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  • Best way to force a TC=1 response?

    From Fred Morris@m3047@m3047.net to bind-users on Tue May 26 13:50:25 2020
    From Newsgroup: comp.protocols.dns.bind

    What's the best way to force an A query via UDP to return a TC=1 result:
    a really long CNAME chain?

    I want to set up a name that can be used in e.g. ping to perform an end
    to end resolution check in application context.


    The longer version is that there was a thread on postfix-users not too
    long ago about the fact that MUSL libc doesn't do TCP (among other
    things) and I want a way to test some hardware and statically built
    apps. No jumbo frames here.

    I was also mildly surprised to discover that glibc doesn't try TCP if
    UDP fails to answer; for some reason I thought it did! Instead it
    reports "Temporary failure in name resolution" in the ping example.

    --

    Fred Morris


    --- Synchronet 3.18a-Linux NewsLink 1.113
  • From John Levine@johnl@iecc.com to bind-users on Tue May 26 17:27:44 2020
    From Newsgroup: comp.protocols.dns.bind

    In article <mailman.442.1590526210.942.bind-users@lists.isc.org> you write: >What's the best way to force an A query via UDP to return a TC=1 result:
    a really long CNAME chain?

    I'd suggest lots of AAAA records. You could do it with A records but you'd need four times as many

    $ dig wordy.examp1e.com aaaa
    ;; Truncated, retrying in TCP mode.

    ; <<>> DiG 9.10.6 <<>> wordy.examp1e.com aaaa
    ;; global options: +cmd
    ;; Got answer:
    ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 24856
    ;; flags: qr rd ra ad; QUERY: 1, ANSWER: 187, AUTHORITY: 0, ADDITIONAL: 1

    ;; OPT PSEUDOSECTION:
    ; EDNS: version: 0, flags:; udp: 4096
    ;; QUESTION SECTION:
    ;wordy.examp1e.com. IN AAAA

    ;; ANSWER SECTION:
    wordy.examp1e.com. 3594 IN AAAA 2001::1
    wordy.examp1e.com. 3594 IN AAAA 2002::2
    wordy.examp1e.com. 3594 IN AAAA 2003::3
    wordy.examp1e.com. 3594 IN AAAA 2004::4
    wordy.examp1e.com. 3594 IN AAAA 2005::5
    wordy.examp1e.com. 3594 IN AAAA 2006::6
    wordy.examp1e.com. 3594 IN AAAA 2006::7
    wordy.examp1e.com. 3594 IN AAAA 2008::8
    wordy.examp1e.com. 3594 IN AAAA 2009::9
    wordy.examp1e.com. 3594 IN AAAA 200a::a
    wordy.examp1e.com. 3594 IN AAAA 200b::b
    wordy.examp1e.com. 3594 IN AAAA 200c::c
    wordy.examp1e.com. 3594 IN AAAA 200d::d
    wordy.examp1e.com. 3594 IN AAAA 200e::e
    wordy.examp1e.com. 3594 IN AAAA 200f::f
    wordy.examp1e.com. 3594 IN AAAA 2010::10
    wordy.examp1e.com. 3594 IN AAAA 2011::11
    wordy.examp1e.com. 3594 IN AAAA 2012::12
    wordy.examp1e.com. 3594 IN AAAA 2013::13
    wordy.examp1e.com. 3594 IN AAAA 2014::14
    wordy.examp1e.com. 3594 IN AAAA 2015::15
    wordy.examp1e.com. 3594 IN AAAA 2016::16
    wordy.examp1e.com. 3594 IN AAAA 2017::17
    wordy.examp1e.com. 3594 IN AAAA 2018::18
    wordy.examp1e.com. 3594 IN AAAA 2019::19
    wordy.examp1e.com. 3594 IN AAAA 201a::1a
    wordy.examp1e.com. 3594 IN AAAA 201b::1b
    wordy.examp1e.com. 3594 IN AAAA 201c::1c
    wordy.examp1e.com. 3594 IN AAAA 201d::1d
    wordy.examp1e.com. 3594 IN AAAA 201e::1e
    wordy.examp1e.com. 3594 IN AAAA 201f::1f
    wordy.examp1e.com. 3594 IN AAAA 2020::20
    wordy.examp1e.com. 3594 IN AAAA 2021::21
    wordy.examp1e.com. 3594 IN AAAA 2022::22
    wordy.examp1e.com. 3594 IN AAAA 2023::23
    wordy.examp1e.com. 3594 IN AAAA 2024::24
    wordy.examp1e.com. 3594 IN AAAA 2025::25
    wordy.examp1e.com. 3594 IN AAAA 2026::26
    wordy.examp1e.com. 3594 IN AAAA 2027::27
    wordy.examp1e.com. 3594 IN AAAA 2028::28
    wordy.examp1e.com. 3594 IN AAAA 2029::29
    wordy.examp1e.com. 3594 IN AAAA 202a::2a
    wordy.examp1e.com. 3594 IN AAAA 202b::2b
    wordy.examp1e.com. 3594 IN AAAA 202c::2c
    wordy.examp1e.com. 3594 IN AAAA 202d::2d
    wordy.examp1e.com. 3594 IN AAAA 202e::2e
    wordy.examp1e.com. 3594 IN AAAA 202f::2f
    wordy.examp1e.com. 3594 IN AAAA 2030::30
    wordy.examp1e.com. 3594 IN AAAA 2031::31
    wordy.examp1e.com. 3594 IN AAAA 2032::32
    wordy.examp1e.com. 3594 IN AAAA 2033::33
    wordy.examp1e.com. 3594 IN AAAA 2034::34
    wordy.examp1e.com. 3594 IN AAAA 2035::35
    wordy.examp1e.com. 3594 IN AAAA 2036::36
    wordy.examp1e.com. 3594 IN AAAA 2037::37
    wordy.examp1e.com. 3594 IN AAAA 2038::38
    wordy.examp1e.com. 3594 IN AAAA 2039::39
    wordy.examp1e.com. 3594 IN AAAA 203a::3a
    wordy.examp1e.com. 3594 IN AAAA 203b::3b
    wordy.examp1e.com. 3594 IN AAAA 203c::3c
    wordy.examp1e.com. 3594 IN AAAA 203d::3d
    wordy.examp1e.com. 3594 IN AAAA 203e::3e
    wordy.examp1e.com. 3594 IN AAAA 203f::3f
    wordy.examp1e.com. 3594 IN AAAA 2040::40
    wordy.examp1e.com. 3594 IN AAAA 2041::41
    wordy.examp1e.com. 3594 IN AAAA 2042::42
    wordy.examp1e.com. 3594 IN AAAA 2043::43
    wordy.examp1e.com. 3594 IN AAAA 2044::44
    wordy.examp1e.com. 3594 IN AAAA 2045::45
    wordy.examp1e.com. 3594 IN AAAA 2046::46
    wordy.examp1e.com. 3594 IN AAAA 2047::47
    wordy.examp1e.com. 3594 IN AAAA 2048::48
    wordy.examp1e.com. 3594 IN AAAA 2049::49
    wordy.examp1e.com. 3594 IN AAAA 204a::4a
    wordy.examp1e.com. 3594 IN AAAA 204b::4b
    wordy.examp1e.com. 3594 IN AAAA 204c::4c
    wordy.examp1e.com. 3594 IN AAAA 204d::4d
    wordy.examp1e.com. 3594 IN AAAA 204e::4e
    wordy.examp1e.com. 3594 IN AAAA 204f::4f
    wordy.examp1e.com. 3594 IN AAAA 2050::50
    wordy.examp1e.com. 3594 IN AAAA 2051::51
    wordy.examp1e.com. 3594 IN AAAA 2052::52
    wordy.examp1e.com. 3594 IN AAAA 2053::53
    wordy.examp1e.com. 3594 IN AAAA 2054::54
    wordy.examp1e.com. 3594 IN AAAA 2055::55
    wordy.examp1e.com. 3594 IN AAAA 2056::56
    wordy.examp1e.com. 3594 IN AAAA 2057::57
    wordy.examp1e.com. 3594 IN AAAA 2058::58
    wordy.examp1e.com. 3594 IN AAAA 2059::59
    wordy.examp1e.com. 3594 IN AAAA 205a::5a
    wordy.examp1e.com. 3594 IN AAAA 205b::5b
    wordy.examp1e.com. 3594 IN AAAA 205c::5c
    wordy.examp1e.com. 3594 IN AAAA 205d::5d
    wordy.examp1e.com. 3594 IN AAAA 205e::5e
    wordy.examp1e.com. 3594 IN AAAA 205f::5f
    wordy.examp1e.com. 3594 IN AAAA 2060::60
    wordy.examp1e.com. 3594 IN AAAA 2061::61
    wordy.examp1e.com. 3594 IN AAAA 2062::62
    wordy.examp1e.com. 3594 IN AAAA 2063::63
    wordy.examp1e.com. 3594 IN AAAA 2064::64
    wordy.examp1e.com. 3594 IN AAAA 2065::65
    wordy.examp1e.com. 3594 IN AAAA 2066::66
    wordy.examp1e.com. 3594 IN AAAA 2067::67
    wordy.examp1e.com. 3594 IN AAAA 2068::68
    wordy.examp1e.com. 3594 IN AAAA 2069::69
    wordy.examp1e.com. 3594 IN AAAA 206a::6a
    wordy.examp1e.com. 3594 IN AAAA 206b::6b
    wordy.examp1e.com. 3594 IN AAAA 206c::6c
    wordy.examp1e.com. 3594 IN AAAA 206d::6d
    wordy.examp1e.com. 3594 IN AAAA 206e::6e
    wordy.examp1e.com. 3594 IN AAAA 206f::6f
    wordy.examp1e.com. 3594 IN AAAA 2070::70
    wordy.examp1e.com. 3594 IN AAAA 2071::71
    wordy.examp1e.com. 3594 IN AAAA 2072::72
    wordy.examp1e.com. 3594 IN AAAA 2073::73
    wordy.examp1e.com. 3594 IN AAAA 2074::74
    wordy.examp1e.com. 3594 IN AAAA 2075::75
    wordy.examp1e.com. 3594 IN AAAA 2076::76
    wordy.examp1e.com. 3594 IN AAAA 2077::77
    wordy.examp1e.com. 3594 IN AAAA 2078::78
    wordy.examp1e.com. 3594 IN AAAA 2079::79
    wordy.examp1e.com. 3594 IN AAAA 207a::7a
    wordy.examp1e.com. 3594 IN AAAA 207b::7b
    wordy.examp1e.com. 3594 IN AAAA 207c::7c
    wordy.examp1e.com. 3594 IN AAAA 207d::7d
    wordy.examp1e.com. 3594 IN AAAA 207e::7e
    wordy.examp1e.com. 3594 IN AAAA 207f::7f
    wordy.examp1e.com. 3594 IN AAAA 2080::80
    wordy.examp1e.com. 3594 IN AAAA 2081::81
    wordy.examp1e.com. 3594 IN AAAA 2082::82
    wordy.examp1e.com. 3594 IN AAAA 2083::83
    wordy.examp1e.com. 3594 IN AAAA 2084::84
    wordy.examp1e.com. 3594 IN AAAA 2085::85
    wordy.examp1e.com. 3594 IN AAAA 2086::86
    wordy.examp1e.com. 3594 IN AAAA 2087::87
    wordy.examp1e.com. 3594 IN AAAA 2088::88
    wordy.examp1e.com. 3594 IN AAAA 2089::89
    wordy.examp1e.com. 3594 IN AAAA 208a::8a
    wordy.examp1e.com. 3594 IN AAAA 208b::8b
    wordy.examp1e.com. 3594 IN AAAA 208c::8c
    wordy.examp1e.com. 3594 IN AAAA 208d::8d
    wordy.examp1e.com. 3594 IN AAAA 208e::8e
    wordy.examp1e.com. 3594 IN AAAA 208f::8f
    wordy.examp1e.com. 3594 IN AAAA 2090::90
    wordy.examp1e.com. 3594 IN AAAA 2091::91
    wordy.examp1e.com. 3594 IN AAAA 2092::92
    wordy.examp1e.com. 3594 IN AAAA 2093::93
    wordy.examp1e.com. 3594 IN AAAA 2094::94
    wordy.examp1e.com. 3594 IN AAAA 2095::95
    wordy.examp1e.com. 3594 IN AAAA 2096::96
    wordy.examp1e.com. 3594 IN AAAA 2097::97
    wordy.examp1e.com. 3594 IN AAAA 2098::98
    wordy.examp1e.com. 3594 IN AAAA 2099::99
    wordy.examp1e.com. 3594 IN AAAA 209a::9a
    wordy.examp1e.com. 3594 IN AAAA 209b::9b
    wordy.examp1e.com. 3594 IN AAAA 209c::9c
    wordy.examp1e.com. 3594 IN AAAA 209d::9d
    wordy.examp1e.com. 3594 IN AAAA 209e::9e
    wordy.examp1e.com. 3594 IN AAAA 209f::9f
    wordy.examp1e.com. 3594 IN AAAA 20a0::a0
    wordy.examp1e.com. 3594 IN AAAA 20a1::a1
    wordy.examp1e.com. 3594 IN AAAA 20a2::a2
    wordy.examp1e.com. 3594 IN AAAA 20a3::a3
    wordy.examp1e.com. 3594 IN AAAA 20a4::a4
    wordy.examp1e.com. 3594 IN AAAA 20a5::a5
    wordy.examp1e.com. 3594 IN AAAA 20a6::a6
    wordy.examp1e.com. 3594 IN AAAA 20a7::a7
    wordy.examp1e.com. 3594 IN AAAA 20a8::a8
    wordy.examp1e.com. 3594 IN AAAA 20a9::a9
    wordy.examp1e.com. 3594 IN AAAA 20aa::aa
    wordy.examp1e.com. 3594 IN AAAA 20ab::ab
    wordy.examp1e.com. 3594 IN AAAA 20ac::ac
    wordy.examp1e.com. 3594 IN AAAA 20ad::ad
    wordy.examp1e.com. 3594 IN AAAA 20ae::ae
    wordy.examp1e.com. 3594 IN AAAA 20af::af
    wordy.examp1e.com. 3594 IN AAAA 20b0::b0
    wordy.examp1e.com. 3594 IN AAAA 20b1::b1
    wordy.examp1e.com. 3594 IN AAAA 20b2::b2
    wordy.examp1e.com. 3594 IN AAAA 20b3::b3
    wordy.examp1e.com. 3594 IN AAAA 20b4::b4
    wordy.examp1e.com. 3594 IN AAAA 20b5::b5
    wordy.examp1e.com. 3594 IN AAAA 20b6::b6
    wordy.examp1e.com. 3594 IN AAAA 20b7::b7
    wordy.examp1e.com. 3594 IN AAAA 20b8::b8
    wordy.examp1e.com. 3594 IN AAAA 20b9::b9
    wordy.examp1e.com. 3594 IN AAAA 20ba::ba
    wordy.examp1e.com. 3594 IN AAAA 20bb::bb

    ;; Query time: 0 msec
    ;; SERVER: 192.168.80.2#53(192.168.80.2)
    ;; WHEN: Tue May 26 17:24:43 EDT 2020
    ;; MSG SIZE rcvd: 5282

    --- Synchronet 3.18a-Linux NewsLink 1.113
  • From Mark Andrews@marka@isc.org to comp.protocols.dns.bind on Wed May 27 09:28:47 2020
    From Newsgroup: comp.protocols.dns.bind


    On 27 May 2020, at 07:27, John Levine <johnl@iecc.com> wrote:

    In article <mailman.442.1590526210.942.bind-users@lists.isc.org> you write:
    What's the best way to force an A query via UDP to return a TC=1 result:
    a really long CNAME chain?

    I'd suggest lots of AAAA records. You could do it with A records but you'd need four times as many
    Well ~2 times as many. Each additional A record requires 16 bytes and each addition AAAA records requires 28 bytes. That means ~256 A records and ~146 AAAA records to force TCP with a 4096 byte UDP buffer size.
    John’s example had 187 AAAA records.
    Mark
    --
    Mark Andrews, ISC
    1 Seymour St., Dundas Valley, NSW 2117, Australia
    PHONE: +61 2 9871 4742 INTERNET: marka@isc.org
    --- Synchronet 3.18a-Linux NewsLink 1.113