Re: [PATCH v1 net-next 2/2] ipv6: Remove IPV6_ADDRFORM.

On 9/4/26 5:35 AM, Kuniyuki Iwashima wrote:

Recently, IPV6_ADDRFORM has received many AI-driven bug reports.
Fixing them properly would needlessly churn the fast paths in TCP
and UDP.

IPV6_ADDRFORM was initially introduced in RFC 2133 in 1997,
but only two years later, it was removed from RFC 2553 in 1999.

In 2026, modern applications natively support dual-stack sockets;
notably, systemd's socket activation does not use IPV6_ADDRFORM.

Also, getsockopt(IPV6_ADDRFORM) can be replaced with SO_DOMAIN.

Let's remove IPV6_ADDRFORM.

Yes please!

Acked-by: Paolo Abeni <pabeni@redhat.com>

Later, we can remove sk->sk_prot_creator and revert commit
c26c192c3d48 ("udp: properly deal with xfrm encap and ADDRFORM").

I'm not 110% sure syzkaller or others will find a way to still trigger
the race addressed there, but I guess we will see.

Also I guess we can get rid of several READ_ONCE(sk->sk_family).

/P