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,
-                               TCPSocketHandler* socket_handler, int family)
+void DNSHandler::gethostbyname(const std::string& name, ares_host_callback callback,
+                               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,
-                     int family);
+  void gethostbyname(const std::string& name, ares_host_callback callback,
+                     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

+#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

+#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->resolved)
+      if (!this->resolver.is_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;
-          DNSHandler::instance.gethostbyname(address, this, AF_INET6);
-          DNSHandler::instance.gethostbyname(address, this, AF_INET);
+          this->resolver.resolve(address, port,
+                                 [this](const struct addrinfo*)
+                                 {
+                                   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,
-              &reinterpret_cast<sockaddr_in*>(rp->ai_addr)->sin_addr,
-                                                         buf, sizeof(buf)));
+    log_debug("Trying IPv4 address " << addr_to_string(rp));
   else if (rp->ai_family == AF_INET6)
-    log_debug("Connecting to IPv6 address " << ::inet_ntop(rp->ai_family,
-              &reinterpret_cast<sockaddr_in6*>(rp->ai_addr)->sin6_addr,
-                                                           buf, sizeof(buf)));
+    log_debug("Trying IPv6 address " << addr_to_string(rp));
 }
 
 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->resolving;
-#else
-  return this->connecting;
-#endif
+  return this->connecting || this->resolver.is_resolving();
 }
 
 void* TCPSocketHandler::get_receive_buffer(const size_t) const
@@ -506,122 +455,11 @@ void TCPSocketHandler::on_tls_activated()
 }
 
 void Permissive_Credentials_Manager::verify_certificate_chain(const std::string& type,
-                                                const std::string& purported_hostname,
-                                                const std::vector<Botan::X509_Certificate>&)
+                                                              const std::string& purported_hostname,
+                                                              const std::vector<Botan::X509_Certificate>&)
 { // TODO: Offer the admin to disallow connection on untrusted
   // certificates
   log_debug("Checking remote certificate (" << type << ") for hostname " << purported_hostname);
 }
 
 #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;