| /* |
| * |
| * 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 |
| |
| #include <limits.h> |
| #include <stdio.h> |
| #include <string.h> |
| |
| #include <grpc/support/alloc.h> |
| #include <grpc/support/string_util.h> |
| |
| #include <address_sorting/address_sorting.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/dns/dns_resolver_selection.h" |
| #include "src/core/ext/filters/client_channel/resolver_registry.h" |
| #include "src/core/ext/filters/client_channel/server_address.h" |
| #include "src/core/ext/filters/client_channel/service_config.h" |
| #include "src/core/lib/backoff/backoff.h" |
| #include "src/core/lib/channel/channel_args.h" |
| #include "src/core/lib/gpr/string.h" |
| #include "src/core/lib/gprpp/manual_constructor.h" |
| #include "src/core/lib/iomgr/combiner.h" |
| #include "src/core/lib/iomgr/gethostname.h" |
| #include "src/core/lib/iomgr/iomgr_custom.h" |
| #include "src/core/lib/iomgr/resolve_address.h" |
| #include "src/core/lib/iomgr/timer.h" |
| #include "src/core/lib/json/json.h" |
| |
| #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 |
| |
| namespace grpc_core { |
| |
| namespace { |
| |
| const char kDefaultPort[] = "https"; |
| |
| class AresDnsResolver : public Resolver { |
| public: |
| explicit AresDnsResolver(ResolverArgs args); |
| |
| void StartLocked() override; |
| |
| void RequestReresolutionLocked() override; |
| |
| void ResetBackoffLocked() override; |
| |
| void ShutdownLocked() override; |
| |
| private: |
| virtual ~AresDnsResolver(); |
| |
| void MaybeStartResolvingLocked(); |
| void StartResolvingLocked(); |
| |
| static void OnNextResolutionLocked(void* arg, grpc_error* error); |
| static void OnResolvedLocked(void* arg, grpc_error* error); |
| |
| /// DNS server to use (if not system default) |
| char* dns_server_; |
| /// name to resolve (usually the same as target_name) |
| char* name_to_resolve_; |
| /// 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 on_next_resolution_; |
| grpc_closure on_resolved_; |
| /// are we currently resolving? |
| bool resolving_ = false; |
| /// the pending resolving request |
| grpc_ares_request* pending_request_ = nullptr; |
| /// next resolution timer |
| bool have_next_resolution_timer_ = false; |
| grpc_timer next_resolution_timer_; |
| /// min interval between DNS requests |
| grpc_millis min_time_between_resolutions_; |
| /// timestamp of last DNS request |
| grpc_millis last_resolution_timestamp_ = -1; |
| /// retry backoff state |
| BackOff backoff_; |
| /// currently resolving addresses |
| UniquePtr<ServerAddressList> addresses_; |
| /// currently resolving service config |
| char* service_config_json_ = nullptr; |
| // has shutdown been initiated |
| bool shutdown_initiated_ = false; |
| // timeout in milliseconds for active DNS queries |
| int query_timeout_ms_; |
| // whether or not to enable SRV DNS queries |
| bool enable_srv_queries_; |
| }; |
| |
| AresDnsResolver::AresDnsResolver(ResolverArgs args) |
| : Resolver(args.combiner, std::move(args.result_handler)), |
| backoff_( |
| BackOff::Options() |
| .set_initial_backoff(GRPC_DNS_INITIAL_CONNECT_BACKOFF_SECONDS * |
| 1000) |
| .set_multiplier(GRPC_DNS_RECONNECT_BACKOFF_MULTIPLIER) |
| .set_jitter(GRPC_DNS_RECONNECT_JITTER) |
| .set_max_backoff(GRPC_DNS_RECONNECT_MAX_BACKOFF_SECONDS * 1000)) { |
| // Get name to resolve from URI path. |
| const char* path = args.uri->path; |
| if (path[0] == '/') ++path; |
| name_to_resolve_ = gpr_strdup(path); |
| // Get DNS server from URI authority. |
| dns_server_ = nullptr; |
| if (0 != strcmp(args.uri->authority, "")) { |
| dns_server_ = gpr_strdup(args.uri->authority); |
| } |
| channel_args_ = grpc_channel_args_copy(args.args); |
| // Disable service config option |
| const grpc_arg* arg = grpc_channel_args_find( |
| channel_args_, GRPC_ARG_SERVICE_CONFIG_DISABLE_RESOLUTION); |
| request_service_config_ = !grpc_channel_arg_get_bool(arg, true); |
| // Min time b/t resolutions option |
| arg = grpc_channel_args_find(channel_args_, |
| GRPC_ARG_DNS_MIN_TIME_BETWEEN_RESOLUTIONS_MS); |
| min_time_between_resolutions_ = |
| grpc_channel_arg_get_integer(arg, {1000 * 30, 0, INT_MAX}); |
| // Enable SRV queries option |
| arg = grpc_channel_args_find(channel_args_, GRPC_ARG_DNS_ENABLE_SRV_QUERIES); |
| enable_srv_queries_ = grpc_channel_arg_get_bool(arg, false); |
| interested_parties_ = grpc_pollset_set_create(); |
| if (args.pollset_set != nullptr) { |
| grpc_pollset_set_add_pollset_set(interested_parties_, args.pollset_set); |
| } |
| GRPC_CLOSURE_INIT(&on_next_resolution_, OnNextResolutionLocked, this, |
| grpc_combiner_scheduler(combiner())); |
| GRPC_CLOSURE_INIT(&on_resolved_, OnResolvedLocked, this, |
| grpc_combiner_scheduler(combiner())); |
| const grpc_arg* query_timeout_ms_arg = |
| grpc_channel_args_find(channel_args_, GRPC_ARG_DNS_ARES_QUERY_TIMEOUT_MS); |
| query_timeout_ms_ = grpc_channel_arg_get_integer( |
| query_timeout_ms_arg, |
| {GRPC_DNS_ARES_DEFAULT_QUERY_TIMEOUT_MS, 0, INT_MAX}); |
| } |
| |
| AresDnsResolver::~AresDnsResolver() { |
| GRPC_CARES_TRACE_LOG("resolver:%p destroying AresDnsResolver", this); |
| grpc_pollset_set_destroy(interested_parties_); |
| gpr_free(dns_server_); |
| gpr_free(name_to_resolve_); |
| grpc_channel_args_destroy(channel_args_); |
| } |
| |
| void AresDnsResolver::StartLocked() { |
| GRPC_CARES_TRACE_LOG("resolver:%p AresDnsResolver::StartLocked() is called.", |
| this); |
| MaybeStartResolvingLocked(); |
| } |
| |
| void AresDnsResolver::RequestReresolutionLocked() { |
| if (!resolving_) { |
| MaybeStartResolvingLocked(); |
| } |
| } |
| |
| void AresDnsResolver::ResetBackoffLocked() { |
| if (have_next_resolution_timer_) { |
| grpc_timer_cancel(&next_resolution_timer_); |
| } |
| backoff_.Reset(); |
| } |
| |
| void AresDnsResolver::ShutdownLocked() { |
| shutdown_initiated_ = true; |
| if (have_next_resolution_timer_) { |
| grpc_timer_cancel(&next_resolution_timer_); |
| } |
| if (pending_request_ != nullptr) { |
| grpc_cancel_ares_request_locked(pending_request_); |
| } |
| } |
| |
| void AresDnsResolver::OnNextResolutionLocked(void* arg, grpc_error* error) { |
| AresDnsResolver* r = static_cast<AresDnsResolver*>(arg); |
| GRPC_CARES_TRACE_LOG( |
| "resolver:%p re-resolution timer fired. error: %s. shutdown_initiated_: " |
| "%d", |
| r, grpc_error_string(error), r->shutdown_initiated_); |
| r->have_next_resolution_timer_ = false; |
| if (error == GRPC_ERROR_NONE && !r->shutdown_initiated_) { |
| if (!r->resolving_) { |
| GRPC_CARES_TRACE_LOG( |
| "resolver:%p start resolving due to re-resolution timer", r); |
| r->StartResolvingLocked(); |
| } |
| } |
| r->Unref(DEBUG_LOCATION, "next_resolution_timer"); |
| } |
| |
| bool ValueInJsonArray(grpc_json* array, const char* value) { |
| for (grpc_json* entry = array->child; entry != nullptr; entry = entry->next) { |
| if (entry->type == GRPC_JSON_STRING && strcmp(entry->value, value) == 0) { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| char* ChooseServiceConfig(char* service_config_choice_json, |
| grpc_error** error) { |
| grpc_json* choices_json = grpc_json_parse_string(service_config_choice_json); |
| if (choices_json == nullptr) { |
| *error = GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "Service Config JSON Parsing, error: could not parse"); |
| return nullptr; |
| } |
| if (choices_json->type != GRPC_JSON_ARRAY) { |
| *error = GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "Service Config Choices, error: should be of type array"); |
| return nullptr; |
| } |
| char* service_config = nullptr; |
| InlinedVector<grpc_error*, 4> error_list; |
| bool found_choice = false; // have we found a choice? |
| for (grpc_json* choice = choices_json->child; choice != nullptr; |
| choice = choice->next) { |
| if (choice->type != GRPC_JSON_OBJECT) { |
| error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "Service Config Choice, error: should be of type object")); |
| continue; |
| } |
| grpc_json* service_config_json = nullptr; |
| bool selected = true; // has this choice been rejected? |
| for (grpc_json* field = choice->child; field != nullptr; |
| field = field->next) { |
| // Check client language, if specified. |
| if (strcmp(field->key, "clientLanguage") == 0) { |
| if (field->type != GRPC_JSON_ARRAY) { |
| error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "field:clientLanguage error:should be of type array")); |
| } else if (!ValueInJsonArray(field, "c++")) { |
| selected = false; |
| } |
| } |
| // Check client hostname, if specified. |
| if (strcmp(field->key, "clientHostname") == 0) { |
| if (field->type != GRPC_JSON_ARRAY) { |
| error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "field:clientHostname error:should be of type array")); |
| continue; |
| } |
| char* hostname = grpc_gethostname(); |
| if (hostname == nullptr || !ValueInJsonArray(field, hostname)) { |
| selected = false; |
| } |
| } |
| // Check percentage, if specified. |
| if (strcmp(field->key, "percentage") == 0) { |
| if (field->type != GRPC_JSON_NUMBER) { |
| error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "field:percentage error:should be of type number")); |
| continue; |
| } |
| int random_pct = rand() % 100; |
| int percentage; |
| if (sscanf(field->value, "%d", &percentage) != 1) { |
| error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "field:percentage error:should be of type integer")); |
| continue; |
| } |
| if (random_pct > percentage || percentage == 0) { |
| selected = false; |
| } |
| } |
| // Save service config. |
| if (strcmp(field->key, "serviceConfig") == 0) { |
| if (field->type == GRPC_JSON_OBJECT) { |
| service_config_json = field; |
| } else { |
| error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "field:serviceConfig error:should be of type object")); |
| } |
| } |
| } |
| if (!found_choice && selected && service_config_json != nullptr) { |
| service_config = grpc_json_dump_to_string(service_config_json, 0); |
| found_choice = true; |
| } |
| } |
| grpc_json_destroy(choices_json); |
| if (!error_list.empty()) { |
| gpr_free(service_config); |
| service_config = nullptr; |
| *error = GRPC_ERROR_CREATE_FROM_VECTOR("Service Config Choices Parser", |
| &error_list); |
| } |
| return service_config; |
| } |
| |
| void AresDnsResolver::OnResolvedLocked(void* arg, grpc_error* error) { |
| AresDnsResolver* r = static_cast<AresDnsResolver*>(arg); |
| GPR_ASSERT(r->resolving_); |
| r->resolving_ = false; |
| gpr_free(r->pending_request_); |
| r->pending_request_ = nullptr; |
| if (r->shutdown_initiated_) { |
| r->Unref(DEBUG_LOCATION, "OnResolvedLocked() shutdown"); |
| return; |
| } |
| if (r->addresses_ != nullptr) { |
| Result result; |
| result.addresses = std::move(*r->addresses_); |
| if (r->service_config_json_ != nullptr) { |
| char* service_config_string = ChooseServiceConfig( |
| r->service_config_json_, &result.service_config_error); |
| gpr_free(r->service_config_json_); |
| if (result.service_config_error == GRPC_ERROR_NONE && |
| service_config_string != nullptr) { |
| GRPC_CARES_TRACE_LOG("resolver:%p selected service config choice: %s", |
| r, service_config_string); |
| result.service_config = ServiceConfig::Create( |
| service_config_string, &result.service_config_error); |
| } |
| gpr_free(service_config_string); |
| } |
| result.args = grpc_channel_args_copy(r->channel_args_); |
| r->result_handler()->ReturnResult(std::move(result)); |
| r->addresses_.reset(); |
| // Reset backoff state so that we start from the beginning when the |
| // next request gets triggered. |
| r->backoff_.Reset(); |
| } else { |
| GRPC_CARES_TRACE_LOG("resolver:%p dns resolution failed: %s", r, |
| grpc_error_string(error)); |
| r->result_handler()->ReturnError(grpc_error_set_int( |
| GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING( |
| "DNS resolution failed", &error, 1), |
| GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_UNAVAILABLE)); |
| // Set retry timer. |
| grpc_millis next_try = r->backoff_.NextAttemptTime(); |
| grpc_millis timeout = next_try - ExecCtx::Get()->Now(); |
| GRPC_CARES_TRACE_LOG("resolver:%p dns resolution failed (will retry): %s", |
| r, grpc_error_string(error)); |
| GPR_ASSERT(!r->have_next_resolution_timer_); |
| r->have_next_resolution_timer_ = true; |
| // TODO(roth): We currently deal with this ref manually. Once the |
| // new closure API is done, find a way to track this ref with the timer |
| // callback as part of the type system. |
| r->Ref(DEBUG_LOCATION, "retry-timer").release(); |
| if (timeout > 0) { |
| GRPC_CARES_TRACE_LOG("resolver:%p retrying in %" PRId64 " milliseconds", |
| r, timeout); |
| } else { |
| GRPC_CARES_TRACE_LOG("resolver:%p retrying immediately", r); |
| } |
| grpc_timer_init(&r->next_resolution_timer_, next_try, |
| &r->on_next_resolution_); |
| } |
| r->Unref(DEBUG_LOCATION, "dns-resolving"); |
| } |
| |
| void AresDnsResolver::MaybeStartResolvingLocked() { |
| // If there is an existing timer, the time it fires is the earliest time we |
| // can start the next resolution. |
| if (have_next_resolution_timer_) return; |
| if (last_resolution_timestamp_ >= 0) { |
| const grpc_millis earliest_next_resolution = |
| last_resolution_timestamp_ + min_time_between_resolutions_; |
| const grpc_millis ms_until_next_resolution = |
| earliest_next_resolution - grpc_core::ExecCtx::Get()->Now(); |
| if (ms_until_next_resolution > 0) { |
| const grpc_millis last_resolution_ago = |
| grpc_core::ExecCtx::Get()->Now() - last_resolution_timestamp_; |
| GRPC_CARES_TRACE_LOG( |
| "resolver:%p In cooldown from last resolution (from %" PRId64 |
| " ms ago). Will resolve again in %" PRId64 " ms", |
| this, last_resolution_ago, ms_until_next_resolution); |
| have_next_resolution_timer_ = true; |
| // TODO(roth): We currently deal with this ref manually. Once the |
| // new closure API is done, find a way to track this ref with the timer |
| // callback as part of the type system. |
| Ref(DEBUG_LOCATION, "next_resolution_timer_cooldown").release(); |
| grpc_timer_init(&next_resolution_timer_, |
| ExecCtx::Get()->Now() + ms_until_next_resolution, |
| &on_next_resolution_); |
| return; |
| } |
| } |
| StartResolvingLocked(); |
| } |
| |
| void AresDnsResolver::StartResolvingLocked() { |
| // TODO(roth): We currently deal with this ref manually. Once the |
| // new closure API is done, find a way to track this ref with the timer |
| // callback as part of the type system. |
| Ref(DEBUG_LOCATION, "dns-resolving").release(); |
| GPR_ASSERT(!resolving_); |
| resolving_ = true; |
| service_config_json_ = nullptr; |
| pending_request_ = grpc_dns_lookup_ares_locked( |
| dns_server_, name_to_resolve_, kDefaultPort, interested_parties_, |
| &on_resolved_, &addresses_, enable_srv_queries_ /* check_grpclb */, |
| request_service_config_ ? &service_config_json_ : nullptr, |
| query_timeout_ms_, combiner()); |
| last_resolution_timestamp_ = grpc_core::ExecCtx::Get()->Now(); |
| GRPC_CARES_TRACE_LOG("resolver:%p Started resolving. pending_request_:%p", |
| this, pending_request_); |
| } |
| |
| // |
| // Factory |
| // |
| |
| class AresDnsResolverFactory : public ResolverFactory { |
| public: |
| bool IsValidUri(const grpc_uri* uri) const override { return true; } |
| |
| OrphanablePtr<Resolver> CreateResolver(ResolverArgs args) const override { |
| return OrphanablePtr<Resolver>(New<AresDnsResolver>(std::move(args))); |
| } |
| |
| const char* scheme() const override { return "dns"; } |
| }; |
| |
| } // namespace |
| |
| } // namespace grpc_core |
| |
| extern grpc_address_resolver_vtable* grpc_resolve_address_impl; |
| static grpc_address_resolver_vtable* default_resolver; |
| |
| static grpc_error* blocking_resolve_address_ares( |
| const char* name, const char* default_port, |
| grpc_resolved_addresses** addresses) { |
| return default_resolver->blocking_resolve_address(name, default_port, |
| addresses); |
| } |
| |
| static grpc_address_resolver_vtable ares_resolver = { |
| grpc_resolve_address_ares, blocking_resolve_address_ares}; |
| |
| #ifdef GRPC_UV |
| /* TODO(murgatroid99): Remove this when we want the cares resolver to be the |
| * default when using libuv */ |
| static bool should_use_ares(const char* resolver_env) { |
| return resolver_env != nullptr && gpr_stricmp(resolver_env, "ares") == 0; |
| } |
| #else /* GRPC_UV */ |
| static bool should_use_ares(const char* resolver_env) { |
| // TODO(lidiz): Remove the "g_custom_iomgr_enabled" flag once c-ares support |
| // custom IO managers (e.g. gevent). |
| return !g_custom_iomgr_enabled && |
| (resolver_env == nullptr || strlen(resolver_env) == 0 || |
| gpr_stricmp(resolver_env, "ares") == 0); |
| } |
| #endif /* GRPC_UV */ |
| |
| static bool g_use_ares_dns_resolver; |
| |
| void grpc_resolver_dns_ares_init() { |
| grpc_core::UniquePtr<char> resolver = |
| GPR_GLOBAL_CONFIG_GET(grpc_dns_resolver); |
| if (should_use_ares(resolver.get())) { |
| g_use_ares_dns_resolver = true; |
| gpr_log(GPR_DEBUG, "Using ares dns resolver"); |
| address_sorting_init(); |
| grpc_error* error = grpc_ares_init(); |
| if (error != GRPC_ERROR_NONE) { |
| GRPC_LOG_IF_ERROR("grpc_ares_init() failed", error); |
| return; |
| } |
| if (default_resolver == nullptr) { |
| default_resolver = grpc_resolve_address_impl; |
| } |
| grpc_set_resolver_impl(&ares_resolver); |
| grpc_core::ResolverRegistry::Builder::RegisterResolverFactory( |
| grpc_core::UniquePtr<grpc_core::ResolverFactory>( |
| grpc_core::New<grpc_core::AresDnsResolverFactory>())); |
| } else { |
| g_use_ares_dns_resolver = false; |
| } |
| } |
| |
| void grpc_resolver_dns_ares_shutdown() { |
| if (g_use_ares_dns_resolver) { |
| address_sorting_shutdown(); |
| grpc_ares_cleanup(); |
| } |
| } |
| |
| #else /* GRPC_ARES == 1 */ |
| |
| void grpc_resolver_dns_ares_init(void) {} |
| |
| void grpc_resolver_dns_ares_shutdown(void) {} |
| |
| #endif /* GRPC_ARES == 1 */ |