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[76.102.12.149]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2ca792f3f54sm144003eec.7.2026.04.01.09.20.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Apr 2026 09:20:59 -0700 (PDT) Date: Wed, 1 Apr 2026 09:20:58 -0700 From: Stanislav Fomichev To: David Woodhouse Cc: Saeed Mahameed , Leon Romanovsky , Tariq Toukan , Mark Bloch , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Nikolay Aleksandrov , Ido Schimmel , Martin KaFai Lau , Daniel Borkmann , John Fastabend , Stanislav Fomichev , Alexei Starovoitov , Andrii Nakryiko , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Hao Luo , Jiri Olsa , Kuniyuki Iwashima , Willem de Bruijn , David Ahern , Neal Cardwell , Johannes Berg , Pablo Neira Ayuso , Florian Westphal , Phil Sutter , Guillaume Nault , David Woodhouse , Kees Cook , Alexei Lazar , Gal Pressman , Paul Moore , netdev@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, oss-drivers@corigine.com, bridge@lists.linux.dev, bpf@vger.kernel.org, linux-wireless@vger.kernel.org, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, torvalds@linux-foundation.org, jon.maddog.hall@gmail.com Subject: Re: [PATCH 6/6] net: Warn when processes listen on AF_INET sockets Message-ID: Mail-Followup-To: Stanislav Fomichev , David Woodhouse , Saeed Mahameed , Leon Romanovsky , Tariq Toukan , Mark Bloch , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Nikolay Aleksandrov , Ido Schimmel , Martin KaFai Lau , Daniel Borkmann , John Fastabend , Stanislav Fomichev , Alexei Starovoitov , Andrii Nakryiko , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Hao Luo , Jiri Olsa , Kuniyuki Iwashima , Willem de Bruijn , David Ahern , Neal Cardwell , Johannes Berg , Pablo Neira Ayuso , Florian Westphal , Phil Sutter , Guillaume Nault , David Woodhouse , Kees Cook , Alexei Lazar , Gal Pressman , Paul Moore , netdev@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, oss-drivers@corigine.com, bridge@lists.linux.dev, bpf@vger.kernel.org, linux-wireless@vger.kernel.org, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, torvalds@linux-foundation.org, jon.maddog.hall@gmail.com References: <20260401074509.1897527-1-dwmw2@infradead.org> <20260401074509.1897527-7-dwmw2@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260401074509.1897527-7-dwmw2@infradead.org> On 04/01, David Woodhouse wrote: > From: David Woodhouse > > 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 > --- > 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)); > + > lock_sock(sk); > > if (sock->state != SS_UNCONNECTED || sock->type != SOCK_STREAM) > -- > 2.51.0 > Does this also need to look at the proto? inet6_stream_ops seem to be using inet_listen as well. const struct proto_ops inet6_stream_ops = { .family = PF_INET6, .owner = THIS_MODULE, .release = inet6_release, .bind = inet6_bind, .connect = inet_stream_connect, /* ok */ .socketpair = sock_no_socketpair, /* a do nothing */ .accept = inet_accept, /* ok */ .getname = inet6_getname, .poll = tcp_poll, /* ok */ .ioctl = inet6_ioctl, /* must change */ .gettstamp = sock_gettstamp, .listen = inet_listen, /* ok */