dns_utils: factor the fetching code for different DNS record types

src/common/dns_utils.cpp

@@ -100,8 +100,10 @@ namespace tools
 {
 
 // fuck it, I'm tired of dealing with getnameinfo()/inet_ntop/etc
-std::string ipv4_to_string(const char* src)
+std::string ipv4_to_string(const char* src, size_t len)
 {
+  assert(memchr(src, 0, len));
+
   std::stringstream ss;
   unsigned int bytes[4];
   for (int i = 0; i < 4; i++)
@@ -118,8 +120,10 @@ std::string ipv4_to_string(const char* src)
 
 // this obviously will need to change, but is here to reflect the above
 // stop-gap measure and to make the tests pass at least...
-std::string ipv6_to_string(const char* src)
+std::string ipv6_to_string(const char* src, size_t len)
 {
+  assert(memchr(src, 0, len));
+
   std::stringstream ss;
   unsigned int bytes[8];
   for (int i = 0; i < 8; i++)
@@ -138,6 +142,11 @@ std::string ipv6_to_string(const char* src)
   return ss.str();
 }
 
+std::string txt_to_string(const char* src, size_t len)
+{
+  return std::string(src+1, len-1);
+}
+
 // custom smart pointer.
 // TODO: see if std::auto_ptr and the like support custom destructors
 template<typename type, void (*freefunc)(type*)>
@@ -215,7 +224,7 @@ DNSResolver::~DNSResolver()
   }
 }
 
-std::vector<std::string> DNSResolver::get_ipv4(const std::string& url, bool& dnssec_available, bool& dnssec_valid)
+std::vector<std::string> DNSResolver::get_record(const std::string& url, int record_type, std::string (*reader)(const char *,size_t), bool& dnssec_available, bool& dnssec_valid)
 {
   std::vector<std::string> addresses;
   dnssec_available = false;
@@ -231,7 +240,7 @@ std::vector<std::string> DNSResolver::get_ipv4(const std::string& url, bool& dns
   ub_result_ptr result;
 
   // call DNS resolver, blocking.  if return value not zero, something went wrong
-  if (!ub_resolve(m_data->m_ub_context, urlC, DNS_TYPE_A, DNS_CLASS_IN, &result))
+  if (!ub_resolve(m_data->m_ub_context, urlC, record_type, DNS_CLASS_IN, &result))
   {
     dnssec_available = (result->secure || (!result->secure && result->bogus));
     dnssec_valid = result->secure && !result->bogus;
@@ -239,7 +248,7 @@ std::vector<std::string> DNSResolver::get_ipv4(const std::string& url, bool& dns
     {
       for (size_t i=0; result->data[i] != NULL; i++)
       {
-        addresses.push_back(ipv4_to_string(result->data[i]));
+        addresses.push_back((*reader)(result->data[i], result->len[i]));
       }
     }
   }
@@ -247,66 +256,19 @@ std::vector<std::string> DNSResolver::get_ipv4(const std::string& url, bool& dns
   return addresses;
 }
 
-std::vector<std::string> DNSResolver::get_ipv6(const std::string& url, bool& dnssec_available, bool& dnssec_valid)
+std::vector<std::string> DNSResolver::get_ipv4(const std::string& url, bool& dnssec_available, bool& dnssec_valid)
 {
-  std::vector<std::string> addresses;
+  return get_record(url, DNS_TYPE_A, ipv4_to_string, dnssec_available, dnssec_valid);
-  dnssec_available = false;
+}
-  dnssec_valid = false;
-
-  string_ptr urlC(strdup(url.c_str()));
-  if (!check_address_syntax(urlC))
-  {
-    return addresses;
-  }
-
-  ub_result_ptr result;
-
-  // call DNS resolver, blocking.  if return value not zero, something went wrong
-  if (!ub_resolve(m_data->m_ub_context, urlC, DNS_TYPE_AAAA, DNS_CLASS_IN, &result))
-  {
-    dnssec_available = (result->secure || (!result->secure && result->bogus));
-    dnssec_valid = result->secure && !result->bogus;
-    if (result->havedata)
-    {
-      for (size_t i=0; result->data[i] != NULL; i++)
-      {
-        addresses.push_back(ipv6_to_string(result->data[i]));
-      }
-    }
-  }
 
-  return addresses;
+std::vector<std::string> DNSResolver::get_ipv6(const std::string& url, bool& dnssec_available, bool& dnssec_valid)
+{
+  return get_record(url, DNS_TYPE_AAAA, ipv6_to_string, dnssec_available, dnssec_valid);
 }
 
 std::vector<std::string> DNSResolver::get_txt_record(const std::string& url, bool& dnssec_available, bool& dnssec_valid)
 {
-  std::vector<std::string> records;
+  return get_record(url, DNS_TYPE_TXT, txt_to_string, dnssec_available, dnssec_valid);
-  dnssec_available = false;
-  dnssec_valid = false;
-
-  string_ptr urlC(strdup(url.c_str()));
-  if (!check_address_syntax(urlC))
-  {
-    return records;
-  }
-
-  ub_result_ptr result;
-
-  // call DNS resolver, blocking.  if return value not zero, something went wrong
-  if (!ub_resolve(m_data->m_ub_context, urlC, DNS_TYPE_TXT, DNS_CLASS_IN, &result))
-  {
-    dnssec_available = (result->secure || (!result->secure && result->bogus));
-    dnssec_valid = result->secure && !result->bogus;
-    if (result->havedata)
-    {
-      for (size_t i=0; result->data[i] != NULL; i++)
-      {
-        records.push_back(std::string(result->data[i]+1, result->len[i]-1));
-      }
-    }
-  }
-
-  return records;
 }
 
 std::string DNSResolver::get_dns_format_from_oa_address(const std::string& oa_addr)

src/common/dns_utils.h

@@ -130,6 +130,19 @@ public:
 
 private:
 
+  /**
+   * @brief gets all records of a given type from a DNS query for the supplied URL;
+   * if no such record is present returns an empty vector.
+   *
+   * @param url A string containing a URL to query for
+   * @param record_type the record type to retrieve (DNS_TYPE_A, etc)
+   * @param reader a function that converts a record data to a string
+   *
+   * @return A vector of strings containing the requested record; or an empty vector
+   */
+  // TODO: modify this to accomodate DNSSEC
+  std::vector<std::string> get_record(const std::string& url, int record_type, std::string (*reader)(const char *,size_t), bool& dnssec_available, bool& dnssec_valid);
+
   /**
    * @brief Checks a string to see if it looks like a URL
    *