Knot 1.6.4 synthesising incorrect NXDOMAIN response
We have Knot 1.6.4 serving d.0.1.0.0.2.ip6.arpa. When queried for 8.b.d.0.1.0.0.2.ip6.arpa (2001:db8::/32), it returns an NXDOMAIN response as expected, with the following in the authority section:
;; AUTHORITY SECTION:
d.0.1.0.0.2.ip6.arpa. 172800 IN SOA ns1.apnic.net. read-txt-record-of-zone-first-dns-admin.apnic.net. 3005124571 7200 1800 604800 172800
0.b.d.0.1.0.0.2.ip6.arpa. 172800 IN NSEC 0.c.d.0.1.0.0.2.ip6.arpa. NS RRSIG NSEC
d.0.1.0.0.2.ip6.arpa. 172800 IN NSEC 8.0.d.0.1.0.0.2.ip6.arpa. NS SOA TXT RRSIG NSEC DNSKEY
d.0.1.0.0.2.ip6.arpa. 172800 IN RRSIG SOA 5 8 172800 20150921180409 20150822170409 14425 d.0.1.0.0.2.ip6.arpa. SN+KPHQltgUBY43DKYLDSMYmBytOEN6A0wN4zhxV33OdphjTN1aKOU1T DsUInmF2qyyMZWx4K9PWM6H0+92vhJ4IU4wmxHeZE86boSYtTVgR5JMK 8RkcK53C2QVaFjenhyIlXoJy2YI0jywtHqNYZV3CZMzzgHVLHyEBw2PJ K5w=
0.b.d.0.1.0.0.2.ip6.arpa. 172800 IN RRSIG NSEC 5 10 172800 20150921180409 20150822170409 14425 d.0.1.0.0.2.ip6.arpa. CqkCPcwlf4Ep1iBKQnQJHNgsQ+Qm3LCwzbjQm6gdMF1ddzAXXMmxHxkz 2dzWqdZbMUIneOXK3O5RxF+Ji3o+GXUvKmR4+e9nRoSmHX3sacqVX5dp zufDK2x//eHaP13xJeKLLoSKs+NuKsHNn4NaJ2fTecIArII/ul2DOtyb Yu0=
d.0.1.0.0.2.ip6.arpa. 172800 IN RRSIG NSEC 5 8 172800 20150921180409 20150822170409 14425 d.0.1.0.0.2.ip6.arpa. PMpsrr0O2KQFyGY/Jv1FiBXkVruXOq6EyX1rIgTj3qJVJ60nP+lq72w3 ehgKZN3aql/hagutJHeSIa5L6korUpHJk4nKhD9vfkgHZEZYIBgj6OY0 DqaO8JX+TyG8Y7EzZccM65tyHISthaGy+rH16wCF4BAGDvvjOEvcBgkl SyM=
Now, in comparison, our BIND and NSD servers return:
;; AUTHORITY SECTION:
d.0.1.0.0.2.ip6.arpa. 172800 IN SOA ns1.apnic.net. read-txt-record-of-zone-first-dns-admin.apnic.net. 3005124571 7200 1800 604800 172800
d.0.1.0.0.2.ip6.arpa. 172800 IN RRSIG SOA 5 8 172800 20150921180409 20150822170409 14425 d.0.1.0.0.2.ip6.arpa. SN+KPHQltgUBY43DKYLDSMYmBytOEN6A0wN4zhxV33OdphjTN1aKOU1T DsUInmF2qyyMZWx4K9PWM6H0+92vhJ4IU4wmxHeZE86boSYtTVgR5JMK 8RkcK53C2QVaFjenhyIlXoJy2YI0jywtHqNYZV3CZMzzgHVLHyEBw2PJ K5w=
0.b.d.0.1.0.0.2.ip6.arpa. 172800 IN NSEC 0.c.d.0.1.0.0.2.ip6.arpa. NS RRSIG NSEC
0.b.d.0.1.0.0.2.ip6.arpa. 172800 IN RRSIG NSEC 5 10 172800 20150921180409 20150822170409 14425 d.0.1.0.0.2.ip6.arpa. CqkCPcwlf4Ep1iBKQnQJHNgsQ+Qm3LCwzbjQm6gdMF1ddzAXXMmxHxkz 2dzWqdZbMUIneOXK3O5RxF+Ji3o+GXUvKmR4+e9nRoSmHX3sacqVX5dp zufDK2x//eHaP13xJeKLLoSKs+NuKsHNn4NaJ2fTecIArII/ul2DOtyb Yu0=
a.a.d.0.1.0.0.2.ip6.arpa. 172800 IN NSEC 0.b.d.0.1.0.0.2.ip6.arpa. NS RRSIG NSEC
a.a.d.0.1.0.0.2.ip6.arpa. 172800 IN RRSIG NSEC 5 10 172800 20150921180409 20150822170409 14425 d.0.1.0.0.2.ip6.arpa. Krxq2HJQOnouZs2z/cucMLch9VB1/2iE6UNUfVZqNW//SKuKSRbu0KDG ENd+R4/SvpSPkgfYkeitTBsNoguDiRE/I56IqaK2sqqWKxLan2GUYYgx j6QaJ95s4hRTbTJqdxmQiXB6anyotiMa8GXsywRepLuQpFFFsAyCfgxx Yqw=
Is this a bug in Knot?