Better nameservers configuration

doc/configuration.md

@@ -84,6 +84,14 @@
 | ----- | ----- | ----- |
 | **STS** | `int` | Defines the strict transport security header value (in seconds) for the reverse proxy, in case the value is zero the strict transport security is disabled (defaults to `0`). |
 
+#### DNS
+
+| Name | Type | Description |
+| ----- | ----- | ----- |
+| **NAMESERVERS** | `sttr` | The sequence of DNS servers to be used for forward of resolution requests (defaults to `[]`). |
+| **NAMESERVERS_IP4** | `str` | Same as `NAMESERVERS` but just for IPv4 resolution (defaults to `[]`). |
+| **NAMESERVERS_IP6** | `str` | Same as `NAMESERVERS` but just for IPv6 resolution (defaults to `[]`). |
+
 #### Blacklist Middleware
 
 | Name | Type | Description |

src/netius/clients/dns.py

@@ -312,6 +312,8 @@ class DNSProtocol(netius.DatagramProtocol):
 
     @classmethod
     def ns_system(cls, type = "ip4"):
+        ns = cls.ns_conf(type = type)
+        if ns: return ns[0]
         ns = cls.ns_file(type = type)
         if ns: return ns[0]
         ns = cls.ns_google(type = type)
@@ -320,6 +322,14 @@ def ns_system(cls, type = "ip4"):
         if ns: return ns[0]
         return None
 
+    @classmethod
+    def ns_conf(cls, type = "ip4", force = False):
+        ns =  netius.conf("NAMESERVERS_%s" % type.upper(), [], cast = list)
+        if ns: return ns
+        ns = netius.conf("NAMESERVERS", [], cast = list)
+        if ns: return ns
+        return []
+
     @classmethod
     def ns_file(cls, type = "ip4", force = False):
         # verifies if the list value for the file based name server