1. watchA

2. EDNS

EDNSに無返答設定しているqmail.jpに問い合わせると、

$ dig +qr -t soa qmail.jp @1.1.1.1

; <<>> DiG 9.12.1 <<>> +qr -t soa qmail.jp @1.1.1.1
;; global options: +cmd
;; Sending:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20311
;; flags: rd ad; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: 38325f429498a9b8
;; QUESTION SECTION:
;qmail.jp.                      IN      SOA

;; QUERY SIZE: 49

;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20311
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1452
;; QUESTION SECTION:
;qmail.jp.                      IN      SOA

;; ANSWER SECTION:
qmail.jp.               900     IN      SOA     a.ns.qmail.jp. hostmaster.m.qmail.jp. 1532009589 16384 2048 1048576 900

;; Query time: 2227 msec
;; SERVER: 1.1.1.1#53(1.1.1.1)
;; WHEN: Sun Jul 22 07:51:31 JST 2018
;; MSG SIZE  rcvd: 91

3. qmail.jp log

UDP(EDNS)で返答をないのを確認して、TCPで問合せてくる。

UDP(tinydns)

2018-07-22 07:51:29.179901500 a29e7448:e1a5:0000 / S0000 .
2018-07-22 07:51:29.580482500 a29e7448:7eaa:0000 / S0000 .
2018-07-22 07:51:29.779953500 a29e7448:fe2c:0000 / S0000 .
2018-07-22 07:51:29.979883500 a29e7448:cb01:0000 / S0000 .

TCP (axfrdns)

2018-07-22 07:51:31.395391500 tcpserver: ok 46952 0:14.192.44.5:53 :162.158.116.72::51536
2018-07-22 07:51:31.395395500 a29e7448:c950:0aa4 S0006 qmAil.Jp

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