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-rw-r--r--src/network/resolver.cpp281
1 files changed, 281 insertions, 0 deletions
diff --git a/src/network/resolver.cpp b/src/network/resolver.cpp
new file mode 100644
index 0000000..db7fb32
--- /dev/null
+++ b/src/network/resolver.cpp
@@ -0,0 +1,281 @@
+#include <network/dns_handler.hpp>
+#include <utils/timed_events.hpp>
+#include <network/resolver.hpp>
+#include <string.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#ifdef UDNS_FOUND
+# include <udns.h>
+#endif
+
+#include <fstream>
+#include <cstdlib>
+#include <sstream>
+#include <chrono>
+#include <map>
+
+using namespace std::string_literals;
+
+#ifdef UDNS_FOUND
+static std::map<int, std::string> dns_error_messages {
+ {DNS_E_TEMPFAIL, "Timeout while contacting DNS servers"},
+ {DNS_E_PROTOCOL, "Misformatted DNS reply"},
+ {DNS_E_NXDOMAIN, "Domain name not found"},
+ {DNS_E_NOMEM, "Out of memory"},
+ {DNS_E_BADQUERY, "Misformatted domain name"}
+};
+#endif
+
+Resolver::Resolver():
+#ifdef UDNS_FOUND
+ resolved4(false),
+ resolved6(false),
+ resolving(false),
+ 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;
+#ifdef UDNS_FOUND
+ this->port = port;
+#endif
+
+ this->start_resolving(hostname, port);
+}
+
+int Resolver::call_getaddrinfo(const char *name, const char* port, int flags)
+{
+ struct addrinfo hints;
+ memset(&hints, 0, sizeof(struct addrinfo));
+ hints.ai_flags = flags;
+ hints.ai_family = AF_UNSPEC;
+ hints.ai_socktype = SOCK_STREAM;
+ hints.ai_protocol = 0;
+
+ struct addrinfo* addr_res = nullptr;
+ const int res = ::getaddrinfo(name, port,
+ &hints, &addr_res);
+
+ if (res == 0 && addr_res)
+ {
+ if (!this->addr)
+ this->addr.reset(addr_res);
+ else
+ { // Append this result at the end of the linked list
+ struct addrinfo *rp = this->addr.get();
+ while (rp->ai_next)
+ rp = rp->ai_next;
+ rp->ai_next = addr_res;
+ }
+ }
+
+ return res;
+}
+
+#ifdef UDNS_FOUND
+void Resolver::start_resolving(const std::string& hostname, const std::string& port)
+{
+ this->resolving = true;
+ this->resolved = false;
+ this->resolved4 = false;
+ this->resolved6 = false;
+
+ this->error_msg.clear();
+ this->addr.reset(nullptr);
+
+ // We first try to use it as an IP address directly. We tell getaddrinfo
+ // to NOT use any DNS resolution.
+ if (this->call_getaddrinfo(hostname.data(), port.data(), AI_NUMERICHOST) == 0)
+ {
+ this->on_resolved();
+ return;
+ }
+
+ // Then we look into /etc/hosts to translate the given hostname
+ const auto hosts = this->look_in_etc_hosts(hostname);
+ if (!hosts.empty())
+ {
+ for (const auto &host: hosts)
+ this->call_getaddrinfo(host.data(), port.data(), AI_NUMERICHOST);
+ this->on_resolved();
+ return;
+ }
+
+ // And finally, we try a DNS resolution
+ auto hostname6_resolved = [](dns_ctx*, dns_rr_a6* result, void* data)
+ {
+ Resolver* resolver = static_cast<Resolver*>(data);
+ resolver->on_hostname6_resolved(result);
+ resolver->after_resolved();
+ std::free(result);
+ };
+
+ auto hostname4_resolved = [](dns_ctx*, dns_rr_a4* result, void* data)
+ {
+ Resolver* resolver = static_cast<Resolver*>(data);
+ resolver->on_hostname4_resolved(result);
+ resolver->after_resolved();
+ std::free(result);
+ };
+
+ DNSHandler::watch();
+ auto res = dns_submit_a4(nullptr, hostname.data(), 0, hostname4_resolved, this);
+ if (!res)
+ this->on_hostname4_resolved(nullptr);
+ res = dns_submit_a6(nullptr, hostname.data(), 0, hostname6_resolved, this);
+ if (!res)
+ this->on_hostname6_resolved(nullptr);
+
+ this->start_timer();
+}
+
+void Resolver::start_timer()
+{
+ const auto timeout = dns_timeouts(nullptr, -1, 0);
+ if (timeout < 0)
+ return;
+ TimedEvent event(std::chrono::steady_clock::now() + std::chrono::seconds(timeout), [this]() { this->start_timer(); }, "DNS");
+ TimedEventsManager::instance().add_event(std::move(event));
+}
+
+std::vector<std::string> Resolver::look_in_etc_hosts(const std::string &hostname)
+{
+ std::ifstream hosts("/etc/hosts");
+ std::string line;
+
+ std::vector<std::string> results;
+ while (std::getline(hosts, line))
+ {
+ if (line.empty())
+ continue;
+
+ std::string ip;
+ std::istringstream line_stream(line);
+ line_stream >> ip;
+ if (ip.empty() || ip[0] == '#')
+ continue;
+
+ std::string host;
+ while (line_stream >> host && !host.empty() && host[0] != '#')
+ {
+ if (hostname == host)
+ {
+ results.push_back(ip);
+ break;
+ }
+ }
+ }
+ return results;
+}
+
+void Resolver::on_hostname4_resolved(dns_rr_a4 *result)
+{
+ this->resolved4 = true;
+
+ const auto status = dns_status(nullptr);
+
+ if (status >= 0 && result)
+ {
+ char buf[INET6_ADDRSTRLEN];
+
+ for (auto i = 0; i < result->dnsa4_nrr; ++i)
+ {
+ inet_ntop(AF_INET, &result->dnsa4_addr[i], buf, sizeof(buf));
+ this->call_getaddrinfo(buf, this->port.data(), AI_NUMERICHOST);
+ }
+ }
+ else
+ {
+ const auto error = dns_error_messages.find(status);
+ if (error != end(dns_error_messages))
+ this->error_msg = error->second;
+ }
+}
+
+void Resolver::on_hostname6_resolved(dns_rr_a6 *result)
+{
+ this->resolved6 = true;
+
+ const auto status = dns_status(nullptr);
+
+ if (status >= 0 && result)
+ {
+ char buf[INET6_ADDRSTRLEN];
+ for (auto i = 0; i < result->dnsa6_nrr; ++i)
+ {
+ inet_ntop(AF_INET6, &result->dnsa6_addr[i], buf, sizeof(buf));
+ this->call_getaddrinfo(buf, this->port.data(), AI_NUMERICHOST);
+ }
+ }
+}
+
+void Resolver::after_resolved()
+{
+ if (dns_active(nullptr) == 0)
+ DNSHandler::unwatch();
+
+ if (this->resolved6 && this->resolved4)
+ this->on_resolved();
+}
+
+void Resolver::on_resolved()
+{
+ this->resolved = true;
+ this->resolving = false;
+ if (!this->addr)
+ {
+ if (this->error_cb)
+ this->error_cb(this->error_msg.data());
+ }
+ else
+ {
+ if (this->success_cb)
+ this->success_cb(this->addr.get());
+ }
+}
+
+#else // ifdef UDNS_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);
+
+ const auto res = this->call_getaddrinfo(hostname.data(), port.data(), 0);
+
+ this->resolved = true;
+
+ if (res != 0)
+ {
+ this->error_msg = gai_strerror(res);
+ if (this->error_cb)
+ this->error_cb(this->error_msg.data());
+ }
+ else
+ {
+ if (this->success_cb)
+ this->success_cb(this->addr.get());
+ }
+}
+#endif // ifdef UDNS_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 {};
+}