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Hardening the DNSClient code

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- add a timeout to avoid deadlock without a dns server
- test against existing terrasync.flightgear.org RR's
This commit is contained in:
Torsten Dreyer
2016-05-02 16:21:42 +02:00
parent 06f888d38c
commit 6b31646d61
3 changed files with 164 additions and 86 deletions
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107
simgear/io/DNSClient.cxx
View File

@@ -31,23 +31,25 @@ namespace DNS {
class Client::ClientPrivate {
public:
ClientPrivate() {
if (dns_init(NULL, 0) < 0)
SG_LOG(SG_IO, SG_ALERT, "Can't init udns library" );
ClientPrivate() {
if (dns_init(NULL, 0) < 0)
SG_LOG(SG_IO, SG_ALERT, "Can't init udns library" );
if( dns_open(NULL) < 0 )
SG_LOG(SG_IO, SG_ALERT, "Can't open udns context" );
}
if( dns_open(NULL) < 0 )
SG_LOG(SG_IO, SG_ALERT, "Can't open udns context" );
}
~ClientPrivate() {
dns_close(NULL);
}
~ClientPrivate() {
dns_close(NULL);
}
};
Request::Request( const std::string & dn ) :
_dn(dn),
_type(DNS_T_ANY),
_complete(false)
_dn(dn),
_type(DNS_T_ANY),
_complete(false),
_timeout_secs(5),
_start(0)
{
}
@@ -55,40 +57,61 @@ Request::~Request()
{
}
NAPTRRequest::NAPTRRequest( const std::string & dn ) :
Request(dn)
bool Request::isTimeout() const
{
_type = DNS_T_NAPTR;
return (time(NULL) - _start) > _timeout_secs;
}
NAPTRRequest::NAPTRRequest( const std::string & dn ) :
Request(dn)
{
_type = DNS_T_NAPTR;
}
static bool sortNAPTR( const NAPTRRequest::NAPTR_ptr a, const NAPTRRequest::NAPTR_ptr b )
{
if( a->order > b->order ) return false;
if( a->order < b->order ) return true;
return a->preference < b->preference;
}
static void dnscbNAPTR(struct dns_ctx *ctx, struct dns_rr_naptr *result, void *data)
{
NAPTRRequest * r = static_cast<NAPTRRequest*>(data);
if (result) {
r->cname = result->dnsnaptr_cname;
r->qname = result->dnsnaptr_qname;
r->ttl = result->dnsnaptr_ttl;
for (int i = 0; i < result->dnsnaptr_nrr; i++) {
NAPTRRequest::NAPTR_ptr naptr(new NAPTRRequest::NAPTR);
r->entries.push_back(naptr);
naptr->order = result->dnsnaptr_naptr[i].order;
naptr->preference = result->dnsnaptr_naptr[i].preference;
naptr->flags = result->dnsnaptr_naptr[i].flags;
naptr->service = result->dnsnaptr_naptr[i].service;
naptr->regexp = result->dnsnaptr_naptr[i].regexp;
naptr->replacement = result->dnsnaptr_naptr[i].replacement;
}
free(result);
}
r->setComplete();
NAPTRRequest * r = static_cast<NAPTRRequest*>(data);
if (result) {
r->cname = result->dnsnaptr_cname;
r->qname = result->dnsnaptr_qname;
r->ttl = result->dnsnaptr_ttl;
for (int i = 0; i < result->dnsnaptr_nrr; i++) {
if( !r->qservice.empty() && r->qservice != result->dnsnaptr_naptr[i].service )
return;
//TODO: case ignore and result flags may have more than one flag
if( !r->qflags.empty() && r->qflags != result->dnsnaptr_naptr[i].flags )
return;
NAPTRRequest::NAPTR_ptr naptr(new NAPTRRequest::NAPTR);
r->entries.push_back(naptr);
naptr->order = result->dnsnaptr_naptr[i].order;
naptr->preference = result->dnsnaptr_naptr[i].preference;
naptr->flags = result->dnsnaptr_naptr[i].flags;
naptr->service = result->dnsnaptr_naptr[i].service;
naptr->regexp = result->dnsnaptr_naptr[i].regexp;
naptr->replacement = result->dnsnaptr_naptr[i].replacement;
}
std::sort( r->entries.begin(), r->entries.end(), sortNAPTR );
free(result);
}
r->setComplete();
}
void NAPTRRequest::submit()
{
if (!dns_submit_naptr(NULL, getDn().c_str(), 0, dnscbNAPTR, this )) {
SG_LOG(SG_IO, SG_ALERT, "Can't submit dns request for " << getDn());
return;
}
if (!dns_submit_naptr(NULL, getDn().c_str(), 0, dnscbNAPTR, this )) {
SG_LOG(SG_IO, SG_ALERT, "Can't submit dns request for " << getDn());
return;
}
_start = time(NULL);
}
@@ -97,21 +120,21 @@ Client::~Client()
}
Client::Client() :
d(new ClientPrivate)
d(new ClientPrivate)
{
}
void Client::makeRequest(const Request_ptr& r)
{
r->submit();
r->submit();
}
void Client::update(int waitTimeout)
{
time_t now = time(NULL);
if( dns_timeouts( NULL, waitTimeout, now ) < 0 )
return;
time_t now = time(NULL);
if( dns_timeouts( NULL, waitTimeout, now ) < 0 )
return;
dns_ioevent(NULL, now);
}

59
simgear/io/DNSClient.hxx
View File

@@ -39,40 +39,47 @@ namespace DNS
class Request : public SGReferenced
{
public:
Request( const std::string & dn );
virtual ~Request();
std::string getDn() const { return _dn; }
int getType() const { return _type; }
bool complete() const { return _complete; }
void setComplete( bool b = true ) { _complete = b; }
Request( const std::string & dn );
virtual ~Request();
std::string getDn() const { return _dn; }
int getType() const { return _type; }
bool isComplete() const { return _complete; }
bool isTimeout() const;
void setComplete( bool b = true ) { _complete = b; }
virtual void submit() = 0;
virtual void submit() = 0;
std::string cname;
std::string qname;
unsigned ttl;
protected:
std::string _dn;
int _type;
bool _complete;
std::string _dn;
int _type;
bool _complete;
time_t _timeout_secs;
time_t _start;
};
class NAPTRRequest : public Request
{
public:
NAPTRRequest( const std::string & dn );
virtual void submit();
NAPTRRequest( const std::string & dn );
virtual void submit();
struct NAPTR : SGReferenced {
int order;
int preference;
std::string flags;
std::string service;
std::string regexp;
std::string replacement;
};
typedef SGSharedPtr<NAPTR> NAPTR_ptr;
typedef std::vector<NAPTR_ptr> NAPTR_list;
std::string cname;
std::string qname;
unsigned ttl;
NAPTR_list entries;
struct NAPTR : SGReferenced {
int order;
int preference;
std::string flags;
std::string service;
std::string regexp;
std::string replacement;
};
typedef SGSharedPtr<NAPTR> NAPTR_ptr;
typedef std::vector<NAPTR_ptr> NAPTR_list;
NAPTR_list entries;
std::string qflags;
std::string qservice;
};
typedef SGSharedPtr<Request> Request_ptr;

84
simgear/io/test_DNS.cxx
View File

@@ -14,6 +14,7 @@
#include "test_DNS.hxx"
#include <simgear/debug/logstream.hxx>
#include <simgear/misc/strutils.hxx>
using std::cout;
using std::cerr;
@@ -34,33 +35,80 @@ int main(int argc, char* argv[])
sglog().setLogLevels( SG_ALL, SG_DEBUG );
DNS::Client cl;
#define EXISTING_RECORD "terrasync.flightgear.org"
// test existing NAPTR
// fgtest.t3r.de. 600 IN NAPTR 999 99 "U" "test" "!^.*$!http://dnstest.flightgear.org/!" .
// fgtest.t3r.de. 600 IN NAPTR 999 99 "U" "test" "!^.*$!http://dnstest.flightgear.org/!" .
{
DNS::NAPTRRequest * naptrRequest = new DNS::NAPTRRequest("fgtest.t3r.de");
DNS::Request_ptr r(naptrRequest);
cl.makeRequest(r);
while( !r->complete() )
cl.update(0);
DNS::NAPTRRequest * naptrRequest = new DNS::NAPTRRequest(EXISTING_RECORD);
DNS::Request_ptr r(naptrRequest);
cl.makeRequest(r);
while( !r->isComplete() && !r->isTimeout()) {
usleep(200000);
cl.update(0);
}
COMPARE(naptrRequest->entries.size(), 1 );
COMPARE(naptrRequest->entries[0]->order, 999 );
COMPARE(naptrRequest->entries[0]->preference, 99 );
COMPARE(naptrRequest->entries[0]->service, "test" );
COMPARE(naptrRequest->entries[0]->regexp, "!^.*$!http://dnstest.flightgear.org/!" );
COMPARE(naptrRequest->entries[0]->replacement, "" );
if( r->isTimeout() ) {
cerr << "timeout testing existing record " EXISTING_RECORD << endl;
return EXIT_FAILURE;
}
if(naptrRequest->entries.empty()) {
cerr << "no results for " EXISTING_RECORD << endl;
return EXIT_FAILURE;
}
// test for ascending preference/order
int order = -1, preference = -1;
for( DNS::NAPTRRequest::NAPTR_list::const_iterator it = naptrRequest->entries.begin(); it != naptrRequest->entries.end(); ++it ) {
// currently only support "U" which implies empty replacement
COMPARE((*it)->flags, "U" );
COMPARE(naptrRequest->entries[0]->replacement, "" );
// currently only support ws20
COMPARE((*it)->service, "ws20" );
if( (*it)->order < order ) {
cerr << "NAPTR entries not ascending for field 'order'" << endl;
return EXIT_FAILURE;
} else if( (*it)->order > order ) {
order = (*it)->order;
preference = (*it)->preference;
} else {
if( (*it)->preference < preference ) {
cerr << "NAPTR entries not ascending for field 'preference', order=" << order << endl;
return EXIT_FAILURE;
}
preference = (*it)->preference;
}
if( false == simgear::strutils::starts_with( (*it)->regexp, "!^.*$!" ) ) {
cerr << "NAPTR entry with unsupported regexp: " << (*it)->regexp << endl;
return EXIT_FAILURE;
}
if( false == simgear::strutils::ends_with( (*it)->regexp, "!" ) ) {
cerr << "NAPTR entry with unsupported regexp: " << (*it)->regexp << endl;
return EXIT_FAILURE;
}
}
}
// test non-existing NAPTR
{
DNS::NAPTRRequest * naptrRequest = new DNS::NAPTRRequest("jurkxkqdiufqzpfvzqok.prozhqrlcaavbxifkkhf");
DNS::Request_ptr r(naptrRequest);
cl.makeRequest(r);
while( !r->complete() )
cl.update(0);
DNS::NAPTRRequest * naptrRequest = new DNS::NAPTRRequest("jurkxkqdiufqzpfvzqok.prozhqrlcaavbxifkkhf");
DNS::Request_ptr r(naptrRequest);
cl.makeRequest(r);
while( !r->isComplete() && !r->isTimeout()) {
usleep(200000);
cl.update(0);
}
COMPARE(naptrRequest->entries.size(), 0 );
if( r->isTimeout() ) {
cerr << "timeout testing non-existing record." << endl;
return EXIT_FAILURE;
}
COMPARE(naptrRequest->entries.size(), 0 );
}
cout << "all tests passed ok" << endl;