Read in a file, and respond to any query received with the contents of that file in the CNAME target.

scapy_dns_response.py

from __future__ import print_function
from scapy.all import *

domain_name = "nhlscore.riebart.ca"
dns_server_ip = '172.31.15.145'
bpf_filter = 'dst port 53 and ip dst {0}'.format(dns_server_ip)

def dns_respond(pkt, rcode=0):
    if (DNS in pkt and pkt[DNS].opcode == 0 and pkt[DNS].ancount == 0):
        print('Responding to query for "%s" from "%s"' % (pkt[DNSQR].qname, pkt[IP].src))
        with open("source.in", "r") as fp:
            resp_val = fp.read().strip()
        
        an = (None, DNSRR(rrname=pkt[DNSQR].qname, type=pkt[DNSQR].qtype, rdata=resp_val + ".actual." + domain_name, ttl=60))[rcode == 0]

        resp_pkt = IP(dst=pkt[IP].src, src=pkt[IP].dst)/\
            UDP(dport=pkt[UDP].sport, sport=pkt[UDP].dport)/\
            DNS(id=pkt[DNS].id, qr=1, rd=1, ra=1, rcode=rcode, qd=pkt[DNS].qd, an=an, ns=None)
        send(resp_pkt, verbose=1)

sniff(filter=bpf_filter, prn=dns_respond)