npt lacks the support for nat reflection (hairpinning); why 2 binat per one npt?

bob2022

When reading the source code generates rules for npt, I find there is no additional rules to do nat reflections for npt, and the option "enable nat reflection for 1:1 nat" do not have any effects here.

According to https://tools.ietf.org/id/draft-mrw-nat66-08.html#requirements, a npt translator should support hairpinning behavior. Maybe this can be a feature to add in the future.

Also, I am not quite understand why there are 2 binat pf.conf rules for each npt entry.

$natrules .= "binat on \${$natif} inet6 from {$srcaddr} to any -> {$dstaddr}\n";
$natrules .= "binat on \${$natif} inet6 from any to {$dstaddr} -> {$srcaddr}\n";

According to the example in the manual of pf.conf, one binat clause should be enough

 # BINAT
 # Translate outgoing packets' source address (any protocol).
 # Translate incoming packets' destination address to an internal machine
 # (bidirectional).
 binat on $ext_if from 10.1.2.150 to any -> $ext_if

A brief look into the source code of opnsense seems also confirm my guest that the first binat is enough.
After commenting out the second binat on my instance, everything works well.

This is also mentioned in a post several years ago.

Any help or clarification is appreciated!