CL_RFC1034_5_2_2_Encounter_CNAME - Encounters a CNAME
Verify that a NUT restarts the query when it encounters a CNAME
- In most cases a resolver simply restarts the query at the new name when
- it encounters a CNAME.
- If the response contains a CNAME, the search is restarted at the CNAME
- unless the response has the data for the canonical name or if the CNAME
- is the answer itself.
Client (with recursive function)
CL_RFC1034_5_2_2_Encounter_CNAME.seq [-tooloption ...]: KOI tool option
See also DNSConfig.pm
AP Server1(TN) DNS Server1(TN)
|3ffe:501:ffff:101::10 |3ffe:501:ffff:101::20
|192.168.1.10 |192.168.1.20
| |
Net-y --+--------+-----------------------+-------- 3ffe:501:ffff:101::/64
| 192.168.1/24
|
|
ROUTER1(TN)
|3ffe:501:ffff:100::1
|192.168.0.1
|
Net-z --+--------+-------------------------------- 3ffe:501:ffff:100::/64
| 192.168.0/24
DNS Client1(NUT)
3ffe:501:ffff:100:XXXX
192.168.0.10
XXXX: EUI64 address
Setup
Set the DNS Server1(TN)'s address on NUT as above mentioned Network Topology.
Pre-Sequence
In order to send the query for A type(IN class) of AP Server1(TN):B.example.com(CNAME) with RD=0 to the DNS Server1(TN),
NUT is configured.
This test sequence is following.
DNS Client1 (NUT) DNS Server1 (TN)
| |
|--------------------------------------------->|
| 1. Send standard query |
| QNAME=B.example.com |
| |
|<---------------------------------------------|
| 2. Standard query response |
| CNAME=A.example.com |
| |
|--------------------------------------------->|
| 3. Send standard query |
| QNAME=A.example.com |
v v
1. NUT send standard query to TN.
Judgment (Check *1)
2. TN send standard query response to NUT.
3. NUT send standard query to TN.*Send query automatically.
Judgment (Check *3)
Packet Description
1st Packet
|
1. Standard query from DNS Client1 (NUT) to DNS Server1 (TN)
|
| IP Header |
Source Address |
NUT_NETZ |
| Destination Address |
SV_NETY |
UDP Header
|
Src Port
|
any
|
Dst Port
|
53
|
DNS Header
|
ID |
any |
QR
|
0
|
OPCODE
|
0
|
AA
|
any
|
| TC |
0 |
| RD |
0 |
RA
|
any
|
Z
|
any
|
RCODE
|
any
|
QDCOUNT
|
1
|
ANCOUNT
|
0
|
NSCOUNT
|
0
|
ARCOUNT
|
any
|
DNS Question section
|
QNAME |
B.example.com
|
QTYPE
|
A (0x0001)
|
QCLASS
|
IN (0x0001)
|
2nd packet.
|
2. Standard query response from DNS Server1 (TN) to Client1 (NUT)
|
| IP Header |
Source Address |
SV_NETY |
| Destination Address |
NUT_NETZ |
| UDP Header |
Src Port |
53 |
| Dst Port |
Same as 1st Packet's Src Port |
| DNS Header |
ID |
Same as 1st Packet's ID |
| QR |
1 |
| OPCODE |
0 |
| AA |
1 |
| TC |
0 |
| RD |
Same as 1st Packet's RD |
| RA |
0 |
| Z |
0 |
| RCODE |
0 |
| QDCOUNT |
1 |
| ANCOUNT |
1 |
| NSCOUNT |
1 |
| ARCOUNT |
1 |
| DNS Question section |
QNAME |
B.example.com |
| QTYPE |
A (0x0001) |
| QCLASS |
IN (0x0001) |
| DNS Answer section |
NAME |
B.example.com (Pointer 0xC00C) |
| TYPE |
CNAME (0x0005) |
| CLASS |
IN (0x0001) |
| TTL |
1 day (86400) |
| RDLENGTH |
4 |
| CNAME |
A.example.com (A + Pointer 0xC00E) |
| DNS Authority section |
NAME |
example.com (Pointer 0xC00E) |
| TYPE |
NS (0x0002) |
| CLASS |
IN (0x0001) |
| TTL |
1 day (86400) |
| RDLENGTH |
6 |
| NSDNAME |
NS1.example.com (NS1 + Pointer 0xC00E) |
| DNS Additional section |
NAME |
NS1.example.com (Pointer 0xC03B) |
TYPE
|
A (0x0001) |
| CLASS |
IN (0x0001) |
| TTL |
0 |
| RDLENGTH |
4 |
| ADDRESS |
192.168.1.20 |
3rd Packet
|
3. Standard query from DNS Client1 (NUT) to DNS Server1 (TN)
|
| IP Header |
Source Address |
NUT_NETZ |
| Destination Address |
SV_NETY |
UDP Header
|
Src Port
|
any
|
Dst Port
|
53
|
DNS Header
|
ID |
any |
QR
|
0
|
OPCODE
|
0
|
AA
|
any
|
| TC |
0 |
| RD |
any |
RA
|
any
|
Z
|
any
|
RCODE
|
any
|
QDCOUNT
|
1
|
ANCOUNT
|
0
|
NSCOUNT
|
0
|
ARCOUNT
|
any
|
DNS Question section
|
QNAME |
A.example.com
|
QTYPE
|
A (0x0001)
|
QCLASS
|
IN (0x0001)
|
NUT_NETZ : DNS Client1(NUT)'s address
SV_NETY : DNS Server1(TN)'s address
1. Received standard query QNAME=B.example.com from NUT.
3. Received standard query QNAME=A.example.com from NUT.
If NUT has cache function, clear the cache.
RFC1034 DOMAIN NAMES - CONCEPTS AND FACILITIES
5.2.2. Aliases
5.3.3. Algorithm
RFC2308 Negative Caching of DNS Queries (DNS NCACHE)
2.2.1 Special Handling of No Data