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[34.83.123.78]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a0320b6ad5sm621499a91.0.2026.09.19.14.52.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 14:52:35 -0700 (PDT) From: Hui Peng To: edumazet@google.com, ncardwell@google.com, kuniyu@google.com, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] ipv6: tcp: restore ipv6_specific icsk_af_ops when reconnecting IPv6 after v4-mapped Date: Sat, 19 Sep 2026 21:52:34 +0000 Message-ID: <20260919215234.3470646-1-benquike@gmail.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When an AF_INET6 TCP socket connects to an IPv4-mapped IPv6 address (::ffff:a.b.c.d), tcp_v6_connect() switches icsk->icsk_af_ops to &ipv6_mapped, sk->sk_backlog_rcv to tcp_v4_do_rcv, and tp->af_specific to &tcp_sock_ipv4_specific. If the connection fails or is disconnected with AF_UNSPEC and the socket subsequently connects to a native IPv6 address, tcp_v6_connect() leaves icsk_af_ops set to &ipv6_mapped, causing IPv4 operations (such as ip_queue_xmit() and IPv4 setsockopt handlers) to run on an IPv6 flow and corrupt the socket/routing state. Restore icsk_af_ops to &ipv6_specific, sk_backlog_rcv to tcp_v6_do_rcv, tp->af_specific to &tcp_sock_ipv6_specific, and notify MPTCP when tcp_v6_connect() connects to a native IPv6 destination after ipv6_mapped. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Fixes: 31484d56ca95 ("mptcp: Fix undefined mptcp_handle_ipv6_mapped for modular IPV6") Assisted-by: LLM Signed-off-by: Hui Peng --- diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 7fa4ed2fd4f1..49a6f89481cb 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -255,6 +255,17 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr_unsized *uaddr, return err; } + if (icsk->icsk_af_ops == &ipv6_mapped) { + /* Paired with READ_ONCE() in tcp_(get|set)sockopt() */ + WRITE_ONCE(icsk->icsk_af_ops, &ipv6_specific); + if (sk_is_mptcp(sk)) + mptcpv6_handle_mapped(sk, false); + sk->sk_backlog_rcv = tcp_v6_do_rcv; +#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO) + tp->af_specific = &tcp_sock_ipv6_specific; +#endif + } + if (!ipv6_addr_any(&sk->sk_v6_rcv_saddr)) saddr = &sk->sk_v6_rcv_saddr;