1 files changed, 458 insertions, 0 deletions
diff --git a/src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc b/src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc
new file mode 100644
index 0000000000..69f5877b00
--- /dev/null
+++ b/src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc
@@ -0,0 +1,458 @@
+/*
+ *
+ * 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>
+#if GRPC_ARES == 1 && !defined(GRPC_UV)
+
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/host_port.h>
+#include <grpc/support/string_util.h>
+
+#include "src/core/ext/filters/client_channel/http_connect_handshaker.h"
+#include "src/core/ext/filters/client_channel/lb_policy_registry.h"
+#include "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h"
+#include "src/core/ext/filters/client_channel/resolver_registry.h"
+#include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/iomgr/combiner.h"
+#include "src/core/lib/iomgr/gethostname.h"
+#include "src/core/lib/iomgr/resolve_address.h"
+#include "src/core/lib/iomgr/timer.h"
+#include "src/core/lib/json/json.h"
+#include "src/core/lib/support/backoff.h"
+#include "src/core/lib/support/env.h"
+#include "src/core/lib/support/string.h"
+#include "src/core/lib/transport/service_config.h"
+
+#define GRPC_DNS_MIN_CONNECT_TIMEOUT_SECONDS 1
+#define GRPC_DNS_INITIAL_CONNECT_BACKOFF_SECONDS 1
+#define GRPC_DNS_RECONNECT_BACKOFF_MULTIPLIER 1.6
+#define GRPC_DNS_RECONNECT_MAX_BACKOFF_SECONDS 120
+#define GRPC_DNS_RECONNECT_JITTER 0.2
+
+typedef struct {
+  /** base class: must be first */
+  grpc_resolver base;
+  /** DNS server to use (if not system default) */
+  char *dns_server;
+  /** name to resolve (usually the same as target_name) */
+  char *name_to_resolve;
+  /** default port to use */
+  char *default_port;
+  /** channel args. */
+  grpc_channel_args *channel_args;
+  /** whether to request the service config */
+  bool request_service_config;
+  /** pollset_set to drive the name resolution process */
+  grpc_pollset_set *interested_parties;
+
+  /** Closures used by the combiner */
+  grpc_closure dns_ares_on_retry_timer_locked;
+  grpc_closure dns_ares_on_resolved_locked;
+
+  /** Combiner guarding the rest of the state */
+  grpc_combiner *combiner;
+  /** are we currently resolving? */
+  bool resolving;
+  /** the pending resolving request */
+  grpc_ares_request *pending_request;
+  /** which version of the result have we published? */
+  int published_version;
+  /** which version of the result is current? */
+  int resolved_version;
+  /** pending next completion, or NULL */
+  grpc_closure *next_completion;
+  /** target result address for next completion */
+  grpc_channel_args **target_result;
+  /** current (fully resolved) result */
+  grpc_channel_args *resolved_result;
+  /** retry timer */
+  bool have_retry_timer;
+  grpc_timer retry_timer;
+  /** retry backoff state */
+  gpr_backoff backoff_state;
+
+  /** currently resolving addresses */
+  grpc_lb_addresses *lb_addresses;
+  /** currently resolving service config */
+  char *service_config_json;
+} ares_dns_resolver;
+
+static void dns_ares_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
+
+static void dns_ares_start_resolving_locked(grpc_exec_ctx *exec_ctx,
+                                            ares_dns_resolver *r);
+static void dns_ares_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
+                                              ares_dns_resolver *r);
+
+static void dns_ares_shutdown_locked(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
+static void dns_ares_channel_saw_error_locked(grpc_exec_ctx *exec_ctx,
+                                              grpc_resolver *r);
+static void dns_ares_next_locked(grpc_exec_ctx *exec_ctx, grpc_resolver *r,
+                                 grpc_channel_args **target_result,
+                                 grpc_closure *on_complete);
+
+static const grpc_resolver_vtable dns_ares_resolver_vtable = {
+    dns_ares_destroy, dns_ares_shutdown_locked,
+    dns_ares_channel_saw_error_locked, dns_ares_next_locked};
+
+static void dns_ares_shutdown_locked(grpc_exec_ctx *exec_ctx,
+                                     grpc_resolver *resolver) {
+  ares_dns_resolver *r = (ares_dns_resolver *)resolver;
+  if (r->have_retry_timer) {
+    grpc_timer_cancel(exec_ctx, &r->retry_timer);
+  }
+  if (r->pending_request != NULL) {
+    grpc_cancel_ares_request(exec_ctx, r->pending_request);
+  }
+  if (r->next_completion != NULL) {
+    *r->target_result = NULL;
+    GRPC_CLOSURE_SCHED(
+        exec_ctx, r->next_completion,
+        GRPC_ERROR_CREATE_FROM_STATIC_STRING("Resolver Shutdown"));
+    r->next_completion = NULL;
+  }
+}
+
+static void dns_ares_channel_saw_error_locked(grpc_exec_ctx *exec_ctx,
+                                              grpc_resolver *resolver) {
+  ares_dns_resolver *r = (ares_dns_resolver *)resolver;
+  if (!r->resolving) {
+    gpr_backoff_reset(&r->backoff_state);
+    dns_ares_start_resolving_locked(exec_ctx, r);
+  }
+}
+
+static void dns_ares_on_retry_timer_locked(grpc_exec_ctx *exec_ctx, void *arg,
+                                           grpc_error *error) {
+  ares_dns_resolver *r = (ares_dns_resolver *)arg;
+  r->have_retry_timer = false;
+  if (error == GRPC_ERROR_NONE) {
+    if (!r->resolving) {
+      dns_ares_start_resolving_locked(exec_ctx, r);
+    }
+  }
+  GRPC_RESOLVER_UNREF(exec_ctx, &r->base, "retry-timer");
+}
+
+static bool value_in_json_array(grpc_json *array, const char *value) {
+  for (grpc_json *entry = array->child; entry != NULL; entry = entry->next) {
+    if (entry->type == GRPC_JSON_STRING && strcmp(entry->value, value) == 0) {
+      return true;
+    }
+  }
+  return false;
+}
+
+static char *choose_service_config(char *service_config_choice_json) {
+  grpc_json *choices_json = grpc_json_parse_string(service_config_choice_json);
+  if (choices_json == NULL || choices_json->type != GRPC_JSON_ARRAY) {
+    gpr_log(GPR_ERROR, "cannot parse service config JSON string");
+    return NULL;
+  }
+  char *service_config = NULL;
+  for (grpc_json *choice = choices_json->child; choice != NULL;
+       choice = choice->next) {
+    if (choice->type != GRPC_JSON_OBJECT) {
+      gpr_log(GPR_ERROR, "cannot parse service config JSON string");
+      break;
+    }
+    grpc_json *service_config_json = NULL;
+    for (grpc_json *field = choice->child; field != NULL; field = field->next) {
+      // Check client language, if specified.
+      if (strcmp(field->key, "clientLanguage") == 0) {
+        if (field->type != GRPC_JSON_ARRAY ||
+            !value_in_json_array(field, "c++")) {
+          service_config_json = NULL;
+          break;
+        }
+      }
+      // Check client hostname, if specified.
+      if (strcmp(field->key, "clientHostname") == 0) {
+        char *hostname = grpc_gethostname();
+        if (hostname == NULL || field->type != GRPC_JSON_ARRAY ||
+            !value_in_json_array(field, hostname)) {
+          service_config_json = NULL;
+          break;
+        }
+      }
+      // Check percentage, if specified.
+      if (strcmp(field->key, "percentage") == 0) {
+        if (field->type != GRPC_JSON_NUMBER) {
+          service_config_json = NULL;
+          break;
+        }
+        int random_pct = rand() % 100;
+        int percentage;
+        if (sscanf(field->value, "%d", &percentage) != 1 ||
+            random_pct > percentage || percentage == 0) {
+          service_config_json = NULL;
+          break;
+        }
+      }
+      // Save service config.
+      if (strcmp(field->key, "serviceConfig") == 0) {
+        if (field->type == GRPC_JSON_OBJECT) {
+          service_config_json = field;
+        }
+      }
+    }
+    if (service_config_json != NULL) {
+      service_config = grpc_json_dump_to_string(service_config_json, 0);
+      break;
+    }
+  }
+  grpc_json_destroy(choices_json);
+  return service_config;
+}
+
+static void dns_ares_on_resolved_locked(grpc_exec_ctx *exec_ctx, void *arg,
+                                        grpc_error *error) {
+  ares_dns_resolver *r = (ares_dns_resolver *)arg;
+  grpc_channel_args *result = NULL;
+  GPR_ASSERT(r->resolving);
+  r->resolving = false;
+  r->pending_request = NULL;
+  if (r->lb_addresses != NULL) {
+    static const char *args_to_remove[2];
+    size_t num_args_to_remove = 0;
+    grpc_arg new_args[3];
+    size_t num_args_to_add = 0;
+    new_args[num_args_to_add++] =
+        grpc_lb_addresses_create_channel_arg(r->lb_addresses);
+    grpc_service_config *service_config = NULL;
+    char *service_config_string = NULL;
+    if (r->service_config_json != NULL) {
+      service_config_string = choose_service_config(r->service_config_json);
+      gpr_free(r->service_config_json);
+      if (service_config_string != NULL) {
+        gpr_log(GPR_INFO, "selected service config choice: %s",
+                service_config_string);
+        args_to_remove[num_args_to_remove++] = GRPC_ARG_SERVICE_CONFIG;
+        new_args[num_args_to_add++] = grpc_channel_arg_string_create(
+            (char *)GRPC_ARG_SERVICE_CONFIG, service_config_string);
+        service_config = grpc_service_config_create(service_config_string);
+        if (service_config != NULL) {
+          const char *lb_policy_name =
+              grpc_service_config_get_lb_policy_name(service_config);
+          if (lb_policy_name != NULL) {
+            args_to_remove[num_args_to_remove++] = GRPC_ARG_LB_POLICY_NAME;
+            new_args[num_args_to_add++] = grpc_channel_arg_string_create(
+                (char *)GRPC_ARG_LB_POLICY_NAME, (char *)lb_policy_name);
+          }
+        }
+      }
+    }
+    result = grpc_channel_args_copy_and_add_and_remove(
+        r->channel_args, args_to_remove, num_args_to_remove, new_args,
+        num_args_to_add);
+    if (service_config != NULL) grpc_service_config_destroy(service_config);
+    gpr_free(service_config_string);
+    grpc_lb_addresses_destroy(exec_ctx, r->lb_addresses);
+  } else {
+    const char *msg = grpc_error_string(error);
+    gpr_log(GPR_DEBUG, "dns resolution failed: %s", msg);
+    gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC);
+    gpr_timespec next_try = gpr_backoff_step(&r->backoff_state, now);
+    gpr_timespec timeout = gpr_time_sub(next_try, now);
+    gpr_log(GPR_INFO, "dns resolution failed (will retry): %s",
+            grpc_error_string(error));
+    GPR_ASSERT(!r->have_retry_timer);
+    r->have_retry_timer = true;
+    GRPC_RESOLVER_REF(&r->base, "retry-timer");
+    if (gpr_time_cmp(timeout, gpr_time_0(timeout.clock_type)) > 0) {
+      gpr_log(GPR_DEBUG, "retrying in %" PRId64 ".%09d seconds", timeout.tv_sec,
+              timeout.tv_nsec);
+    } else {
+      gpr_log(GPR_DEBUG, "retrying immediately");
+    }
+    grpc_timer_init(exec_ctx, &r->retry_timer, next_try,
+                    &r->dns_ares_on_retry_timer_locked, now);
+  }
+  if (r->resolved_result != NULL) {
+    grpc_channel_args_destroy(exec_ctx, r->resolved_result);
+  }
+  r->resolved_result = result;
+  r->resolved_version++;
+  dns_ares_maybe_finish_next_locked(exec_ctx, r);
+  GRPC_RESOLVER_UNREF(exec_ctx, &r->base, "dns-resolving");
+}
+
+static void dns_ares_next_locked(grpc_exec_ctx *exec_ctx,
+                                 grpc_resolver *resolver,
+                                 grpc_channel_args **target_result,
+                                 grpc_closure *on_complete) {
+  gpr_log(GPR_DEBUG, "dns_ares_next is called.");
+  ares_dns_resolver *r = (ares_dns_resolver *)resolver;
+  GPR_ASSERT(!r->next_completion);
+  r->next_completion = on_complete;
+  r->target_result = target_result;
+  if (r->resolved_version == 0 && !r->resolving) {
+    gpr_backoff_reset(&r->backoff_state);
+    dns_ares_start_resolving_locked(exec_ctx, r);
+  } else {
+    dns_ares_maybe_finish_next_locked(exec_ctx, r);
+  }
+}
+
+static void dns_ares_start_resolving_locked(grpc_exec_ctx *exec_ctx,
+                                            ares_dns_resolver *r) {
+  GRPC_RESOLVER_REF(&r->base, "dns-resolving");
+  GPR_ASSERT(!r->resolving);
+  r->resolving = true;
+  r->lb_addresses = NULL;
+  r->service_config_json = NULL;
+  r->pending_request = grpc_dns_lookup_ares(
+      exec_ctx, r->dns_server, r->name_to_resolve, r->default_port,
+      r->interested_parties, &r->dns_ares_on_resolved_locked, &r->lb_addresses,
+      true /* check_grpclb */,
+      r->request_service_config ? &r->service_config_json : NULL);
+}
+
+static void dns_ares_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
+                                              ares_dns_resolver *r) {
+  if (r->next_completion != NULL &&
+      r->resolved_version != r->published_version) {
+    *r->target_result = r->resolved_result == NULL
+                            ? NULL
+                            : grpc_channel_args_copy(r->resolved_result);
+    gpr_log(GPR_DEBUG, "dns_ares_maybe_finish_next_locked");
+    GRPC_CLOSURE_SCHED(exec_ctx, r->next_completion, GRPC_ERROR_NONE);
+    r->next_completion = NULL;
+    r->published_version = r->resolved_version;
+  }
+}
+
+static void dns_ares_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *gr) {
+  gpr_log(GPR_DEBUG, "dns_ares_destroy");
+  ares_dns_resolver *r = (ares_dns_resolver *)gr;
+  if (r->resolved_result != NULL) {
+    grpc_channel_args_destroy(exec_ctx, r->resolved_result);
+  }
+  grpc_pollset_set_destroy(exec_ctx, r->interested_parties);
+  gpr_free(r->dns_server);
+  gpr_free(r->name_to_resolve);
+  gpr_free(r->default_port);
+  grpc_channel_args_destroy(exec_ctx, r->channel_args);
+  gpr_free(r);
+}
+
+static grpc_resolver *dns_ares_create(grpc_exec_ctx *exec_ctx,
+                                      grpc_resolver_args *args,
+                                      const char *default_port) {
+  /* Get name from args. */
+  const char *path = args->uri->path;
+  if (path[0] == '/') ++path;
+  /* Create resolver. */
+  ares_dns_resolver *r =
+      (ares_dns_resolver *)gpr_zalloc(sizeof(ares_dns_resolver));
+  grpc_resolver_init(&r->base, &dns_ares_resolver_vtable, args->combiner);
+  if (0 != strcmp(args->uri->authority, "")) {
+    r->dns_server = gpr_strdup(args->uri->authority);
+  }
+  r->name_to_resolve = gpr_strdup(path);
+  r->default_port = gpr_strdup(default_port);
+  r->channel_args = grpc_channel_args_copy(args->args);
+  const grpc_arg *arg = grpc_channel_args_find(
+      r->channel_args, GRPC_ARG_SERVICE_CONFIG_DISABLE_RESOLUTION);
+  r->request_service_config = !grpc_channel_arg_get_integer(
+      arg, (grpc_integer_options){false, false, true});
+  r->interested_parties = grpc_pollset_set_create();
+  if (args->pollset_set != NULL) {
+    grpc_pollset_set_add_pollset_set(exec_ctx, r->interested_parties,
+                                     args->pollset_set);
+  }
+  gpr_backoff_init(&r->backoff_state, GRPC_DNS_INITIAL_CONNECT_BACKOFF_SECONDS,
+                   GRPC_DNS_RECONNECT_BACKOFF_MULTIPLIER,
+                   GRPC_DNS_RECONNECT_JITTER,
+                   GRPC_DNS_MIN_CONNECT_TIMEOUT_SECONDS * 1000,
+                   GRPC_DNS_RECONNECT_MAX_BACKOFF_SECONDS * 1000);
+  GRPC_CLOSURE_INIT(&r->dns_ares_on_retry_timer_locked,
+                    dns_ares_on_retry_timer_locked, r,
+                    grpc_combiner_scheduler(r->base.combiner));
+  GRPC_CLOSURE_INIT(&r->dns_ares_on_resolved_locked,
+                    dns_ares_on_resolved_locked, r,
+                    grpc_combiner_scheduler(r->base.combiner));
+  return &r->base;
+}
+
+/*
+ * FACTORY
+ */
+
+static void dns_ares_factory_ref(grpc_resolver_factory *factory) {}
+
+static void dns_ares_factory_unref(grpc_resolver_factory *factory) {}
+
+static grpc_resolver *dns_factory_create_resolver(
+    grpc_exec_ctx *exec_ctx, grpc_resolver_factory *factory,
+    grpc_resolver_args *args) {
+  return dns_ares_create(exec_ctx, args, "https");
+}
+
+static char *dns_ares_factory_get_default_host_name(
+    grpc_resolver_factory *factory, grpc_uri *uri) {
+  const char *path = uri->path;
+  if (path[0] == '/') ++path;
+  return gpr_strdup(path);
+}
+
+static const grpc_resolver_factory_vtable dns_ares_factory_vtable = {
+    dns_ares_factory_ref, dns_ares_factory_unref, dns_factory_create_resolver,
+    dns_ares_factory_get_default_host_name, "dns"};
+static grpc_resolver_factory dns_resolver_factory = {&dns_ares_factory_vtable};
+
+static grpc_resolver_factory *dns_ares_resolver_factory_create() {
+  return &dns_resolver_factory;
+}
+
+extern "C" void grpc_resolver_dns_ares_init(void) {
+  char *resolver = gpr_getenv("GRPC_DNS_RESOLVER");
+  /* TODO(zyc): Turn on c-ares based resolver by default after the address
+     sorter and the CNAME support are added. */
+  if (resolver != NULL && gpr_stricmp(resolver, "ares") == 0) {
+    grpc_error *error = grpc_ares_init();
+    if (error != GRPC_ERROR_NONE) {
+      GRPC_LOG_IF_ERROR("ares_library_init() failed", error);
+      return;
+    }
+    grpc_resolve_address = grpc_resolve_address_ares;
+    grpc_register_resolver_type(dns_ares_resolver_factory_create());
+  }
+  gpr_free(resolver);
+}
+
+extern "C" void grpc_resolver_dns_ares_shutdown(void) {
+  char *resolver = gpr_getenv("GRPC_DNS_RESOLVER");
+  if (resolver != NULL && gpr_stricmp(resolver, "ares") == 0) {
+    grpc_ares_cleanup();
+  }
+  gpr_free(resolver);
+}
+
+#else /* GRPC_ARES == 1 && !defined(GRPC_UV) */
+
+extern "C" void grpc_resolver_dns_ares_init(void) {}
+
+extern "C" void grpc_resolver_dns_ares_shutdown(void) {}
+
+#endif /* GRPC_ARES == 1 && !defined(GRPC_UV) */