lib/60740: NPF const table does not report errors well

["joe%ns1.eloisystems.com@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60740
>Category:       lib
>Synopsis:       NPF const table does not report errors well
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    lib-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Sep 18 10:15:00 +0000 2026
>Originator:     Emmanuel Nyarko
>Release:        NetBSD 11
>Organization:
NetBSD
>Environment:
NetBSD Joe 11.99.8 NetBSD 11.99.8 (GENERIC) #6: Wed Sep 16 18:42:10 UTC 2026
>Description:

NPF const tables algorithm uses cdbw(3) and uses the IP as key and data.

so no duplicate IPs are tolerated in a table file.

when it encounters a duplicate IP, it reports table already defined like 

/etc/npf.conf:1:46: table 'limited' is already defined near '"/etc/npf_tab"'.

it is a bit misleading as users might be confused when they encounter an error and won't know what to do.
>How-To-Repeat:

in /etc/tab file

192.168.100.0
192.168.100.0


in /etc/npf.conf

table <blocklist> type const file "/etc/tab

user# npfctl reload
>Fix:

just get the error return and know if an IP already exists and report a proper error message


IP already exists.