1 files changed, 493 insertions, 15 deletions

diff --git a/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver_windows.cc b/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver_windows.cc
index 5d65ae3ab3..02121aa0ab 100644
--- a/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver_windows.cc
+++ b/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver_windows.cc
@@ -21,38 +21,516 @@
 #if GRPC_ARES == 1 && defined(GPR_WINDOWS)
 
 #include <ares.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/log_windows.h>
+#include <grpc/support/string_util.h>
+#include <grpc/support/time.h>
 #include <string.h>
+#include "src/core/lib/gpr/string.h"
 #include "src/core/lib/gprpp/memory.h"
+#include "src/core/lib/iomgr/combiner.h"
+#include "src/core/lib/iomgr/socket_windows.h"
+#include "src/core/lib/iomgr/tcp_windows.h"
+#include "src/core/lib/slice/slice_internal.h"
 
 #include "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.h"
+#include "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h"
+
+/* TODO(apolcyn): remove this hack after fixing upstream.
+ * Our grpc/c-ares code on Windows uses the ares_set_socket_functions API,
+ * which uses "struct iovec" type, which on Windows is defined inside of
+ * a c-ares header that is not public.
+ * See https://github.com/c-ares/c-ares/issues/206. */
+struct iovec {
+  void* iov_base;
+  size_t iov_len;
+};
 
 namespace grpc_core {
 
-/* TODO: fill in the body of GrpcPolledFdWindows to enable c-ares on Windows.
-   This dummy implementation only allows grpc to compile on windows with
-   GRPC_ARES=1. */
+/* c-ares creates its own sockets and is meant to read them when readable and
+ * write them when writeable. To fit this socket usage model into the grpc
+ * windows poller (which gives notifications when attempted reads and writes are
+ * actually fulfilled rather than possible), this GrpcPolledFdWindows class
+ * takes advantage of the ares_set_socket_functions API and acts as a virtual
+ * socket. It holds its own read and write buffers which are written to and read
+ * from c-ares and are used with the grpc windows poller, and it, e.g.,
+ * manufactures virtual socket error codes when it e.g. needs to tell the c-ares
+ * library to wait for an async read. */
 class GrpcPolledFdWindows : public GrpcPolledFd {
  public:
-  GrpcPolledFdWindows() { abort(); }
-  ~GrpcPolledFdWindows() { abort(); }
+  enum WriteState {
+    WRITE_IDLE,
+    WRITE_REQUESTED,
+    WRITE_PENDING,
+    WRITE_WAITING_FOR_VERIFICATION_UPON_RETRY,
+  };
+
+  GrpcPolledFdWindows(ares_socket_t as, grpc_combiner* combiner)
+      : read_buf_(grpc_empty_slice()),
+        write_buf_(grpc_empty_slice()),
+        write_state_(WRITE_IDLE),
+        gotten_into_driver_list_(false) {
+    gpr_asprintf(&name_, "c-ares socket: %" PRIdPTR, as);
+    winsocket_ = grpc_winsocket_create(as, name_);
+    combiner_ = GRPC_COMBINER_REF(combiner, name_);
+    GRPC_CLOSURE_INIT(&outer_read_closure_,
+                      &GrpcPolledFdWindows::OnIocpReadable, this,
+                      grpc_combiner_scheduler(combiner_));
+    GRPC_CLOSURE_INIT(&outer_write_closure_,
+                      &GrpcPolledFdWindows::OnIocpWriteable, this,
+                      grpc_combiner_scheduler(combiner_));
+  }
+
+  ~GrpcPolledFdWindows() {
+    GRPC_COMBINER_UNREF(combiner_, name_);
+    grpc_slice_unref_internal(read_buf_);
+    grpc_slice_unref_internal(write_buf_);
+    GPR_ASSERT(read_closure_ == nullptr);
+    GPR_ASSERT(write_closure_ == nullptr);
+    grpc_winsocket_destroy(winsocket_);
+    gpr_free(name_);
+  }
+
+  void ScheduleAndNullReadClosure(grpc_error* error) {
+    GRPC_CLOSURE_SCHED(read_closure_, error);
+    read_closure_ = nullptr;
+  }
+
+  void ScheduleAndNullWriteClosure(grpc_error* error) {
+    GRPC_CLOSURE_SCHED(write_closure_, error);
+    write_closure_ = nullptr;
+  }
+
   void RegisterForOnReadableLocked(grpc_closure* read_closure) override {
-    abort();
+    GPR_ASSERT(read_closure_ == nullptr);
+    read_closure_ = read_closure;
+    GPR_ASSERT(GRPC_SLICE_LENGTH(read_buf_) == 0);
+    grpc_slice_unref_internal(read_buf_);
+    read_buf_ = GRPC_SLICE_MALLOC(4192);
+    WSABUF buffer;
+    buffer.buf = (char*)GRPC_SLICE_START_PTR(read_buf_);
+    buffer.len = GRPC_SLICE_LENGTH(read_buf_);
+    memset(&winsocket_->read_info.overlapped, 0, sizeof(OVERLAPPED));
+    recv_from_source_addr_len_ = sizeof(recv_from_source_addr_);
+    DWORD flags = 0;
+    if (WSARecvFrom(grpc_winsocket_wrapped_socket(winsocket_), &buffer, 1,
+                    nullptr, &flags, (sockaddr*)recv_from_source_addr_,
+                    &recv_from_source_addr_len_,
+                    &winsocket_->read_info.overlapped, nullptr)) {
+      char* msg = gpr_format_message(WSAGetLastError());
+      grpc_error* error = GRPC_ERROR_CREATE_FROM_COPIED_STRING(msg);
+      GRPC_CARES_TRACE_LOG(
+          "RegisterForOnReadableLocked: WSARecvFrom error:|%s|. fd:|%s|", msg,
+          GetName());
+      gpr_free(msg);
+      if (WSAGetLastError() != WSA_IO_PENDING) {
+        ScheduleAndNullReadClosure(error);
+        return;
+      }
+    }
+    grpc_socket_notify_on_read(winsocket_, &outer_read_closure_);
   }
+
   void RegisterForOnWriteableLocked(grpc_closure* write_closure) override {
+    GRPC_CARES_TRACE_LOG(
+        "RegisterForOnWriteableLocked. fd:|%s|. Current write state: %d",
+        GetName(), write_state_);
+    GPR_ASSERT(write_closure_ == nullptr);
+    write_closure_ = write_closure;
+    switch (write_state_) {
+      case WRITE_IDLE:
+        ScheduleAndNullWriteClosure(GRPC_ERROR_NONE);
+        break;
+      case WRITE_REQUESTED:
+        write_state_ = WRITE_PENDING;
+        SendWriteBuf(nullptr, &winsocket_->write_info.overlapped);
+        grpc_socket_notify_on_write(winsocket_, &outer_write_closure_);
+        break;
+      case WRITE_PENDING:
+      case WRITE_WAITING_FOR_VERIFICATION_UPON_RETRY:
+        abort();
+    }
+  }
+
+  bool IsFdStillReadableLocked() override {
+    return GRPC_SLICE_LENGTH(read_buf_) > 0;
+  }
+
+  void ShutdownLocked(grpc_error* error) override {
+    grpc_winsocket_shutdown(winsocket_);
+  }
+
+  ares_socket_t GetWrappedAresSocketLocked() override {
+    return grpc_winsocket_wrapped_socket(winsocket_);
+  }
+
+  const char* GetName() override { return name_; }
+
+  ares_ssize_t RecvFrom(void* data, ares_socket_t data_len, int flags,
+                        struct sockaddr* from, ares_socklen_t* from_len) {
+    GRPC_CARES_TRACE_LOG(
+        "RecvFrom called on fd:|%s|. Current read buf length:|%d|", GetName(),
+        GRPC_SLICE_LENGTH(read_buf_));
+    if (GRPC_SLICE_LENGTH(read_buf_) == 0) {
+      WSASetLastError(WSAEWOULDBLOCK);
+      return -1;
+    }
+    ares_ssize_t bytes_read = 0;
+    for (size_t i = 0; i < GRPC_SLICE_LENGTH(read_buf_) && i < data_len; i++) {
+      ((char*)data)[i] = GRPC_SLICE_START_PTR(read_buf_)[i];
+      bytes_read++;
+    }
+    read_buf_ = grpc_slice_sub_no_ref(read_buf_, bytes_read,
+                                      GRPC_SLICE_LENGTH(read_buf_));
+    /* c-ares overloads this recv_from virtual socket function to receive
+     * data on both UDP and TCP sockets, and from is nullptr for TCP. */
+    if (from != nullptr) {
+      GPR_ASSERT(*from_len <= recv_from_source_addr_len_);
+      memcpy(from, &recv_from_source_addr_, recv_from_source_addr_len_);
+      *from_len = recv_from_source_addr_len_;
+    }
+    return bytes_read;
+  }
+
+  grpc_slice FlattenIovec(const struct iovec* iov, int iov_count) {
+    int total = 0;
+    for (int i = 0; i < iov_count; i++) {
+      total += iov[i].iov_len;
+    }
+    grpc_slice out = GRPC_SLICE_MALLOC(total);
+    size_t cur = 0;
+    for (int i = 0; i < iov_count; i++) {
+      for (int k = 0; k < iov[i].iov_len; k++) {
+        GRPC_SLICE_START_PTR(out)[cur++] = ((char*)iov[i].iov_base)[k];
+      }
+    }
+    return out;
+  }
+
+  int SendWriteBuf(LPDWORD bytes_sent_ptr, LPWSAOVERLAPPED overlapped) {
+    WSABUF buf;
+    buf.len = GRPC_SLICE_LENGTH(write_buf_);
+    buf.buf = (char*)GRPC_SLICE_START_PTR(write_buf_);
+    DWORD flags = 0;
+    int out = WSASend(grpc_winsocket_wrapped_socket(winsocket_), &buf, 1,
+                      bytes_sent_ptr, flags, overlapped, nullptr);
+    GRPC_CARES_TRACE_LOG(
+        "WSASend: name:%s. buf len:%d. bytes sent: %d. overlapped %p. return "
+        "val: %d",
+        GetName(), buf.len, *bytes_sent_ptr, overlapped, out);
+    return out;
+  }
+
+  ares_ssize_t TrySendWriteBufSyncNonBlocking() {
+    GPR_ASSERT(write_state_ == WRITE_IDLE);
+    ares_ssize_t total_sent;
+    DWORD bytes_sent = 0;
+    if (SendWriteBuf(&bytes_sent, nullptr) != 0) {
+      char* msg = gpr_format_message(WSAGetLastError());
+      GRPC_CARES_TRACE_LOG(
+          "TrySendWriteBufSyncNonBlocking: SendWriteBuf error:|%s|. fd:|%s|",
+          msg, GetName());
+      gpr_free(msg);
+      if (WSAGetLastError() == WSA_IO_PENDING) {
+        WSASetLastError(WSAEWOULDBLOCK);
+        write_state_ = WRITE_REQUESTED;
+      }
+    }
+    write_buf_ = grpc_slice_sub_no_ref(write_buf_, bytes_sent,
+                                       GRPC_SLICE_LENGTH(write_buf_));
+    return bytes_sent;
+  }
+
+  ares_ssize_t SendV(const struct iovec* iov, int iov_count) {
+    GRPC_CARES_TRACE_LOG("SendV called on fd:|%s|. Current write state: %d",
+                         GetName(), write_state_);
+    switch (write_state_) {
+      case WRITE_IDLE:
+        GPR_ASSERT(GRPC_SLICE_LENGTH(write_buf_) == 0);
+        grpc_slice_unref_internal(write_buf_);
+        write_buf_ = FlattenIovec(iov, iov_count);
+        return TrySendWriteBufSyncNonBlocking();
+      case WRITE_REQUESTED:
+      case WRITE_PENDING:
+        WSASetLastError(WSAEWOULDBLOCK);
+        return -1;
+      case WRITE_WAITING_FOR_VERIFICATION_UPON_RETRY:
+        grpc_slice currently_attempted = FlattenIovec(iov, iov_count);
+        GPR_ASSERT(GRPC_SLICE_LENGTH(currently_attempted) >=
+                   GRPC_SLICE_LENGTH(write_buf_));
+        ares_ssize_t total_sent = 0;
+        for (size_t i = 0; i < GRPC_SLICE_LENGTH(write_buf_); i++) {
+          GPR_ASSERT(GRPC_SLICE_START_PTR(currently_attempted)[i] ==
+                     GRPC_SLICE_START_PTR(write_buf_)[i]);
+          total_sent++;
+        }
+        grpc_slice_unref_internal(write_buf_);
+        write_buf_ =
+            grpc_slice_sub_no_ref(currently_attempted, total_sent,
+                                  GRPC_SLICE_LENGTH(currently_attempted));
+        write_state_ = WRITE_IDLE;
+        total_sent += TrySendWriteBufSyncNonBlocking();
+        return total_sent;
+    }
     abort();
   }
-  bool IsFdStillReadableLocked() override { abort(); }
-  void ShutdownLocked(grpc_error* error) override { abort(); }
-  ares_socket_t GetWrappedAresSocketLocked() override { abort(); }
-  const char* GetName() override { abort(); }
+
+  int Connect(const struct sockaddr* target, ares_socklen_t target_len) {
+    SOCKET s = grpc_winsocket_wrapped_socket(winsocket_);
+    GRPC_CARES_TRACE_LOG("Connect: fd:|%s|", GetName());
+    int out =
+        WSAConnect(s, target, target_len, nullptr, nullptr, nullptr, nullptr);
+    if (out != 0) {
+      char* msg = gpr_format_message(WSAGetLastError());
+      GRPC_CARES_TRACE_LOG("Connect error code:|%d|, msg:|%s|. fd:|%s|",
+                           WSAGetLastError(), msg, GetName());
+      gpr_free(msg);
+      // c-ares expects a posix-style connect API
+      out = -1;
+    }
+    return out;
+  }
+
+  static void OnIocpReadable(void* arg, grpc_error* error) {
+    GrpcPolledFdWindows* polled_fd = static_cast<GrpcPolledFdWindows*>(arg);
+    polled_fd->OnIocpReadableInner(error);
+  }
+
+  void OnIocpReadableInner(grpc_error* error) {
+    if (error == GRPC_ERROR_NONE) {
+      if (winsocket_->read_info.wsa_error != 0) {
+        /* WSAEMSGSIZE would be due to receiving more data
+         * than our read buffer's fixed capacity. Assume that
+         * the connection is TCP and read the leftovers
+         * in subsequent c-ares reads. */
+        if (winsocket_->read_info.wsa_error != WSAEMSGSIZE) {
+          GRPC_ERROR_UNREF(error);
+          char* msg = gpr_format_message(winsocket_->read_info.wsa_error);
+          GRPC_CARES_TRACE_LOG(
+              "OnIocpReadableInner. winsocket error:|%s|. fd:|%s|", msg,
+              GetName());
+          error = GRPC_ERROR_CREATE_FROM_COPIED_STRING(msg);
+          gpr_free(msg);
+        }
+      }
+    }
+    if (error == GRPC_ERROR_NONE) {
+      read_buf_ = grpc_slice_sub_no_ref(read_buf_, 0,
+                                        winsocket_->read_info.bytes_transfered);
+    } else {
+      grpc_slice_unref_internal(read_buf_);
+      read_buf_ = grpc_empty_slice();
+    }
+    GRPC_CARES_TRACE_LOG(
+        "OnIocpReadable finishing. read buf length now:|%d|. :fd:|%s|",
+        GRPC_SLICE_LENGTH(read_buf_), GetName());
+    ScheduleAndNullReadClosure(error);
+  }
+
+  static void OnIocpWriteable(void* arg, grpc_error* error) {
+    GrpcPolledFdWindows* polled_fd = static_cast<GrpcPolledFdWindows*>(arg);
+    polled_fd->OnIocpWriteableInner(error);
+  }
+
+  void OnIocpWriteableInner(grpc_error* error) {
+    GRPC_CARES_TRACE_LOG("OnIocpWriteableInner. fd:|%s|", GetName());
+    if (error == GRPC_ERROR_NONE) {
+      if (winsocket_->write_info.wsa_error != 0) {
+        char* msg = gpr_format_message(winsocket_->write_info.wsa_error);
+        GRPC_CARES_TRACE_LOG(
+            "OnIocpWriteableInner. winsocket error:|%s|. fd:|%s|", msg,
+            GetName());
+        GRPC_ERROR_UNREF(error);
+        error = GRPC_ERROR_CREATE_FROM_COPIED_STRING(msg);
+        gpr_free(msg);
+      }
+    }
+    GPR_ASSERT(write_state_ == WRITE_PENDING);
+    if (error == GRPC_ERROR_NONE) {
+      write_state_ = WRITE_WAITING_FOR_VERIFICATION_UPON_RETRY;
+      write_buf_ = grpc_slice_sub_no_ref(
+          write_buf_, 0, winsocket_->write_info.bytes_transfered);
+    } else {
+      grpc_slice_unref_internal(write_buf_);
+      write_buf_ = grpc_empty_slice();
+    }
+    ScheduleAndNullWriteClosure(error);
+  }
+
+  bool gotten_into_driver_list() const { return gotten_into_driver_list_; }
+  void set_gotten_into_driver_list() { gotten_into_driver_list_ = true; }
+
+  grpc_combiner* combiner_;
+  char recv_from_source_addr_[200];
+  ares_socklen_t recv_from_source_addr_len_;
+  grpc_slice read_buf_;
+  grpc_slice write_buf_;
+  grpc_closure* read_closure_ = nullptr;
+  grpc_closure* write_closure_ = nullptr;
+  grpc_closure outer_read_closure_;
+  grpc_closure outer_write_closure_;
+  grpc_winsocket* winsocket_;
+  WriteState write_state_;
+  char* name_ = nullptr;
+  bool gotten_into_driver_list_;
 };
 
-GrpcPolledFd* NewGrpcPolledFdLocked(ares_socket_t as,
-                                    grpc_pollset_set* driver_pollset_set) {
-  return nullptr;
-}
+struct SockToPolledFdEntry {
+  SockToPolledFdEntry(SOCKET s, GrpcPolledFdWindows* fd)
+      : socket(s), polled_fd(fd) {}
+  SOCKET socket;
+  GrpcPolledFdWindows* polled_fd;
+  SockToPolledFdEntry* next = nullptr;
+};
+
+/* A SockToPolledFdMap can make ares_socket_t types (SOCKET's on windows)
+ * to GrpcPolledFdWindow's, and is used to find the appropriate
+ * GrpcPolledFdWindows to handle a virtual socket call when c-ares makes that
+ * socket call on the ares_socket_t type. Instances are owned by and one-to-one
+ * with a GrpcPolledFdWindows factory and event driver */
+class SockToPolledFdMap {
+ public:
+  SockToPolledFdMap(grpc_combiner* combiner) {
+    combiner_ = GRPC_COMBINER_REF(combiner, "sock to polled fd map");
+  }
+
+  ~SockToPolledFdMap() {
+    GPR_ASSERT(head_ == nullptr);
+    GRPC_COMBINER_UNREF(combiner_, "sock to polled fd map");
+  }
+
+  void AddNewSocket(SOCKET s, GrpcPolledFdWindows* polled_fd) {
+    SockToPolledFdEntry* new_node = New<SockToPolledFdEntry>(s, polled_fd);
+    new_node->next = head_;
+    head_ = new_node;
+  }
+
+  GrpcPolledFdWindows* LookupPolledFd(SOCKET s) {
+    for (SockToPolledFdEntry* node = head_; node != nullptr;
+         node = node->next) {
+      if (node->socket == s) {
+        GPR_ASSERT(node->polled_fd != nullptr);
+        return node->polled_fd;
+      }
+    }
+    abort();
+  }
+
+  void RemoveEntry(SOCKET s) {
+    GPR_ASSERT(head_ != nullptr);
+    SockToPolledFdEntry** prev = &head_;
+    for (SockToPolledFdEntry* node = head_; node != nullptr;
+         node = node->next) {
+      if (node->socket == s) {
+        *prev = node->next;
+        Delete(node);
+        return;
+      }
+      prev = &node->next;
+    }
+    abort();
+  }
+
+  /* These virtual socket functions are called from within the c-ares
+   * library. These methods generally dispatch those socket calls to the
+   * appropriate methods. The virtual "socket" and "close" methods are
+   * special and instead create/add and remove/destroy GrpcPolledFdWindows
+   * objects.
+   */
+  static ares_socket_t Socket(int af, int type, int protocol, void* user_data) {
+    SockToPolledFdMap* map = static_cast<SockToPolledFdMap*>(user_data);
+    SOCKET s = WSASocket(af, type, protocol, nullptr, 0, WSA_FLAG_OVERLAPPED);
+    if (s == INVALID_SOCKET) {
+      return s;
+    }
+    grpc_tcp_set_non_block(s);
+    GrpcPolledFdWindows* polled_fd =
+        New<GrpcPolledFdWindows>(s, map->combiner_);
+    map->AddNewSocket(s, polled_fd);
+    return s;
+  }
+
+  static int Connect(ares_socket_t as, const struct sockaddr* target,
+                     ares_socklen_t target_len, void* user_data) {
+    SockToPolledFdMap* map = static_cast<SockToPolledFdMap*>(user_data);
+    GrpcPolledFdWindows* polled_fd = map->LookupPolledFd(as);
+    return polled_fd->Connect(target, target_len);
+  }
+
+  static ares_ssize_t SendV(ares_socket_t as, const struct iovec* iov,
+                            int iovec_count, void* user_data) {
+    SockToPolledFdMap* map = static_cast<SockToPolledFdMap*>(user_data);
+    GrpcPolledFdWindows* polled_fd = map->LookupPolledFd(as);
+    return polled_fd->SendV(iov, iovec_count);
+  }
+
+  static ares_ssize_t RecvFrom(ares_socket_t as, void* data, size_t data_len,
+                               int flags, struct sockaddr* from,
+                               ares_socklen_t* from_len, void* user_data) {
+    SockToPolledFdMap* map = static_cast<SockToPolledFdMap*>(user_data);
+    GrpcPolledFdWindows* polled_fd = map->LookupPolledFd(as);
+    return polled_fd->RecvFrom(data, data_len, flags, from, from_len);
+  }
+
+  static int CloseSocket(SOCKET s, void* user_data) {
+    SockToPolledFdMap* map = static_cast<SockToPolledFdMap*>(user_data);
+    GrpcPolledFdWindows* polled_fd = map->LookupPolledFd(s);
+    map->RemoveEntry(s);
+    // If a gRPC polled fd has not made it in to the driver's list yet, then
+    // the driver has not and will never see this socket.
+    if (!polled_fd->gotten_into_driver_list()) {
+      polled_fd->ShutdownLocked(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+          "Shut down c-ares fd before without it ever having made it into the "
+          "driver's list"));
+      return 0;
+    }
+    return 0;
+  }
+
+ private:
+  SockToPolledFdEntry* head_ = nullptr;
+  grpc_combiner* combiner_;
+};
+
+const struct ares_socket_functions custom_ares_sock_funcs = {
+    &SockToPolledFdMap::Socket /* socket */,
+    &SockToPolledFdMap::CloseSocket /* close */,
+    &SockToPolledFdMap::Connect /* connect */,
+    &SockToPolledFdMap::RecvFrom /* recvfrom */,
+    &SockToPolledFdMap::SendV /* sendv */,
+};
+
+class GrpcPolledFdFactoryWindows : public GrpcPolledFdFactory {
+ public:
+  GrpcPolledFdFactoryWindows(grpc_combiner* combiner)
+      : sock_to_polled_fd_map_(combiner) {}
+
+  GrpcPolledFd* NewGrpcPolledFdLocked(ares_socket_t as,
+                                      grpc_pollset_set* driver_pollset_set,
+                                      grpc_combiner* combiner) override {
+    GrpcPolledFdWindows* polled_fd = sock_to_polled_fd_map_.LookupPolledFd(as);
+    // Set a flag so that the virtual socket "close" method knows it
+    // doesn't need to call ShutdownLocked, since now the driver will.
+    polled_fd->set_gotten_into_driver_list();
+    return polled_fd;
+  }
 
-void ConfigureAresChannelLocked(ares_channel* channel) { abort(); }
+  void ConfigureAresChannelLocked(ares_channel channel) override {
+    ares_set_socket_functions(channel, &custom_ares_sock_funcs,
+                              &sock_to_polled_fd_map_);
+  }
+
+ private:
+  SockToPolledFdMap sock_to_polled_fd_map_;
+};
+
+UniquePtr<GrpcPolledFdFactory> NewGrpcPolledFdFactory(grpc_combiner* combiner) {
+  return UniquePtr<GrpcPolledFdFactory>(
+      New<GrpcPolledFdFactoryWindows>(combiner));
+}
 
 }  // namespace grpc_core