Reorganize ext tree

- filters live under filters
- lb_policy, resolver implementations (being part of client_channel) live under client_channel
diff --git a/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.c b/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.c
new file mode 100644
index 0000000..09c46a6
--- /dev/null
+++ b/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.c
@@ -0,0 +1,289 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+#if GRPC_ARES == 1 && !defined(GRPC_UV)
+
+#include "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h"
+#include "src/core/lib/iomgr/sockaddr.h"
+#include "src/core/lib/iomgr/socket_utils_posix.h"
+
+#include <string.h>
+#include <sys/types.h>
+
+#include <ares.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/host_port.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
+#include <grpc/support/time.h>
+#include <grpc/support/useful.h>
+#include "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.h"
+#include "src/core/lib/iomgr/executor.h"
+#include "src/core/lib/iomgr/iomgr_internal.h"
+#include "src/core/lib/iomgr/sockaddr_utils.h"
+#include "src/core/lib/support/string.h"
+
+static gpr_once g_basic_init = GPR_ONCE_INIT;
+static gpr_mu g_init_mu;
+
+typedef struct grpc_ares_request {
+  /** following members are set in grpc_resolve_address_ares_impl */
+  /** host to resolve, parsed from the name to resolve */
+  char *host;
+  /** port to fill in sockaddr_in, parsed from the name to resolve */
+  char *port;
+  /** default port to use */
+  char *default_port;
+  /** closure to call when the request completes */
+  grpc_closure *on_done;
+  /** the pointer to receive the resolved addresses */
+  grpc_resolved_addresses **addrs_out;
+  /** the evernt driver used by this request */
+  grpc_ares_ev_driver *ev_driver;
+  /** number of ongoing queries */
+  gpr_refcount pending_queries;
+
+  /** mutex guarding the rest of the state */
+  gpr_mu mu;
+  /** is there at least one successful query, set in on_done_cb */
+  bool success;
+  /** the errors explaining the request failure, set in on_done_cb */
+  grpc_error *error;
+} grpc_ares_request;
+
+static void do_basic_init(void) { gpr_mu_init(&g_init_mu); }
+
+static uint16_t strhtons(const char *port) {
+  if (strcmp(port, "http") == 0) {
+    return htons(80);
+  } else if (strcmp(port, "https") == 0) {
+    return htons(443);
+  }
+  return htons((unsigned short)atoi(port));
+}
+
+static void grpc_ares_request_unref(grpc_exec_ctx *exec_ctx,
+                                    grpc_ares_request *r) {
+  /* If there are no pending queries, invoke on_done callback and destroy the
+     request */
+  if (gpr_unref(&r->pending_queries)) {
+    /* TODO(zyc): Sort results with RFC6724 before invoking on_done. */
+    if (exec_ctx == NULL) {
+      /* A new exec_ctx is created here, as the c-ares interface does not
+         provide one in ares_host_callback. It's safe to schedule on_done with
+         the newly created exec_ctx, since the caller has been warned not to
+         acquire locks in on_done. ares_dns_resolver is using combiner to
+         protect resources needed by on_done. */
+      grpc_exec_ctx new_exec_ctx = GRPC_EXEC_CTX_INIT;
+      grpc_closure_sched(&new_exec_ctx, r->on_done, r->error);
+      grpc_exec_ctx_finish(&new_exec_ctx);
+    } else {
+      grpc_closure_sched(exec_ctx, r->on_done, r->error);
+    }
+    gpr_mu_destroy(&r->mu);
+    grpc_ares_ev_driver_destroy(r->ev_driver);
+    gpr_free(r->host);
+    gpr_free(r->port);
+    gpr_free(r->default_port);
+    gpr_free(r);
+  }
+}
+
+static void on_done_cb(void *arg, int status, int timeouts,
+                       struct hostent *hostent) {
+  grpc_ares_request *r = (grpc_ares_request *)arg;
+  gpr_mu_lock(&r->mu);
+  if (status == ARES_SUCCESS) {
+    GRPC_ERROR_UNREF(r->error);
+    r->error = GRPC_ERROR_NONE;
+    r->success = true;
+    grpc_resolved_addresses **addresses = r->addrs_out;
+    if (*addresses == NULL) {
+      *addresses = gpr_malloc(sizeof(grpc_resolved_addresses));
+      (*addresses)->naddrs = 0;
+      (*addresses)->addrs = NULL;
+    }
+    size_t prev_naddr = (*addresses)->naddrs;
+    size_t i;
+    for (i = 0; hostent->h_addr_list[i] != NULL; i++) {
+    }
+    (*addresses)->naddrs += i;
+    (*addresses)->addrs =
+        gpr_realloc((*addresses)->addrs,
+                    sizeof(grpc_resolved_address) * (*addresses)->naddrs);
+    for (i = prev_naddr; i < (*addresses)->naddrs; i++) {
+      memset(&(*addresses)->addrs[i], 0, sizeof(grpc_resolved_address));
+      if (hostent->h_addrtype == AF_INET6) {
+        (*addresses)->addrs[i].len = sizeof(struct sockaddr_in6);
+        struct sockaddr_in6 *addr =
+            (struct sockaddr_in6 *)&(*addresses)->addrs[i].addr;
+        addr->sin6_family = (sa_family_t)hostent->h_addrtype;
+        addr->sin6_port = strhtons(r->port);
+
+        char output[INET6_ADDRSTRLEN];
+        memcpy(&addr->sin6_addr, hostent->h_addr_list[i - prev_naddr],
+               sizeof(struct in6_addr));
+        ares_inet_ntop(AF_INET6, &addr->sin6_addr, output, INET6_ADDRSTRLEN);
+        gpr_log(GPR_DEBUG,
+                "c-ares resolver gets a AF_INET6 result: \n"
+                "  addr: %s\n  port: %s\n  sin6_scope_id: %d\n",
+                output, r->port, addr->sin6_scope_id);
+      } else {
+        (*addresses)->addrs[i].len = sizeof(struct sockaddr_in);
+        struct sockaddr_in *addr =
+            (struct sockaddr_in *)&(*addresses)->addrs[i].addr;
+        memcpy(&addr->sin_addr, hostent->h_addr_list[i - prev_naddr],
+               sizeof(struct in_addr));
+        addr->sin_family = (sa_family_t)hostent->h_addrtype;
+        addr->sin_port = strhtons(r->port);
+
+        char output[INET_ADDRSTRLEN];
+        ares_inet_ntop(AF_INET, &addr->sin_addr, output, INET_ADDRSTRLEN);
+        gpr_log(GPR_DEBUG,
+                "c-ares resolver gets a AF_INET result: \n"
+                "  addr: %s\n  port: %s\n",
+                output, r->port);
+      }
+    }
+  } else if (!r->success) {
+    char *error_msg;
+    gpr_asprintf(&error_msg, "C-ares status is not ARES_SUCCESS: %s",
+                 ares_strerror(status));
+    grpc_error *error = GRPC_ERROR_CREATE_FROM_COPIED_STRING(error_msg);
+    gpr_free(error_msg);
+    if (r->error == GRPC_ERROR_NONE) {
+      r->error = error;
+    } else {
+      r->error = grpc_error_add_child(error, r->error);
+    }
+  }
+  gpr_mu_unlock(&r->mu);
+  grpc_ares_request_unref(NULL, r);
+}
+
+void grpc_resolve_address_ares_impl(grpc_exec_ctx *exec_ctx, const char *name,
+                                    const char *default_port,
+                                    grpc_pollset_set *interested_parties,
+                                    grpc_closure *on_done,
+                                    grpc_resolved_addresses **addrs) {
+  /* TODO(zyc): Enable tracing after #9603 is checked in */
+  /* if (grpc_dns_trace) {
+      gpr_log(GPR_DEBUG, "resolve_address (blocking): name=%s, default_port=%s",
+              name, default_port);
+     } */
+
+  /* parse name, splitting it into host and port parts */
+  char *host;
+  char *port;
+  gpr_split_host_port(name, &host, &port);
+  if (host == NULL) {
+    grpc_error *err = grpc_error_set_str(
+        GRPC_ERROR_CREATE_FROM_STATIC_STRING("unparseable host:port"),
+        GRPC_ERROR_STR_TARGET_ADDRESS, grpc_slice_from_copied_string(name));
+    grpc_closure_sched(exec_ctx, on_done, err);
+    goto error_cleanup;
+  } else if (port == NULL) {
+    if (default_port == NULL) {
+      grpc_error *err = grpc_error_set_str(
+          GRPC_ERROR_CREATE_FROM_STATIC_STRING("no port in name"),
+          GRPC_ERROR_STR_TARGET_ADDRESS, grpc_slice_from_copied_string(name));
+      grpc_closure_sched(exec_ctx, on_done, err);
+      goto error_cleanup;
+    }
+    port = gpr_strdup(default_port);
+  }
+
+  grpc_ares_ev_driver *ev_driver;
+  grpc_error *err = grpc_ares_ev_driver_create(&ev_driver, interested_parties);
+  if (err != GRPC_ERROR_NONE) {
+    GRPC_LOG_IF_ERROR("grpc_ares_ev_driver_create() failed", err);
+    goto error_cleanup;
+  }
+
+  grpc_ares_request *r = gpr_malloc(sizeof(grpc_ares_request));
+  gpr_mu_init(&r->mu);
+  r->ev_driver = ev_driver;
+  r->on_done = on_done;
+  r->addrs_out = addrs;
+  r->default_port = gpr_strdup(default_port);
+  r->port = port;
+  r->host = host;
+  r->success = false;
+  r->error = GRPC_ERROR_NONE;
+  ares_channel *channel = grpc_ares_ev_driver_get_channel(r->ev_driver);
+  gpr_ref_init(&r->pending_queries, 2);
+  if (grpc_ipv6_loopback_available()) {
+    gpr_ref(&r->pending_queries);
+    ares_gethostbyname(*channel, r->host, AF_INET6, on_done_cb, r);
+  }
+  ares_gethostbyname(*channel, r->host, AF_INET, on_done_cb, r);
+  /* TODO(zyc): Handle CNAME records here. */
+  grpc_ares_ev_driver_start(exec_ctx, r->ev_driver);
+  grpc_ares_request_unref(exec_ctx, r);
+  return;
+
+error_cleanup:
+  gpr_free(host);
+  gpr_free(port);
+}
+
+void (*grpc_resolve_address_ares)(
+    grpc_exec_ctx *exec_ctx, const char *name, const char *default_port,
+    grpc_pollset_set *interested_parties, grpc_closure *on_done,
+    grpc_resolved_addresses **addrs) = grpc_resolve_address_ares_impl;
+
+grpc_error *grpc_ares_init(void) {
+  gpr_once_init(&g_basic_init, do_basic_init);
+  gpr_mu_lock(&g_init_mu);
+  int status = ares_library_init(ARES_LIB_INIT_ALL);
+  gpr_mu_unlock(&g_init_mu);
+
+  if (status != ARES_SUCCESS) {
+    char *error_msg;
+    gpr_asprintf(&error_msg, "ares_library_init failed: %s",
+                 ares_strerror(status));
+    grpc_error *error = GRPC_ERROR_CREATE_FROM_COPIED_STRING(error_msg);
+    gpr_free(error_msg);
+    return error;
+  }
+  return GRPC_ERROR_NONE;
+}
+
+void grpc_ares_cleanup(void) {
+  gpr_mu_lock(&g_init_mu);
+  ares_library_cleanup();
+  gpr_mu_unlock(&g_init_mu);
+}
+
+#endif /* GRPC_ARES == 1 && !defined(GRPC_UV) */