tcp.c

/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <assert.h>

#include "uv.h"
#include "../uv-common.h"
#include "internal.h"


/*
 * Threshold of active tcp streams for which to preallocate tcp read buffers.
 * (Due to node slab allocator performing poorly under this pattern,
 *  the optimization is temporarily disabled (threshold=0).  This will be
 *  revisited once node allocator is improved.)
 */
const unsigned int uv_active_tcp_streams_threshold = 0;

/*
 * Number of simultaneous pending AcceptEx calls.
 */
const unsigned int uv_simultaneous_server_accepts = 32;

/* A zero-size buffer for use by uv_tcp_read */
static char uv_zero_[] = "";

/* Counter to keep track of active tcp streams */
static unsigned int active_tcp_streams = 0;


static int uv_tcp_set_socket(uv_loop_t* loop, uv_tcp_t* handle,
    SOCKET socket) {
  DWORD yes = 1;

  assert(handle->socket == INVALID_SOCKET);

  /* Set the socket to nonblocking mode */
  if (ioctlsocket(socket, FIONBIO, &yes) == SOCKET_ERROR) {
    uv_set_sys_error(loop, WSAGetLastError());
    return -1;
  }

  /* Make the socket non-inheritable */
  if (!SetHandleInformation((HANDLE)socket, HANDLE_FLAG_INHERIT, 0)) {
    uv_set_sys_error(loop, GetLastError());
    return -1;
  }

  /* Associate it with the I/O completion port. */
  /* Use uv_handle_t pointer as completion key. */
  if (CreateIoCompletionPort((HANDLE)socket,
                             loop->iocp,
                             (ULONG_PTR)socket,
                             0) == NULL) {
    uv_set_sys_error(loop, GetLastError());
    return -1;
  }

  if (pSetFileCompletionNotificationModes) {
    if (pSetFileCompletionNotificationModes((HANDLE) socket,
        FILE_SKIP_SET_EVENT_ON_HANDLE |
        FILE_SKIP_COMPLETION_PORT_ON_SUCCESS)) {
      handle->flags |= UV_HANDLE_SYNC_BYPASS_IOCP;
    } else if (GetLastError() != ERROR_INVALID_FUNCTION) {
      uv_set_sys_error(loop, GetLastError());
      return -1;
    }
  }

  handle->socket = socket;

  return 0;
}


int uv_tcp_init(uv_loop_t* loop, uv_tcp_t* handle) {
  uv_stream_init(loop, (uv_stream_t*)handle);

  handle->accept_reqs = NULL;
  handle->pending_accepts = NULL;
  handle->socket = INVALID_SOCKET;
  handle->type = UV_TCP;
  handle->reqs_pending = 0;

  loop->counters.tcp_init++;

  return 0;
}


void uv_tcp_endgame(uv_loop_t* loop, uv_tcp_t* handle) {
  uv_err_t err;
  int status;

  if (handle->flags & UV_HANDLE_CONNECTION &&
      handle->flags & UV_HANDLE_SHUTTING &&
      !(handle->flags & UV_HANDLE_SHUT) &&
      handle->write_reqs_pending == 0) {

    if (shutdown(handle->socket, SD_SEND) != SOCKET_ERROR) {
      status = 0;
      handle->flags |= UV_HANDLE_SHUT;
    } else {
      status = -1;
      err = uv_new_sys_error(WSAGetLastError());
    }
    if (handle->shutdown_req->cb) {
      if (status == -1) {
        loop->last_error = err;
      }
      handle->shutdown_req->cb(handle->shutdown_req, status);
    }

    DECREASE_PENDING_REQ_COUNT(handle);
    return;
  }

  if (handle->flags & UV_HANDLE_CLOSING &&
      handle->reqs_pending == 0) {
    assert(!(handle->flags & UV_HANDLE_CLOSED));
    handle->flags |= UV_HANDLE_CLOSED;

    if (!(handle->flags & UV_HANDLE_CONNECTION) && handle->accept_reqs) {
      free(handle->accept_reqs);
      handle->accept_reqs = NULL;
    }

    if (handle->close_cb) {
      handle->close_cb((uv_handle_t*)handle);
    }

    active_tcp_streams--;

    uv_unref(loop);
  }
}


static int uv__bind(uv_loop_t* loop, uv_tcp_t* handle, int domain,
    struct sockaddr* addr, int addrsize) {
  DWORD err;
  int r;
  SOCKET sock;

  if (handle->socket == INVALID_SOCKET) {
    sock = socket(domain, SOCK_STREAM, 0);
    if (sock == INVALID_SOCKET) {
      uv_set_sys_error(loop, WSAGetLastError());
      return -1;
    }

    if (uv_tcp_set_socket(loop, handle, sock) == -1) {
      closesocket(sock);
      return -1;
    }
  }

  r = bind(handle->socket, addr, addrsize);

  if (r == SOCKET_ERROR) {
    err = WSAGetLastError();
    if (err == WSAEADDRINUSE) {
      /* Some errors are not to be reported until connect() or listen() */
      handle->bind_error = uv_new_sys_error(err);
      handle->flags |= UV_HANDLE_BIND_ERROR;
    } else {
      uv_set_sys_error(loop, err);
      return -1;
    }
  }

  handle->flags |= UV_HANDLE_BOUND;

  return 0;
}


int uv_tcp_bind(uv_tcp_t* handle, struct sockaddr_in addr) {
  uv_loop_t* loop = handle->loop;

  if (handle->type != UV_TCP || addr.sin_family != AF_INET) {
    uv_set_sys_error(loop, WSAEFAULT);
    return -1;
  }

  return uv__bind(loop,
                  handle,
                  AF_INET,
                  (struct sockaddr*)&addr,
                  sizeof(struct sockaddr_in));
}


int uv_tcp_bind6(uv_tcp_t* handle, struct sockaddr_in6 addr) {
  uv_loop_t* loop = handle->loop;

  if (handle->type != UV_TCP || addr.sin6_family != AF_INET6) {
    uv_set_sys_error(loop, WSAEFAULT);
    return -1;
  }

  if (uv_allow_ipv6) {
    handle->flags |= UV_HANDLE_IPV6;
    return uv__bind(loop,
                    handle,
                    AF_INET6,
                    (struct sockaddr*)&addr,
                    sizeof(struct sockaddr_in6));

  } else {
    uv_set_sys_error(loop, WSAEAFNOSUPPORT);
    return -1;
  }
}


static void uv_tcp_queue_accept(uv_tcp_t* handle, uv_tcp_accept_t* req) {
  uv_loop_t* loop = handle->loop;
  BOOL success;
  DWORD bytes;
  SOCKET accept_socket;
  short family;
  LPFN_ACCEPTEX pAcceptExFamily;

  assert(handle->flags & UV_HANDLE_LISTENING);
  assert(req->accept_socket == INVALID_SOCKET);

  /* choose family and extension function */
  if ((handle->flags & UV_HANDLE_IPV6) != 0) {
    family = AF_INET6;
    pAcceptExFamily = pAcceptEx6;
  } else {
    family = AF_INET;
    pAcceptExFamily = pAcceptEx;
  }

  /* Open a socket for the accepted connection. */
  accept_socket = socket(family, SOCK_STREAM, 0);
  if (accept_socket == INVALID_SOCKET) {
    SET_REQ_ERROR(req, WSAGetLastError());
    uv_insert_pending_req(loop, (uv_req_t*)req);
    handle->reqs_pending++;
    return;
  }

  /* Prepare the overlapped structure. */
  memset(&(req->overlapped), 0, sizeof(req->overlapped));

  success = pAcceptExFamily(handle->socket,
                          accept_socket,
                          (void*)req->accept_buffer,
                          0,
                          sizeof(struct sockaddr_storage),
                          sizeof(struct sockaddr_storage),
                          &bytes,
                          &req->overlapped);

  if (UV_SUCCEEDED_WITHOUT_IOCP(success)) {
    /* Process the req without IOCP. */
    req->accept_socket = accept_socket;
    handle->reqs_pending++;
    uv_insert_pending_req(loop, (uv_req_t*)req);
  } else if (UV_SUCCEEDED_WITH_IOCP(success)) {
    /* The req will be processed with IOCP. */
    req->accept_socket = accept_socket;
    handle->reqs_pending++;
  } else {
    /* Make this req pending reporting an error. */
    SET_REQ_ERROR(req, WSAGetLastError());
    uv_insert_pending_req(loop, (uv_req_t*)req);
    handle->reqs_pending++;
    /* Destroy the preallocated client socket. */
    closesocket(accept_socket);
  }
}


static void uv_tcp_queue_read(uv_loop_t* loop, uv_tcp_t* handle) {
  uv_req_t* req;
  uv_buf_t buf;
  int result;
  DWORD bytes, flags;

  assert(handle->flags & UV_HANDLE_READING);
  assert(!(handle->flags & UV_HANDLE_READ_PENDING));

  req = &handle->read_req;
  memset(&req->overlapped, 0, sizeof(req->overlapped));

  /*
   * Preallocate a read buffer if the number of active streams is below
   * the threshold.
  */
  if (active_tcp_streams < uv_active_tcp_streams_threshold) {
    handle->flags &= ~UV_HANDLE_ZERO_READ;
    handle->read_buffer = handle->alloc_cb((uv_handle_t*) handle, 65536);
    assert(handle->read_buffer.len > 0);
    buf = handle->read_buffer;
  } else {
    handle->flags |= UV_HANDLE_ZERO_READ;
    buf.base = (char*) &uv_zero_;
    buf.len = 0;
  }

  flags = 0;
  result = WSARecv(handle->socket,
                   (WSABUF*)&buf,
                   1,
                   &bytes,
                   &flags,
                   &req->overlapped,
                   NULL);

  if (UV_SUCCEEDED_WITHOUT_IOCP(result == 0)) {
    /* Process the req without IOCP. */
    handle->flags |= UV_HANDLE_READ_PENDING;
    req->overlapped.InternalHigh = bytes;
    handle->reqs_pending++;
    uv_insert_pending_req(loop, req);
  } else if (UV_SUCCEEDED_WITH_IOCP(result == 0)) {
    /* The req will be processed with IOCP. */
    handle->flags |= UV_HANDLE_READ_PENDING;
    handle->reqs_pending++;
  } else {
    /* Make this req pending reporting an error. */
    SET_REQ_ERROR(req, WSAGetLastError());
    uv_insert_pending_req(loop, req);
    handle->reqs_pending++;
  }
}


int uv_tcp_listen(uv_tcp_t* handle, int backlog, uv_connection_cb cb) {
  uv_loop_t* loop = handle->loop;
  unsigned int i;
  uv_tcp_accept_t* req;

  assert(backlog > 0);

  if (handle->flags & UV_HANDLE_BIND_ERROR) {
    loop->last_error = handle->bind_error;
    return -1;
  }

  if (handle->flags & UV_HANDLE_LISTENING ||
      handle->flags & UV_HANDLE_READING) {
    /* Already listening. */
    uv_set_sys_error(loop, WSAEALREADY);
    return -1;
  }

  if (!(handle->flags & UV_HANDLE_BOUND) &&
      uv_tcp_bind(handle, uv_addr_ip4_any_) < 0)
    return -1;

  if (listen(handle->socket, backlog) == SOCKET_ERROR) {
    uv_set_sys_error(loop, WSAGetLastError());
    return -1;
  }

  handle->flags |= UV_HANDLE_LISTENING;
  handle->connection_cb = cb;

  assert(!handle->accept_reqs);
  handle->accept_reqs = (uv_tcp_accept_t*)
    malloc(uv_simultaneous_server_accepts * sizeof(uv_tcp_accept_t));
  if (!handle->accept_reqs) {
    uv_fatal_error(ERROR_OUTOFMEMORY, "malloc");
  }

  for (i = 0; i < uv_simultaneous_server_accepts; i++) {
    req = &handle->accept_reqs[i];
    uv_req_init(loop, (uv_req_t*)req);
    req->type = UV_ACCEPT;
    req->accept_socket = INVALID_SOCKET;
    req->data = handle;
    uv_tcp_queue_accept(handle, req);
  }

  return 0;
}


int uv_tcp_accept(uv_tcp_t* server, uv_tcp_t* client) {
  uv_loop_t* loop = server->loop;
  int rv = 0;

  uv_tcp_accept_t* req = server->pending_accepts;

  if (!req) {
    /* No valid connections found, so we error out. */
    uv_set_sys_error(loop, WSAEWOULDBLOCK);
    return -1;
  }

  if (req->accept_socket == INVALID_SOCKET) {
    uv_set_sys_error(loop, WSAENOTCONN);
    return -1;
  }

  if (uv_tcp_set_socket(client->loop, client, req->accept_socket) == -1) {
    closesocket(req->accept_socket);
    rv = -1;
  } else {
    uv_connection_init((uv_stream_t*) client);
    /* AcceptEx() implicitly binds the accepted socket. */
    client->flags |= UV_HANDLE_BOUND;
  }

  /* Prepare the req to pick up a new connection */
  server->pending_accepts = req->next_pending;
  req->next_pending = NULL;
  req->accept_socket = INVALID_SOCKET;

  if (!(server->flags & UV_HANDLE_CLOSING)) {
    uv_tcp_queue_accept(server, req);
  }

  active_tcp_streams++;

  return rv;
}


int uv_tcp_read_start(uv_tcp_t* handle, uv_alloc_cb alloc_cb,
    uv_read_cb read_cb) {
  uv_loop_t* loop = handle->loop;

  if (!(handle->flags & UV_HANDLE_CONNECTION)) {
    uv_set_sys_error(loop, WSAEINVAL);
    return -1;
  }

  if (handle->flags & UV_HANDLE_READING) {
    uv_set_sys_error(loop, WSAEALREADY);
    return -1;
  }

  if (handle->flags & UV_HANDLE_EOF) {
    uv_set_sys_error(loop, WSAESHUTDOWN);
    return -1;
  }

  handle->flags |= UV_HANDLE_READING;
  handle->read_cb = read_cb;
  handle->alloc_cb = alloc_cb;

  /* If reading was stopped and then started again, there could stell be a */
  /* read request pending. */
  if (!(handle->flags & UV_HANDLE_READ_PENDING))
    uv_tcp_queue_read(loop, handle);

  return 0;
}


int uv_tcp_connect(uv_connect_t* req, uv_tcp_t* handle,
    struct sockaddr_in address, uv_connect_cb cb) {
  uv_loop_t* loop = handle->loop;
  int addrsize = sizeof(struct sockaddr_in);
  BOOL success;
  DWORD bytes;

  if (handle->flags & UV_HANDLE_BIND_ERROR) {
    loop->last_error = handle->bind_error;
    return -1;
  }

  if (handle->type != UV_TCP || address.sin_family != AF_INET) {
    uv_set_sys_error(loop, WSAEFAULT);
    return -1;
  }

  if (!(handle->flags & UV_HANDLE_BOUND) &&
      uv_tcp_bind(handle, uv_addr_ip4_any_) < 0)
    return -1;

  uv_req_init(loop, (uv_req_t*) req);
  req->type = UV_CONNECT;
  req->handle = (uv_stream_t*) handle;
  req->cb = cb;
  memset(&req->overlapped, 0, sizeof(req->overlapped));

  success = pConnectEx(handle->socket,
                       (struct sockaddr*) &address,
                       addrsize,
                       NULL,
                       0,
                       &bytes,
                       &req->overlapped);

  if (UV_SUCCEEDED_WITHOUT_IOCP(success)) {
    /* Process the req without IOCP. */
    handle->reqs_pending++;
    uv_insert_pending_req(loop, (uv_req_t*)req);
  } else if (UV_SUCCEEDED_WITH_IOCP(success)) {
    /* The req will be processed with IOCP. */
    handle->reqs_pending++;
  } else {
    uv_set_sys_error(loop, WSAGetLastError());
    return -1;
  }

  return 0;
}


int uv_tcp_connect6(uv_connect_t* req, uv_tcp_t* handle,
    struct sockaddr_in6 address, uv_connect_cb cb) {
  uv_loop_t* loop = handle->loop;
  int addrsize = sizeof(struct sockaddr_in6);
  BOOL success;
  DWORD bytes;

  if (!uv_allow_ipv6) {
    uv_new_sys_error(WSAEAFNOSUPPORT);
    return -1;
  }

  if (handle->flags & UV_HANDLE_BIND_ERROR) {
    loop->last_error = handle->bind_error;
    return -1;
  }

  if (handle->type != UV_TCP || address.sin6_family != AF_INET6) {
    uv_set_sys_error(loop, WSAEFAULT);
    return -1;
  }

  if (!(handle->flags & UV_HANDLE_BOUND) &&
      uv_tcp_bind6(handle, uv_addr_ip6_any_) < 0)
    return -1;

  uv_req_init(loop, (uv_req_t*) req);
  req->type = UV_CONNECT;
  req->handle = (uv_stream_t*) handle;
  req->cb = cb;
  memset(&req->overlapped, 0, sizeof(req->overlapped));

  success = pConnectEx6(handle->socket,
                       (struct sockaddr*) &address,
                       addrsize,
                       NULL,
                       0,
                       &bytes,
                       &req->overlapped);

  if (UV_SUCCEEDED_WITHOUT_IOCP(success)) {
    handle->reqs_pending++;
    uv_insert_pending_req(loop, (uv_req_t*)req);
  } else if (UV_SUCCEEDED_WITH_IOCP(success)) {
    handle->reqs_pending++;
  } else {
    uv_set_sys_error(loop, WSAGetLastError());
    return -1;
  }

  return 0;
}


int uv_tcp_getsockname(uv_tcp_t* handle, struct sockaddr* name,
    int* namelen) {
  uv_loop_t* loop = handle->loop;
  int result;

  if (!(handle->flags & UV_HANDLE_BOUND)) {
    uv_set_sys_error(loop, WSAEINVAL);
    return -1;
  }

  if (handle->flags & UV_HANDLE_BIND_ERROR) {
    loop->last_error = handle->bind_error;
    return -1;
  }

  result = getsockname(handle->socket, name, namelen);
  if (result != 0) {
    uv_set_sys_error(loop, WSAGetLastError());
    return -1;
  }

  return 0;
}


int uv_tcp_getpeername(uv_tcp_t* handle, struct sockaddr* name,
    int* namelen) {
  uv_loop_t* loop = handle->loop;
  int result;

  if (!(handle->flags & UV_HANDLE_BOUND)) {
    uv_set_sys_error(loop, WSAEINVAL);
    return -1;
  }

  if (handle->flags & UV_HANDLE_BIND_ERROR) {
    loop->last_error = handle->bind_error;
    return -1;
  }

  result = getpeername(handle->socket, name, namelen);
  if (result != 0) {
    uv_set_sys_error(loop, WSAGetLastError());
    return -1;
  }

  return 0;
}


int uv_tcp_write(uv_loop_t* loop, uv_write_t* req, uv_tcp_t* handle,
    uv_buf_t bufs[], int bufcnt, uv_write_cb cb) {
  int result;
  DWORD bytes;

  if (!(handle->flags & UV_HANDLE_CONNECTION)) {
    uv_set_sys_error(loop, WSAEINVAL);
    return -1;
  }

  if (handle->flags & UV_HANDLE_SHUTTING) {
    uv_set_sys_error(loop, WSAESHUTDOWN);
    return -1;
  }

  uv_req_init(loop, (uv_req_t*) req);
  req->type = UV_WRITE;
  req->handle = (uv_stream_t*) handle;
  req->cb = cb;
  memset(&req->overlapped, 0, sizeof(req->overlapped));

  result = WSASend(handle->socket,
                   (WSABUF*)bufs,
                   bufcnt,
                   &bytes,
                   0,
                   &req->overlapped,
                   NULL);

  if (UV_SUCCEEDED_WITHOUT_IOCP(result == 0)) {
    /* Request completed immediately. */
    req->queued_bytes = 0;
    handle->reqs_pending++;
    handle->write_reqs_pending++;
    uv_insert_pending_req(loop, (uv_req_t*) req);
  } else if (UV_SUCCEEDED_WITH_IOCP(result == 0)) {
    /* Request queued by the kernel. */
    req->queued_bytes = uv_count_bufs(bufs, bufcnt);
    handle->reqs_pending++;
    handle->write_reqs_pending++;
    handle->write_queue_size += req->queued_bytes;
  } else {
    /* Send failed due to an error. */
    uv_set_sys_error(loop, WSAGetLastError());
    return -1;
  }

  return 0;
}


void uv_process_tcp_read_req(uv_loop_t* loop, uv_tcp_t* handle,
    uv_req_t* req) {
  DWORD bytes, flags, err;
  uv_buf_t buf;

  assert(handle->type == UV_TCP);

  handle->flags &= ~UV_HANDLE_READ_PENDING;

  if (!REQ_SUCCESS(req)) {
    /* An error occurred doing the read. */
    if ((handle->flags & UV_HANDLE_READING)) {
      handle->flags &= ~UV_HANDLE_READING;
      loop->last_error = GET_REQ_UV_SOCK_ERROR(req);
      buf = (handle->flags & UV_HANDLE_ZERO_READ) ?
            uv_buf_init(NULL, 0) : handle->read_buffer;
      handle->read_cb((uv_stream_t*)handle, -1, buf);
    }
  } else {
    if (!(handle->flags & UV_HANDLE_ZERO_READ)) {
      /* The read was done with a non-zero buffer length. */
      if (req->overlapped.InternalHigh > 0) {
        /* Successful read */
        handle->read_cb((uv_stream_t*)handle,
                        req->overlapped.InternalHigh,
                        handle->read_buffer);
        /* Read again only if bytes == buf.len */
        if (req->overlapped.InternalHigh < handle->read_buffer.len) {
          goto done;
        }
      } else {
        /* Connection closed */
        handle->flags &= ~UV_HANDLE_READING;
        handle->flags |= UV_HANDLE_EOF;
        loop->last_error.code = UV_EOF;
        loop->last_error.sys_errno_ = ERROR_SUCCESS;
        buf.base = 0;
        buf.len = 0;
        handle->read_cb((uv_stream_t*)handle, -1, handle->read_buffer);
        goto done;
      }
    }

    /* Do nonblocking reads until the buffer is empty */
    while (handle->flags & UV_HANDLE_READING) {
      buf = handle->alloc_cb((uv_handle_t*) handle, 65536);
      assert(buf.len > 0);
      flags = 0;
      if (WSARecv(handle->socket,
                  (WSABUF*)&buf,
                  1,
                  &bytes,
                  &flags,
                  NULL,
                  NULL) != SOCKET_ERROR) {
        if (bytes > 0) {
          /* Successful read */
          handle->read_cb((uv_stream_t*)handle, bytes, buf);
          /* Read again only if bytes == buf.len */
          if (bytes < buf.len) {
            break;
          }
        } else {
          /* Connection closed */
          handle->flags &= ~UV_HANDLE_READING;
          handle->flags |= UV_HANDLE_EOF;
          loop->last_error.code = UV_EOF;
          loop->last_error.sys_errno_ = ERROR_SUCCESS;
          handle->read_cb((uv_stream_t*)handle, -1, buf);
          break;
        }
      } else {
        err = WSAGetLastError();
        if (err == WSAEWOULDBLOCK) {
          /* Read buffer was completely empty, report a 0-byte read. */
          uv_set_sys_error(loop, WSAEWOULDBLOCK);
          handle->read_cb((uv_stream_t*)handle, 0, buf);
        } else {
          /* Ouch! serious error. */
          uv_set_sys_error(loop, err);
          handle->flags &= ~UV_HANDLE_READING;
          handle->read_cb((uv_stream_t*)handle, -1, buf);
        }
        break;
      }
    }

done:
    /* Post another read if still reading and not closing. */
    if ((handle->flags & UV_HANDLE_READING) &&
        !(handle->flags & UV_HANDLE_READ_PENDING)) {
      uv_tcp_queue_read(loop, handle);
    }
  }

  DECREASE_PENDING_REQ_COUNT(handle);
}


void uv_process_tcp_write_req(uv_loop_t* loop, uv_tcp_t* handle,
    uv_write_t* req) {
  assert(handle->type == UV_TCP);

  handle->write_queue_size -= req->queued_bytes;

  if (req->cb) {
    loop->last_error = GET_REQ_UV_SOCK_ERROR(req);
    ((uv_write_cb)req->cb)(req, loop->last_error.code == UV_OK ? 0 : -1);
  }

  handle->write_reqs_pending--;
  if (handle->flags & UV_HANDLE_SHUTTING &&
      handle->write_reqs_pending == 0) {
    uv_want_endgame(loop, (uv_handle_t*)handle);
  }

  DECREASE_PENDING_REQ_COUNT(handle);
}


void uv_process_tcp_accept_req(uv_loop_t* loop, uv_tcp_t* handle,
    uv_req_t* raw_req) {
  uv_tcp_accept_t* req = (uv_tcp_accept_t*) raw_req;

  assert(handle->type == UV_TCP);

  /* If handle->accepted_socket is not a valid socket, then */
  /* uv_queue_accept must have failed. This is a serious error. We stop */
  /* accepting connections and report this error to the connection */
  /* callback. */
  if (req->accept_socket == INVALID_SOCKET) {
    if (handle->flags & UV_HANDLE_LISTENING) {
      handle->flags &= ~UV_HANDLE_LISTENING;
      if (handle->connection_cb) {
        loop->last_error = GET_REQ_UV_SOCK_ERROR(req);
        handle->connection_cb((uv_stream_t*)handle, -1);
      }
    }
  } else if (REQ_SUCCESS(req) &&
      setsockopt(req->accept_socket,
                  SOL_SOCKET,
                  SO_UPDATE_ACCEPT_CONTEXT,
                  (char*)&handle->socket,
                  sizeof(handle->socket)) == 0) {
    req->next_pending = handle->pending_accepts;
    handle->pending_accepts = req;

    /* Accept and SO_UPDATE_ACCEPT_CONTEXT were successful. */
    if (handle->connection_cb) {
      handle->connection_cb((uv_stream_t*)handle, 0);
    }
  } else {
    /* Error related to accepted socket is ignored because the server */
    /* socket may still be healthy. If the server socket is broken
    /* uv_queue_accept will detect it. */
    closesocket(req->accept_socket);
    req->accept_socket = INVALID_SOCKET;
    if (handle->flags & UV_HANDLE_LISTENING) {
      uv_tcp_queue_accept(handle, req);
    }
  }

  DECREASE_PENDING_REQ_COUNT(handle);
}


void uv_process_tcp_connect_req(uv_loop_t* loop, uv_tcp_t* handle,
    uv_connect_t* req) {
  assert(handle->type == UV_TCP);

  if (req->cb) {
    if (REQ_SUCCESS(req)) {
      if (setsockopt(handle->socket,
                      SOL_SOCKET,
                      SO_UPDATE_CONNECT_CONTEXT,
                      NULL,
                      0) == 0) {
        uv_connection_init((uv_stream_t*)handle);
        active_tcp_streams++;
        ((uv_connect_cb)req->cb)(req, 0);
      } else {
        uv_set_sys_error(loop, WSAGetLastError());
        ((uv_connect_cb)req->cb)(req, -1);
      }
    } else {
      loop->last_error = GET_REQ_UV_SOCK_ERROR(req);
      ((uv_connect_cb)req->cb)(req, -1);
    }
  }

  DECREASE_PENDING_REQ_COUNT(handle);
}