A class for performing asynchronous DNS lookups. More...

#include <AsyncDnsLookup.h>

Inheritance diagram for Async::DnsLookup:

Public Types
using	Type = DnsResourceRecord::Type

template<class RR >
using	RRList = std::vector<std::unique_ptr<RR>>

template<class RR >
using	SharedRRList = std::vector<std::shared_ptr<RR>>

Public Member Functions
	DnsLookup (void)
	Default Constructor.

	DnsLookup (const std::string &label, Type type=Type::A)
	Constructor.

	~DnsLookup (void)
	Destructor.

DnsLookup &	operator= (DnsLookup &&other)
	Move assignment operator.

void	setLookupParams (const std::string &label, Type type=Type::A)
	Prepare a lookup by setting up query parameters.

bool	lookup (const std::string &label, Type type=Type::A)
	Start a DNS lookup.

bool	lookup (void)
	Start a DNS lookup using previously configured parameters.

void	abort (void)
	Abort a pending lookup.

Type	type (void) const
	Return the type of lookup.

std::string	typeStr (void) const
	Return the type of lookup as a string.

const std::string &	label (void) const
	Return the associated label.

bool	isPending (void) const
	Check if a DNS lookup is pending.

bool	lookupFailed (void) const
	Check if the lookup failed.

bool	resultsAreReady (void) const
	Check if the DNS lookup is done or not.

bool	recordsValid (void) const
	Check if the cached records are valid.

bool	empty (void) const
	Check if the query returned any answers.

void	clear (void)
	Remove any cached DNS resource records.

void	addStaticResourceRecord (DnsResourceRecord *rr)
	Add a static resource record to the lookup result.

const RRList< DnsResourceRecord > &	staticResourceRecords (void) const
	Get all previously added static resource records.

std::vector< IpAddress >	addresses (void)
	Return the addresses for the host in the query.

DnsResourceRecord::List	resourceRecords (Type type=Type::ANY) const
	Return all matching resource records.

template<class RR >
void	resourceRecords (RRList< RR > &rrs) const
	Return resource records of a specific type.

template<class RR >
void	resourceRecords (SharedRRList< RR > &rrs) const

Public Attributes
sigc::signal< void, DnsLookup & >	resultsReady
	A signal to indicate that the query has been completed.

Detailed Description

A class for performing asynchronous DNS lookups.

Author: Tobias Blomberg

Date: 2003-04-12

Use this class to make DNS lookups. Right now it supports looking up A, PTR, CNAME and SRV records. An example usage can be seen below.

#include <iostream>
#include <AsyncCppApplication.h>
#include <AsyncDnsLookup.h>
 
using namespace Async;
 
class MyClass : public sigc::trackable
{
  public:
    MyClass(void)
    {
      dns.resultsReady.connect(mem_fun(*this, &MyClass::onResultsReady));
 
      dns.lookup("www.svxlink.org");
      //dns.lookup("www.svxlink.org", DnsLookup::Type::CNAME);
      //dns.lookup("185.199.110.153");
      //dns.lookup("185.199.110.153", DnsLookup::Type::PTR);
      //dns.lookup("153.110.199.185.in-addr.arpa.", DnsLookup::Type::PTR);
 
      //std::string srv = "_svxreflector._tcp.test.svxlink.org";
      //dns.addStaticResourceRecord(
      //    new DnsResourceRecordSRV(srv, 3600, 15, 10, 5304, "localhost."));
      //dns.lookup(srv, DnsLookup::Type::SRV);
 
      std::cout << "Starting " << dns.typeStr() << " record query for \""
                << dns.label() << "\"..." << std::endl;
    }
 
    void onResultsReady(DnsLookup& dns)
    {
      if (!dns.lookupFailed())
      {
          // Simple IP address lookup API
        std::cout << "IP addresses received:\n";
        for (auto& addr : dns.addresses())
        {
          std::cout << addr << std::endl;
        }
        std::cout << std::endl;
 
          // Access to all resource records
        std::cout << "All resource records received:\n";
        for (auto& rr : dns.resourceRecords())
        {
          std::cout << rr->toString() << std::endl;
        }
        std::cout << std::endl;
 
          // Access A records with full detail
        DnsResourceRecordA::List a_rrs;
        dns.resourceRecords(a_rrs);
        if (!a_rrs.empty())
        {
          std::cout << "A records received:\n";
          for (auto& rr : a_rrs)
          {
            std::cout << rr->name() << "\t" << rr->ttl() << "\t" << rr->ip()
                      << std::endl;
          }
          std::cout << std::endl;
        }
 
          // Access PTR records with full detail
        DnsResourceRecordPTR::List ptr_rrs;
        dns.resourceRecords(ptr_rrs);
        if (!ptr_rrs.empty())
        {
          std::cout << "PTR records received:\n";
          for (auto& rr : ptr_rrs)
          {
            std::cout << rr->name() << "\t" << rr->ttl() << "\t" << rr->dname()
                      << std::endl;
          }
          std::cout << std::endl;
        }
 
          // Access CNAME records with full detail
        DnsResourceRecordCNAME::List cname_rrs;
        dns.resourceRecords(cname_rrs);
        if (!cname_rrs.empty())
        {
          std::cout << "CNAME records received:\n";
          for (auto& rr : cname_rrs)
          {
            std::cout << rr->name() << "\t" << rr->ttl() << "\t" << rr->cname()
                      << std::endl;
          }
          std::cout << std::endl;
        }
 
          // Access SRV records with full detail
        DnsResourceRecordSRV::List srv_rrs;
        dns.resourceRecords(srv_rrs);
        if (!srv_rrs.empty())
        {
          std::cout << "SRV records received:\n";
          for (auto& rr : srv_rrs)
          {
            std::cout << rr->name() << "\t" << rr->ttl() << "\t" << rr->prio()
                      << " " << rr->weight() << " " << rr->port() << " "
                      << rr->target() << std::endl;
          }
        }
      }
      else
      {
        std::cout << "*** ERROR: The " << dns.typeStr()
                  << " record DNS lookup for " << dns.label()
                  << " failed" << std::endl;
      }
 
      Application::app().quit();
    }
 
  private:
    DnsLookup dns;
};
 
int main(int argc, char **argv)
{
  CppApplication app;
  MyClass dns;
  app.exec();
}

Examples: AsyncDnsLookup_demo.cpp.

Definition at line 122 of file AsyncDnsLookup.h.

Member Typedef Documentation

◆ RRList

template<class RR >

using Async::DnsLookup::RRList = std::vector<std::unique_ptr<RR>>

Definition at line 126 of file AsyncDnsLookup.h.

◆ SharedRRList

template<class RR >

using Async::DnsLookup::SharedRRList = std::vector<std::shared_ptr<RR>>

Definition at line 127 of file AsyncDnsLookup.h.

◆ Type

using Async::DnsLookup::Type = DnsResourceRecord::Type

Definition at line 125 of file AsyncDnsLookup.h.

Constructor & Destructor Documentation

◆ DnsLookup() [1/2]

Async::DnsLookup::DnsLookup ( void )

Default Constructor.

◆ DnsLookup() [2/2]

Async::DnsLookup::DnsLookup	(	const std::string &	label,
		Type	type = Type::A )

Constructor.

Parameters

label	The label (e.g. hostname) to lookup
type	What kind of resource record to look up

◆ ~DnsLookup()

Async::DnsLookup::~DnsLookup ( void )

Destructor.

Member Function Documentation

◆ abort()

void Async::DnsLookup::abort ( void )

Abort a pending lookup.

◆ addresses()

std::vector< IpAddress > Async::DnsLookup::addresses ( void )

Return the addresses for the host in the query.

Returns: Return a stl vector which contains all the addresses associated with the hostname in the query.

Precondition: The result is not available before the resultsReay signal has been emitted

Use this function to retrieve all the IP-addresses associated with the hostname in the query. Use the lookupFailed() function to find out if the query was successful or not.

The order of the hosts in the returned vector will be randomized on each call to this function.

Examples: AsyncDnsLookup_demo.cpp.

◆ addStaticResourceRecord()

void Async::DnsLookup::addStaticResourceRecord ( DnsResourceRecord * rr )

Add a static resource record to the lookup result.

Parameters

rr	The resource record to add

Use this function to add a static resource record to the DNS lookup result. Static resource records will be added to the looked up resource records before signalling that the results are ready, just as if they have been received from the DNS system. If the lookup label is empty when a lookup is initiated, no real lookup will be performed. Only static resource records will be returned in that case.

◆ clear()

void Async::DnsLookup::clear ( void )

Remove any cached DNS resource records.

◆ empty()

bool Async::DnsLookup::empty ( void ) const

inline

Check if the query returned any answers.

Returns: Return true if there are any answer records

Definition at line 252 of file AsyncDnsLookup.h.

◆ isPending()

bool Async::DnsLookup::isPending ( void ) const

Check if a DNS lookup is pending.

Returns: Return true if a DNS lookup is pending

Referenced by Async::TcpClientBase::isIdle().

◆ label()

const std::string & Async::DnsLookup::label ( void ) const

inline

Return the associated label.

Returns: Returns the label associated with this DNS lookup

Examples: AsyncDnsLookup_demo.cpp.

Definition at line 214 of file AsyncDnsLookup.h.

Referenced by Async::TcpClientBase::remoteHostName().

◆ lookup() [1/2]

bool Async::DnsLookup::lookup	(	const std::string &	label,
		Type	type = Type::A )

Start a DNS lookup.

Parameters

label	The label (e.g. hostname) to lookup
type	What kind of resource record to look up

Returns: Return true if the lookup process has been started

Use this function to start a DNS lookup. If a lookup is already running for the given label/type the lookup request will be ignored. If the label or type does not match a currently pending query, the pending query will be aborted. NOTE: This function may emit the resultsReady signal before returning.

◆ lookup() [2/2]

bool Async::DnsLookup::lookup ( void )

Start a DNS lookup using previously configured parameters.

Returns: Return true if the lookup process has been started

Use this function to start a DNS lookup using parameters previously configured. If a lookup is already running the request will be ignored. NOTE: This function may emit the resultsReady signal before returning.

◆ lookupFailed()

bool Async::DnsLookup::lookupFailed ( void ) const

Check if the lookup failed.

Returns: Returns true if the lookup failed in any way

Use this function to check if the DNS lookup completed without any errors. Even if the lookup is marked as failed it may still contain valid records.

Examples: AsyncDnsLookup_demo.cpp.

◆ operator=()

DnsLookup & Async::DnsLookup::operator= ( DnsLookup && other )

Move assignment operator.

Parameters

other The other object to move data from

Returns: Returns this object

◆ recordsValid()

bool Async::DnsLookup::recordsValid ( void ) const

Check if the cached records are valid.

Returns: Return true if all records in the cache is valid

This function is used to check if the cache contain resource records that are still valid. A cached record become invalid when the time-to-live, TTL, expires.

◆ resourceRecords() [1/3]

template<class RR >

void Async::DnsLookup::resourceRecords ( RRList< RR > & rrs ) const

inline

Return resource records of a specific type.

Parameters

rrs	Store RRs in this vector that match the RR type

Use this template function to get all resource records of a specific type. E.g.

std::vector<Async::DnsResourceRecordA> rrs; dns_lookup.resourceRecords(rrs);

That code will return only the A records.

Definition at line 326 of file AsyncDnsLookup.h.

◆ resourceRecords() [2/3]

template<class RR >

void Async::DnsLookup::resourceRecords ( SharedRRList< RR > & rrs ) const

inline

Definition at line 333 of file AsyncDnsLookup.h.

◆ resourceRecords() [3/3]

DnsResourceRecord::List Async::DnsLookup::resourceRecords ( Type type = Type::ANY ) const

inline

Return all matching resource records.

Returns: Returns all matching resource records in an stl vector

Use this function to return all resource records, that is of the given type, that the query resulted in. If no type is given the function will return all resource records.

Examples: AsyncDnsLookup_demo.cpp.

Definition at line 306 of file AsyncDnsLookup.h.

References type().

◆ resultsAreReady()

bool Async::DnsLookup::resultsAreReady ( void ) const

Check if the DNS lookup is done or not.

Returns: Returns true if results are ready or false if not

◆ setLookupParams()

void Async::DnsLookup::setLookupParams	(	const std::string &	label,
		Type	type = Type::A )

Prepare a lookup by setting up query parameters.

Parameters

label	The label (e.g. hostname) to lookup
type	What kind of resource record to look up

Returns: Return true if the lookup process has been started

Use this function to prepare a DNS lookup by setting up the query parameters. If the label or type does not match a currently pending query, the pending query will be aborted. To start a query, the lookup() function need to be called.

◆ staticResourceRecords()

const RRList< DnsResourceRecord > & Async::DnsLookup::staticResourceRecords ( void ) const

inline

Get all previously added static resource records.

Returns: Returns a vector of resource records

Definition at line 277 of file AsyncDnsLookup.h.

◆ type()

Type Async::DnsLookup::type ( void ) const

inline

Return the type of lookup.

Returns: Returns the lookup type

Definition at line 199 of file AsyncDnsLookup.h.

Referenced by resourceRecords(), and typeStr().

◆ typeStr()

std::string Async::DnsLookup::typeStr ( void ) const

inline

Return the type of lookup as a string.

Returns: Returns a string representation of the lookup type

Examples: AsyncDnsLookup_demo.cpp.

Definition at line 205 of file AsyncDnsLookup.h.

References type(), and Async::DnsResourceRecord::typeToString().

Member Data Documentation

◆ resultsReady

sigc::signal<void, DnsLookup&> Async::DnsLookup::resultsReady

A signal to indicate that the query has been completed.

Parameters

dns	A reference to the DNS object associated with the query

Definition at line 343 of file AsyncDnsLookup.h.

The documentation for this class was generated from the following file:

AsyncDnsLookup.h

Public Types

Public Member Functions

Public Attributes

Detailed Description

Member Typedef Documentation

◆ RRList

◆ SharedRRList

◆ Type

Constructor & Destructor Documentation

◆ DnsLookup() [1/2]

◆ DnsLookup() [2/2]

◆ ~DnsLookup()

Member Function Documentation

◆ abort()

◆ addresses()

◆ addStaticResourceRecord()

◆ clear()

◆ empty()

◆ isPending()

◆ label()

◆ lookup() [1/2]

◆ lookup() [2/2]

◆ lookupFailed()

◆ operator=()

◆ recordsValid()

◆ resourceRecords() [1/3]

◆ resourceRecords() [2/3]

◆ resourceRecords() [3/3]

◆ resultsAreReady()

◆ setLookupParams()

◆ staticResourceRecords()

◆ type()

◆ typeStr()

Member Data Documentation

◆ resultsReady