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|
/**
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
* SPDX-License-Identifier: Apache-2.0.
*/
#include <aws/io/host_resolver.h>
#include <aws/common/atomics.h>
#include <aws/common/clock.h>
#include <aws/common/condition_variable.h>
#include <aws/common/hash_table.h>
#include <aws/common/lru_cache.h>
#include <aws/common/mutex.h>
#include <aws/common/string.h>
#include <aws/common/thread.h>
#include <aws/io/logging.h>
#include <inttypes.h>
const uint64_t NS_PER_SEC = 1000000000;
int aws_host_address_copy(const struct aws_host_address *from, struct aws_host_address *to) {
to->allocator = from->allocator;
to->address = aws_string_new_from_string(to->allocator, from->address);
if (!to->address) {
return AWS_OP_ERR;
}
to->host = aws_string_new_from_string(to->allocator, from->host);
if (!to->host) {
aws_string_destroy((void *)to->address);
return AWS_OP_ERR;
}
to->record_type = from->record_type;
to->use_count = from->use_count;
to->connection_failure_count = from->connection_failure_count;
to->expiry = from->expiry;
to->weight = from->weight;
return AWS_OP_SUCCESS;
}
void aws_host_address_move(struct aws_host_address *from, struct aws_host_address *to) {
to->allocator = from->allocator;
to->address = from->address;
to->host = from->host;
to->record_type = from->record_type;
to->use_count = from->use_count;
to->connection_failure_count = from->connection_failure_count;
to->expiry = from->expiry;
to->weight = from->weight;
AWS_ZERO_STRUCT(*from);
}
void aws_host_address_clean_up(struct aws_host_address *address) {
if (address->address) {
aws_string_destroy((void *)address->address);
}
if (address->host) {
aws_string_destroy((void *)address->host);
}
AWS_ZERO_STRUCT(*address);
}
int aws_host_resolver_resolve_host(
struct aws_host_resolver *resolver,
const struct aws_string *host_name,
aws_on_host_resolved_result_fn *res,
struct aws_host_resolution_config *config,
void *user_data) {
AWS_ASSERT(resolver->vtable && resolver->vtable->resolve_host);
return resolver->vtable->resolve_host(resolver, host_name, res, config, user_data);
}
int aws_host_resolver_purge_cache(struct aws_host_resolver *resolver) {
AWS_ASSERT(resolver->vtable && resolver->vtable->purge_cache);
return resolver->vtable->purge_cache(resolver);
}
int aws_host_resolver_record_connection_failure(struct aws_host_resolver *resolver, struct aws_host_address *address) {
AWS_ASSERT(resolver->vtable && resolver->vtable->record_connection_failure);
return resolver->vtable->record_connection_failure(resolver, address);
}
struct aws_host_listener *aws_host_resolver_add_host_listener(
struct aws_host_resolver *resolver,
const struct aws_host_listener_options *options) {
AWS_PRECONDITION(resolver);
AWS_PRECONDITION(resolver->vtable);
if (resolver->vtable->add_host_listener) {
return resolver->vtable->add_host_listener(resolver, options);
}
aws_raise_error(AWS_ERROR_UNSUPPORTED_OPERATION);
return NULL;
}
int aws_host_resolver_remove_host_listener(struct aws_host_resolver *resolver, struct aws_host_listener *listener) {
AWS_PRECONDITION(resolver);
AWS_PRECONDITION(resolver->vtable);
if (resolver->vtable->remove_host_listener) {
return resolver->vtable->remove_host_listener(resolver, listener);
}
aws_raise_error(AWS_ERROR_UNSUPPORTED_OPERATION);
return AWS_OP_ERR;
}
/*
* Used by both the resolver for its lifetime state as well as individual host entries for theirs.
*/
enum default_resolver_state {
DRS_ACTIVE,
DRS_SHUTTING_DOWN,
};
struct default_host_resolver {
struct aws_allocator *allocator;
/*
* Mutually exclusion for the whole resolver, includes all member data and all host_entry_table operations. Once
* an entry is retrieved, this lock MAY be dropped but certain logic may hold both the resolver and the entry lock.
* The two locks must be taken in that order.
*/
struct aws_mutex resolver_lock;
/* host_name (aws_string*) -> host_entry* */
struct aws_hash_table host_entry_table;
/* Hash table of listener entries per host name. We keep this decoupled from the host entry table to allow for
* listeners to be added/removed regardless of whether or not a corresponding host entry exists.
*
* Any time the listener list in the listener entry becomes empty, we remove the entry from the table. This
* includes when a resolver thread moves all of the available listeners to its local list.
*/
/* host_name (aws_string*) -> host_listener_entry* */
struct aws_hash_table listener_entry_table;
enum default_resolver_state state;
/*
* Tracks the number of launched resolution threads that have not yet invoked their shutdown completion
* callback.
*/
uint32_t pending_host_entry_shutdown_completion_callbacks;
/*
* Function to use to query current time. Overridable in construction options.
*/
aws_io_clock_fn *system_clock_fn;
};
/* Default host resolver implementation for listener. */
struct host_listener {
/* Reference to the host resolver that owns this listener */
struct aws_host_resolver *resolver;
/* String copy of the host name */
struct aws_string *host_name;
/* User-supplied callbacks/user_data */
aws_host_listener_resolved_address_fn *resolved_address_callback;
aws_host_listener_expired_address_fn *expired_address_callback;
aws_host_listener_shutdown_fn *shutdown_callback;
void *user_data;
/* Synchronous data, requires host resolver lock to read/modify*/
/* TODO Add a lock-synced-data function for the host resolver, replacing all current places where the host resolver
* mutex is locked. */
struct host_listener_synced_data {
/* It's important that the node structure is always first, so that the HOST_LISTENER_FROM_SYNCED_NODE macro
* works properly.*/
struct aws_linked_list_node node;
uint32_t owned_by_resolver_thread : 1;
uint32_t pending_destroy : 1;
} synced_data;
/* Threaded data that can only be used in the resolver thread. */
struct host_listener_threaded_data {
/* It's important that the node structure is always first, so that the HOST_LISTENER_FROM_THREADED_NODE macro
* works properly.*/
struct aws_linked_list_node node;
bool pin_host_entry;
} threaded_data;
};
/* AWS_CONTAINER_OF does not compile under Clang when using a member in a nested structure, ie, synced_data.node or
* threaded_data.node. To get around this, we define two local macros that rely on the node being the first member of
* the synced_data/threaded_data structures.*/
#define HOST_LISTENER_FROM_SYNCED_NODE(listener_node) \
AWS_CONTAINER_OF((listener_node), struct host_listener, synced_data)
#define HOST_LISTENER_FROM_THREADED_NODE(listener_node) \
AWS_CONTAINER_OF((listener_node), struct host_listener, threaded_data)
/* Structure for holding all listeners for a particular host name. */
struct host_listener_entry {
struct default_host_resolver *resolver;
/* Linked list of struct host_listener */
struct aws_linked_list listeners;
};
struct host_entry {
/* immutable post-creation */
struct aws_allocator *allocator;
struct aws_host_resolver *resolver;
struct aws_thread resolver_thread;
const struct aws_string *host_name;
int64_t resolve_frequency_ns;
struct aws_host_resolution_config resolution_config;
/* synchronized data and its lock */
struct aws_mutex entry_lock;
struct aws_condition_variable entry_signal;
struct aws_cache *aaaa_records;
struct aws_cache *a_records;
struct aws_cache *failed_connection_aaaa_records;
struct aws_cache *failed_connection_a_records;
struct aws_linked_list pending_resolution_callbacks;
uint32_t resolves_since_last_request;
uint64_t last_resolve_request_timestamp_ns;
enum default_resolver_state state;
struct aws_array_list new_addresses;
struct aws_array_list expired_addresses;
};
/*
* A host entry's caches hold things of this type. By using this and not the host_address directly, our
* on_remove callbacks for the cache have access to the host_entry. We wouldn't need to do this if those
* callbacks supported user data injection, but they don't and too many internal code bases already depend
* on the public API.
*/
struct aws_host_address_cache_entry {
struct aws_host_address address;
struct host_entry *entry;
};
int aws_host_address_cache_entry_copy(
const struct aws_host_address_cache_entry *from,
struct aws_host_address_cache_entry *to) {
if (aws_host_address_copy(&from->address, &to->address)) {
return AWS_OP_ERR;
}
to->entry = from->entry;
return AWS_OP_SUCCESS;
}
static void s_shutdown_host_entry(struct host_entry *entry) {
aws_mutex_lock(&entry->entry_lock);
entry->state = DRS_SHUTTING_DOWN;
aws_mutex_unlock(&entry->entry_lock);
}
static struct aws_host_listener *default_add_host_listener(
struct aws_host_resolver *host_resolver,
const struct aws_host_listener_options *options);
static int default_remove_host_listener(
struct aws_host_resolver *host_resolver,
struct aws_host_listener *listener_opaque);
static void s_host_listener_entry_destroy(void *listener_entry_void);
static struct host_listener *s_pop_host_listener_from_entry(
struct default_host_resolver *resolver,
const struct aws_string *host_name,
struct host_listener_entry **in_out_listener_entry);
static int s_add_host_listener_to_listener_entry(
struct default_host_resolver *resolver,
const struct aws_string *host_name,
struct host_listener *listener);
static void s_remove_host_listener_from_entry(
struct default_host_resolver *resolver,
const struct aws_string *host_name,
struct host_listener *listener);
static void s_host_listener_destroy(struct host_listener *listener);
/*
* resolver lock must be held before calling this function
*/
static void s_clear_default_resolver_entry_table(struct default_host_resolver *resolver) {
struct aws_hash_table *table = &resolver->host_entry_table;
for (struct aws_hash_iter iter = aws_hash_iter_begin(table); !aws_hash_iter_done(&iter);
aws_hash_iter_next(&iter)) {
struct host_entry *entry = iter.element.value;
s_shutdown_host_entry(entry);
}
aws_hash_table_clear(table);
}
static int resolver_purge_cache(struct aws_host_resolver *resolver) {
struct default_host_resolver *default_host_resolver = resolver->impl;
aws_mutex_lock(&default_host_resolver->resolver_lock);
s_clear_default_resolver_entry_table(default_host_resolver);
aws_mutex_unlock(&default_host_resolver->resolver_lock);
return AWS_OP_SUCCESS;
}
static void s_cleanup_default_resolver(struct aws_host_resolver *resolver) {
struct default_host_resolver *default_host_resolver = resolver->impl;
aws_hash_table_clean_up(&default_host_resolver->host_entry_table);
aws_hash_table_clean_up(&default_host_resolver->listener_entry_table);
aws_mutex_clean_up(&default_host_resolver->resolver_lock);
aws_simple_completion_callback *shutdown_callback = resolver->shutdown_options.shutdown_callback_fn;
void *shutdown_completion_user_data = resolver->shutdown_options.shutdown_callback_user_data;
aws_mem_release(resolver->allocator, resolver);
/* invoke shutdown completion finally */
if (shutdown_callback != NULL) {
shutdown_callback(shutdown_completion_user_data);
}
}
static void resolver_destroy(struct aws_host_resolver *resolver) {
struct default_host_resolver *default_host_resolver = resolver->impl;
bool cleanup_resolver = false;
aws_mutex_lock(&default_host_resolver->resolver_lock);
AWS_FATAL_ASSERT(default_host_resolver->state == DRS_ACTIVE);
s_clear_default_resolver_entry_table(default_host_resolver);
default_host_resolver->state = DRS_SHUTTING_DOWN;
if (default_host_resolver->pending_host_entry_shutdown_completion_callbacks == 0) {
cleanup_resolver = true;
}
aws_mutex_unlock(&default_host_resolver->resolver_lock);
if (cleanup_resolver) {
s_cleanup_default_resolver(resolver);
}
}
struct pending_callback {
aws_on_host_resolved_result_fn *callback;
void *user_data;
struct aws_linked_list_node node;
};
static void s_clear_address_list(struct aws_array_list *address_list) {
for (size_t i = 0; i < aws_array_list_length(address_list); ++i) {
struct aws_host_address *address = NULL;
aws_array_list_get_at_ptr(address_list, (void **)&address, i);
aws_host_address_clean_up(address);
}
aws_array_list_clear(address_list);
}
static void s_clean_up_host_entry(struct host_entry *entry) {
if (entry == NULL) {
return;
}
/*
* This can happen if the resolver's final reference drops while an unanswered query is pending on an entry.
*
* You could add an assertion that the resolver is in the shut down state if this condition hits but that
* requires additional locking just to make the assert.
*/
if (!aws_linked_list_empty(&entry->pending_resolution_callbacks)) {
aws_raise_error(AWS_IO_DNS_HOST_REMOVED_FROM_CACHE);
}
while (!aws_linked_list_empty(&entry->pending_resolution_callbacks)) {
struct aws_linked_list_node *resolution_callback_node =
aws_linked_list_pop_front(&entry->pending_resolution_callbacks);
struct pending_callback *pending_callback =
AWS_CONTAINER_OF(resolution_callback_node, struct pending_callback, node);
pending_callback->callback(
entry->resolver, entry->host_name, AWS_IO_DNS_HOST_REMOVED_FROM_CACHE, NULL, pending_callback->user_data);
aws_mem_release(entry->allocator, pending_callback);
}
aws_cache_destroy(entry->aaaa_records);
aws_cache_destroy(entry->a_records);
aws_cache_destroy(entry->failed_connection_a_records);
aws_cache_destroy(entry->failed_connection_aaaa_records);
aws_string_destroy((void *)entry->host_name);
s_clear_address_list(&entry->new_addresses);
aws_array_list_clean_up(&entry->new_addresses);
s_clear_address_list(&entry->expired_addresses);
aws_array_list_clean_up(&entry->expired_addresses);
aws_mem_release(entry->allocator, entry);
}
static void s_on_host_entry_shutdown_completion(void *user_data) {
struct host_entry *entry = user_data;
struct aws_host_resolver *resolver = entry->resolver;
struct default_host_resolver *default_host_resolver = resolver->impl;
s_clean_up_host_entry(entry);
bool cleanup_resolver = false;
aws_mutex_lock(&default_host_resolver->resolver_lock);
--default_host_resolver->pending_host_entry_shutdown_completion_callbacks;
if (default_host_resolver->state == DRS_SHUTTING_DOWN &&
default_host_resolver->pending_host_entry_shutdown_completion_callbacks == 0) {
cleanup_resolver = true;
}
aws_mutex_unlock(&default_host_resolver->resolver_lock);
if (cleanup_resolver) {
s_cleanup_default_resolver(resolver);
}
}
static int s_copy_address_into_array_list(struct aws_host_address *address, struct aws_array_list *address_list) {
/*
* This is the worst.
*
* We have to copy the cache address while we still have a write lock. Otherwise, connection failures
* can sneak in and destroy our address by moving the address to/from the various lru caches.
*
* But there's no nice copy construction into an array list, so we get to
* (1) Push a zeroed dummy element onto the array list
* (2) Get its pointer
* (3) Call aws_host_address_copy onto it. If that fails, pop the dummy element.
*/
struct aws_host_address dummy;
AWS_ZERO_STRUCT(dummy);
if (aws_array_list_push_back(address_list, &dummy)) {
return AWS_OP_ERR;
}
struct aws_host_address *dest_copy = NULL;
aws_array_list_get_at_ptr(address_list, (void **)&dest_copy, aws_array_list_length(address_list) - 1);
AWS_FATAL_ASSERT(dest_copy != NULL);
if (aws_host_address_copy(address, dest_copy)) {
aws_array_list_pop_back(address_list);
return AWS_OP_ERR;
}
return AWS_OP_SUCCESS;
}
static uint64_t s_get_system_time_for_default_resolver(struct aws_host_resolver *resolver) {
struct default_host_resolver *default_resolver = resolver->impl;
uint64_t timestamp = 0;
(*default_resolver->system_clock_fn)(×tamp);
return timestamp;
}
/* this only ever gets called after resolution has already run. We expect that the entry's lock
has been acquired for writing before this function is called and released afterwards. */
static inline void process_records(
struct host_entry *host_entry,
struct aws_cache *records,
struct aws_cache *failed_records) {
struct aws_host_resolver *resolver = host_entry->resolver;
uint64_t timestamp = s_get_system_time_for_default_resolver(resolver);
size_t record_count = aws_cache_get_element_count(records);
size_t expired_records = 0;
/* since this only ever gets called after resolution has already run, we're in a dns outage
* if everything is expired. Leave an element so we can keep trying. */
for (size_t index = 0; index < record_count && expired_records < record_count - 1; ++index) {
struct aws_host_address_cache_entry *lru_element_entry = aws_lru_cache_use_lru_element(records);
if (lru_element_entry->address.expiry < timestamp) {
AWS_LOGF_DEBUG(
AWS_LS_IO_DNS,
"static: purging expired record %s for %s",
lru_element_entry->address.address->bytes,
lru_element_entry->address.host->bytes);
expired_records++;
aws_cache_remove(records, lru_element_entry->address.address);
}
}
record_count = aws_cache_get_element_count(records);
AWS_LOGF_TRACE(AWS_LS_IO_DNS, "static: remaining record count for host %d", (int)record_count);
/* if we don't have any known good addresses, take the least recently used, but not expired address with a history
* of spotty behavior and upgrade it for reuse. If it's expired, leave it and let the resolve fail. Better to fail
* than accidentally give a kids' app an IP address to somebody's adult website when the IP address gets rebound to
* a different endpoint. The moral of the story here is to not disable SSL verification! */
if (!record_count) {
size_t failed_count = aws_cache_get_element_count(failed_records);
for (size_t index = 0; index < failed_count; ++index) {
struct aws_host_address_cache_entry *lru_element_entry = aws_lru_cache_use_lru_element(failed_records);
if (timestamp >= lru_element_entry->address.expiry) {
continue;
}
struct aws_host_address_cache_entry *to_add =
aws_mem_calloc(host_entry->allocator, 1, sizeof(struct aws_host_address_cache_entry));
if (to_add == NULL) {
continue;
}
if (aws_host_address_cache_entry_copy(lru_element_entry, to_add) ||
aws_cache_put(records, to_add->address.address, to_add)) {
aws_host_address_clean_up(&to_add->address);
aws_mem_release(host_entry->allocator, to_add);
continue;
}
/*
* Promoting an address from failed to good should trigger the new address callback
*/
s_copy_address_into_array_list(&lru_element_entry->address, &host_entry->new_addresses);
AWS_LOGF_INFO(
AWS_LS_IO_DNS,
"static: promoting spotty record %s for %s back to good list",
lru_element_entry->address.address->bytes,
lru_element_entry->address.host->bytes);
aws_cache_remove(failed_records, lru_element_entry->address.address);
/* we only want to promote one per process run.*/
break;
}
}
}
static int resolver_record_connection_failure(struct aws_host_resolver *resolver, struct aws_host_address *address) {
struct default_host_resolver *default_host_resolver = resolver->impl;
AWS_LOGF_INFO(
AWS_LS_IO_DNS,
"id=%p: recording failure for record %s for %s, moving to bad list",
(void *)resolver,
address->address->bytes,
address->host->bytes);
aws_mutex_lock(&default_host_resolver->resolver_lock);
struct aws_hash_element *element = NULL;
if (aws_hash_table_find(&default_host_resolver->host_entry_table, address->host, &element)) {
aws_mutex_unlock(&default_host_resolver->resolver_lock);
return AWS_OP_ERR;
}
struct host_entry *host_entry = NULL;
if (element != NULL) {
host_entry = element->value;
AWS_FATAL_ASSERT(host_entry);
}
if (host_entry) {
struct aws_host_address_cache_entry *cached_address_entry = NULL;
aws_mutex_lock(&host_entry->entry_lock);
aws_mutex_unlock(&default_host_resolver->resolver_lock);
struct aws_cache *address_table =
address->record_type == AWS_ADDRESS_RECORD_TYPE_AAAA ? host_entry->aaaa_records : host_entry->a_records;
struct aws_cache *failed_table = address->record_type == AWS_ADDRESS_RECORD_TYPE_AAAA
? host_entry->failed_connection_aaaa_records
: host_entry->failed_connection_a_records;
aws_cache_find(address_table, address->address, (void **)&cached_address_entry);
struct aws_host_address_cache_entry *address_entry_copy = NULL;
if (cached_address_entry) {
address_entry_copy = aws_mem_calloc(resolver->allocator, 1, sizeof(struct aws_host_address_cache_entry));
if (!address_entry_copy || aws_host_address_cache_entry_copy(cached_address_entry, address_entry_copy)) {
goto error_host_entry_cleanup;
}
/*
* This will trigger an expiration callback since the good caches add the removed address to the
* host_entry's expired list, via the cache's on_delete callback
*/
if (aws_cache_remove(address_table, cached_address_entry->address.address)) {
goto error_host_entry_cleanup;
}
address_entry_copy->address.connection_failure_count += 1;
if (aws_cache_put(failed_table, address_entry_copy->address.address, address_entry_copy)) {
goto error_host_entry_cleanup;
}
} else {
if (aws_cache_find(failed_table, address->address, (void **)&cached_address_entry)) {
goto error_host_entry_cleanup;
}
if (cached_address_entry) {
cached_address_entry->address.connection_failure_count += 1;
}
}
aws_mutex_unlock(&host_entry->entry_lock);
return AWS_OP_SUCCESS;
error_host_entry_cleanup:
if (address_entry_copy) {
aws_host_address_clean_up(&address_entry_copy->address);
aws_mem_release(resolver->allocator, address_entry_copy);
}
aws_mutex_unlock(&host_entry->entry_lock);
return AWS_OP_ERR;
}
aws_mutex_unlock(&default_host_resolver->resolver_lock);
return AWS_OP_SUCCESS;
}
/*
* A bunch of convenience functions for the host resolver background thread function
*/
static struct aws_host_address_cache_entry *s_find_cached_address_entry_aux(
struct aws_cache *primary_records,
struct aws_cache *fallback_records,
const struct aws_string *address) {
struct aws_host_address_cache_entry *found = NULL;
aws_cache_find(primary_records, address, (void **)&found);
if (found == NULL) {
aws_cache_find(fallback_records, address, (void **)&found);
}
return found;
}
/*
* Looks in both the good and failed connection record sets for a given host record
*/
static struct aws_host_address_cache_entry *s_find_cached_address_entry(
struct host_entry *entry,
const struct aws_string *address,
enum aws_address_record_type record_type) {
switch (record_type) {
case AWS_ADDRESS_RECORD_TYPE_AAAA:
return s_find_cached_address_entry_aux(entry->aaaa_records, entry->failed_connection_aaaa_records, address);
case AWS_ADDRESS_RECORD_TYPE_A:
return s_find_cached_address_entry_aux(entry->a_records, entry->failed_connection_a_records, address);
default:
return NULL;
}
}
static struct aws_host_address_cache_entry *s_get_lru_address_entry_aux(
struct aws_cache *primary_records,
struct aws_cache *fallback_records) {
struct aws_host_address_cache_entry *address_entry = aws_lru_cache_use_lru_element(primary_records);
if (address_entry == NULL) {
aws_lru_cache_use_lru_element(fallback_records);
}
return address_entry;
}
/*
* Looks in both the good and failed connection record sets for the LRU host record
*/
static struct aws_host_address_cache_entry *s_get_lru_address(
struct host_entry *entry,
enum aws_address_record_type record_type) {
switch (record_type) {
case AWS_ADDRESS_RECORD_TYPE_AAAA:
return s_get_lru_address_entry_aux(entry->aaaa_records, entry->failed_connection_aaaa_records);
case AWS_ADDRESS_RECORD_TYPE_A:
return s_get_lru_address_entry_aux(entry->a_records, entry->failed_connection_a_records);
default:
return NULL;
}
}
static void s_update_address_cache(
struct host_entry *host_entry,
struct aws_array_list *address_list,
uint64_t new_expiration) {
AWS_PRECONDITION(host_entry);
AWS_PRECONDITION(address_list);
for (size_t i = 0; i < aws_array_list_length(address_list); ++i) {
struct aws_host_address *fresh_resolved_address = NULL;
aws_array_list_get_at_ptr(address_list, (void **)&fresh_resolved_address, i);
struct aws_host_address_cache_entry *address_to_cache_entry = s_find_cached_address_entry(
host_entry, fresh_resolved_address->address, fresh_resolved_address->record_type);
if (address_to_cache_entry) {
address_to_cache_entry->address.expiry = new_expiration;
AWS_LOGF_TRACE(
AWS_LS_IO_DNS,
"static: updating expiry for %s for host %s to %llu",
address_to_cache_entry->address.address->bytes,
host_entry->host_name->bytes,
(unsigned long long)new_expiration);
} else {
address_to_cache_entry =
aws_mem_calloc(host_entry->allocator, 1, sizeof(struct aws_host_address_cache_entry));
aws_host_address_move(fresh_resolved_address, &address_to_cache_entry->address);
address_to_cache_entry->address.expiry = new_expiration;
address_to_cache_entry->entry = host_entry;
struct aws_cache *address_table =
address_to_cache_entry->address.record_type == AWS_ADDRESS_RECORD_TYPE_AAAA ? host_entry->aaaa_records
: host_entry->a_records;
if (aws_cache_put(address_table, address_to_cache_entry->address.address, address_to_cache_entry)) {
AWS_LOGF_ERROR(
AWS_LS_IO_DNS,
"static: could not add new address to host entry cache for host '%s' in "
"s_update_address_cache.",
host_entry->host_name->bytes);
continue;
}
AWS_LOGF_DEBUG(
AWS_LS_IO_DNS,
"static: new address resolved %s for host %s caching",
address_to_cache_entry->address.address->bytes,
host_entry->host_name->bytes);
struct aws_host_address new_address_copy;
if (aws_host_address_copy(&address_to_cache_entry->address, &new_address_copy)) {
AWS_LOGF_ERROR(
AWS_LS_IO_DNS,
"static: could not copy address for new-address list for host '%s' in s_update_address_cache.",
host_entry->host_name->bytes);
continue;
}
if (aws_array_list_push_back(&host_entry->new_addresses, &new_address_copy)) {
aws_host_address_clean_up(&new_address_copy);
AWS_LOGF_ERROR(
AWS_LS_IO_DNS,
"static: could not push address to new-address list for host '%s' in s_update_address_cache.",
host_entry->host_name->bytes);
continue;
}
}
}
}
static void s_copy_address_into_callback_set(
struct aws_host_address_cache_entry *entry,
struct aws_array_list *callback_addresses,
const struct aws_string *host_name) {
if (entry != NULL) {
if (s_copy_address_into_array_list(&entry->address, callback_addresses)) {
AWS_LOGF_ERROR(
AWS_LS_IO_DNS,
"static: failed to vend address %s for host %s to caller",
entry->address.address->bytes,
host_name->bytes);
return;
}
entry->address.use_count += 1;
AWS_LOGF_TRACE(
AWS_LS_IO_DNS,
"static: vending address %s for host %s to caller",
entry->address.address->bytes,
host_name->bytes);
}
}
static bool s_host_entry_finished_pred(void *user_data) {
struct host_entry *entry = user_data;
return entry->state == DRS_SHUTTING_DOWN;
}
/* Move all of the listeners in the host-resolver-owned listener entry to the resolver thread owned list. */
/* Assumes resolver_lock is held so that we can pop from the listener entry and access the listener's synced_data. */
static void s_resolver_thread_move_listeners_from_listener_entry(
struct default_host_resolver *resolver,
const struct aws_string *host_name,
struct aws_linked_list *listener_list) {
AWS_PRECONDITION(resolver);
AWS_PRECONDITION(host_name);
AWS_PRECONDITION(listener_list);
struct host_listener_entry *listener_entry = NULL;
struct host_listener *listener = s_pop_host_listener_from_entry(resolver, host_name, &listener_entry);
while (listener != NULL) {
/* Flag this listener as in-use by the resolver thread so that it can't be destroyed from outside of that
* thread. */
listener->synced_data.owned_by_resolver_thread = true;
aws_linked_list_push_back(listener_list, &listener->threaded_data.node);
listener = s_pop_host_listener_from_entry(resolver, host_name, &listener_entry);
}
}
/* When the thread is ready to exit, we move all of the listeners back to the host-resolver-owned listener entry.*/
/* Assumes that we have already removed all pending_destroy listeners via
* s_resolver_thread_cull_pending_destroy_listeners. */
/* Assumes resolver_lock is held so that we can write to the listener entry and read/write from the listener's
* synced_data. */
static int s_resolver_thread_move_listeners_to_listener_entry(
struct default_host_resolver *resolver,
const struct aws_string *host_name,
struct aws_linked_list *listener_list) {
AWS_PRECONDITION(resolver);
AWS_PRECONDITION(host_name);
AWS_PRECONDITION(listener_list);
int result = 0;
size_t num_listeners_not_moved = 0;
while (!aws_linked_list_empty(listener_list)) {
struct aws_linked_list_node *listener_node = aws_linked_list_pop_back(listener_list);
struct host_listener *listener = HOST_LISTENER_FROM_THREADED_NODE(listener_node);
/* Flag this listener as no longer in-use by the resolver thread. */
listener->synced_data.owned_by_resolver_thread = false;
AWS_ASSERT(!listener->synced_data.pending_destroy);
if (s_add_host_listener_to_listener_entry(resolver, host_name, listener)) {
result = AWS_OP_ERR;
++num_listeners_not_moved;
}
}
if (result == AWS_OP_ERR) {
AWS_LOGF_ERROR(
AWS_LS_IO_DNS,
"static: could not move %" PRIu64 " listeners back to listener entry",
(uint64_t)num_listeners_not_moved);
}
return result;
}
/* Remove the listeners from the resolver-thread-owned listener_list that are marked pending destroy, and move them into
* the destroy list. */
/* Assumes resolver_lock is held. (This lock is necessary for reading from the listener's synced_data.) */
static void s_resolver_thread_cull_pending_destroy_listeners(
struct aws_linked_list *listener_list,
struct aws_linked_list *listener_destroy_list) {
AWS_PRECONDITION(listener_list);
AWS_PRECONDITION(listener_destroy_list);
struct aws_linked_list_node *listener_node = aws_linked_list_begin(listener_list);
/* Find all listeners in our current list that are marked for destroy. */
while (listener_node != aws_linked_list_end(listener_list)) {
struct host_listener *listener = HOST_LISTENER_FROM_THREADED_NODE(listener_node);
/* Advance our node pointer early to allow for a removal. */
listener_node = aws_linked_list_next(listener_node);
/* If listener is pending destroy, remove it from the local list, and push it into the destroy list. */
if (listener->synced_data.pending_destroy) {
aws_linked_list_remove(&listener->threaded_data.node);
aws_linked_list_push_back(listener_destroy_list, &listener->threaded_data.node);
}
}
}
/* Destroys all of the listeners in the resolver thread's destroy list. */
/* Assumes no lock is held. (We don't want any lock held so that any shutdown callbacks happen outside of a lock.) */
static void s_resolver_thread_destroy_listeners(struct aws_linked_list *listener_destroy_list) {
AWS_PRECONDITION(listener_destroy_list);
while (!aws_linked_list_empty(listener_destroy_list)) {
struct aws_linked_list_node *listener_node = aws_linked_list_pop_back(listener_destroy_list);
struct host_listener *listener = HOST_LISTENER_FROM_THREADED_NODE(listener_node);
s_host_listener_destroy(listener);
}
}
/* Notify all listeners with resolve address callbacks, and also clean up any that are waiting to be cleaned up. */
/* Assumes no lock is held. The listener_list is owned by the resolver thread, so no lock is necessary. We also don't
* want a lock held when calling the resolver-address callback.*/
static void s_resolver_thread_notify_listeners(
struct aws_linked_list *listener_list,
const struct aws_array_list *new_address_list,
const struct aws_array_list *expired_address_list) {
AWS_PRECONDITION(new_address_list);
AWS_PRECONDITION(listener_list);
AWS_PRECONDITION(expired_address_list);
/* Go through each listener in our list. */
for (struct aws_linked_list_node *listener_node = aws_linked_list_begin(listener_list);
listener_node != aws_linked_list_end(listener_list);
listener_node = aws_linked_list_next(listener_node)) {
struct host_listener *listener = HOST_LISTENER_FROM_THREADED_NODE(listener_node);
/* If we have new addresses, notify the resolved-address callback if one exists */
if (aws_array_list_length(new_address_list) > 0 && listener->resolved_address_callback != NULL) {
listener->resolved_address_callback(
(struct aws_host_listener *)listener, new_address_list, listener->user_data);
}
/* If we have expired addresses, notify the expired-address callback if one exists */
if (aws_array_list_length(expired_address_list) > 0 && listener->expired_address_callback != NULL) {
listener->expired_address_callback(
(struct aws_host_listener *)listener, expired_address_list, listener->user_data);
}
}
}
static bool s_is_host_entry_pinned_by_listener(struct aws_linked_list *listener_list) {
AWS_PRECONDITION(listener_list);
for (struct aws_linked_list_node *listener_node = aws_linked_list_begin(listener_list);
listener_node != aws_linked_list_end(listener_list);
listener_node = aws_linked_list_next(listener_node)) {
struct host_listener *listener = HOST_LISTENER_FROM_THREADED_NODE(listener_node);
if (listener->threaded_data.pin_host_entry) {
return true;
}
}
return false;
}
static void resolver_thread_fn(void *arg) {
struct host_entry *host_entry = arg;
size_t unsolicited_resolve_max = host_entry->resolution_config.max_ttl;
if (unsolicited_resolve_max == 0) {
unsolicited_resolve_max = 1;
}
uint64_t max_no_solicitation_interval =
aws_timestamp_convert(unsolicited_resolve_max, AWS_TIMESTAMP_SECS, AWS_TIMESTAMP_NANOS, NULL);
struct aws_linked_list listener_list;
aws_linked_list_init(&listener_list);
struct aws_linked_list listener_destroy_list;
aws_linked_list_init(&listener_destroy_list);
bool keep_going = true;
struct aws_array_list address_list;
AWS_ZERO_STRUCT(address_list);
struct aws_array_list new_address_list;
AWS_ZERO_STRUCT(new_address_list);
struct aws_array_list expired_address_list;
AWS_ZERO_STRUCT(expired_address_list);
if (aws_array_list_init_dynamic(&address_list, host_entry->allocator, 4, sizeof(struct aws_host_address))) {
goto done;
}
if (aws_array_list_init_dynamic(&new_address_list, host_entry->allocator, 4, sizeof(struct aws_host_address))) {
goto done;
}
if (aws_array_list_init_dynamic(&expired_address_list, host_entry->allocator, 4, sizeof(struct aws_host_address))) {
goto done;
}
while (keep_going) {
/* resolve and then process each record */
int err_code = AWS_ERROR_SUCCESS;
if (host_entry->resolution_config.impl(
host_entry->allocator, host_entry->host_name, &address_list, host_entry->resolution_config.impl_data)) {
err_code = aws_last_error();
}
if (err_code == AWS_ERROR_SUCCESS) {
AWS_LOGF_DEBUG(
AWS_LS_IO_DNS,
"static, resolving host %s successful, returned %d addresses",
aws_string_c_str(host_entry->host_name),
(int)aws_array_list_length(&address_list));
} else {
AWS_LOGF_WARN(
AWS_LS_IO_DNS,
"static, resolving host %s failed, ec %d (%s)",
aws_string_c_str(host_entry->host_name),
err_code,
aws_error_debug_str(err_code));
}
uint64_t timestamp = s_get_system_time_for_default_resolver(host_entry->resolver);
uint64_t new_expiry = timestamp + (host_entry->resolution_config.max_ttl * NS_PER_SEC);
struct aws_linked_list pending_resolve_copy;
aws_linked_list_init(&pending_resolve_copy);
/*
* Within the lock we
* (1) Update the cache with the newly resolved addresses
* (2) Process all held addresses looking for expired or promotable ones
* (3) Prep for callback invocations
*/
aws_mutex_lock(&host_entry->entry_lock);
if (!err_code) {
s_update_address_cache(host_entry, &address_list, new_expiry);
}
/*
* process and clean_up records in the entry. occasionally, failed connect records will be upgraded
* for retry.
*/
process_records(host_entry, host_entry->aaaa_records, host_entry->failed_connection_aaaa_records);
process_records(host_entry, host_entry->a_records, host_entry->failed_connection_a_records);
aws_linked_list_swap_contents(&pending_resolve_copy, &host_entry->pending_resolution_callbacks);
aws_mutex_unlock(&host_entry->entry_lock);
/*
* Clean up resolved addressed outside of the lock
*/
s_clear_address_list(&address_list);
struct aws_host_address address_array[2];
AWS_ZERO_ARRAY(address_array);
/*
* Perform the actual subscriber notifications
*/
while (!aws_linked_list_empty(&pending_resolve_copy)) {
struct aws_linked_list_node *resolution_callback_node = aws_linked_list_pop_front(&pending_resolve_copy);
struct pending_callback *pending_callback =
AWS_CONTAINER_OF(resolution_callback_node, struct pending_callback, node);
struct aws_array_list callback_address_list;
aws_array_list_init_static(&callback_address_list, address_array, 2, sizeof(struct aws_host_address));
aws_mutex_lock(&host_entry->entry_lock);
s_copy_address_into_callback_set(
s_get_lru_address(host_entry, AWS_ADDRESS_RECORD_TYPE_AAAA),
&callback_address_list,
host_entry->host_name);
s_copy_address_into_callback_set(
s_get_lru_address(host_entry, AWS_ADDRESS_RECORD_TYPE_A),
&callback_address_list,
host_entry->host_name);
aws_mutex_unlock(&host_entry->entry_lock);
size_t callback_address_list_size = aws_array_list_length(&callback_address_list);
if (callback_address_list_size > 0) {
AWS_LOGF_DEBUG(
AWS_LS_IO_DNS,
"static, invoking resolution callback for host %s with %d addresses",
aws_string_c_str(host_entry->host_name),
(int)callback_address_list_size);
} else {
AWS_LOGF_DEBUG(
AWS_LS_IO_DNS,
"static, invoking resolution callback for host %s with failure",
aws_string_c_str(host_entry->host_name));
}
if (callback_address_list_size > 0) {
pending_callback->callback(
host_entry->resolver,
host_entry->host_name,
AWS_OP_SUCCESS,
&callback_address_list,
pending_callback->user_data);
} else {
int error_code = (err_code != AWS_ERROR_SUCCESS) ? err_code : AWS_IO_DNS_QUERY_FAILED;
pending_callback->callback(
host_entry->resolver, host_entry->host_name, error_code, NULL, pending_callback->user_data);
}
s_clear_address_list(&callback_address_list);
aws_mem_release(host_entry->allocator, pending_callback);
}
aws_mutex_lock(&host_entry->entry_lock);
++host_entry->resolves_since_last_request;
/* wait for a quit notification or the base resolve frequency time interval */
aws_condition_variable_wait_for_pred(
&host_entry->entry_signal,
&host_entry->entry_lock,
host_entry->resolve_frequency_ns,
s_host_entry_finished_pred,
host_entry);
aws_mutex_unlock(&host_entry->entry_lock);
/*
* This is a bit awkward that we unlock the entry and then relock both the resolver and the entry, but it
* is mandatory that -- in order to maintain the consistent view of the resolver table (entry exist => entry
* is alive and can be queried) -- we have the resolver lock as well before making the decision to remove
* the entry from the table and terminate the thread.
*/
struct default_host_resolver *resolver = host_entry->resolver->impl;
aws_mutex_lock(&resolver->resolver_lock);
/* Remove any listeners from our listener list that have been marked pending destroy, moving them into the
* destroy list. */
s_resolver_thread_cull_pending_destroy_listeners(&listener_list, &listener_destroy_list);
/* Grab any listeners on the listener entry, moving them into the local list. */
s_resolver_thread_move_listeners_from_listener_entry(resolver, host_entry->host_name, &listener_list);
aws_mutex_lock(&host_entry->entry_lock);
uint64_t now = s_get_system_time_for_default_resolver(host_entry->resolver);
bool pinned = s_is_host_entry_pinned_by_listener(&listener_list);
/*
* Ideally this should just be time-based, but given the non-determinism of waits (and spurious wake ups) and
* clock time, I feel much more comfortable keeping an additional constraint in terms of iterations.
*
* Note that we have the entry lock now and if any queries have arrived since our last resolution,
* resolves_since_last_request will be 0 or 1 (depending on timing) and so, regardless of wait and wake up
* timings, this check will always fail in that case leading to another iteration to satisfy the pending
* query(ies).
*
* The only way we terminate the loop with pending queries is if the resolver itself has no more references
* to it and is going away. In that case, the pending queries will be completed (with failure) by the
* final clean up of this entry.
*/
if (host_entry->resolves_since_last_request > unsolicited_resolve_max &&
host_entry->last_resolve_request_timestamp_ns + max_no_solicitation_interval < now && !pinned) {
host_entry->state = DRS_SHUTTING_DOWN;
}
keep_going = host_entry->state == DRS_ACTIVE;
if (!keep_going) {
aws_hash_table_remove(&resolver->host_entry_table, host_entry->host_name, NULL, NULL);
/* Move any local listeners we have back to the listener entry */
if (s_resolver_thread_move_listeners_to_listener_entry(resolver, host_entry->host_name, &listener_list)) {
AWS_LOGF_ERROR(AWS_LS_IO_DNS, "static: could not clean up all listeners from resolver thread.");
}
}
aws_array_list_swap_contents(&host_entry->new_addresses, &new_address_list);
aws_array_list_swap_contents(&host_entry->expired_addresses, &expired_address_list);
aws_mutex_unlock(&host_entry->entry_lock);
aws_mutex_unlock(&resolver->resolver_lock);
/* Destroy any listeners in our destroy list. */
s_resolver_thread_destroy_listeners(&listener_destroy_list);
/* Notify our local listeners of new addresses. */
s_resolver_thread_notify_listeners(&listener_list, &new_address_list, &expired_address_list);
s_clear_address_list(&new_address_list);
s_clear_address_list(&expired_address_list);
}
AWS_LOGF_DEBUG(
AWS_LS_IO_DNS,
"static: Either no requests have been made for an address for %s for the duration "
"of the ttl, or this thread is being forcibly shutdown. Killing thread.",
host_entry->host_name->bytes)
done:
AWS_FATAL_ASSERT(aws_array_list_length(&address_list) == 0);
AWS_FATAL_ASSERT(aws_array_list_length(&new_address_list) == 0);
AWS_FATAL_ASSERT(aws_array_list_length(&expired_address_list) == 0);
aws_array_list_clean_up(&address_list);
aws_array_list_clean_up(&new_address_list);
aws_array_list_clean_up(&expired_address_list);
/* please don't fail */
aws_thread_current_at_exit(s_on_host_entry_shutdown_completion, host_entry);
}
static void on_cache_entry_removed_helper(struct aws_host_address_cache_entry *entry) {
AWS_LOGF_DEBUG(
AWS_LS_IO_DNS,
"static: purging address %s for host %s from "
"the cache due to cache eviction or shutdown",
entry->address.address->bytes,
entry->address.host->bytes);
struct aws_allocator *allocator = entry->address.allocator;
aws_host_address_clean_up(&entry->address);
aws_mem_release(allocator, entry);
}
static void on_good_address_entry_removed(void *value) {
struct aws_host_address_cache_entry *entry = value;
if (entry == NULL) {
return;
}
s_copy_address_into_array_list(&entry->address, &entry->entry->expired_addresses);
on_cache_entry_removed_helper(entry);
}
static void on_failed_address_entry_removed(void *value) {
struct aws_host_address_cache_entry *entry = value;
on_cache_entry_removed_helper(entry);
}
/*
* The resolver lock must be held before calling this function
*/
static inline int create_and_init_host_entry(
struct aws_host_resolver *resolver,
const struct aws_string *host_name,
aws_on_host_resolved_result_fn *res,
struct aws_host_resolution_config *config,
uint64_t timestamp,
void *user_data) {
struct host_entry *new_host_entry = aws_mem_calloc(resolver->allocator, 1, sizeof(struct host_entry));
if (!new_host_entry) {
return AWS_OP_ERR;
}
new_host_entry->resolver = resolver;
new_host_entry->allocator = resolver->allocator;
new_host_entry->last_resolve_request_timestamp_ns = timestamp;
new_host_entry->resolves_since_last_request = 0;
new_host_entry->resolve_frequency_ns = NS_PER_SEC;
new_host_entry->state = DRS_ACTIVE;
bool thread_init = false;
struct pending_callback *pending_callback = NULL;
const struct aws_string *host_string_copy = aws_string_new_from_string(resolver->allocator, host_name);
if (AWS_UNLIKELY(!host_string_copy)) {
goto setup_host_entry_error;
}
new_host_entry->host_name = host_string_copy;
new_host_entry->a_records = aws_cache_new_lru(
new_host_entry->allocator,
aws_hash_string,
aws_hash_callback_string_eq,
NULL,
on_good_address_entry_removed,
config->max_ttl);
if (AWS_UNLIKELY(!new_host_entry->a_records)) {
goto setup_host_entry_error;
}
new_host_entry->aaaa_records = aws_cache_new_lru(
new_host_entry->allocator,
aws_hash_string,
aws_hash_callback_string_eq,
NULL,
on_good_address_entry_removed,
config->max_ttl);
if (AWS_UNLIKELY(!new_host_entry->aaaa_records)) {
goto setup_host_entry_error;
}
new_host_entry->failed_connection_a_records = aws_cache_new_lru(
new_host_entry->allocator,
aws_hash_string,
aws_hash_callback_string_eq,
NULL,
on_failed_address_entry_removed,
config->max_ttl);
if (AWS_UNLIKELY(!new_host_entry->failed_connection_a_records)) {
goto setup_host_entry_error;
}
new_host_entry->failed_connection_aaaa_records = aws_cache_new_lru(
new_host_entry->allocator,
aws_hash_string,
aws_hash_callback_string_eq,
NULL,
on_failed_address_entry_removed,
config->max_ttl);
if (AWS_UNLIKELY(!new_host_entry->failed_connection_aaaa_records)) {
goto setup_host_entry_error;
}
if (aws_array_list_init_dynamic(
&new_host_entry->new_addresses, new_host_entry->allocator, 4, sizeof(struct aws_host_address))) {
goto setup_host_entry_error;
}
if (aws_array_list_init_dynamic(
&new_host_entry->expired_addresses, new_host_entry->allocator, 4, sizeof(struct aws_host_address))) {
goto setup_host_entry_error;
}
aws_linked_list_init(&new_host_entry->pending_resolution_callbacks);
pending_callback = aws_mem_acquire(resolver->allocator, sizeof(struct pending_callback));
if (AWS_UNLIKELY(!pending_callback)) {
goto setup_host_entry_error;
}
/*add the current callback here */
pending_callback->user_data = user_data;
pending_callback->callback = res;
aws_linked_list_push_back(&new_host_entry->pending_resolution_callbacks, &pending_callback->node);
aws_mutex_init(&new_host_entry->entry_lock);
new_host_entry->resolution_config = *config;
aws_condition_variable_init(&new_host_entry->entry_signal);
if (aws_thread_init(&new_host_entry->resolver_thread, resolver->allocator)) {
goto setup_host_entry_error;
}
thread_init = true;
struct default_host_resolver *default_host_resolver = resolver->impl;
if (AWS_UNLIKELY(
aws_hash_table_put(&default_host_resolver->host_entry_table, host_string_copy, new_host_entry, NULL))) {
goto setup_host_entry_error;
}
struct aws_thread_options thread_options = *aws_default_thread_options();
thread_options.join_strategy = AWS_TJS_MANAGED;
aws_thread_launch(&new_host_entry->resolver_thread, resolver_thread_fn, new_host_entry, &thread_options);
++default_host_resolver->pending_host_entry_shutdown_completion_callbacks;
return AWS_OP_SUCCESS;
setup_host_entry_error:
if (thread_init) {
aws_thread_clean_up(&new_host_entry->resolver_thread);
}
s_clean_up_host_entry(new_host_entry);
return AWS_OP_ERR;
}
static int default_resolve_host(
struct aws_host_resolver *resolver,
const struct aws_string *host_name,
aws_on_host_resolved_result_fn *res,
struct aws_host_resolution_config *config,
void *user_data) {
int result = AWS_OP_SUCCESS;
AWS_LOGF_DEBUG(AWS_LS_IO_DNS, "id=%p: Host resolution requested for %s", (void *)resolver, host_name->bytes);
uint64_t timestamp = s_get_system_time_for_default_resolver(resolver);
struct default_host_resolver *default_host_resolver = resolver->impl;
aws_mutex_lock(&default_host_resolver->resolver_lock);
struct aws_hash_element *element = NULL;
/* we don't care about the error code here, only that the host_entry was found or not. */
aws_hash_table_find(&default_host_resolver->host_entry_table, host_name, &element);
struct host_entry *host_entry = NULL;
if (element != NULL) {
host_entry = element->value;
AWS_FATAL_ASSERT(host_entry != NULL);
}
if (!host_entry) {
AWS_LOGF_DEBUG(
AWS_LS_IO_DNS,
"id=%p: No cached entries found for %s starting new resolver thread.",
(void *)resolver,
host_name->bytes);
result = create_and_init_host_entry(resolver, host_name, res, config, timestamp, user_data);
aws_mutex_unlock(&default_host_resolver->resolver_lock);
return result;
}
aws_mutex_lock(&host_entry->entry_lock);
/*
* We don't need to make any resolver side-affects in the remaining logic and it's impossible for the entry
* to disappear underneath us while holding its lock, so its safe to release the resolver lock and let other
* things query other entries.
*/
aws_mutex_unlock(&default_host_resolver->resolver_lock);
host_entry->last_resolve_request_timestamp_ns = timestamp;
host_entry->resolves_since_last_request = 0;
struct aws_host_address_cache_entry *aaaa_entry = aws_lru_cache_use_lru_element(host_entry->aaaa_records);
struct aws_host_address *aaaa_record = (aaaa_entry != NULL) ? &aaaa_entry->address : NULL;
struct aws_host_address_cache_entry *a_entry = aws_lru_cache_use_lru_element(host_entry->a_records);
struct aws_host_address *a_record = (a_entry != NULL) ? &a_entry->address : NULL;
struct aws_host_address address_array[2];
AWS_ZERO_ARRAY(address_array);
struct aws_array_list callback_address_list;
aws_array_list_init_static(&callback_address_list, address_array, 2, sizeof(struct aws_host_address));
if ((aaaa_record || a_record)) {
AWS_LOGF_DEBUG(
AWS_LS_IO_DNS,
"id=%p: cached entries found for %s returning to caller.",
(void *)resolver,
host_name->bytes);
/* these will all need to be copied so that we don't hold the lock during the callback. */
if (aaaa_record) {
struct aws_host_address aaaa_record_cpy;
if (!aws_host_address_copy(aaaa_record, &aaaa_record_cpy)) {
aws_array_list_push_back(&callback_address_list, &aaaa_record_cpy);
AWS_LOGF_TRACE(
AWS_LS_IO_DNS,
"id=%p: vending address %s for host %s to caller",
(void *)resolver,
aaaa_record->address->bytes,
host_entry->host_name->bytes);
}
}
if (a_record) {
struct aws_host_address a_record_cpy;
if (!aws_host_address_copy(a_record, &a_record_cpy)) {
aws_array_list_push_back(&callback_address_list, &a_record_cpy);
AWS_LOGF_TRACE(
AWS_LS_IO_DNS,
"id=%p: vending address %s for host %s to caller",
(void *)resolver,
a_record->address->bytes,
host_entry->host_name->bytes);
}
}
aws_mutex_unlock(&host_entry->entry_lock);
/* we don't want to do the callback WHILE we hold the lock someone may reentrantly call us. */
if (aws_array_list_length(&callback_address_list)) {
res(resolver, host_name, AWS_OP_SUCCESS, &callback_address_list, user_data);
} else {
res(resolver, host_name, aws_last_error(), NULL, user_data);
result = AWS_OP_ERR;
}
for (size_t i = 0; i < aws_array_list_length(&callback_address_list); ++i) {
struct aws_host_address *address_ptr = NULL;
aws_array_list_get_at_ptr(&callback_address_list, (void **)&address_ptr, i);
aws_host_address_clean_up(address_ptr);
}
aws_array_list_clean_up(&callback_address_list);
return result;
}
struct pending_callback *pending_callback =
aws_mem_acquire(default_host_resolver->allocator, sizeof(struct pending_callback));
if (pending_callback != NULL) {
pending_callback->user_data = user_data;
pending_callback->callback = res;
aws_linked_list_push_back(&host_entry->pending_resolution_callbacks, &pending_callback->node);
} else {
result = AWS_OP_ERR;
}
aws_mutex_unlock(&host_entry->entry_lock);
return result;
}
static size_t default_get_host_address_count(
struct aws_host_resolver *host_resolver,
const struct aws_string *host_name,
uint32_t flags) {
struct default_host_resolver *default_host_resolver = host_resolver->impl;
size_t address_count = 0;
aws_mutex_lock(&default_host_resolver->resolver_lock);
struct aws_hash_element *element = NULL;
aws_hash_table_find(&default_host_resolver->host_entry_table, host_name, &element);
if (element != NULL) {
struct host_entry *host_entry = element->value;
if (host_entry != NULL) {
aws_mutex_lock(&host_entry->entry_lock);
if ((flags & AWS_GET_HOST_ADDRESS_COUNT_RECORD_TYPE_A) != 0) {
address_count += aws_cache_get_element_count(host_entry->a_records);
}
if ((flags & AWS_GET_HOST_ADDRESS_COUNT_RECORD_TYPE_AAAA) != 0) {
address_count += aws_cache_get_element_count(host_entry->aaaa_records);
}
aws_mutex_unlock(&host_entry->entry_lock);
}
}
aws_mutex_unlock(&default_host_resolver->resolver_lock);
return address_count;
}
static struct aws_host_resolver_vtable s_vtable = {
.purge_cache = resolver_purge_cache,
.resolve_host = default_resolve_host,
.record_connection_failure = resolver_record_connection_failure,
.get_host_address_count = default_get_host_address_count,
.add_host_listener = default_add_host_listener,
.remove_host_listener = default_remove_host_listener,
.destroy = resolver_destroy,
};
static void s_aws_host_resolver_destroy(struct aws_host_resolver *resolver) {
AWS_ASSERT(resolver->vtable && resolver->vtable->destroy);
resolver->vtable->destroy(resolver);
}
struct aws_host_resolver *aws_host_resolver_new_default(
struct aws_allocator *allocator,
struct aws_host_resolver_default_options *options) {
AWS_FATAL_ASSERT(options != NULL);
/* NOTE: we don't use el_group yet, but we will in the future. Also, we
don't want host resolvers getting cleaned up after el_groups; this will force that
in bindings, and encourage it in C land. */
AWS_ASSERT(options->el_group);
struct aws_host_resolver *resolver = NULL;
struct default_host_resolver *default_host_resolver = NULL;
if (!aws_mem_acquire_many(
allocator,
2,
&resolver,
sizeof(struct aws_host_resolver),
&default_host_resolver,
sizeof(struct default_host_resolver))) {
return NULL;
}
AWS_ZERO_STRUCT(*resolver);
AWS_ZERO_STRUCT(*default_host_resolver);
AWS_LOGF_INFO(
AWS_LS_IO_DNS,
"id=%p: Initializing default host resolver with %llu max host entries.",
(void *)resolver,
(unsigned long long)options->max_entries);
resolver->vtable = &s_vtable;
resolver->allocator = allocator;
resolver->impl = default_host_resolver;
default_host_resolver->allocator = allocator;
default_host_resolver->pending_host_entry_shutdown_completion_callbacks = 0;
default_host_resolver->state = DRS_ACTIVE;
aws_mutex_init(&default_host_resolver->resolver_lock);
if (aws_hash_table_init(
&default_host_resolver->host_entry_table,
allocator,
options->max_entries,
aws_hash_string,
aws_hash_callback_string_eq,
NULL,
NULL)) {
goto on_error;
}
if (aws_hash_table_init(
&default_host_resolver->listener_entry_table,
allocator,
options->max_entries,
aws_hash_string,
aws_hash_callback_string_eq,
aws_hash_callback_string_destroy,
s_host_listener_entry_destroy)) {
goto on_error;
}
aws_ref_count_init(&resolver->ref_count, resolver, (aws_simple_completion_callback *)s_aws_host_resolver_destroy);
if (options->shutdown_options != NULL) {
resolver->shutdown_options = *options->shutdown_options;
}
if (options->system_clock_override_fn != NULL) {
default_host_resolver->system_clock_fn = options->system_clock_override_fn;
} else {
default_host_resolver->system_clock_fn = aws_sys_clock_get_ticks;
}
return resolver;
on_error:
s_cleanup_default_resolver(resolver);
return NULL;
}
struct aws_host_resolver *aws_host_resolver_acquire(struct aws_host_resolver *resolver) {
if (resolver != NULL) {
aws_ref_count_acquire(&resolver->ref_count);
}
return resolver;
}
void aws_host_resolver_release(struct aws_host_resolver *resolver) {
if (resolver != NULL) {
aws_ref_count_release(&resolver->ref_count);
}
}
size_t aws_host_resolver_get_host_address_count(
struct aws_host_resolver *resolver,
const struct aws_string *host_name,
uint32_t flags) {
return resolver->vtable->get_host_address_count(resolver, host_name, flags);
}
enum find_listener_entry_flags {
FIND_LISTENER_ENTRY_FLAGS_CREATE_IF_NOT_FOUND = 0x00000001,
};
static struct host_listener_entry *s_find_host_listener_entry(
struct default_host_resolver *default_resolver,
const struct aws_string *host_name,
uint32_t flags);
static struct aws_host_listener *default_add_host_listener(
struct aws_host_resolver *resolver,
const struct aws_host_listener_options *options) {
AWS_PRECONDITION(resolver);
bool success = false;
if (options == NULL) {
AWS_LOGF_ERROR(AWS_LS_IO_DNS, "Cannot create host resolver listener; options structure is NULL.");
aws_raise_error(AWS_ERROR_INVALID_ARGUMENT);
return NULL;
}
if (options->host_name.len == 0) {
AWS_LOGF_ERROR(AWS_LS_IO_DNS, "Cannot create host resolver listener; invalid host name specified.");
aws_raise_error(AWS_ERROR_INVALID_ARGUMENT);
return NULL;
}
/* Allocate and set up the listener. */
struct host_listener *listener = aws_mem_calloc(resolver->allocator, 1, sizeof(struct host_listener));
AWS_LOGF_TRACE(
AWS_LS_IO_DNS,
"id=%p Adding listener %p for host name %s",
(void *)resolver,
(void *)listener,
(const char *)options->host_name.ptr);
struct default_host_resolver *default_host_resolver = resolver->impl;
listener->resolver = aws_host_resolver_acquire(resolver);
listener->host_name = aws_string_new_from_cursor(resolver->allocator, &options->host_name);
if (listener->host_name == NULL) {
goto done;
}
listener->resolved_address_callback = options->resolved_address_callback;
listener->expired_address_callback = options->expired_address_callback;
listener->user_data = options->user_data;
listener->threaded_data.pin_host_entry = options->pin_host_entry;
/* Add the listener to a host listener entry in the host listener entry table. */
aws_mutex_lock(&default_host_resolver->resolver_lock);
if (s_add_host_listener_to_listener_entry(default_host_resolver, listener->host_name, listener)) {
goto done;
}
success = true;
listener->shutdown_callback = options->shutdown_callback;
done:
aws_mutex_unlock(&default_host_resolver->resolver_lock);
if (!success) {
s_host_listener_destroy(listener);
listener = NULL;
}
return (struct aws_host_listener *)listener;
}
static int default_remove_host_listener(
struct aws_host_resolver *host_resolver,
struct aws_host_listener *listener_opaque) {
AWS_PRECONDITION(host_resolver);
AWS_PRECONDITION(listener_opaque);
struct host_listener *listener = (struct host_listener *)listener_opaque;
struct default_host_resolver *default_host_resolver = host_resolver->impl;
if (listener->resolver != host_resolver) {
AWS_LOGF_ERROR(
AWS_LS_IO_DNS,
"id=%p Trying to remove listener from incorrect host resolver. Listener belongs to host resolver %p",
(void *)host_resolver,
(void *)listener->resolver);
aws_raise_error(AWS_ERROR_INVALID_ARGUMENT);
return AWS_OP_ERR;
}
AWS_LOGF_TRACE(
AWS_LS_IO_DNS,
"id=%p Removing listener %p for host name %s",
(void *)host_resolver,
(void *)listener,
(const char *)listener->host_name->bytes);
bool destroy_listener_immediate = false;
aws_mutex_lock(&default_host_resolver->resolver_lock);
/* If owned by the resolver thread, flag the listener as pending destroy, so that resolver thread knows to destroy
* it. */
if (listener->synced_data.owned_by_resolver_thread) {
listener->synced_data.pending_destroy = true;
} else {
/* Else, remove the listener from the listener entry and clean it up once outside of the mutex. */
s_remove_host_listener_from_entry(default_host_resolver, listener->host_name, listener);
destroy_listener_immediate = true;
}
aws_mutex_unlock(&default_host_resolver->resolver_lock);
if (destroy_listener_immediate) {
s_host_listener_destroy(listener);
}
return AWS_OP_SUCCESS;
}
/* Find listener entry on the host resolver, optionally creating it if it doesn't exist. */
/* Assumes host resolver lock is held. */
static struct host_listener_entry *s_find_host_listener_entry(
struct default_host_resolver *resolver,
const struct aws_string *host_name,
uint32_t flags) {
AWS_PRECONDITION(resolver);
AWS_PRECONDITION(host_name);
struct host_listener_entry *listener_entry = NULL;
struct aws_string *host_string_copy = NULL;
struct aws_hash_element *listener_entry_hash_element = NULL;
bool create_if_not_found = (flags & FIND_LISTENER_ENTRY_FLAGS_CREATE_IF_NOT_FOUND) != 0;
if (aws_hash_table_find(&resolver->listener_entry_table, host_name, &listener_entry_hash_element)) {
AWS_LOGF_ERROR(
AWS_LS_IO_DNS, "static: error when trying to find a listener entry in the listener entry table.");
goto error_clean_up;
}
if (listener_entry_hash_element != NULL) {
listener_entry = listener_entry_hash_element->value;
AWS_FATAL_ASSERT(listener_entry);
} else if (create_if_not_found) {
listener_entry = aws_mem_calloc(resolver->allocator, 1, sizeof(struct host_listener_entry));
listener_entry->resolver = resolver;
aws_linked_list_init(&listener_entry->listeners);
host_string_copy = aws_string_new_from_string(resolver->allocator, host_name);
if (aws_hash_table_put(&resolver->listener_entry_table, host_string_copy, listener_entry, NULL)) {
AWS_LOGF_ERROR(AWS_LS_IO_DNS, "static: could not put new listener entry into listener entry table.");
goto error_clean_up;
}
}
return listener_entry;
error_clean_up:
s_host_listener_entry_destroy(listener_entry);
aws_string_destroy(host_string_copy);
return NULL;
}
/* Destroy function for listener entries. Takes a void* so that it can be used by the listener entry hash table. */
static void s_host_listener_entry_destroy(void *listener_entry_void) {
if (listener_entry_void == NULL) {
return;
}
struct host_listener_entry *listener_entry = listener_entry_void;
struct default_host_resolver *resolver = listener_entry->resolver;
aws_mem_release(resolver->allocator, listener_entry);
}
/* Add a listener to the relevant host listener entry. */
/* Assumes host resolver lock is held. */
static int s_add_host_listener_to_listener_entry(
struct default_host_resolver *resolver,
const struct aws_string *host_name,
struct host_listener *listener) {
AWS_PRECONDITION(resolver);
AWS_PRECONDITION(host_name);
AWS_PRECONDITION(listener);
struct host_listener_entry *listener_entry =
s_find_host_listener_entry(resolver, host_name, FIND_LISTENER_ENTRY_FLAGS_CREATE_IF_NOT_FOUND);
if (listener_entry == NULL) {
return AWS_OP_ERR;
}
aws_linked_list_push_back(&listener_entry->listeners, &listener->synced_data.node);
return AWS_OP_SUCCESS;
}
/* Assumes host resolver lock is held. */
static struct host_listener *s_pop_host_listener_from_entry(
struct default_host_resolver *resolver,
const struct aws_string *host_name,
struct host_listener_entry **in_out_listener_entry) {
AWS_PRECONDITION(resolver);
AWS_PRECONDITION(host_name);
struct host_listener_entry *listener_entry = NULL;
if (in_out_listener_entry) {
listener_entry = *in_out_listener_entry;
}
if (listener_entry == NULL) {
listener_entry = s_find_host_listener_entry(resolver, host_name, 0);
if (listener_entry == NULL) {
return NULL;
}
}
/* We should never have a listener entry without any listeners. Whenever a listener entry has no listeners, it
* should be cleaned up immediately. */
AWS_ASSERT(!aws_linked_list_empty(&listener_entry->listeners));
struct aws_linked_list_node *node = aws_linked_list_pop_back(&listener_entry->listeners);
struct host_listener *listener = HOST_LISTENER_FROM_SYNCED_NODE(node);
AWS_FATAL_ASSERT(listener);
/* If the listener list on the listener entry is now empty, remove it. */
if (aws_linked_list_empty(&listener_entry->listeners)) {
aws_hash_table_remove(&resolver->listener_entry_table, host_name, NULL, NULL);
listener_entry = NULL;
}
if (in_out_listener_entry) {
*in_out_listener_entry = listener_entry;
}
return listener;
}
/* Assumes host resolver lock is held. */
static void s_remove_host_listener_from_entry(
struct default_host_resolver *resolver,
const struct aws_string *host_name,
struct host_listener *listener) {
AWS_PRECONDITION(resolver);
AWS_PRECONDITION(host_name);
AWS_PRECONDITION(listener);
struct host_listener_entry *listener_entry = s_find_host_listener_entry(resolver, host_name, 0);
if (listener_entry == NULL) {
AWS_LOGF_WARN(AWS_LS_IO_DNS, "id=%p: Could not find listener entry for listener.", (void *)listener);
return;
}
/* We should never have a listener entry without any listeners. Whenever a listener entry has no listeners, it
* should be cleaned up immediately. */
AWS_ASSERT(!aws_linked_list_empty(&listener_entry->listeners));
aws_linked_list_remove(&listener->synced_data.node);
/* If the listener list on the listener entry is now empty, remove it. */
if (aws_linked_list_empty(&listener_entry->listeners)) {
aws_hash_table_remove(&resolver->listener_entry_table, host_name, NULL, NULL);
}
}
/* Finish destroying a default resolver listener, releasing any remaining memory for it and triggering its shutdown
* callack. Since a shutdown callback is triggered, no lock should be held when calling this function. */
static void s_host_listener_destroy(struct host_listener *listener) {
if (listener == NULL) {
return;
}
AWS_LOGF_TRACE(AWS_LS_IO_DNS, "id=%p: Finishing clean up of host listener.", (void *)listener);
struct aws_host_resolver *host_resolver = listener->resolver;
aws_host_listener_shutdown_fn *shutdown_callback = listener->shutdown_callback;
void *shutdown_user_data = listener->user_data;
aws_string_destroy(listener->host_name);
listener->host_name = NULL;
aws_mem_release(host_resolver->allocator, listener);
listener = NULL;
if (shutdown_callback != NULL) {
shutdown_callback(shutdown_user_data);
}
if (host_resolver != NULL) {
aws_host_resolver_release(host_resolver);
host_resolver = NULL;
}
}
#undef HOST_LISTENER_FROM_SYNCED_NODE
#undef HOST_LISTENER_FROM_THREADED_NODE
|