ac;
   // Special handling for Android Studio Profilers.
   // Check Unix-specific socket types.
   auto* un = reinterpret_cast<const struct sockaddr_un*>(addr->addr);
   if (un->sun_path[0] == '&') {
     // A connected fd is provided by the caller of gRPC.
     // No need to call connect(). Do nothing here.
   } else {
     // Make a copy of addr so it can be modified to support abstract socket.
     grpc_resolved_address addr_copy = *addr;
     auto* un_copy = reinterpret_cast<struct sockaddr_un*>(&addr_copy.addr);
     if (un_copy->sun_path[0] == '@') {
       // This is a Unix abstract domain socket. Set the first char to '\0'.
       un_copy->sun_path[0] = '\0';
       // The length includes the leading '\0' but not the terminating '\0'.
       // Not including the terminating null byte to make the socket name easy to
       // see and type in shell (e.g., adb forward).
       addr_copy.len =
           1 + strlen(&un_copy->sun_path[1]) + sizeof(un_copy->sun_family);
     }
     do {
       err = connect(fd, reinterpret_cast<const grpc_sockaddr*>(addr_copy.addr),
                     addr_copy.len);
     } while (err < 0 && errno == EINTR);
   }
   if (err >= 0) {
     // Use addr not addr_copy to obtain the string representation as
     // grpc_sockaddr_to_uri(..) considers string null-terminated.
     char* addr_str = grpc_sockaddr_to_uri(addr);
     *ep = grpc_tcp_client_create_from_fd(fdobj, channel_args, addr_str);
     gpr_free(addr_str);
     GRPC_CLOSURE_SCHED(closure, GRPC_ERROR_NONE);
     return;
   }
   if (errno != EWOULDBLOCK && errno != EINPROGRESS) {
     grpc_fd_orphan(fdobj, nullptr, nullptr, "tcp_client_connect_error");
     GRPC_CLOSURE_SCHED(closure, GRPC_OS_ERROR(errno, "connect"));
     return;
   }

   grpc_pollset_set_add_fd(interested_parties, fdobj);

   ac = static_cast<async_connect*>(gpr_malloc(sizeof(async_connect)));
   ac->closure = closure;
   ac->ep = ep;
   ac->fd = fdobj;
   ac->interested_parties = interested_parties;
   // Use addr not addr_copy to obtain the string representation as
   // grpc_sockaddr_to_uri(..) considers strings null-terminated.
   ac->addr_str = grpc_sockaddr_to_uri(addr);
   gpr_mu_init(&ac->mu);
   ac->refs = 2;
   GRPC_CLOSURE_INIT(&ac->write_closure, on_writable, ac,
                     grpc_schedule_on_exec_ctx);
   ac->channel_args = grpc_channel_args_copy(channel_args);

   if (GRPC_TRACE_FLAG_ENABLED(grpc_tcp_trace)) {
     gpr_log(GPR_INFO, "CLIENT_CONNECT: %s: asynchronously connecting fd %p",
             ac->addr_str, fdobj);
   }

   gpr_mu_lock(&ac->mu);
   GRPC_CLOSURE_INIT(&ac->on_alarm, tc_on_alarm, ac, grpc_schedule_on_exec_ctx);
   grpc_timer_init(&ac->alarm, deadline, &ac->on_alarm);
   grpc_fd_notify_on_write(ac->fd, &ac->write_closure);
   gpr_mu_unlock(&ac->mu);
 }

 static void tcp_connect(grpc_closure* closure, grpc_endpoint** ep,
                         grpc_pollset_set* interested_parties,
                         const grpc_channel_args* channel_args,
                         const grpc_resolved_address* addr,
                         grpc_millis deadline) {
   grpc_resolved_address mapped_addr;
   grpc_fd* fdobj = nullptr;
   grpc_error* error;
   *ep = nullptr;
   if ((error = grpc_tcp_client_prepare_fd(channel_args, addr, &mapped_addr,
                                           &fdobj)) != GRPC_ERROR_NONE) {
     GRPC_CLOSURE_SCHED(closure, error);
     return;
   }
   grpc_tcp_client_create_from_prepared_fd(interested_parties, closure, fdobj,
                                           channel_args, &mapped_addr, deadline,
                                           ep);
 }

 grpc_tcp_client_vtable grpc_posix_tcp_client_vtable = {tcp_connect};
 #endif
	/*
	*
	* Copyright 2015 gRPC authors.
	*
	* 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 <grpc/support/port_platform.h>

	#include "src/core/lib/iomgr/port.h"

	#ifdef GRPC_POSIX_SOCKET_TCP_CLIENT

	#include "src/core/lib/iomgr/tcp_client_posix.h"

	#include <errno.h>
	#include <netinet/in.h>
	#include <string.h>
	#include <unistd.h>
	#include <sys/un.h>

	#include <grpc/support/alloc.h>
	#include <grpc/support/log.h>
	#include <grpc/support/string_util.h>
	#include <grpc/support/time.h>

	#include "src/core/lib/channel/channel_args.h"
	#include "src/core/lib/gpr/string.h"
	#include "src/core/lib/iomgr/ev_posix.h"
	#include "src/core/lib/iomgr/iomgr_posix.h"
	#include "src/core/lib/iomgr/sockaddr.h"
	#include "src/core/lib/iomgr/sockaddr_utils.h"
	#include "src/core/lib/iomgr/socket_mutator.h"
	#include "src/core/lib/iomgr/socket_utils_posix.h"
	#include "src/core/lib/iomgr/tcp_posix.h"
	#include "src/core/lib/iomgr/timer.h"
	#include "src/core/lib/iomgr/unix_sockets_posix.h"
	#include "src/core/lib/slice/slice_internal.h"

	extern grpc_core::TraceFlag grpc_tcp_trace;

	typedef struct {
	gpr_mu mu;
	grpc_fd* fd;
	grpc_timer alarm;
	grpc_closure on_alarm;
	int refs;
	grpc_closure write_closure;
	grpc_pollset_set* interested_parties;
	char* addr_str;
	grpc_endpoint** ep;
	grpc_closure* closure;
	grpc_channel_args* channel_args;
	} async_connect;

	static grpc_error* prepare_socket(const grpc_resolved_address* addr, int fd,
	const grpc_channel_args* channel_args) {
	grpc_error* err = GRPC_ERROR_NONE;

	GPR_ASSERT(fd >= 0);

	err = grpc_set_socket_nonblocking(fd, 1);
	if (err != GRPC_ERROR_NONE) goto error;
	err = grpc_set_socket_cloexec(fd, 1);
	if (err != GRPC_ERROR_NONE) goto error;
	if (!grpc_is_unix_socket(addr)) {
	err = grpc_set_socket_low_latency(fd, 1);
	if (err != GRPC_ERROR_NONE) goto error;
	err = grpc_set_socket_reuse_addr(fd, 1);
	if (err != GRPC_ERROR_NONE) goto error;
	err = grpc_set_socket_tcp_user_timeout(fd, channel_args,
	true /* is_client */);
	if (err != GRPC_ERROR_NONE) goto error;
	}
	err = grpc_set_socket_no_sigpipe_if_possible(fd);
	if (err != GRPC_ERROR_NONE) goto error;
	if (channel_args) {
	for (size_t i = 0; i < channel_args->num_args; i++) {
	if (0 == strcmp(channel_args->args[i].key, GRPC_ARG_SOCKET_MUTATOR)) {
	GPR_ASSERT(channel_args->args[i].type == GRPC_ARG_POINTER);
	grpc_socket_mutator* mutator = static_cast<grpc_socket_mutator*>(
	channel_args->args[i].value.pointer.p);
	err = grpc_set_socket_with_mutator(fd, mutator);
	if (err != GRPC_ERROR_NONE) goto error;
	}
	}
	}
	goto done;

	error:
	if (fd >= 0) {
	close(fd);
	}
	done:
	return err;
	}

	static void tc_on_alarm(void* acp, grpc_error* error) {
	int done;
	async_connect* ac = static_cast<async_connect*>(acp);
	if (GRPC_TRACE_FLAG_ENABLED(grpc_tcp_trace)) {
	const char* str = grpc_error_string(error);
	gpr_log(GPR_INFO, "CLIENT_CONNECT: %s: on_alarm: error=%s", ac->addr_str,
	str);
	}
	gpr_mu_lock(&ac->mu);
	if (ac->fd != nullptr) {
	grpc_fd_shutdown(
	ac->fd, GRPC_ERROR_CREATE_FROM_STATIC_STRING("connect() timed out"));
	}
	done = (--ac->refs == 0);
	gpr_mu_unlock(&ac->mu);
	if (done) {
	gpr_mu_destroy(&ac->mu);
	gpr_free(ac->addr_str);
	grpc_channel_args_destroy(ac->channel_args);
	gpr_free(ac);
	}
	}

	grpc_endpoint* grpc_tcp_client_create_from_fd(
	grpc_fd* fd, const grpc_channel_args* channel_args, const char* addr_str) {
	return grpc_tcp_create(fd, channel_args, addr_str);
	}

	static void on_writable(void* acp, grpc_error* error) {
	async_connect* ac = static_cast<async_connect*>(acp);
	int so_error = 0;
	socklen_t so_error_size;
	int err;
	int done;
	grpc_endpoint** ep = ac->ep;
	grpc_closure* closure = ac->closure;
	grpc_fd* fd;

	GRPC_ERROR_REF(error);

	if (GRPC_TRACE_FLAG_ENABLED(grpc_tcp_trace)) {
	const char* str = grpc_error_string(error);
	gpr_log(GPR_INFO, "CLIENT_CONNECT: %s: on_writable: error=%s", ac->addr_str,
	str);
	}

	gpr_mu_lock(&ac->mu);
	GPR_ASSERT(ac->fd);
	fd = ac->fd;
	ac->fd = nullptr;
	gpr_mu_unlock(&ac->mu);

	grpc_timer_cancel(&ac->alarm);

	gpr_mu_lock(&ac->mu);
	if (error != GRPC_ERROR_NONE) {
	error =
	grpc_error_set_str(error, GRPC_ERROR_STR_OS_ERROR,
	grpc_slice_from_static_string("Timeout occurred"));
	goto finish;
	}

	do {
	so_error_size = sizeof(so_error);
	err = getsockopt(grpc_fd_wrapped_fd(fd), SOL_SOCKET, SO_ERROR, &so_error,
	&so_error_size);
	} while (err < 0 && errno == EINTR);
	if (err < 0) {
	error = GRPC_OS_ERROR(errno, "getsockopt");
	goto finish;
	}

	switch (so_error) {
	case 0:
	grpc_pollset_set_del_fd(ac->interested_parties, fd);
	*ep = grpc_tcp_client_create_from_fd(fd, ac->channel_args, ac->addr_str);
	fd = nullptr;
	break;
	case ENOBUFS:
	/* We will get one of these errors if we have run out of
	memory in the kernel for the data structures allocated
	when you connect a socket. If this happens it is very
	likely that if we wait a little bit then try again the
	connection will work (since other programs or this
	program will close their network connections and free up
	memory). This does _not_ indicate that there is anything
	wrong with the server we are connecting to, this is a
	local problem.

	If you are looking at this code, then chances are that
	your program or another program on the same computer
	opened too many network connections. The "easy" fix:
	don't do that! */
	gpr_log(GPR_ERROR, "kernel out of buffers");
	gpr_mu_unlock(&ac->mu);
	grpc_fd_notify_on_write(fd, &ac->write_closure);
	return;
	case ECONNREFUSED:
	/* This error shouldn't happen for anything other than connect(). */
	error = GRPC_OS_ERROR(so_error, "connect");
	break;
	default:
	/* We don't really know which syscall triggered the problem here,
	so punt by reporting getsockopt(). */
	error = GRPC_OS_ERROR(so_error, "getsockopt(SO_ERROR)");
	break;
	}

	finish:
	if (fd != nullptr) {
	grpc_pollset_set_del_fd(ac->interested_parties, fd);
	grpc_fd_orphan(fd, nullptr, nullptr, "tcp_client_orphan");
	fd = nullptr;
	}
	done = (--ac->refs == 0);
	// Create a copy of the data from "ac" to be accessed after the unlock, as
	// "ac" and its contents may be deallocated by the time they are read.
	const grpc_slice addr_str_slice = grpc_slice_from_copied_string(ac->addr_str);
	gpr_mu_unlock(&ac->mu);
	if (error != GRPC_ERROR_NONE) {
	char* error_descr;
	grpc_slice str;
	bool ret = grpc_error_get_str(error, GRPC_ERROR_STR_DESCRIPTION, &str);
	GPR_ASSERT(ret);
	char* desc = grpc_slice_to_c_string(str);
	gpr_asprintf(&error_descr, "Failed to connect to remote host: %s", desc);
	error = grpc_error_set_str(error, GRPC_ERROR_STR_DESCRIPTION,
	grpc_slice_from_copied_string(error_descr));
	gpr_free(error_descr);
	gpr_free(desc);
	error = grpc_error_set_str(error, GRPC_ERROR_STR_TARGET_ADDRESS,
	addr_str_slice /* takes ownership */);
	} else {
	grpc_slice_unref_internal(addr_str_slice);
	}
	if (done) {
	// This is safe even outside the lock, because "done", the sentinel, is
	// populated inside the lock.
	gpr_mu_destroy(&ac->mu);
	gpr_free(ac->addr_str);
	grpc_channel_args_destroy(ac->channel_args);
	gpr_free(ac);
	}
	GRPC_CLOSURE_SCHED(closure, error);
	}

	grpc_error* grpc_tcp_client_prepare_fd(const grpc_channel_args* channel_args,
	const grpc_resolved_address* addr,
	grpc_resolved_address* mapped_addr,
	grpc_fd** fdobj) {
	grpc_dualstack_mode dsmode;
	int fd;
	grpc_error* error;
	char* name;
	char* addr_str;
	*fdobj = nullptr;
	/* Use dualstack sockets where available. Set mapped to v6 or v4 mapped to
	v6. */
	if (!grpc_sockaddr_to_v4mapped(addr, mapped_addr)) {
	/* addr is v4 mapped to v6 or v6. */
	memcpy(mapped_addr, addr, sizeof(*mapped_addr));
	}
	error =
	grpc_create_dualstack_socket(mapped_addr, SOCK_STREAM, 0, &dsmode, &fd);
	if (error != GRPC_ERROR_NONE) {
	return error;
	}
	if (dsmode == GRPC_DSMODE_IPV4) {
	/* Original addr is either v4 or v4 mapped to v6. Set mapped_addr to v4. */
	if (!grpc_sockaddr_is_v4mapped(addr, mapped_addr)) {
	memcpy(mapped_addr, addr, sizeof(*mapped_addr));
	}
	}
	if ((error = prepare_socket(mapped_addr, fd, channel_args)) !=
	GRPC_ERROR_NONE) {
	return error;
	}
	addr_str = grpc_sockaddr_to_uri(mapped_addr);
	gpr_asprintf(&name, "tcp-client:%s", addr_str);
	*fdobj = grpc_fd_create(fd, name, true);
	gpr_free(name);
	gpr_free(addr_str);
	return GRPC_ERROR_NONE;
	}

	void grpc_tcp_client_create_from_prepared_fd(
	grpc_pollset_set* interested_parties, grpc_closure* closure, grpc_fd* fdobj,
	const grpc_channel_args* channel_args, const grpc_resolved_address* addr,
	grpc_millis deadline, grpc_endpoint** ep) {
	const int fd = grpc_fd_wrapped_fd(fdobj);
	int err = 0;
	async_connect* ac;
	// Special handling for Android Studio Profilers.
	// Check Unix-specific socket types.
	auto* un = reinterpret_cast<const struct sockaddr_un*>(addr->addr);
	if (un->sun_path[0] == '&') {
	// A connected fd is provided by the caller of gRPC.
	// No need to call connect(). Do nothing here.
	} else {
	// Make a copy of addr so it can be modified to support abstract socket.
	grpc_resolved_address addr_copy = *addr;
	auto* un_copy = reinterpret_cast<struct sockaddr_un*>(&addr_copy.addr);
	if (un_copy->sun_path[0] == '@') {
	// This is a Unix abstract domain socket. Set the first char to '\0'.
	un_copy->sun_path[0] = '\0';
	// The length includes the leading '\0' but not the terminating '\0'.
	// Not including the terminating null byte to make the socket name easy to
	// see and type in shell (e.g., adb forward).
	addr_copy.len =
	1 + strlen(&un_copy->sun_path[1]) + sizeof(un_copy->sun_family);
	}
	do {
	err = connect(fd, reinterpret_cast<const grpc_sockaddr*>(addr_copy.addr),
	addr_copy.len);
	} while (err < 0 && errno == EINTR);
	}
	if (err >= 0) {
	// Use addr not addr_copy to obtain the string representation as
	// grpc_sockaddr_to_uri(..) considers string null-terminated.
	char* addr_str = grpc_sockaddr_to_uri(addr);
	*ep = grpc_tcp_client_create_from_fd(fdobj, channel_args, addr_str);
	gpr_free(addr_str);
	GRPC_CLOSURE_SCHED(closure, GRPC_ERROR_NONE);
	return;
	}
	if (errno != EWOULDBLOCK && errno != EINPROGRESS) {
	grpc_fd_orphan(fdobj, nullptr, nullptr, "tcp_client_connect_error");
	GRPC_CLOSURE_SCHED(closure, GRPC_OS_ERROR(errno, "connect"));
	return;
	}

	grpc_pollset_set_add_fd(interested_parties, fdobj);

	ac = static_cast<async_connect*>(gpr_malloc(sizeof(async_connect)));
	ac->closure = closure;
	ac->ep = ep;
	ac->fd = fdobj;
	ac->interested_parties = interested_parties;
	// Use addr not addr_copy to obtain the string representation as
	// grpc_sockaddr_to_uri(..) considers strings null-terminated.
	ac->addr_str = grpc_sockaddr_to_uri(addr);
	gpr_mu_init(&ac->mu);
	ac->refs = 2;
	GRPC_CLOSURE_INIT(&ac->write_closure, on_writable, ac,
	grpc_schedule_on_exec_ctx);
	ac->channel_args = grpc_channel_args_copy(channel_args);

	if (GRPC_TRACE_FLAG_ENABLED(grpc_tcp_trace)) {
	gpr_log(GPR_INFO, "CLIENT_CONNECT: %s: asynchronously connecting fd %p",
	ac->addr_str, fdobj);
	}

	gpr_mu_lock(&ac->mu);
	GRPC_CLOSURE_INIT(&ac->on_alarm, tc_on_alarm, ac, grpc_schedule_on_exec_ctx);
	grpc_timer_init(&ac->alarm, deadline, &ac->on_alarm);
	grpc_fd_notify_on_write(ac->fd, &ac->write_closure);
	gpr_mu_unlock(&ac->mu);
	}

	static void tcp_connect(grpc_closure* closure, grpc_endpoint** ep,
	grpc_pollset_set* interested_parties,
	const grpc_channel_args* channel_args,
	const grpc_resolved_address* addr,
	grpc_millis deadline) {
	grpc_resolved_address mapped_addr;
	grpc_fd* fdobj = nullptr;
	grpc_error* error;
	*ep = nullptr;
	if ((error = grpc_tcp_client_prepare_fd(channel_args, addr, &mapped_addr,
	&fdobj)) != GRPC_ERROR_NONE) {
	GRPC_CLOSURE_SCHED(closure, error);
	return;
	}
	grpc_tcp_client_create_from_prepared_fd(interested_parties, closure, fdobj,
	channel_args, &mapped_addr, deadline,
	ep);
	}

	grpc_tcp_client_vtable grpc_posix_tcp_client_vtable = {tcp_connect};
	#endif