Removed ldns dependency

ldns dependency was only still around for constants defined in ldns/rr.h,
but those constants are RFC specified DNS constants, and to reduce deps
have been replicated in dns_utils.h instead of including ldns/rr.h.

src/common/dns_utils.cpp

@@ -29,7 +29,6 @@
 #include "common/dns_utils.h"
 #include <cstring>
 #include <sstream>
-#include <ldns/rr.h> // for RR type and class defs
 #include <unbound.h>
 
 namespace tools
@@ -135,7 +134,7 @@ std::vector<std::string> DNSResolver::get_ipv4(const std::string& url)
   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, LDNS_RR_TYPE_A, LDNS_RR_CLASS_IN, &(result.ptr)))
+  if (!ub_resolve(m_data->m_ub_context, urlC, DNS_TYPE_A, DNS_CLASS_IN, &(result.ptr)))
   {
     if (result.ptr->havedata)
     {
@@ -165,7 +164,7 @@ std::vector<std::string> DNSResolver::get_ipv6(const std::string& url)
   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, LDNS_RR_TYPE_AAAA, LDNS_RR_CLASS_IN, &(result.ptr)))
+  if (!ub_resolve(m_data->m_ub_context, urlC, DNS_TYPE_AAAA, DNS_CLASS_IN, &(result.ptr)))
   {
     if (result.ptr->havedata)
     {
@@ -195,7 +194,7 @@ std::vector<std::string> DNSResolver::get_txt_record(const std::string& url)
   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, LDNS_RR_TYPE_TXT, LDNS_RR_CLASS_IN, &(result.ptr)))
+  if (!ub_resolve(m_data->m_ub_context, urlC, DNS_TYPE_TXT, DNS_CLASS_IN, &(result.ptr)))
   {
     if (result.ptr->havedata)
     {

src/common/dns_utils.h

@@ -32,6 +32,12 @@
 namespace tools
 {
 
+// RFC defines for record types and classes for DNS, gleaned from ldns source
+const static int DNS_CLASS_IN  = 1;
+const static int DNS_TYPE_A    = 1;
+const static int DNS_TYPE_TXT  = 6;
+const static int DNS_TYPE_AAAA = 8;
+
 struct DNSResolverData;
 
 /**