ipv4 and ipv6 resolution working

IPv4 and IPv6 name resolution working.
Unit tests written (and passing).
net_node.{h,inl} code modified to use DNS seeds.

src/common/dns_utils.cpp

@@ -27,29 +27,110 @@
 // THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "common/dns_utils.h"
+#include <ldns/rr.h> // for RR type and class defs
+#include <unbound.h>
+#include <arpa/inet.h> // for inet_ntoa (bytes to text for IPs)
 
 namespace tools
 {
-namespace dns
+
+struct DNSResolverData
 {
+  ub_ctx* m_ub_context;
+};
 
-  std::vector<std::string> get_ipv4(const std::string& uri)
+DNSResolver::DNSResolver() : m_data(new DNSResolverData())
+{
+  // init libunbound context
+  m_data->m_ub_context = ub_ctx_create();
+
+  // look for "/etc/resolv.conf" and "/etc/hosts" or platform equivalent
+  ub_ctx_resolvconf(m_data->m_ub_context, "");
+  ub_ctx_hosts(m_data->m_ub_context, "");
+}
+
+DNSResolver::~DNSResolver()
+{
+  if (m_data)
   {
-    std::vector<std::string retval;
-    return retval;
+    if (m_data->m_ub_context != NULL)
+    {
+      ub_ctx_delete(m_data->m_ub_context);
+    }
+    delete m_data;
+  }
+}
+
+std::vector<std::string> DNSResolver::get_ipv4(const std::string& url)
+{
+  ub_result* result = NULL;
+  std::vector<std::string> retval;
+
+  // call DNS resolver, blocking.  if return value not zero, something went wrong
+  if (!ub_resolve(m_data->m_ub_context, url.c_str(), LDNS_RR_TYPE_A, LDNS_RR_CLASS_IN, &result))
+  {
+    if (result->havedata)
+    {
+      for (int i=0; result->data[i] != NULL; i++)
+      {
+        char as_str[INET_ADDRSTRLEN];
+
+        // convert bytes to string, append if no error
+        if (inet_ntop(AF_INET, result->data[0], as_str, sizeof(as_str)))
+        {
+          retval.push_back(as_str);
+        }
+      }
+    }
   }
 
-  std::vector<std::string> get_ipv6(const std::string& uri)
-  {
-    std::vector<std::string retval;
+  // cleanup
+  ub_resolve_free(result);
   return retval;
+}
+
+std::vector<std::string> DNSResolver::get_ipv6(const std::string& url)
+{
+  ub_result* result = NULL;
+  std::vector<std::string> retval;
+
+  // call DNS resolver, blocking.  if return value not zero, something went wrong
+  if (!ub_resolve(m_data->m_ub_context, url.c_str(), LDNS_RR_TYPE_AAAA, LDNS_RR_CLASS_IN, &result))
+  {
+    if (result->havedata)
+    {
+      for (int i=0; result->data[i] != NULL; i++)
+      {
+        char as_str[INET6_ADDRSTRLEN];
+
+        // convert bytes to string, append if no error
+        if (inet_ntop(AF_INET6, result->data[0], as_str, sizeof(as_str)))
+        {
+          retval.push_back(as_str);
+        }
+      }
+    }
   }
 
-  std::string get_payment_address(const std::string& uri)
-  {
+  // cleanup
+  ub_resolve_free(result);
+  return retval;
+}
+
+std::string DNSResolver::get_payment_address(const std::string& url)
+{
   std::string retval;
   return retval;
-  }
+}
+
+DNSResolver& DNSResolver::instance()
+{
+  static DNSResolver* staticInstance = NULL;
+  if (staticInstance == NULL)
+  {
+    staticInstance = new DNSResolver();
+  }
+  return *staticInstance;
+}
 
-}  // namespace dns
 }  // namespace tools

src/common/dns_utils.h

@@ -32,6 +32,8 @@
 namespace tools
 {
 
+struct DNSResolverData;
+
 /**
  * @brief Provides high-level access to DNS resolution
  *
@@ -44,43 +46,64 @@ class DNSResolver
 public:
 
   /**
-   * @brief Constructs and sets the URI to be resolved
+   * @brief Constructs an instance of DNSResolver
    *
-   * @param uri the URI to be resolved
+   * Constructs a class instance and does setup stuff for the backend resolver.
    */
-  DNSResolver(const std::string& uri);
+  DNSResolver();
 
   /**
-   * @brief gets ipv4 addresses from DNS query
+   * @brief takes care of freeing C pointers and such
+   */
+  ~DNSResolver();
+
+  /**
+   * @brief gets ipv4 addresses from DNS query of a URL
    *
-   * returns a vector of all IPv4 "A" records for given URI.
+   * returns a vector of all IPv4 "A" records for given URL.
    * If no "A" records found, returns an empty vector.
    *
+   * @param url A string containing a URL to query for
+   *
    * @return vector of strings containing ipv4 addresses
    */
-  std::vector<std::string> get_ipv4();
+  std::vector<std::string> get_ipv4(const std::string& url);
 
   /**
    * @brief gets ipv6 addresses from DNS query
    *
-   * returns a vector of all IPv6 "A" records for given URI.
+   * returns a vector of all IPv6 "A" records for given URL.
    * If no "A" records found, returns an empty vector.
    *
+   * @param url A string containing a URL to query for
+   *
    * @return vector of strings containing ipv6 addresses
    */
-  std::vector<std::string> get_ipv6();
+   std::vector<std::string> get_ipv6(const std::string& url);
 
   /**
    * @brief gets a monero address from the TXT record of the DNS query response
    *
-   * returns a monero address string from the TXT record associated with URI
+   * returns a monero address string from the TXT record associated with URL
    * if no TXT record present, or no valid monero address in TXT,
    * returns an empty string.
    *
+   * @param url A string containing a URL to query for
+   *
    * @return 
    */
-  std::string get_payment_address();
+  std::string get_payment_address(const std::string& url);
 
+  /**
+   * @brief Gets the singleton instance of DNSResolver
+   *
+   * @return returns a pointer to the singleton
+   */
+  static DNSResolver& instance();
+
+private:
+
+  DNSResolverData *m_data;
 }; // class DNSResolver
 
 }  // namespace tools

src/p2p/net_node.h

@@ -112,6 +112,13 @@ namespace nodetool
     size_t get_outgoing_connections_count();
     peerlist_manager& get_peerlist_manager(){return m_peerlist;}
   private:
+    const std::vector<std::string> m_seed_nodes_list =
+    { "seeds.moneroseeds.se"
+    , "seeds.moneroseeds.ae.org"
+    , "seeds.moneroseeds.ch"
+    , "seeds.moneroseeds.li"
+    };
+
     typedef COMMAND_REQUEST_STAT_INFO_T<typename t_payload_net_handler::stat_info> COMMAND_REQUEST_STAT_INFO;
 
     CHAIN_LEVIN_INVOKE_MAP2(p2p_connection_context); //move levin_commands_handler interface invoke(...) callbacks into invoke map

src/p2p/net_node.inl

@@ -244,6 +244,21 @@ namespace nodetool
       add_hardcoded_seed_node(m_seed_nodes, "107.152.130.98:28080");
     }
     else
+    {
+      // for each hostname in the seed nodes list, attempt to DNS resolve and
+      // add the result addresses as seed nodes
+      // TODO: at some point add IPv6 support, but that won't be relevant
+      // for some time yet.
+      for (const std::string& addr_str : m_seed_nodes_list)
+      {
+        std::vector<std::string> addr_list = tools::DNSResolver::instance().get_ipv4(addr_str);
+        for (const std::string& a : addr_list)
+        {
+          append_net_address(m_seed_nodes, a + ":18080");
+        }
+      }
+
+      if (!m_seed_nodes.size())
       {
         add_hardcoded_seed_node(m_seed_nodes, "62.210.78.186:18080");
         add_hardcoded_seed_node(m_seed_nodes, "195.12.60.154:18080");
@@ -257,6 +272,7 @@ namespace nodetool
         add_hardcoded_seed_node(m_seed_nodes, "107.158.233.98:18080");
         add_hardcoded_seed_node(m_seed_nodes, "64.22.111.2:18080");
       }
+    }
 
     bool res = handle_command_line(vm, testnet);
     CHECK_AND_ASSERT_MES(res, false, "Failed to handle command line");

tests/unit_tests/dns_resolver.cpp

@@ -0,0 +1,65 @@
+#include "gtest/gtest.h"
+
+#include "common/dns_utils.h"
+
+TEST(DNSResolver, IPv4Success)
+{
+  tools::DNSResolver resolver;
+
+  auto ips = resolver.get_ipv4("example.com");
+
+  ASSERT_EQ(1, ips.size());
+
+  ASSERT_STREQ("93.184.216.119", ips[0].c_str());
+
+  ips = tools::DNSResolver::instance().get_ipv4("example.com");
+
+  ASSERT_EQ(1, ips.size());
+
+  ASSERT_STREQ("93.184.216.119", ips[0].c_str());
+}
+
+TEST(DNSResolver, IPv4Failure)
+{
+  // guaranteed by IANA/ICANN/RFC to be invalid
+  tools::DNSResolver resolver;
+
+  auto ips = resolver.get_ipv4("example.invalid");
+
+  ASSERT_EQ(0, ips.size());
+
+  ips = tools::DNSResolver::instance().get_ipv4("example.invalid");
+
+  ASSERT_EQ(0, ips.size());
+}
+
+TEST(DNSResolver, IPv6Success)
+{
+  tools::DNSResolver resolver;
+
+  auto ips = resolver.get_ipv6("example.com");
+
+  ASSERT_EQ(1, ips.size());
+
+  ASSERT_STREQ("2606:2800:220:6d:26bf:1447:1097:aa7", ips[0].c_str());
+
+  ips = tools::DNSResolver::instance().get_ipv6("example.com");
+
+  ASSERT_EQ(1, ips.size());
+
+  ASSERT_STREQ("2606:2800:220:6d:26bf:1447:1097:aa7", ips[0].c_str());
+}
+
+TEST(DNSResolver, IPv6Failure)
+{
+  // guaranteed by IANA/ICANN/RFC to be invalid
+  tools::DNSResolver resolver;
+
+  auto ips = resolver.get_ipv6("example.invalid");
+
+  ASSERT_EQ(0, ips.size());
+
+  ips = tools::DNSResolver::instance().get_ipv6("example.invalid");
+
+  ASSERT_EQ(0, ips.size());
+}