On Wed, Apr 1, 2026 at 12:45 AM David Woodhouse <[email protected]> wrote: > > From: David Woodhouse <[email protected]> > > There is no need to listen on AF_INET sockets; a modern application can > listen on IPv6 (without IPV6_V6ONLY) and will accept connections from > the 20th century via IPv4-mapped addresses (::ffff:x.x.x.x) on the IPv6 > socket. > > Signed-off-by: David Woodhouse <[email protected]> > --- > net/ipv4/af_inet.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c > index dc358faa1647..3838782a8437 100644 > --- a/net/ipv4/af_inet.c > +++ b/net/ipv4/af_inet.c > @@ -240,6 +240,9 @@ int inet_listen(struct socket *sock, int backlog) > struct sock *sk = sock->sk; > int err = -EINVAL; > > + pr_warn_once("process '%s' (pid %d) is listening on an AF_INET > socket. Consider using AF_INET6 with IPV6_V6ONLY=0 instead.\n", > + current->comm, task_pid_nr(current)); > +
Some kernels are built without CONFIG_IPV6, so this warning would be quite misleading.
