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. Later, we can remove sk->sk_prot_creator and revert commit c26c192c3d48 ("udp: properly deal with xfrm encap and ADDRFORM"). Reported-by: Daehyeon Ko <4ncienth@gmail.com> Closes: https://lore.kernel.org/netdev/20260902010408.1057857-1-4ncienth@gmail.com/ Reported-by: Hyunwoo Kim Closes: https://lore.kernel.org/netdev/20260824033331.1084971-1-imv4bel@gmail.com/ Signed-off-by: Kuniyuki Iwashima --- include/linux/net.h | 2 +- net/core/sock.c | 4 +- net/ipv4/af_inet.c | 3 -- net/ipv6/af_inet6.c | 4 -- net/ipv6/ipv6_sockglue.c | 87 ---------------------------------------- 5 files changed, 2 insertions(+), 98 deletions(-) diff --git a/include/linux/net.h b/include/linux/net.h index 3d82966e2243..470100ae7107 100644 --- a/include/linux/net.h +++ b/include/linux/net.h @@ -166,7 +166,7 @@ struct socket { struct file *file; struct sock *sk; - const struct proto_ops *ops; /* Might change with IPV6_ADDRFORM or MPTCP. */ + const struct proto_ops *ops; /* Might change with MPTCP. */ struct socket_wq wq; }; diff --git a/net/core/sock.c b/net/core/sock.c index fa60b7494c58..1d5927cd49a1 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -770,7 +770,7 @@ bool sk_mc_loop(const struct sock *sk) return false; if (!sk) return true; - /* IPV6_ADDRFORM can change sk->sk_family under us. */ + switch (READ_ONCE(sk->sk_family)) { case AF_INET: return inet_test_bit(MC_LOOP, sk); @@ -4010,7 +4010,6 @@ int sock_common_getsockopt(struct socket *sock, int level, int optname, { struct sock *sk = sock->sk; - /* IPV6_ADDRFORM can change sk->sk_prot under us. */ return READ_ONCE(sk->sk_prot)->getsockopt(sk, level, optname, optval, optlen); } EXPORT_SYMBOL(sock_common_getsockopt); @@ -4032,7 +4031,6 @@ int sock_common_setsockopt(struct socket *sock, int level, int optname, { struct sock *sk = sock->sk; - /* IPV6_ADDRFORM can change sk->sk_prot under us. */ return READ_ONCE(sk->sk_prot)->setsockopt(sk, level, optname, optval, optlen); } EXPORT_SYMBOL(sock_common_setsockopt); diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index 32d006c1a8ee..d9421ac38d78 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -582,7 +582,6 @@ int inet_dgram_connect(struct socket *sock, struct sockaddr_unsized *uaddr, if (addr_len < sizeof(uaddr->sa_family)) return -EINVAL; - /* IPV6_ADDRFORM can change sk->sk_prot under us. */ prot = READ_ONCE(sk->sk_prot); if (uaddr->sa_family == AF_UNSPEC) @@ -789,7 +788,6 @@ int inet_accept(struct socket *sock, struct socket *newsock, { struct sock *sk1 = sock->sk, *sk2; - /* IPV6_ADDRFORM can change sk->sk_prot under us. */ arg->err = -EINVAL; sk2 = READ_ONCE(sk1->sk_prot)->accept(sk1, arg); if (!sk2) @@ -875,7 +873,6 @@ void inet_splice_eof(struct socket *sock) if (unlikely(inet_send_prepare(sk))) return; - /* IPV6_ADDRFORM can change sk->sk_prot under us. */ prot = READ_ONCE(sk->sk_prot); if (prot->splice_eof) prot->splice_eof(sock); diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c index 282912a11999..f0efdc13baf4 100644 --- a/net/ipv6/af_inet6.c +++ b/net/ipv6/af_inet6.c @@ -429,7 +429,6 @@ int inet6_bind_sk(struct sock *sk, struct sockaddr_unsized *uaddr, int addr_len) const struct proto *prot; int err = 0; - /* IPV6_ADDRFORM can change sk->sk_prot under us. */ prot = READ_ONCE(sk->sk_prot); /* If the socket has its own bind function then use it. */ if (prot->bind) @@ -567,7 +566,6 @@ int inet6_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg) case SIOCSIFDSTADDR: return addrconf_set_dstaddr(net, argp); default: - /* IPV6_ADDRFORM can change sk->sk_prot under us. */ prot = READ_ONCE(sk->sk_prot); if (!prot->ioctl) return -ENOIOCTLCMD; @@ -636,7 +634,6 @@ int inet6_sendmsg(struct socket *sock, struct msghdr *msg, size_t size) if (unlikely(inet_send_prepare(sk))) return -EAGAIN; - /* IPV6_ADDRFORM can change sk->sk_prot under us. */ prot = READ_ONCE(sk->sk_prot); return INDIRECT_CALL_2(prot->sendmsg, tcp_sendmsg, udpv6_sendmsg, sk, msg, size); @@ -651,7 +648,6 @@ int inet6_recvmsg(struct socket *sock, struct msghdr *msg, size_t size, if (likely(!(flags & MSG_ERRQUEUE))) sock_rps_record_flow(sk); - /* IPV6_ADDRFORM can change sk->sk_prot under us. */ prot = READ_ONCE(sk->sk_prot); return INDIRECT_CALL_2(prot->recvmsg, tcp_recvmsg, udpv6_recvmsg, sk, msg, size, flags); diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c index b4c977434c2e..1f68fb64a43e 100644 --- a/net/ipv6/ipv6_sockglue.c +++ b/net/ipv6/ipv6_sockglue.c @@ -547,86 +547,7 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname, sockopt_lock_sock(sk); - /* Another thread has converted the socket into IPv4 with - * IPV6_ADDRFORM concurrently. - */ - if (unlikely(sk->sk_family != AF_INET6)) - goto unlock; - switch (optname) { - - case IPV6_ADDRFORM: - if (optlen < sizeof(int)) - goto e_inval; - if (val == PF_INET) { - if (sk->sk_type == SOCK_RAW) - break; - - if (sk->sk_protocol == IPPROTO_UDP) { - if (udp_sk(sk)->pending == AF_INET6) { - retv = -EBUSY; - break; - } - } else if (sk->sk_protocol == IPPROTO_TCP) { - if (sk->sk_prot != &tcpv6_prot) { - retv = -EBUSY; - break; - } - } else { - break; - } - - if (sk->sk_state != TCP_ESTABLISHED) { - retv = -ENOTCONN; - break; - } - - if (ipv6_only_sock(sk) || - !ipv6_addr_v4mapped(&sk->sk_v6_daddr)) { - retv = -EADDRNOTAVAIL; - break; - } - - __ipv6_sock_mc_close(sk); - __ipv6_sock_ac_close(sk); - - if (sk->sk_protocol == IPPROTO_TCP) { - struct inet_connection_sock *icsk = inet_csk(sk); - - sock_prot_inuse_add(net, sk->sk_prot, -1); - sock_prot_inuse_add(net, &tcp_prot, 1); - - /* Paired with READ_ONCE(sk->sk_prot) in inet6_stream_ops */ - WRITE_ONCE(sk->sk_prot, &tcp_prot); - /* Paired with READ_ONCE() in tcp_(get|set)sockopt() */ - WRITE_ONCE(icsk->icsk_af_ops, &ipv4_specific); - WRITE_ONCE(sk->sk_socket->ops, &inet_stream_ops); - WRITE_ONCE(sk->sk_family, PF_INET); - tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); - } else { - sock_prot_inuse_add(net, sk->sk_prot, -1); - sock_prot_inuse_add(net, &udp_prot, 1); - - /* Paired with READ_ONCE(sk->sk_prot) in inet6_dgram_ops */ - WRITE_ONCE(sk->sk_prot, &udp_prot); - WRITE_ONCE(sk->sk_socket->ops, &inet_dgram_ops); - WRITE_ONCE(sk->sk_family, PF_INET); - } - - /* Disable all options not to allocate memory anymore, - * but there is still a race. See the lockless path - * in udpv6_sendmsg() and ipv6_local_rxpmtu(). - */ - np->rxopt.all = 0; - - inet6_cleanup_sock(sk); - - module_put(THIS_MODULE); - retv = 0; - break; - } - goto e_inval; - case IPV6_V6ONLY: if (optlen < sizeof(int) || inet_sk(sk)->inet_num) @@ -1088,14 +1009,6 @@ int do_ipv6_getsockopt(struct sock *sk, int level, int optname, if (copy_from_sockptr(&len, optlen, sizeof(int))) return -EFAULT; switch (optname) { - case IPV6_ADDRFORM: - if (sk->sk_protocol != IPPROTO_UDP && - sk->sk_protocol != IPPROTO_TCP) - return -ENOPROTOOPT; - if (sk->sk_state != TCP_ESTABLISHED) - return -ENOTCONN; - val = sk->sk_family; - break; case MCAST_MSFILTER: if (in_compat_syscall()) return compat_ipv6_get_msfilter(sk, optval, optlen, len); -- 2.55.0.1003.g10538fe699-goog