net_gateway works, but net_gateway_ipv6 is wrong

I'm running an OpenVPN client from my home broadband. I need to forward DNS resolution to my home broadband provider, however they only allow their own client networks to query their DNS resolvers. Therefore, I need to ensure that this traffic doesn't go through the OpenVPN tunnel but stays on the broadband.

Easy enough to configure:

route dns3.telefonica.de 255.255.255.255 net_gateway
route-ipv6 dns3.telefonica.de/128 net_gateway_ipv6

Given

# host dns3.telefonica.de
dns3.telefonica.de has address 62.109.121.1
dns3.telefonica.de has IPv6 address 2a01:c30::530

the result is wrong however:

# netstat -rn | egrep '62.109.121.1|2a01:c30::530|Dest'
Destination        Gateway            Flags         Netif Expire
62.109.121.1       192.168.178.1      UGHS            re0
Destination                       Gateway                       Flags         Netif Expire
2a01:c30::530                     link#4                        UHS            tun0

Clearly visible that the IPv4 case is correct (and I have verified it works) but the IPv6 case points to the tunnel (tun0) instead of the broadband (re0) interface.

There's been some discussion around this years ago. However the patch provided (applies to OpenVPN 2.6) had not been committed apparently, and is also not committed to 2.7. I have modified this patch slightly so that it applies cleanly to 2.7.1, see patch.patch. With the patch applied, the result is correct:

# netstat -rn | egrep '62.109.121.1|2a01:c30::530|Dest'
Destination        Gateway            Flags         Netif Expire
62.109.121.1       192.168.178.1      UGHS            re0
Destination                       Gateway                       Flags         Netif Expire
2a01:c30::530                     fe80::5e49:79ff:fecc:ecf3%re0 UGHS            re0

OS: FreeBSD 15.0-STABLE
OpenVPN version: 2.7.1

Start by reviewing the linked historical patch and the attached patch.patch, then reproduce the route-ipv6 net_gateway_ipv6 behavior on FreeBSD 15.0-STABLE with the configuration shown. Done means the IPv6 route for 2a01:c30::530 uses the broadband interface re0 rather than the OpenVPN tunnel tun0.