DNS/KnotResolver/cookies/dnslib-exampleについて、ここに記述してください。 BIND 9.11.0-P4付属のdigからのquery $ dig +qr -p 5053 moin.qmail.jp @127.0.0.1 {{{ ; <<>> DiG 9.11.0-P3 <<>> +qr -p 5053 moin.qmail.jp @127.0.0.1 ;; global options: +cmd ;; Sending: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34014 ;; flags: rd ad; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ; COOKIE: 7fb5bff48329a7cf ;; QUESTION SECTION: ;moin.qmail.jp. IN A ;; QUERY SIZE: 54 ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34014 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 3, ADDITIONAL: 0 ;; QUESTION SECTION: ;moin.qmail.jp. IN A ;; AUTHORITY SECTION: qmail.jp. 300 IN NS ns1.qmail.jp. qmail.jp. 300 IN NS ns2.qmail.jp. qmail.jp. 300 IN SOA ns1.qmail.jp. tmaeno.qmail.jp. 201607241 3600 10800 86400 3600 ;; Query time: 1 msec ;; SERVER: 127.0.0.1#5053(127.0.0.1) ;; WHEN: Fri Apr 14 10:16:37 JST 2017 ;; MSG SIZE rcvd: 110 }}} == server 側 == @127.0.0.1 port 5053 をlisten (simpledns.py) (; COOKIE: 7fb5bff48329a7cf はパケットの最後にある） {{{ UDP request 2017-04-14 01:16:37.380669 (127.0.0.1 38071): 54 84de01200001000000000001046d6f696e05716d61696c026a700000010001000029100000000000000c000a00087fb5bff48329a7cf ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34014 ;; flags: rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1 ;; QUESTION SECTION: ;moin.qmail.jp. IN A ;; ADDITIONAL SECTION: ;OPT PSEUDOSECTION ;EDNS: version: 0, flags: ; udp: 4096 ;EDNS: code: 10; data: 7fb5bff48329a7cf }}} ---- Reply: {{{ ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34014 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 3, ADDITIONAL: 0 ;; QUESTION SECTION: ;moin.qmail.jp. IN A ;; AUTHORITY SECTION: qmail.jp. 300 IN NS ns1.qmail.jp. qmail.jp. 300 IN NS ns2.qmail.jp. qmail.jp. 300 IN SOA ns1.qmail.jp. tmaeno.qmail.jp. 201607241 3600 10800 86400 3600 }}} https://moin.qmail.jp/DNS/RFC/1035/4#A495 https://tools.ietf.org/html/rfc6891 {{{ The fixed part of an OPT RR is structured as follows: +------------+--------------+------------------------------+ | Field Name | Field Type | Description | +------------+--------------+------------------------------+ | NAME | domain name | MUST be 0 (root domain) | | TYPE | u_int16_t | OPT (41) | | CLASS | u_int16_t | requestor's UDP payload size | | TTL | u_int32_t | extended RCODE and flags | | RDLEN | u_int16_t | length of all RDATA | | RDATA | octet stream | {attribute,value} pairs | +------------+--------------+------------------------------+ OPT RR Format }}} {{{ 54 84de 0120 (ID, OPCODE 0, RD, Z=2) Z は通常は0のはずなので、cookie関連か。 0001 0000 0000 0001 (Count) 046d 6f69 6e05 716d 6169 6c02 6a70 m o i n q m a i l j p 0000 0100 0100 0029 1000 0000 0000 END root 41 4096 (version, flags) 000c length 000a00087fb5bff48329a7cf (code 10, client cookie 8 octet) }}} https://tools.ietf.org/html/rfc7873#page-8 {{{ In a request sent by a client to a server when the client does not know the server's cookie, its length is 8, consisting of an 8-byte Client Cookie, as shown in Figure 1. 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTION-CODE = 10 | OPTION-LENGTH = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+- Client Cookie (fixed size, 8 bytes) -+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: COOKIE Option, Unknown Server Cookie }}} python print: clientからのcookie(s)の取り出しはできそう） 　server側で、cookies 返答を作るには？　-- ToshinoriMaeno <> {{{ UDP request 2017-04-15 10:16:52.532021 (192.168.10.7 33428): 51 1e4101200001000000000001016405716d61696c026a700000020001000029100000000000000c000a0008b706f0820936cc37 ------- ('query :', ) ------- }}} interactive: {{{ >>> packet = binascii.unhexlify(b'84de01200001000000000001046d6f696e05716d61696c026a700000010001000029100000000000000c000a00087fb5bff48329a7cf') >>> d = DNSRecord.parse(packet) >>> d >>> }}}