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dns: fix resolve failed starts without network
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Fix the bug that you start process without network at first, but it
connected lately, `dns.resolve` will stay failed with ECONNREFUSED
because c-ares servers fallback to 127.0.0.1 at the very beginning.

If c-ares servers "127.0.0.1" is detected and its not set by user self,
and last query is not OK, recreating `ares_channel` operation will be
triggered to reload servers.

Fixes: #1644
Backport-PR-URL: #14434
PR-URL: #13076
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
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@XadillaX @MylesBorins
XadillaX authored and MylesBorins committed Aug 16, 2017
1 parent a1cef1f commit 6518932
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Showing 3 changed files with 110 additions and 74 deletions.
160 changes: 86 additions & 74 deletions src/cares_wrap.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -372,6 +372,69 @@ struct CaresAsyncData {
uv_async_t async_handle;
};

void SetupCaresChannel(Environment* env) {
struct ares_options options;
memset(&options, 0, sizeof(options));
options.flags = ARES_FLAG_NOCHECKRESP;
options.sock_state_cb = ares_sockstate_cb;
options.sock_state_cb_data = env;

/* We do the call to ares_init_option for caller. */
int r = ares_init_options(env->cares_channel_ptr(),
&options,
ARES_OPT_FLAGS | ARES_OPT_SOCK_STATE_CB);

if (r != ARES_SUCCESS) {
ares_library_cleanup();
return env->ThrowError(ToErrorCodeString(r));
}
}


/**
* This function is to check whether current servers are fallback servers
* when cares initialized.
*
* The fallback servers of cares is [ "127.0.0.1" ] with no user additional
* setting.
*/
void AresEnsureServers(Environment* env) {
/* if last query is OK or servers are set by user self, do not check */
if (env->cares_query_last_ok() || !env->cares_is_servers_default()) {
return;
}

ares_channel channel = env->cares_channel();
ares_addr_node* servers = nullptr;

ares_get_servers(channel, &servers);

/* if no server or multi-servers, ignore */
if (servers == nullptr) return;
if (servers->next != nullptr) {
ares_free_data(servers);
env->set_cares_is_servers_default(false);
return;
}

/* if the only server is not 127.0.0.1, ignore */
if (servers[0].family != AF_INET ||
servers[0].addr.addr4.s_addr != htonl(INADDR_LOOPBACK)) {
ares_free_data(servers);
env->set_cares_is_servers_default(false);
return;
}

ares_free_data(servers);
servers = nullptr;

/* destroy channel and reset channel */
ares_destroy(channel);

SetupCaresChannel(env);
}


class QueryWrap : public AsyncWrap {
public:
QueryWrap(Environment* env, Local<Object> req_wrap_obj)
Expand Down Expand Up @@ -402,6 +465,13 @@ class QueryWrap : public AsyncWrap {
return static_cast<void*>(this);
}

static void AresQuery(Environment* env, const char* name,
int dnsclass, int type, ares_callback callback,
void* arg) {
AresEnsureServers(env);
ares_query(env->cares_channel(), name, dnsclass, type, callback, arg);
}

static void CaresAsyncClose(uv_handle_t* handle) {
uv_async_t* async = reinterpret_cast<uv_async_t*>(handle);
auto data = static_cast<struct CaresAsyncData*>(async->data);
Expand Down Expand Up @@ -453,6 +523,7 @@ class QueryWrap : public AsyncWrap {
async_handle,
CaresAsyncCb));

wrap->env()->set_cares_query_last_ok(status != ARES_ECONNREFUSED);
async_handle->data = data;
uv_async_send(async_handle);
}
Expand All @@ -478,6 +549,7 @@ class QueryWrap : public AsyncWrap {
async_handle,
CaresAsyncCb));

wrap->env()->set_cares_query_last_ok(status != ARES_ECONNREFUSED);
async_handle->data = data;
uv_async_send(async_handle);
}
Expand Down Expand Up @@ -522,12 +594,7 @@ class QueryAWrap: public QueryWrap {
}

int Send(const char* name) override {
ares_query(env()->cares_channel(),
name,
ns_c_in,
ns_t_a,
Callback,
GetQueryArg());
AresQuery(env(), name, ns_c_in, ns_t_a, Callback, GetQueryArg());
return 0;
}

Expand Down Expand Up @@ -570,12 +637,7 @@ class QueryAaaaWrap: public QueryWrap {
}

int Send(const char* name) override {
ares_query(env()->cares_channel(),
name,
ns_c_in,
ns_t_aaaa,
Callback,
GetQueryArg());
AresQuery(env(), name, ns_c_in, ns_t_aaaa, Callback, GetQueryArg());
return 0;
}

Expand Down Expand Up @@ -618,12 +680,7 @@ class QueryCnameWrap: public QueryWrap {
}

int Send(const char* name) override {
ares_query(env()->cares_channel(),
name,
ns_c_in,
ns_t_cname,
Callback,
GetQueryArg());
AresQuery(env(), name, ns_c_in, ns_t_cname, Callback, GetQueryArg());
return 0;
}

Expand Down Expand Up @@ -659,12 +716,7 @@ class QueryMxWrap: public QueryWrap {
}

int Send(const char* name) override {
ares_query(env()->cares_channel(),
name,
ns_c_in,
ns_t_mx,
Callback,
GetQueryArg());
AresQuery(env(), name, ns_c_in, ns_t_mx, Callback, GetQueryArg());
return 0;
}

Expand Down Expand Up @@ -710,12 +762,7 @@ class QueryNsWrap: public QueryWrap {
}

int Send(const char* name) override {
ares_query(env()->cares_channel(),
name,
ns_c_in,
ns_t_ns,
Callback,
GetQueryArg());
AresQuery(env(), name, ns_c_in, ns_t_ns, Callback, GetQueryArg());
return 0;
}

Expand Down Expand Up @@ -748,12 +795,7 @@ class QueryTxtWrap: public QueryWrap {
}

int Send(const char* name) override {
ares_query(env()->cares_channel(),
name,
ns_c_in,
ns_t_txt,
Callback,
GetQueryArg());
AresQuery(env(), name, ns_c_in, ns_t_txt, Callback, GetQueryArg());
return 0;
}

Expand Down Expand Up @@ -805,12 +847,7 @@ class QuerySrvWrap: public QueryWrap {
}

int Send(const char* name) override {
ares_query(env()->cares_channel(),
name,
ns_c_in,
ns_t_srv,
Callback,
GetQueryArg());
AresQuery(env(), name, ns_c_in, ns_t_srv, Callback, GetQueryArg());
return 0;
}

Expand Down Expand Up @@ -861,12 +898,7 @@ class QueryPtrWrap: public QueryWrap {
}

int Send(const char* name) override {
ares_query(env()->cares_channel(),
name,
ns_c_in,
ns_t_ptr,
Callback,
GetQueryArg());
AresQuery(env(), name, ns_c_in, ns_t_ptr, Callback, GetQueryArg());
return 0;
}

Expand Down Expand Up @@ -904,12 +936,7 @@ class QueryNaptrWrap: public QueryWrap {
}

int Send(const char* name) override {
ares_query(env()->cares_channel(),
name,
ns_c_in,
ns_t_naptr,
Callback,
GetQueryArg());
AresQuery(env(), name, ns_c_in, ns_t_naptr, Callback, GetQueryArg());
return 0;
}

Expand Down Expand Up @@ -968,12 +995,7 @@ class QuerySoaWrap: public QueryWrap {
}

int Send(const char* name) override {
ares_query(env()->cares_channel(),
name,
ns_c_in,
ns_t_soa,
Callback,
GetQueryArg());
AresQuery(env(), name, ns_c_in, ns_t_soa, Callback, GetQueryArg());
return 0;
}

Expand Down Expand Up @@ -1434,6 +1456,9 @@ static void SetServers(const FunctionCallbackInfo<Value>& args) {

delete[] servers;

if (err == ARES_SUCCESS)
env->set_cares_is_servers_default(false);

args.GetReturnValue().Set(err);
}

Expand Down Expand Up @@ -1468,20 +1493,7 @@ static void Initialize(Local<Object> target,
if (r != ARES_SUCCESS)
return env->ThrowError(ToErrorCodeString(r));

struct ares_options options;
memset(&options, 0, sizeof(options));
options.flags = ARES_FLAG_NOCHECKRESP;
options.sock_state_cb = ares_sockstate_cb;
options.sock_state_cb_data = env;

/* We do the call to ares_init_option for caller. */
r = ares_init_options(env->cares_channel_ptr(),
&options,
ARES_OPT_FLAGS | ARES_OPT_SOCK_STATE_CB);
if (r != ARES_SUCCESS) {
ares_library_cleanup();
return env->ThrowError(ToErrorCodeString(r));
}
SetupCaresChannel(env);

/* Initialize the timeout timer. The timer won't be started until the */
/* first socket is opened. */
Expand Down
18 changes: 18 additions & 0 deletions src/env-inl.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -219,6 +219,8 @@ inline Environment::Environment(v8::Local<v8::Context> context,
: isolate_(context->GetIsolate()),
isolate_data_(IsolateData::GetOrCreate(context->GetIsolate(), loop)),
timer_base_(uv_now(loop)),
cares_query_last_ok_(true),
cares_is_servers_default_(true),
using_domains_(false),
printed_error_(false),
trace_sync_io_(false),
Expand Down Expand Up @@ -453,6 +455,22 @@ inline ares_channel* Environment::cares_channel_ptr() {
return &cares_channel_;
}

inline bool Environment::cares_query_last_ok() {
return cares_query_last_ok_;
}

inline void Environment::set_cares_query_last_ok(bool ok) {
cares_query_last_ok_ = ok;
}

inline bool Environment::cares_is_servers_default() {
return cares_is_servers_default_;
}

inline void Environment::set_cares_is_servers_default(bool is_default) {
cares_is_servers_default_ = is_default;
}

inline node_ares_task_list* Environment::cares_task_list() {
return &cares_task_list_;
}
Expand Down
6 changes: 6 additions & 0 deletions src/env.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -437,6 +437,10 @@ class Environment {
inline uv_timer_t* cares_timer_handle();
inline ares_channel cares_channel();
inline ares_channel* cares_channel_ptr();
inline bool cares_query_last_ok();
inline void set_cares_query_last_ok(bool ok);
inline bool cares_is_servers_default();
inline void set_cares_is_servers_default(bool is_default);
inline node_ares_task_list* cares_task_list();

inline bool using_domains() const;
Expand Down Expand Up @@ -555,6 +559,8 @@ class Environment {
const uint64_t timer_base_;
uv_timer_t cares_timer_handle_;
ares_channel cares_channel_;
bool cares_query_last_ok_;
bool cares_is_servers_default_;
node_ares_task_list cares_task_list_;
bool using_domains_;
bool printed_error_;
Expand Down

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