Separate the DNS resolution logic from the TCP communication logic

fix #3137

louloulibs/network/dns_handler.cpp

@@ -2,7 +2,6 @@
 #ifdef CARES_FOUND
 
 #include <network/dns_socket_handler.hpp>
-#include <network/tcp_socket_handler.hpp>
 #include <network/dns_handler.hpp>
 #include <network/poller.hpp>
 
@@ -14,19 +13,6 @@
 DNSHandler DNSHandler::instance;
 
 using namespace std::string_literals;
-
-void on_hostname4_resolved(void* arg, int status, int, struct hostent* hostent)
-{
-  TCPSocketHandler* socket_handler = static_cast<TCPSocketHandler*>(arg);
-  socket_handler->on_hostname4_resolved(status, hostent);
-}
-
-void on_hostname6_resolved(void* arg, int status, int, struct hostent* hostent)
-{
-  TCPSocketHandler* socket_handler = static_cast<TCPSocketHandler*>(arg);
-  socket_handler->on_hostname6_resolved(status, hostent);
-}
-
 DNSHandler::DNSHandler()
 {
   int ares_error;
@@ -54,16 +40,15 @@ void DNSHandler::destroy()
   ::ares_library_cleanup();
 }
 
-void DNSHandler::gethostbyname(const std::string& name,
+void DNSHandler::gethostbyname(const std::string& name, ares_host_callback callback,
-                               TCPSocketHandler* socket_handler, int family)
+                               void* data, int family)
 {
-  socket_handler->free_cares_addrinfo();
   if (family == AF_INET)
     ::ares_gethostbyname(this->channel, name.data(), family,
-                         &::on_hostname4_resolved, socket_handler);
+                         callback, data);
   else
     ::ares_gethostbyname(this->channel, name.data(), family,
-                         &::on_hostname6_resolved, socket_handler);
+                         callback, data);
 }
 
 void DNSHandler::watch_dns_sockets(std::shared_ptr<Poller>& poller)

louloulibs/network/dns_handler.hpp

@@ -13,9 +13,6 @@ class DNSSocketHandler;
 # include <string>
 # include <vector>
 
-void on_hostname4_resolved(void* arg, int status, int, struct hostent* hostent);
-void on_hostname6_resolved(void* arg, int status, int, struct hostent* hostent);
-
 /**
  * Class managing DNS resolution.  It should only be statically instanciated
  * once in SocketHandler.  It manages ares channel and calls various
@@ -27,8 +24,8 @@ class DNSHandler
 public:
   DNSHandler();
   ~DNSHandler() = default;
-  void gethostbyname(const std::string& name, TCPSocketHandler* socket_handler,
+  void gethostbyname(const std::string& name, ares_host_callback callback,
-                     int family);
+                     void* socket_handler, int family);
   /**
    * Call ares_fds to know what fd needs to be watched by the poller, create
    * or destroy DNSSocketHandlers depending on the result.

louloulibs/network/resolver.cpp

@@ -0,0 +1,219 @@
+#include <network/dns_handler.hpp>
+#include <network/resolver.hpp>
+#include <string.h>
+#include <arpa/inet.h>
+
+// remove me
+#include <iostream>
+
+using namespace std::string_literals;
+
+Resolver::Resolver():
+#ifdef CARES_FOUND
+  resolved4(false),
+  resolved6(false),
+  resolving(false),
+  cares_addrinfo(nullptr),
+  port{},
+#endif
+  resolved(false),
+  error_msg{}
+{
+}
+
+void Resolver::resolve(const std::string& hostname, const std::string& port,
+                       SuccessCallbackType success_cb, ErrorCallbackType error_cb)
+{
+  this->error_cb = error_cb;
+  this->success_cb = success_cb;
+  this->port = port;
+
+  this->start_resolving(hostname, port);
+}
+
+#ifdef CARES_FOUND
+void Resolver::start_resolving(const std::string& hostname, const std::string& port)
+{
+  std::cout << "start_resolving: " << hostname << port << std::endl;
+  this->resolving = true;
+  this->resolved = false;
+  this->resolved4 = false;
+  this->resolved6 = false;
+
+  this->error_msg.clear();
+  this->cares_addrinfo = nullptr;
+
+  auto hostname4_resolved = [](void* arg, int status, int,
+                                  struct hostent* hostent)
+    {
+      Resolver* resolver = static_cast<Resolver*>(arg);
+      resolver->on_hostname4_resolved(status, hostent);
+    };
+  auto hostname6_resolved = [](void* arg, int status, int,
+                                  struct hostent* hostent)
+    {
+      Resolver* resolver = static_cast<Resolver*>(arg);
+      resolver->on_hostname6_resolved(status, hostent);
+    };
+
+  DNSHandler::instance.gethostbyname(hostname, hostname6_resolved,
+                                     this, AF_INET6);
+  DNSHandler::instance.gethostbyname(hostname, hostname4_resolved,
+                                     this, AF_INET);
+}
+
+void Resolver::on_hostname4_resolved(int status, struct hostent* hostent)
+{
+  this->resolved4 = true;
+  if (status == ARES_SUCCESS)
+    this->fill_ares_addrinfo4(hostent);
+  else
+    this->error_msg = ::ares_strerror(status);
+
+  if (this->resolved4 && this->resolved6)
+    this->on_resolved();
+}
+
+void Resolver::on_hostname6_resolved(int status, struct hostent* hostent)
+{
+  this->resolved6 = true;
+  if (status == ARES_SUCCESS)
+    this->fill_ares_addrinfo6(hostent);
+  else
+    this->error_msg = ::ares_strerror(status);
+
+  if (this->resolved4 && this->resolved6)
+    this->on_resolved();
+}
+
+void Resolver::on_resolved()
+{
+  this->resolved = true;
+  this->resolving = false;
+  if (!this->cares_addrinfo)
+    {
+      if (this->error_cb)
+        this->error_cb(this->error_msg.data());
+    }
+  else
+    {
+      this->addr.reset(this->cares_addrinfo);
+      if (this->success_cb)
+        this->success_cb(this->addr.get());
+    }
+}
+
+void Resolver::fill_ares_addrinfo4(const struct hostent* hostent)
+{
+  std::cout << "fill_ares_addrinfo4" << this->port << std::endl;
+  struct addrinfo* prev = this->cares_addrinfo;
+  struct in_addr** address = reinterpret_cast<struct in_addr**>(hostent->h_addr_list);
+
+  while (*address)
+    {
+      // Create a new addrinfo list element, and fill it
+      struct addrinfo* current = new struct addrinfo;
+      current->ai_flags = 0;
+      current->ai_family = hostent->h_addrtype;
+      current->ai_socktype = SOCK_STREAM;
+      current->ai_protocol = 0;
+      current->ai_addrlen = sizeof(struct sockaddr_in);
+
+      struct sockaddr_in* addr = new struct sockaddr_in;
+      addr->sin_family = hostent->h_addrtype;
+      addr->sin_port = htons(strtoul(this->port.data(), nullptr, 10));
+      addr->sin_addr.s_addr = (*address)->s_addr;
+
+      current->ai_addr = reinterpret_cast<struct sockaddr*>(addr);
+      current->ai_next = nullptr;
+      current->ai_canonname = nullptr;
+
+      current->ai_next = prev;
+      this->cares_addrinfo = current;
+      prev = current;
+      ++address;
+    }
+}
+
+void Resolver::fill_ares_addrinfo6(const struct hostent* hostent)
+{
+  std::cout << "fill_ares_addrinfo6" << this->port << std::endl;
+  struct addrinfo* prev = this->cares_addrinfo;
+  struct in6_addr** address = reinterpret_cast<struct in6_addr**>(hostent->h_addr_list);
+
+  while (*address)
+    {
+      // Create a new addrinfo list element, and fill it
+      struct addrinfo* current = new struct addrinfo;
+      current->ai_flags = 0;
+      current->ai_family = hostent->h_addrtype;
+      current->ai_socktype = SOCK_STREAM;
+      current->ai_protocol = 0;
+      current->ai_addrlen = sizeof(struct sockaddr_in6);
+
+      struct sockaddr_in6* addr = new struct sockaddr_in6;
+      addr->sin6_family = hostent->h_addrtype;
+      addr->sin6_port = htons(strtoul(this->port.data(), nullptr, 10));
+      ::memcpy(addr->sin6_addr.s6_addr, (*address)->s6_addr, 16);
+      addr->sin6_flowinfo = 0;
+      addr->sin6_scope_id = 0;
+
+      current->ai_addr = reinterpret_cast<struct sockaddr*>(addr);
+      current->ai_next = nullptr;
+      current->ai_canonname = nullptr;
+
+      current->ai_next = prev;
+      this->cares_addrinfo = current;
+      prev = current;
+      ++address;
+    }
+}
+
+#else  // ifdef CARES_FOUND
+
+void Resolver::start_resolving(const std::string& hostname, const std::string& port)
+{
+  // If the resolution fails, the addr will be unset
+  this->addr.reset(nullptr);
+
+  struct addrinfo hints;
+  memset(&hints, 0, sizeof(struct addrinfo));
+  hints.ai_flags = 0;
+  hints.ai_family = AF_UNSPEC;
+  hints.ai_socktype = SOCK_STREAM;
+  hints.ai_protocol = 0;
+
+  struct addrinfo* addr_res = nullptr;
+  const int res = ::getaddrinfo(hostname.data(), port.data(),
+                                &hints, &addr_res);
+
+  this->resolved = true;
+
+  if (res != 0)
+    {
+      this->error_msg = gai_strerror(res);
+      if (this->error_cb)
+        this->error_cb(this->error_msg.data());
+    }
+  else
+    {
+      this->addr.reset(addr_res);
+      if (this->success_cb)
+        this->success_cb(this->addr.get());
+    }
+}
+#endif  // ifdef CARES_FOUND
+
+std::string addr_to_string(const struct addrinfo* rp)
+{
+  char buf[INET6_ADDRSTRLEN];
+  if (rp->ai_family == AF_INET)
+    return ::inet_ntop(rp->ai_family,
+                       &reinterpret_cast<sockaddr_in*>(rp->ai_addr)->sin_addr,
+                       buf, sizeof(buf));
+  else if (rp->ai_family == AF_INET6)
+    return ::inet_ntop(rp->ai_family,
+                       &reinterpret_cast<sockaddr_in6*>(rp->ai_addr)->sin6_addr,
+                       buf, sizeof(buf));
+  return {};
+}

louloulibs/network/resolver.hpp

@@ -0,0 +1,129 @@
+#ifndef RESOLVER_HPP_INCLUDED
+#define RESOLVER_HPP_INCLUDED
+
+#include "louloulibs.h"
+
+#include <functional>
+#include <memory>
+#include <string>
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+
+struct AddrinfoDeleter
+{
+  void operator()(struct addrinfo* addr)
+  {
+#ifdef CARES_FOUND
+    while (addr)
+      {
+        delete addr->ai_addr;
+        auto next = addr->ai_next;
+        delete addr;
+        addr = next;
+      }
+#else
+    freeaddrinfo(addr);
+#endif
+  }
+};
+
+class Resolver
+{
+public:
+  using ErrorCallbackType = std::function<void(const char*)>;
+  using SuccessCallbackType = std::function<void(const struct addrinfo*)>;
+
+  Resolver();
+  ~Resolver() = default;
+
+  bool is_resolving() const
+  {
+#ifdef CARES_FOUND
+    return this->resolving;
+#else
+    return false;
+#endif
+  }
+
+  bool is_resolved() const
+  {
+    return this->resolved;
+  }
+
+  const auto& get_result() const
+  {
+    return this->addr;
+  }
+  std::string get_error_message() const
+  {
+    return this->error_msg;
+  }
+
+  void clear()
+  {
+#ifdef CARES_FOUND
+    this->resolved6 = false;
+    this->resolved4 = false;
+#endif
+    this->resolved = false;
+    this->resolving = false;
+    this->addr.reset();
+    this->cares_addrinfo = nullptr;
+    this->port.clear();
+    this->error_msg.clear();
+  }
+
+  void resolve(const std::string& hostname, const std::string& port,
+               SuccessCallbackType success_cb, ErrorCallbackType error_cb);
+
+private:
+  void start_resolving(const std::string& hostname, const std::string& port);
+#ifdef CARES_FOUND
+  void on_hostname4_resolved(int status, struct hostent* hostent);
+  void on_hostname6_resolved(int status, struct hostent* hostent);
+
+  void fill_ares_addrinfo4(const struct hostent* hostent);
+  void fill_ares_addrinfo6(const struct hostent* hostent);
+
+  void on_resolved();
+
+  bool resolved4;
+  bool resolved6;
+
+  bool resolving;
+
+  /**
+   * When using c-ares to resolve the host asynchronously, we need the
+   * c-ares callbacks to fill a structure (a struct addrinfo, for
+   * compatibility with getaddrinfo and the rest of the code that works when
+   * c-ares is not used) with all returned values (for example an IPv6 and
+   * an IPv4). The pointer is given to the unique_ptr to manage its lifetime.
+   */
+  struct addrinfo* cares_addrinfo;
+  std::string port;
+
+#endif
+ /**
+  * Tells if we finished the resolution process. It doesn't indicate if it
+  * was successful (it is true even if the result is an error).
+  */
+  bool resolved;
+  std::string error_msg;
+
+
+  std::unique_ptr<struct addrinfo, AddrinfoDeleter> addr;
+
+  ErrorCallbackType error_cb;
+  SuccessCallbackType success_cb;
+
+  Resolver(const Resolver&) = delete;
+  Resolver(Resolver&&) = delete;
+  Resolver& operator=(const Resolver&) = delete;
+  Resolver& operator=(Resolver&&) = delete;
+};
+
+std::string addr_to_string(const struct addrinfo* rp);
+
+#endif /* RESOLVER_HPP_INCLUDED */

louloulibs/network/tcp_socket_handler.cpp

@@ -11,13 +11,9 @@
 #include <stdexcept>
 #include <unistd.h>
 #include <errno.h>
-#include <netdb.h>
 #include <cstring>
 #include <fcntl.h>
 
-#include <iostream>
-#include <arpa/inet.h>
-
 #ifdef BOTAN_FOUND
 # include <botan/hex.h>
 # include <botan/tls_exceptn.h>
@@ -43,24 +39,9 @@ TCPSocketHandler::TCPSocketHandler(std::shared_ptr<Poller> poller):
   use_tls(false),
   connected(false),
   connecting(false),
-#ifdef CARES_FOUND
-  resolving(false),
-  resolved(false),
-  resolved4(false),
-  resolved6(false),
-  cares_addrinfo(nullptr),
-  cares_error(),
-#endif
   hostname_resolution_failed(false)
 {}
 
-TCPSocketHandler::~TCPSocketHandler()
-{
-#ifdef CARES_FOUND
-  this->free_cares_addrinfo();
-#endif
-}
-
 void TCPSocketHandler::init_socket(const struct addrinfo* rp)
 {
   if ((this->socket = ::socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol)) == -1)
@@ -91,17 +72,24 @@ void TCPSocketHandler::connect(const std::string& address, const std::string& po
     {
       // Get the addrinfo from getaddrinfo (or ares_gethostbyname), only if
       // this is the first call of this function.
-#ifdef CARES_FOUND
+      if (!this->resolver.is_resolved())
-      if (!this->resolved)
         {
           log_info("Trying to connect to " << address << ":" << port);
           // Start the asynchronous process of resolving the hostname. Once
           // the addresses have been found and `resolved` has been set to true
           // (but connecting will still be false), TCPSocketHandler::connect()
           // needs to be called, again.
-          this->resolving = true;
+          this->resolver.resolve(address, port,
-          DNSHandler::instance.gethostbyname(address, this, AF_INET6);
+                                 [this](const struct addrinfo*)
-          DNSHandler::instance.gethostbyname(address, this, AF_INET);
+                                 {
+                                   log_debug("Resolution success, calling connect() again");
+                                   this->connect();
+                                 },
+                                 [this](const char*)
+                                 {
+                                   log_debug("Resolution failed, calling connect() again");
+                                   this->connect();
+                                 });
           return;
         }
       else
@@ -109,39 +97,16 @@ void TCPSocketHandler::connect(const std::string& address, const std::string& po
           // The c-ares resolved the hostname and the available addresses
           // where saved in the cares_addrinfo linked list. Now, just use
           // this list to try to connect.
-          addr_res = this->cares_addrinfo;
+          addr_res = this->resolver.get_result().get();
           if (!addr_res)
             {
               this->hostname_resolution_failed = true;
-              const auto msg = this->cares_error;
+              const auto msg = this->resolver.get_error_message();
               this->close();
               this->on_connection_failed(msg);
               return ;
             }
         }
-#else
-      log_info("Trying to connect to " << address << ":" << port);
-      struct addrinfo hints;
-      memset(&hints, 0, sizeof(struct addrinfo));
-      hints.ai_flags = 0;
-      hints.ai_family = AF_UNSPEC;
-      hints.ai_socktype = SOCK_STREAM;
-      hints.ai_protocol = 0;
-
-      const int res = ::getaddrinfo(address.c_str(), port.c_str(), &hints, &addr_res);
-
-      if (res != 0)
-        {
-          log_warning("getaddrinfo failed: "s + gai_strerror(res));
-          this->hostname_resolution_failed = true;
-          this->close();
-          this->on_connection_failed(gai_strerror(res));
-          return ;
-        }
-      // Make sure the alloced structure is always freed at the end of the
-      // function
-      sg.add_callback([&addr_res](){ freeaddrinfo(addr_res); });
-#endif
     }
   else
     { // This function is called again, use the saved addrinfo structure,
@@ -335,30 +300,18 @@ void TCPSocketHandler::close()
     }
   this->connected = false;
   this->connecting = false;
-#ifdef CARES_FOUND
-  this->resolving = false;
-  this->resolved = false;
-  this->resolved4 = false;
-  this->resolved6 = false;
-  this->free_cares_addrinfo();
-  this->cares_error.clear();
-#endif
   this->in_buf.clear();
   this->out_buf.clear();
   this->port.clear();
+  this->resolver.clear();
 }
 
 void TCPSocketHandler::display_resolved_ip(struct addrinfo* rp) const
 {
-  char buf[INET6_ADDRSTRLEN];
   if (rp->ai_family == AF_INET)
-    log_debug("Connecting to IP address " << ::inet_ntop(rp->ai_family,
+    log_debug("Trying IPv4 address " << addr_to_string(rp));
-              &reinterpret_cast<sockaddr_in*>(rp->ai_addr)->sin_addr,
-                                                         buf, sizeof(buf)));
   else if (rp->ai_family == AF_INET6)
-    log_debug("Connecting to IPv6 address " << ::inet_ntop(rp->ai_family,
+    log_debug("Trying IPv6 address " << addr_to_string(rp));
-              &reinterpret_cast<sockaddr_in6*>(rp->ai_addr)->sin6_addr,
-                                                           buf, sizeof(buf)));
 }
 
 void TCPSocketHandler::send_data(std::string&& data)
@@ -399,11 +352,7 @@ bool TCPSocketHandler::is_connected() const
 
 bool TCPSocketHandler::is_connecting() const
 {
-#ifdef CARES_FOUND
+  return this->connecting || this->resolver.is_resolving();
-  return this->connecting || this->resolving;
-#else
-  return this->connecting;
-#endif
 }
 
 void* TCPSocketHandler::get_receive_buffer(const size_t) const
@@ -514,114 +463,3 @@ void Permissive_Credentials_Manager::verify_certificate_chain(const std::string&
 }
 
 #endif // BOTAN_FOUND
-
-#ifdef CARES_FOUND
-
-void TCPSocketHandler::on_hostname4_resolved(int status, struct hostent* hostent)
-{
-  this->resolved4 = true;
-  if (status == ARES_SUCCESS)
-    this->fill_ares_addrinfo4(hostent);
-  else
-    this->cares_error = ::ares_strerror(status);
-
-  if (this->resolved4 && this->resolved6)
-    {
-      this->resolved = true;
-      this->resolving = false;
-      this->connect();
-    }
-}
-
-void TCPSocketHandler::on_hostname6_resolved(int status, struct hostent* hostent)
-{
-  this->resolved6 = true;
-  if (status == ARES_SUCCESS)
-    this->fill_ares_addrinfo6(hostent);
-  else
-    this->cares_error = ::ares_strerror(status);
-
-  if (this->resolved4 && this->resolved6)
-    {
-      this->resolved = true;
-      this->resolving = false;
-      this->connect();
-    }
-}
-
-void TCPSocketHandler::fill_ares_addrinfo4(const struct hostent* hostent)
-{
-  struct addrinfo* prev = this->cares_addrinfo;
-  struct in_addr** address = reinterpret_cast<struct in_addr**>(hostent->h_addr_list);
-
-  while (*address)
-    {
-       // Create a new addrinfo list element, and fill it
-      struct addrinfo* current = new struct addrinfo;
-      current->ai_flags = 0;
-      current->ai_family = hostent->h_addrtype;
-      current->ai_socktype = SOCK_STREAM;
-      current->ai_protocol = 0;
-      current->ai_addrlen = sizeof(struct sockaddr_in);
-
-      struct sockaddr_in* addr = new struct sockaddr_in;
-      addr->sin_family = hostent->h_addrtype;
-      addr->sin_port = htons(strtoul(this->port.data(), nullptr, 10));
-      addr->sin_addr.s_addr = (*address)->s_addr;
-
-      current->ai_addr = reinterpret_cast<struct sockaddr*>(addr);
-      current->ai_next = nullptr;
-      current->ai_canonname = nullptr;
-
-      current->ai_next = prev;
-      this->cares_addrinfo = current;
-      prev = current;
-      ++address;
-    }
-}
-
-void TCPSocketHandler::fill_ares_addrinfo6(const struct hostent* hostent)
-{
-  struct addrinfo* prev = this->cares_addrinfo;
-  struct in6_addr** address = reinterpret_cast<struct in6_addr**>(hostent->h_addr_list);
-
-  while (*address)
-    {
-       // Create a new addrinfo list element, and fill it
-      struct addrinfo* current = new struct addrinfo;
-      current->ai_flags = 0;
-      current->ai_family = hostent->h_addrtype;
-      current->ai_socktype = SOCK_STREAM;
-      current->ai_protocol = 0;
-      current->ai_addrlen = sizeof(struct sockaddr_in6);
-
-      struct sockaddr_in6* addr = new struct sockaddr_in6;
-      addr->sin6_family = hostent->h_addrtype;
-      addr->sin6_port = htons(strtoul(this->port.data(), nullptr, 10));
-      ::memcpy(addr->sin6_addr.s6_addr, (*address)->s6_addr, 16);
-      addr->sin6_flowinfo = 0;
-      addr->sin6_scope_id = 0;
-
-      current->ai_addr = reinterpret_cast<struct sockaddr*>(addr);
-      current->ai_next = nullptr;
-      current->ai_canonname = nullptr;
-
-      current->ai_next = prev;
-      this->cares_addrinfo = current;
-      prev = current;
-      ++address;
-    }
-}
-
-void TCPSocketHandler::free_cares_addrinfo()
-{
-  while (this->cares_addrinfo)
-    {
-      delete this->cares_addrinfo->ai_addr;
-      auto next = this->cares_addrinfo->ai_next;
-      delete this->cares_addrinfo;
-      this->cares_addrinfo = next;
-    }
-}
-
-#endif  // CARES_FOUND

louloulibs/network/tcp_socket_handler.hpp

@@ -2,6 +2,7 @@
 # define SOCKET_HANDLER_INCLUDED
 
 #include <network/socket_handler.hpp>
+#include <network/resolver.hpp>
 
 #include <sys/types.h>
 #include <sys/socket.h>
@@ -14,10 +15,6 @@
 
 #include "louloulibs.h"
 
-#ifdef CARES_FOUND
-# include <ares.h>
-#endif
-
 #ifdef BOTAN_FOUND
 # include <botan/botan.h>
 # include <botan/tls_client.h>
@@ -43,7 +40,7 @@ public:
 class TCPSocketHandler: public SocketHandler
 {
 protected:
-  ~TCPSocketHandler();
+  ~TCPSocketHandler() = default;
 
 public:
   explicit TCPSocketHandler(std::shared_ptr<Poller> poller);
@@ -109,16 +106,6 @@ public:
   bool is_connected() const override final;
   bool is_connecting() const;
 
-#ifdef CARES_FOUND
-  void on_hostname4_resolved(int status, struct hostent* hostent);
-  void on_hostname6_resolved(int status, struct hostent* hostent);
-
-  void free_cares_addrinfo();
-
-  void fill_ares_addrinfo4(const struct hostent* hostent);
-  void fill_ares_addrinfo6(const struct hostent* hostent);
-#endif
-
 private:
   /**
    * Initialize the socket with the parameters contained in the given
@@ -194,9 +181,13 @@ private:
    */
   std::list<std::string> out_buf;
   /**
-   * Keep the details of the addrinfo that triggered a EINPROGRESS error when
+   * DNS resolver
-   * connect()ing to it, to reuse it directly when connect() is called
+   */
-   * again.
+  Resolver resolver;
+  /**
+   * Keep the details of the addrinfo returned by the resolver that
+   * triggered a EINPROGRESS error when connect()ing to it, to reuse it
+   * directly when connect() is called again.
    */
   struct addrinfo addrinfo;
   struct sockaddr_in6 ai_addr;
@@ -234,28 +225,6 @@ protected:
   bool connected;
   bool connecting;
 
-#ifdef CARES_FOUND
-  bool resolving;
-  /**
-   * Whether or not the DNS resolution was successfully done
-   */
-  bool resolved;
-  bool resolved4;
-  bool resolved6;
-  /**
-   * When using c-ares to resolve the host asynchronously, we need the
-   * c-ares callback to fill a structure (a struct addrinfo, for
-   * compatibility with getaddrinfo and the rest of the code that works when
-   * c-ares is not used) with all returned values (for example an IPv6 and
-   * an IPv4). The next call of connect() will then try all these values
-   * (exactly like we do with the result of getaddrinfo) and save the one
-   * that worked (or returned EINPROGRESS) in the other struct addrinfo (see
-   * the members addrinfo, ai_addrlen, and ai_addr).
-   */
-  struct addrinfo* cares_addrinfo;
-  std::string cares_error;
-#endif  // CARES_FOUND
-
   bool hostname_resolution_failed;
 
 private:

src/test.cpp

@@ -3,10 +3,13 @@
  */
 
 #include <xmpp/xmpp_component.hpp>
+#include <network/dns_handler.hpp>
 #include <utils/timed_events.hpp>
 #include <database/database.hpp>
 #include <xmpp/xmpp_parser.hpp>
+#include <network/resolver.hpp>
 #include <utils/encoding.hpp>
+#include <network/poller.hpp>
 #include <logger/logger.hpp>
 #include <config/config.hpp>
 #include <bridge/colors.hpp>
@@ -462,7 +465,84 @@ int main()
     res = xdg_data_path("bonjour.txt");
     std::cout << res << std::endl;
     assert(res == "/datadir/biboumi/bonjour.txt");
+  }
 
+
+  {
+    std::cout << color << "Testing the DNS resolver…" << reset << std::endl;
+
+    Resolver resolver;
+
+    /**
+     * If we are using cares, we need to run a poller loop until each
+     * resolution is finished. Without cares we get the result before
+     * resolve() returns because it’s blocking.
+     */
+#ifdef CARES_FOUND
+    auto p = std::make_shared<Poller>();
+
+    const auto loop = [&p]()
+      {
+        do
+          {
+            DNSHandler::instance.watch_dns_sockets(p);
+          }
+        while (p->poll(utils::no_timeout) != -1);
+      };
+#else
+    // We don’t need to do anything if we are not using cares.
+    const auto loop = [](){};
+#endif
+
+    std::string hostname;
+    std::string port = "6667";
+
+    bool success = true;
+
+    auto error_cb = [&success, &hostname, &port](const char* msg)
+      {
+        std::cout << "Failed to resolve " << hostname << ":" << port << ": " << msg << std::endl;
+        success = false;
+      };
+    auto success_cb = [&success, &hostname, &port](const struct addrinfo* addr)
+      {
+        std::cout << "Successfully resolved " << hostname << ":" << port << ": " << addr_to_string(addr) << std::endl;
+        success = true;
+      };
+
+    hostname = "example.com";
+    resolver.resolve(hostname, port,
+                     success_cb, error_cb);
+    loop();
+    assert(success);
+
+    hostname = "this.should.fail.because.it.is..misformatted";
+    resolver.resolve(hostname, port,
+                     success_cb, error_cb);
+    loop();
+    assert(!success);
+
+    hostname = "this.should.fail.because.it.is.does.not.exist.invalid";
+    resolver.resolve(hostname, port,
+                     success_cb, error_cb);
+    loop();
+    assert(!success);
+
+    hostname = "localhost6";
+    resolver.resolve(hostname, port,
+                     success_cb, error_cb);
+    loop();
+    assert(success);
+
+    hostname = "localhost";
+    resolver.resolve(hostname, port,
+                     success_cb, error_cb);
+    loop();
+    assert(success);
+
+#ifdef CARES_FOUND
+    DNSHandler::instance.destroy();
+#endif
   }
 
   return 0;