[dns-operations] creeping poorness of judgement

Paul Vixie paul at redbarn.org
Sat Mar 14 03:04:15 UTC 2020


oh my great goodness. in RFC 7208 we have this:

3.3.  Multiple Strings in a Single DNS Record

    As defined in [RFC1035], Sections 3.3 and 3.3.14, a single text DNS
    record can be composed of more than one string.  If a published
    record contains multiple character-strings, then the record MUST be
    treated as if those strings are concatenated together without adding
    spaces.  For example:

       IN TXT "v=spf1 .... first" "second string..."

    is equivalent to:

       IN TXT "v=spf1 .... firstsecond string..."

    TXT records containing multiple strings are useful in constructing
    records that would exceed the 255-octet maximum length of a
    character-string within a single TXT record.

note the lack of a space between the word "first" and the word "second". 
this means:

> ;; ANSWER SECTION:
> _spf.tisf.net.          120     IN      TXT     "v=spf1" "ip4:140.20.56.0/24" "ip6:2001:4f8:3::/48" "ip4:24.104.150.0/24" "ip6:2001:559:8000::/48" "-all"

is going to get most of my mail bounced, or something. in the zone file 
this looks pretty different:

> _spf                    TXT     ( v=spf1
>                  ip4:140.20.56.0/24 ip6:2001:4f8:3::/48
>                  ip4:24.104.150.0/24 ip6:2001:559:8000::/48
>                  -all )

if anybody is within shouting distance of joe abley, tell him i probably 
can't answer his hopcount.ca e-mail any more. yes, i know that some name 
server implementations break strings at 255-character blocks. i fixed 
that in BIND 4.9 back in 1992. a correct name server interprets a zone 
file having ( and ) as shown.

"creeping poorness of judgement" means that in internet standards, as 
with autonomous vehicles, it's nobody's fault when a crash happens.

paul


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