EDNS Buffer Size and TCP Fallback
+bufsize=2048 オプションで、バッファサイズを指定して EDNS0 による UDP ペイロードサイズを拡張できる。 OPT PSEUDOSECTION にて EDNS0 が使われていることが分かる。
$ dig . +norec +bufsize=2048 NS @a.root-servers.net
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.62.rc1.56.amzn1 <<>> . +norec +bufsize=2048 NS @a.root-servers.net
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 39943
;; flags: qr aa; QUERY: 1, ANSWER: 13, AUTHORITY: 0, ADDITIONAL: 27
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;. IN NS
;; ANSWER SECTION:
. 518400 IN NS e.root-servers.net.
. 518400 IN NS h.root-servers.net.
. 518400 IN NS l.root-servers.net.
. 518400 IN NS i.root-servers.net.
. 518400 IN NS a.root-servers.net.
. 518400 IN NS d.root-servers.net.
. 518400 IN NS c.root-servers.net.
. 518400 IN NS b.root-servers.net.
. 518400 IN NS j.root-servers.net.
. 518400 IN NS k.root-servers.net.
. 518400 IN NS g.root-servers.net.
. 518400 IN NS m.root-servers.net.
. 518400 IN NS f.root-servers.net.
;; ADDITIONAL SECTION:
e.root-servers.net. 518400 IN A 192.203.230.10
e.root-servers.net. 518400 IN AAAA 2001:500:a8::e
h.root-servers.net. 518400 IN A 198.97.190.53
h.root-servers.net. 518400 IN AAAA 2001:500:1::53
l.root-servers.net. 518400 IN A 199.7.83.42
l.root-servers.net. 518400 IN AAAA 2001:500:9f::42
i.root-servers.net. 518400 IN A 192.36.148.17
i.root-servers.net. 518400 IN AAAA 2001:7fe::53
a.root-servers.net. 518400 IN A 198.41.0.4
a.root-servers.net. 518400 IN AAAA 2001:503:ba3e::2:30
d.root-servers.net. 518400 IN A 199.7.91.13
d.root-servers.net. 518400 IN AAAA 2001:500:2d::d
c.root-servers.net. 518400 IN A 192.33.4.12
c.root-servers.net. 518400 IN AAAA 2001:500:2::c
b.root-servers.net. 518400 IN A 199.9.14.201
b.root-servers.net. 518400 IN AAAA 2001:500:200::b
j.root-servers.net. 518400 IN A 192.58.128.30
j.root-servers.net. 518400 IN AAAA 2001:503:c27::2:30
k.root-servers.net. 518400 IN A 193.0.14.129
k.root-servers.net. 518400 IN AAAA 2001:7fd::1
g.root-servers.net. 518400 IN A 192.112.36.4
g.root-servers.net. 518400 IN AAAA 2001:500:12::d0d
m.root-servers.net. 518400 IN A 202.12.27.33
m.root-servers.net. 518400 IN AAAA 2001:dc3::35
f.root-servers.net. 518400 IN A 192.5.5.241
f.root-servers.net. 518400 IN AAAA 2001:500:2f::f
;; Query time: 4 msec
;; SERVER: 198.41.0.4#53(198.41.0.4)
;; WHEN: Fri Mar 16 10:47:52 2018
;; MSG SIZE rcvd: 811指定したサイズを超えると TCP フォールバックに移行。 Truncated, retrying in TCP mode. という文字から確認できる。
$ dig jp. +norec +bufsize=1280 ANY @a.dns.jp
;; Truncated, retrying in TCP mode.
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.62.rc1.56.amzn1 <<>> jp. +norec +bufsize=1280 ANY @a.dns.jp
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 15979
;; flags: qr aa; QUERY: 1, ANSWER: 17, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;jp. IN ANY
;; ANSWER SECTION:
jp. 86400 IN SOA z.dns.jp. root.dns.jp. 1521197104 3600 900 1814400 900
jp. 86400 IN RRSIG SOA 8 1 86400 20180409174503 20180310174503 24819 jp. AZXrTBJV52jMQVmNL/UAGxZevkSadtGhYt6kNUrKXIyQr+QIs4gCd2Mt qZRpD+84+AA/YCTmpD8gdC1D0LJx7G/Zlb+PiJt8HI/iHienop6qbPRI YFeg0+rGodGrX0a6GoeVhBIxYt4KuSKxNx99HxIy9Jx1aXfY3XL3oEuA OF4=
jp. 86400 IN NS e.dns.jp.
jp. 86400 IN NS g.dns.jp.
jp. 86400 IN NS a.dns.jp.
jp. 86400 IN NS h.dns.jp.
jp. 86400 IN NS f.dns.jp.
jp. 86400 IN NS c.dns.jp.
jp. 86400 IN NS b.dns.jp.
jp. 86400 IN NS d.dns.jp.
jp. 86400 IN RRSIG NS 8 1 86400 20180409174503 20180310174503 24819 jp. RMIdqIL7nT6sMonogaVyr1VgeFg~/~/1fvfEy06MeGYWGPwL+IkQuQ+luz vBEY2gazxKafupuQof/hMdxTCUWLSy1j1SThuZkIykrCEGny3Rjp9sTu gZjjsMRSkWyy7TRE6jA1N/P/AcZQnqtcdAjHjKUYMV9jpR8aS+3IgBXK M8c=
jp. 86400 IN DNSKEY 256 3 8 AwEAAe3ck+Qxr75yL9raIqTf5PIaoCSgxUYIhjbv/1rbzXUwtOAuEZgM /vCmAjN8EbbbPo5s+l8OeAUovtlSVmGLdgqQAs9F3dtKx2ES5Hgj6ek3 Sqn7u+CW9i8G0KIo7iUXRZJ5+uFzR8cd8r5Iq95P5Gl1iqEu+Q9eGtB0 pUFVQqPF
jp. 86400 IN DNSKEY 256 3 8 AwEAAcv8UH772UJdtKoBV+0DK5g41kaPBUhrZRRAZOYhvutlolXMMQmz 1IrkPTpNC/72DnbciM5+beMrl0JpLcZronA6Rhh3xIh9gLXxOqsgpoo2 uKl8JYCexz4OPxtAL2FTjk82FO3pSfLkLVYqZagJPIeiO1qkQI5rZKBO 0u9Qgz+/
jp. 86400 IN DNSKEY 257 3 8 AwEAAesFoWjJjxTkeONePXwoXT+RPqOdUsDtcKrsS+Fg2eO3EcJSTt1v shvh6Ml8VIrWHins5bKLxKfBgB12BDRmtbAaYbsK1CElhKcpP1P/Kkj9 Cv82Il+XBl/Gt6uK0rGsQgto5ZKF0BowB6qXTKhCWDdGVJ3q5+c1fld8 EQ8odhChspHFi4IU9zBM17KYRLvDzHbgyq5oAYsOAExNW9kRUfKmLCP/ ZBb1VKaH5XqE/LFbGSsMJkxeIwzBNHw/LP8sdqXJDl2vG2Z/Vez4lRSD rkOFHdRRhUgo/3hsy0jE03ejDMT22Z43tkLhc9qW0jaOZF4EjBokFyq0 LM0G8KI2s3U=
jp. 86400 IN RRSIG DNSKEY 8 1 86400 20180508184500 20180308184500 31714 jp. roXoZ8LC9W53JBg5dyV40Z6Nycx80jlRSamsaNiGUq8zFOmjCUMiaqoR O0jFpR3WHEWPZ7wzF1LLN8AoL4z9YgDumwONfMt/D9MDNGSNKMmtBQ8s YuknLReSQOky/rQfq0nurSrwXs9x4hBI670z5iZ6lpvUumYT+K1l+eje koJg89WKKP0BzdEgTAGIZCXZk6qzO42ZPYRu/4Cz6N/p7j5akpEsKIqE xv+NUZaFS2CAVcnfCk53djlMRSHzfaK6F6iQyU/8LZwxhLuNHTmpi5/X 8HlrN/JSGigkCYiGaA7hrAQbVixZA51URr1VvOhrX4KnsBpsEFgmjBDu 3tONNA==
jp. 0 IN NSEC3PARAM 1 0 8 989956825E
jp. 0 IN RRSIG NSEC3PARAM 8 1 0 20180409174503 20180310174503 24819 jp. K4OJOsst+zc8WMvi2aQRr4NEf7RGsj35I5BKHXHGlQ6fipKgVEeYZXpR m5ws1xhk/ag6oEuHrlvuLNgnqgurbgQcMEsDYiGhW7qLq/RXtSCUR+PC pg/0iZ026w5SMur1KMauy7/4xy+gryNkqTgbxdOP3Ik+OeY8Y2DbGxOn fBs=
;; Query time: 9 msec
;; SERVER: 203.119.1.1#53(203.119.1.1)
;; WHEN: Fri Mar 16 10:50:36 2018
;; MSG SIZE rcvd: 1576