Query serial number

lib.py

@@ -9,6 +9,7 @@ import dns.rdataset
 import dns.rdatatype
 from dns.rdtypes.ANY import CNAME, DNAME, MX, NS, SOA, SSHFP, TXT
 from dns.rdtypes.IN import AAAA, SRV, A
+import dns.resolver
 
 # dns name object '@'
 AT = dns.name.Name(())
@@ -62,6 +63,25 @@ def add_to_zone(zone, name, rdata):
     )
     rdataset.add(rdata)
 
+
+def get_serial(dns_zone):
+    """
+    Query the serial number from the NS
+
+    dns_zone can either be a str or a dns.zone.Zone obj
+    """
+
+    try:
+        answer = dns.resolver.query(dns_zone, 'soa')
+        soa = answer.rrset.items[0]
+        serial = soa.serial
+    except:
+        logging.warning(f"[GET SERIAL] failed to query serial for this zone."
+        "Fallback to default value 0")
+        serial = 0
+
+    return serial
+
 def soa_handler(re2o_zone, dns_zone):
     """Handler for SOA record"""
 
@@ -71,13 +91,16 @@ def soa_handler(re2o_zone, dns_zone):
     ns = re2o_zone["ns_records"][0]["target"]
     ns_obj = dns.name.from_text(ns)
     
+    origin = dns_zone.origin
+    serial = get_serial(origin)
+    logging.debug(f"[SOA] zone_origin={origin} serial={serial}")
+
     soa_obj = SOA.SOA(
         dns.rdataclass.IN,
         dns.rdatatype.SOA,
         ns_obj,
         format_rname(soa["mail"]),
-        #soa["serial"],
-        0,
+        serial,
         soa["refresh"],
         soa["retry"],
         soa["expire"],