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authorFlorent Le Coz <louiz@louiz.org>2014-07-09 13:02:37 +0200
committerFlorent Le Coz <louiz@louiz.org>2015-02-23 13:56:08 +0100
commitb86547dc1ef407ca3838444533bc7145e32a0d90 (patch)
tree3aa692def62796a5debe705ebc29d40b311e38cb /src/network/dns_handler.cpp
parenta17135720e77c03e66679852198e46a070d56f4d (diff)
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Implement async DNS resolution using c-ares
fix #2533
Diffstat (limited to 'src/network/dns_handler.cpp')
-rw-r--r--src/network/dns_handler.cpp112
1 files changed, 112 insertions, 0 deletions
diff --git a/src/network/dns_handler.cpp b/src/network/dns_handler.cpp
new file mode 100644
index 0000000..45bf626
--- /dev/null
+++ b/src/network/dns_handler.cpp
@@ -0,0 +1,112 @@
+#include <config.h>
+#ifdef CARES_FOUND
+
+#include <network/dns_socket_handler.hpp>
+#include <network/tcp_socket_handler.hpp>
+#include <network/dns_handler.hpp>
+#include <network/poller.hpp>
+
+#include <algorithm>
+#include <stdexcept>
+
+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;
+ if ((ares_error = ::ares_library_init(ARES_LIB_INIT_ALL)) != 0)
+ throw std::runtime_error("Failed to initialize c-ares lib: "s + ares_strerror(ares_error));
+ if ((ares_error = ::ares_init(&this->channel)) != ARES_SUCCESS)
+ throw std::runtime_error("Failed to initialize c-ares channel: "s + ares_strerror(ares_error));
+}
+
+ares_channel& DNSHandler::get_channel()
+{
+ return this->channel;
+}
+
+void DNSHandler::destroy()
+{
+ this->socket_handlers.clear();
+ ::ares_destroy(this->channel);
+ ::ares_library_cleanup();
+}
+
+void DNSHandler::gethostbyname(const std::string& name,
+ TCPSocketHandler* socket_handler, int family)
+{
+ socket_handler->free_cares_addrinfo();
+ if (family == AF_INET)
+ ::ares_gethostbyname(this->channel, name.data(), family,
+ &::on_hostname4_resolved, socket_handler);
+ else
+ ::ares_gethostbyname(this->channel, name.data(), family,
+ &::on_hostname6_resolved, socket_handler);
+}
+
+void DNSHandler::watch_dns_sockets(std::shared_ptr<Poller>& poller)
+{
+ fd_set readers;
+ fd_set writers;
+
+ FD_ZERO(&readers);
+ FD_ZERO(&writers);
+
+ int ndfs = ::ares_fds(this->channel, &readers, &writers);
+ // For each existing DNS socket, see if we are still supposed to watch it,
+ // if not then erase it
+ this->socket_handlers.erase(
+ std::remove_if(this->socket_handlers.begin(), this->socket_handlers.end(),
+ [&readers](const auto& dns_socket)
+ {
+ return !FD_ISSET(dns_socket->get_socket(), &readers);
+ }),
+ this->socket_handlers.end());
+
+ for (auto i = 0; i < ndfs; ++i)
+ {
+ bool read = FD_ISSET(i, &readers);
+ bool write = FD_ISSET(i, &writers);
+ // Look for the DNSSocketHandler with this fd
+ auto it = std::find_if(this->socket_handlers.begin(),
+ this->socket_handlers.end(),
+ [i](const auto& socket_handler)
+ {
+ return i == socket_handler->get_socket();
+ });
+ if (!read && !write) // No need to read or write to it
+ { // If found, erase it and stop watching it because it is not
+ // needed anymore
+ if (it != this->socket_handlers.end())
+ // The socket destructor removes it from the poller
+ this->socket_handlers.erase(it);
+ }
+ else // We need to write and/or read to it
+ { // If not found, create it because we need to watch it
+ if (it == this->socket_handlers.end())
+ {
+ this->socket_handlers.emplace_front(std::make_unique<DNSSocketHandler>(poller, i));
+ it = this->socket_handlers.begin();
+ }
+ poller->add_socket_handler(it->get());
+ if (write)
+ poller->watch_send_events(it->get());
+ }
+ }
+}
+
+#endif /* CARES_FOUND */