The BIND 9 Administrator Reference Manual e.g. for version 9.14.11 or 9.17.1 states in
The query log entry first reports a client object identifier in
This term has not been mentioned anywhere else in the ARM, and it's the only mention of any object identifier at all.
It seems not to be related to the client that was sending the query:
123456seems always stay the same
789abcchanges from time to time.
In query log examples it can be 32-bit
@0xffffffff or 48-bit
Alan Clegg, in this BIND Logging presentation from October 2019, only describes it through what it is not:
@0xfollowed by the client object identifier (nothing to do with the client address)
What is it and how is it calculated?
What information can we get out of it? Why is it logged anyway?
According to Tony Finch's reply to bind-users mailing list in August 2019:
It's the address in memory of the data structure BIND uses to hold its working state for the query.
I'm surprised this seems the only place this is actually explained. The naming seems rather misleading as, based on this, it's not about the client nor object identifiers OID (per ITU-T X.660 | ISO/IEC 9834-1).
The explanation seems credible, as it's coherent with both the format and behaviour of the value. This logging comes from ISC's
lib/ns/client.c i.e. the client object (Thanks, Patrick Mevzek!):
2715 isc_log_write(ns_lctx, category, module, level, 2716 "client @%p %s%s%s%s%s%s%s%s: %s", client, peerbuf, sep1, 2717 signer, sep2, qname, sep3, sep4, viewname, msgbuf);
%p indeed is the memory address (pointer) of the
client, as it's written in C, and the
"client @%p %s%s%s%s%s%s%s%s: %s" is a printf format string, where the
% placeholder has:
The syntax for a format placeholder is
s: null-terminated string.
void *(pointer to void) in an implementation-defined format.
Instead, the BIND 9 Administrator Reference Manual COULD simply say something like:
The query log entry first reports the memory address of the data scructure used to hold the working state for the query, in
Well, the whole paragraph could also be formatted as a list instead of a story...
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