[dns-operations] Truncation query

Paul Vixie paul at redbarn.org
Mon Feb 6 15:13:39 UTC 2017

On Monday, February 6, 2017 2:25:05 PM PST Ray Bellis wrote:
> ...
> Should the server have set ANCOUNT=0 in this packet for it to be legal,
> or should the presence of TC=1 be taken to mean that "all bets are off"
> for everything after the question section?

in bind8, i had it process all but the last non-empty section of TC=1 responses, to preserve rrset atomicity. i wished at the time that TC=1 would've meant truncation on an rrset boundary, and bind8 worked that way, but bind4 did not, so bind8 coped.

in answer to your first question, yes, ancount=0 would have been correct. you'd be within your rights to treat this as a format error, but it's probably more constructive to at least also re-try with tcp.

P Vixie
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