I want to build a CDN platform for a project, and for the load balancing part, I decided to use a bind9 server to forward zones to an external DNS server, where I'll also handle the load balancing. The issue is that my custom DNS server perceives the requests and sends responses to bind9, but bind9 doesn't process the response.
req ('3.91.51.202', 56626) b'\\x02\x01\x10\x00\x01\x00\x00\x00\x00\x00\x01\x04idoc\x02ro\x00\x00\x01\x00\x01\x00\x00)\x04\xd0\x00\x00\x80\x00\x00\x0c\x00\n\x00\x08\xd8!A\xc6\xebES\x14'id 1474qr 0opcode 0aa 0tc 0rd 1z 1Rcode 0qdcount 1ancount 0nscount 0arcount 1DOMAIN: idoc.roqtype 1qclass 1ip [192, 168, 1, 232]resp b'\\x02\x85\x10\x00\x00\x00\x01\x00\x00\x00\x00\x04idoc\x02ro\x00\x00\x01\x00\x01\x00\x00\x00\n\x00\x04\xc0\xa8\x01\xe8'
DNS server custom
def handle_request(args): server_socket, buf, client_address = args # Codul pentru tratarea cererii DNS print("Procesez cererea de la ", client_address, buf) print(f"id {(buf[0] & 0xff) * 16 + (buf[1] & 0xff)}") print(f"qr {(buf[2] & 0x80) >> 7}") print(f"opcode {(buf[2] & 0x78) >> 3}") print(f"aa {(buf[2] & 0x04) >> 2}") print(f"tc {(buf[2] & 0x02) >> 1}") print(f"rd {(buf[2] & 0x01)}") print(f"z {(buf[3] & 0x70) >> 4}") print(f"Rcode {(buf[3] & 0x0f)}") print(f"qdcount {((buf[4] & 0xff) * 16 + (buf[5] & 0xff))}") print(f"ancount {((buf[6] & 0xff) * 16 + (buf[7] & 0xff))}") print(f"nscount {((buf[8] & 0xff) * 16 + (buf[9] & 0xff))}") print(f"arcount {((buf[10] & 0xff) * 16 + (buf[11] & 0xff))}") domain = bytearray() for i in range(13, len(buf)): if buf[i] == 0: break domain.append(buf[i]) k = buf[12] for i in range(len(domain)): if i == k: k = i + domain[i] + 1 domain[i] = 0x2e domain_bytes = bytes(domain) print("DOMAIN:", domain.decode('utf-8')) print(f"qtype {((buf[14 + len(domain)] & 0xff) * 16 + (buf[15 + len(domain)] & 0xff))}") print(f"qclass {((buf[16 +len(domain)] & 0xff) * 16 + (buf[17 + len(domain)] & 0xff))}") #Response resp = bytearray(28 + len(domain_bytes)) for i in range(4): resp[i] = buf[i] resp[2] |= 0x84 # qr 1 resp[3] &= 0xF0 # rcode 1 resp[4] = resp[5] = 0 # setez explicit qdcount pe 0 resp[7] = 1 # Ancount 1 for i in range(12, 14 + len(domain_bytes)): resp[i] = buf[i] resp[15 + len(domain)] = 1 # QTYPE A resp[17 + len(domain)] = 1 # QCLASS IN resp[21 + len(domain)] = 10 # TTL 10 seconds resp[23 + len(domain)] = 4 # RDLENGTH 4 bytes ip = load_balancer(client_addr=client_address) print("ip ", ip) for i in range(4): resp[24 + len(domain) + i] = ip[i] response_bytes = bytes(resp) print(f"resp {response_bytes}", f"resp len {len(resp)}") server_socket.sendto(resp, client_address)bind9 zone
zone "idoc.ro" { type forward; //this defines the addresses of the resolvers to which queries fo this zone will be forwarder forwarders { 54.198.10.101; }; forward only;};nslookup -debug idoc.ro localhost;; communications error to 127.0.0.1#53: timed outServer: localhostAddress: 127.0.0.1#53
QUESTIONS:idoc.ro, type = A, class = INANSWERS:AUTHORITY RECORDS:ADDITIONAL RECORDS:** server can't find idoc.ro: SERVFAIL
I expected the BIND9 server to process the requests correctly.
