| /* |
| * |
| * 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; |
| } |
| |
| 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); |
| } |
| |
| 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) */ |
| |
| void grpc_resolver_dns_ares_init(void) {} |
| |
| void grpc_resolver_dns_ares_shutdown(void) {} |
| |
| #endif /* GRPC_ARES == 1 && !defined(GRPC_UV) */ |