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DNSClient: own requests, and cancel them on timeout

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Fixes crashes where a request times-out, but then is completed by
UDN sometime afterwards, with a free-d object. Have the DNS::Client own
requests, and be able to retrieve the udns_query to cancel them, in 
the timeout case.

Fixes a couple of Sentry reports.
This commit is contained in:
James Turner 2020-11-04 22:31:43 +00:00
parent 49484d5e86
commit 7f0a83388d
2 changed files with 99 additions and 51 deletions
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132
simgear/io/DNSClient.cxx
View File

@ -61,6 +61,10 @@ public:
struct dns_ctx * ctx; struct dns_ctx * ctx;
static size_t instanceCounter; static size_t instanceCounter;
using RequestVec = std::vector<Request_ptr>;
RequestVec _activeRequests;
}; };
size_t Client::ClientPrivate::instanceCounter = 0; size_t Client::ClientPrivate::instanceCounter = 0;
@ -78,6 +82,11 @@ Request::~Request()
{ {
} }
void Request::cancel()
{
_cancelled = true;
}
bool Request::isTimeout() const bool Request::isTimeout() const
{ {
return (time(NULL) - _start) > _timeout_secs; return (time(NULL) - _start) > _timeout_secs;
@ -114,18 +123,20 @@ static void dnscbSRV(struct dns_ctx *ctx, struct dns_rr_srv *result, void *data)
{ {
SRVRequest * r = static_cast<SRVRequest*>(data); SRVRequest * r = static_cast<SRVRequest*>(data);
if (result) { if (result) {
r->cname = result->dnssrv_cname; if (!r->isCancelled()) {
r->qname = result->dnssrv_qname; r->cname = result->dnssrv_cname;
r->ttl = result->dnssrv_ttl; r->qname = result->dnssrv_qname;
for (int i = 0; i < result->dnssrv_nrr; i++) { r->ttl = result->dnssrv_ttl;
SRVRequest::SRV_ptr srv(new SRVRequest::SRV); for (int i = 0; i < result->dnssrv_nrr; i++) {
r->entries.push_back(srv); SRVRequest::SRV_ptr srv(new SRVRequest::SRV);
srv->priority = result->dnssrv_srv[i].priority; r->entries.push_back(srv);
srv->weight = result->dnssrv_srv[i].weight; srv->priority = result->dnssrv_srv[i].priority;
srv->port = result->dnssrv_srv[i].port; srv->weight = result->dnssrv_srv[i].weight;
srv->target = result->dnssrv_srv[i].name; srv->port = result->dnssrv_srv[i].port;
srv->target = result->dnssrv_srv[i].name;
}
std::sort(r->entries.begin(), r->entries.end(), sortSRV);
} }
std::sort( r->entries.begin(), r->entries.end(), sortSRV );
free(result); free(result);
} }
r->setComplete(); r->setComplete();
@ -134,11 +145,16 @@ static void dnscbSRV(struct dns_ctx *ctx, struct dns_rr_srv *result, void *data)
void SRVRequest::submit( Client * client ) void SRVRequest::submit( Client * client )
{ {
// if service is defined, pass service and protocol // if service is defined, pass service and protocol
if (!dns_submit_srv(client->d->ctx, getDn().c_str(), _service.empty() ? NULL : _service.c_str(), _service.empty() ? NULL : _protocol.c_str(), 0, dnscbSRV, this )) { auto q = dns_submit_srv(client->d->ctx, getDn().c_str(), _service.empty() ? NULL : _service.c_str(),
_service.empty() ? NULL : _protocol.c_str(),
0, dnscbSRV, this);
if (!q) {
SG_LOG(SG_IO, SG_ALERT, "Can't submit dns request for " << getDn()); SG_LOG(SG_IO, SG_ALERT, "Can't submit dns request for " << getDn());
return; return;
} }
_start = time(NULL); _start = time(NULL);
_query = q;
} }
TXTRequest::TXTRequest( const std::string & dn ) : TXTRequest::TXTRequest( const std::string & dn ) :
@ -151,22 +167,24 @@ static void dnscbTXT(struct dns_ctx *ctx, struct dns_rr_txt *result, void *data)
{ {
TXTRequest * r = static_cast<TXTRequest*>(data); TXTRequest * r = static_cast<TXTRequest*>(data);
if (result) { if (result) {
r->cname = result->dnstxt_cname; if (!r->isCancelled()) {
r->qname = result->dnstxt_qname; r->cname = result->dnstxt_cname;
r->ttl = result->dnstxt_ttl; r->qname = result->dnstxt_qname;
for (int i = 0; i < result->dnstxt_nrr; i++) { r->ttl = result->dnstxt_ttl;
//TODO: interprete the .len field of dnstxt_txt? for (int i = 0; i < result->dnstxt_nrr; i++) {
auto rawTxt = reinterpret_cast<char*>(result->dnstxt_txt[i].txt); //TODO: interprete the .len field of dnstxt_txt?
if (!rawTxt) { auto rawTxt = reinterpret_cast<char*>(result->dnstxt_txt[i].txt);
continue; if (!rawTxt) {
} continue;
}
const string txt{rawTxt}; const string txt{rawTxt};
r->entries.push_back(txt); r->entries.push_back(txt);
string_list tokens = simgear::strutils::split( txt, "=", 1 ); string_list tokens = simgear::strutils::split(txt, "=", 1);
if( tokens.size() == 2 ) { if (tokens.size() == 2) {
r->attributes[tokens[0]] = tokens[1]; r->attributes[tokens[0]] = tokens[1];
} }
}
} }
free(result); free(result);
} }
@ -176,11 +194,13 @@ static void dnscbTXT(struct dns_ctx *ctx, struct dns_rr_txt *result, void *data)
void TXTRequest::submit( Client * client ) void TXTRequest::submit( Client * client )
{ {
// protocol and service an already encoded in DN so pass in NULL for both // protocol and service an already encoded in DN so pass in NULL for both
if (!dns_submit_txt(client->d->ctx, getDn().c_str(), DNS_C_IN, 0, dnscbTXT, this )) { auto q = dns_submit_txt(client->d->ctx, getDn().c_str(), DNS_C_IN, 0, dnscbTXT, this);
if (!q) {
SG_LOG(SG_IO, SG_ALERT, "Can't submit dns request for " << getDn()); SG_LOG(SG_IO, SG_ALERT, "Can't submit dns request for " << getDn());
return; return;
} }
_start = time(NULL); _start = time(NULL);
_query = q;
} }
@ -195,27 +215,29 @@ static void dnscbNAPTR(struct dns_ctx *ctx, struct dns_rr_naptr *result, void *d
{ {
NAPTRRequest * r = static_cast<NAPTRRequest*>(data); NAPTRRequest * r = static_cast<NAPTRRequest*>(data);
if (result) { if (result) {
r->cname = result->dnsnaptr_cname; if (!r->isCancelled()) {
r->qname = result->dnsnaptr_qname; r->cname = result->dnsnaptr_cname;
r->ttl = result->dnsnaptr_ttl; r->qname = result->dnsnaptr_qname;
for (int i = 0; i < result->dnsnaptr_nrr; i++) { r->ttl = result->dnsnaptr_ttl;
if( !r->qservice.empty() && r->qservice != result->dnsnaptr_naptr[i].service ) for (int i = 0; i < result->dnsnaptr_nrr; i++) {
continue; if (!r->qservice.empty() && r->qservice != result->dnsnaptr_naptr[i].service)
continue;
//TODO: case ignore and result flags may have more than one flag //TODO: case ignore and result flags may have more than one flag
if( !r->qflags.empty() && r->qflags != result->dnsnaptr_naptr[i].flags ) if (!r->qflags.empty() && r->qflags != result->dnsnaptr_naptr[i].flags)
continue; continue;
NAPTRRequest::NAPTR_ptr naptr(new NAPTRRequest::NAPTR); NAPTRRequest::NAPTR_ptr naptr(new NAPTRRequest::NAPTR);
r->entries.push_back(naptr); r->entries.push_back(naptr);
naptr->order = result->dnsnaptr_naptr[i].order; naptr->order = result->dnsnaptr_naptr[i].order;
naptr->preference = result->dnsnaptr_naptr[i].preference; naptr->preference = result->dnsnaptr_naptr[i].preference;
naptr->flags = result->dnsnaptr_naptr[i].flags; naptr->flags = result->dnsnaptr_naptr[i].flags;
naptr->service = result->dnsnaptr_naptr[i].service; naptr->service = result->dnsnaptr_naptr[i].service;
naptr->regexp = result->dnsnaptr_naptr[i].regexp; naptr->regexp = result->dnsnaptr_naptr[i].regexp;
naptr->replacement = result->dnsnaptr_naptr[i].replacement; naptr->replacement = result->dnsnaptr_naptr[i].replacement;
}
std::sort(r->entries.begin(), r->entries.end(), sortNAPTR);
} }
std::sort( r->entries.begin(), r->entries.end(), sortNAPTR );
free(result); free(result);
} }
r->setComplete(); r->setComplete();
@ -223,11 +245,13 @@ static void dnscbNAPTR(struct dns_ctx *ctx, struct dns_rr_naptr *result, void *d
void NAPTRRequest::submit( Client * client ) void NAPTRRequest::submit( Client * client )
{ {
if (!dns_submit_naptr(client->d->ctx, getDn().c_str(), 0, dnscbNAPTR, this )) { auto q = dns_submit_naptr(client->d->ctx, getDn().c_str(), 0, dnscbNAPTR, this);
if (!q) {
SG_LOG(SG_IO, SG_ALERT, "Can't submit dns request for " << getDn()); SG_LOG(SG_IO, SG_ALERT, "Can't submit dns request for " << getDn());
return; return;
} }
_start = time(NULL); _start = time(NULL);
_query = q;
} }
@ -242,6 +266,7 @@ Client::Client() :
void Client::makeRequest(const Request_ptr& r) void Client::makeRequest(const Request_ptr& r)
{ {
d->_activeRequests.push_back(r);
r->submit(this); r->submit(this);
} }
@ -252,6 +277,19 @@ void Client::update(int waitTimeout)
return; return;
dns_ioevent(d->ctx, now); dns_ioevent(d->ctx, now);
// drop our owning ref to completed requests,
// and cancel any which timed out
auto it = std::remove_if(d->_activeRequests.begin(), d->_activeRequests.end(),
[this](const Request_ptr& r) {
if (r->isTimeout()) {
dns_cancel(d->ctx, reinterpret_cast<struct dns_query*>(r->_query));
return true;
}
return r->isComplete();
});
d->_activeRequests.erase(it, d->_activeRequests.end());
} }
} // of namespace DNS } // of namespace DNS

18
simgear/io/DNSClient.hxx
View File

@ -40,28 +40,38 @@ namespace DNS
{ {
class Client; class Client;
using UDNSQueryPtr = void*;
class Request : public SGReferenced class Request : public SGReferenced
{ {
public: public:
Request( const std::string & dn ); Request( const std::string & dn );
virtual ~Request(); virtual ~Request();
std::string getDn() const { return _dn; } const std::string& getDn() const { return _dn; }
int getType() const { return _type; } int getType() const { return _type; }
bool isComplete() const { return _complete; } bool isComplete() const { return _complete; }
bool isTimeout() const; bool isTimeout() const;
void setComplete( bool b = true ) { _complete = b; } void setComplete( bool b = true ) { _complete = b; }
bool isCancelled() const { return _cancelled; }
virtual void submit( Client * client) = 0; virtual void submit( Client * client) = 0;
void cancel();
std::string cname; std::string cname;
std::string qname; std::string qname;
unsigned ttl; unsigned ttl;
protected: protected:
friend class Client;
UDNSQueryPtr _query = nullptr;
std::string _dn; std::string _dn;
int _type; int _type;
bool _complete; bool _complete;
time_t _timeout_secs; time_t _timeout_secs;
time_t _start; time_t _start;
bool _cancelled = false;
}; };
typedef SGSharedPtr<Request> Request_ptr; typedef SGSharedPtr<Request> Request_ptr;
@ -69,7 +79,7 @@ class NAPTRRequest : public Request
{ {
public: public:
NAPTRRequest( const std::string & dn ); NAPTRRequest( const std::string & dn );
virtual void submit( Client * client ); void submit(Client* client) override;
struct NAPTR : SGReferenced { struct NAPTR : SGReferenced {
int order; int order;
@ -92,7 +102,7 @@ class SRVRequest : public Request
public: public:
SRVRequest( const std::string & dn ); SRVRequest( const std::string & dn );
SRVRequest( const std::string & dn, const string & service, const string & protocol ); SRVRequest( const std::string & dn, const string & service, const string & protocol );
virtual void submit( Client * client ); void submit(Client* client) override;
struct SRV : SGReferenced { struct SRV : SGReferenced {
int priority; int priority;
@ -112,7 +122,7 @@ class TXTRequest : public Request
{ {
public: public:
TXTRequest( const std::string & dn ); TXTRequest( const std::string & dn );
virtual void submit( Client * client ); void submit(Client* client) override;
typedef std::vector<string> TXT_list; typedef std::vector<string> TXT_list;
typedef std::map<std::string,std::string> TXT_Attribute_map; typedef std::map<std::string,std::string> TXT_Attribute_map;