6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Davide Caratti <dcaratti@xxxxxxxxxx> commit 8e2b8a9fa512709e6fee744dcd4e2a20ee7f5c56 upstream. Eric Dumazet suggests: > The fact that mptcp_is_tcpsk() was able to write over sock->ops was a > bit strange to me. > mptcp_is_tcpsk() should answer a question, with a read-only argument. re-factor code to avoid overwriting sock_ops inside that function. Also, change the helper name to reflect the semantics and to disambiguate from its dual, sk_is_mptcp(). While at it, collapse mptcp_stream_accept() and mptcp_accept() into a single function, where fallback / non-fallback are separated into a single sk_is_mptcp() conditional. Link: https://github.com/multipath-tcp/mptcp_net-next/issues/432 Suggested-by: Eric Dumazet <edumazet@xxxxxxxxxx> Signed-off-by: Davide Caratti <dcaratti@xxxxxxxxxx> Acked-by: Paolo Abeni <pabeni@xxxxxxxxxx> Signed-off-by: Matthieu Baerts <matttbe@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/mptcp/protocol.c | 108 ++++++++++++++++++++------------------------------- 1 file changed, 44 insertions(+), 64 deletions(-) --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -55,28 +55,14 @@ static u64 mptcp_wnd_end(const struct mp return READ_ONCE(msk->wnd_end); } -static bool mptcp_is_tcpsk(struct sock *sk) +static const struct proto_ops *mptcp_fallback_tcp_ops(const struct sock *sk) { - struct socket *sock = sk->sk_socket; - - if (unlikely(sk->sk_prot == &tcp_prot)) { - /* we are being invoked after mptcp_accept() has - * accepted a non-mp-capable flow: sk is a tcp_sk, - * not an mptcp one. - * - * Hand the socket over to tcp so all further socket ops - * bypass mptcp. - */ - WRITE_ONCE(sock->ops, &inet_stream_ops); - return true; #if IS_ENABLED(CONFIG_MPTCP_IPV6) - } else if (unlikely(sk->sk_prot == &tcpv6_prot)) { - WRITE_ONCE(sock->ops, &inet6_stream_ops); - return true; + if (sk->sk_prot == &tcpv6_prot) + return &inet6_stream_ops; #endif - } - - return false; + WARN_ON_ONCE(sk->sk_prot != &tcp_prot); + return &inet_stream_ops; } static int __mptcp_socket_create(struct mptcp_sock *msk) @@ -3328,44 +3314,6 @@ void mptcp_rcv_space_init(struct mptcp_s msk->rcvq_space.space = TCP_INIT_CWND * TCP_MSS_DEFAULT; } -static struct sock *mptcp_accept(struct sock *ssk, int flags, int *err, - bool kern) -{ - struct sock *newsk; - - pr_debug("ssk=%p, listener=%p", ssk, mptcp_subflow_ctx(ssk)); - newsk = inet_csk_accept(ssk, flags, err, kern); - if (!newsk) - return NULL; - - pr_debug("newsk=%p, subflow is mptcp=%d", newsk, sk_is_mptcp(newsk)); - if (sk_is_mptcp(newsk)) { - struct mptcp_subflow_context *subflow; - struct sock *new_mptcp_sock; - - subflow = mptcp_subflow_ctx(newsk); - new_mptcp_sock = subflow->conn; - - /* is_mptcp should be false if subflow->conn is missing, see - * subflow_syn_recv_sock() - */ - if (WARN_ON_ONCE(!new_mptcp_sock)) { - tcp_sk(newsk)->is_mptcp = 0; - goto out; - } - - newsk = new_mptcp_sock; - MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPCAPABLEPASSIVEACK); - } else { - MPTCP_INC_STATS(sock_net(ssk), - MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK); - } - -out: - newsk->sk_kern_sock = kern; - return newsk; -} - void mptcp_destroy_common(struct mptcp_sock *msk, unsigned int flags) { struct mptcp_subflow_context *subflow, *tmp; @@ -3802,7 +3750,6 @@ static struct proto mptcp_prot = { .connect = mptcp_connect, .disconnect = mptcp_disconnect, .close = mptcp_close, - .accept = mptcp_accept, .setsockopt = mptcp_setsockopt, .getsockopt = mptcp_getsockopt, .shutdown = mptcp_shutdown, @@ -3912,18 +3859,36 @@ static int mptcp_stream_accept(struct so if (!ssk) return -EINVAL; - newsk = mptcp_accept(ssk, flags, &err, kern); + pr_debug("ssk=%p, listener=%p", ssk, mptcp_subflow_ctx(ssk)); + newsk = inet_csk_accept(ssk, flags, &err, kern); if (!newsk) return err; - lock_sock(newsk); - - __inet_accept(sock, newsock, newsk); - if (!mptcp_is_tcpsk(newsock->sk)) { - struct mptcp_sock *msk = mptcp_sk(newsk); + pr_debug("newsk=%p, subflow is mptcp=%d", newsk, sk_is_mptcp(newsk)); + if (sk_is_mptcp(newsk)) { struct mptcp_subflow_context *subflow; + struct sock *new_mptcp_sock; + + subflow = mptcp_subflow_ctx(newsk); + new_mptcp_sock = subflow->conn; + + /* is_mptcp should be false if subflow->conn is missing, see + * subflow_syn_recv_sock() + */ + if (WARN_ON_ONCE(!new_mptcp_sock)) { + tcp_sk(newsk)->is_mptcp = 0; + goto tcpfallback; + } + + newsk = new_mptcp_sock; + MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPCAPABLEPASSIVEACK); + + newsk->sk_kern_sock = kern; + lock_sock(newsk); + __inet_accept(sock, newsock, newsk); set_bit(SOCK_CUSTOM_SOCKOPT, &newsock->flags); + msk = mptcp_sk(newsk); msk->in_accept_queue = 0; /* set ssk->sk_socket of accept()ed flows to mptcp socket. @@ -3945,6 +3910,21 @@ static int mptcp_stream_accept(struct so if (unlikely(list_is_singular(&msk->conn_list))) mptcp_set_state(newsk, TCP_CLOSE); } + } else { + MPTCP_INC_STATS(sock_net(ssk), + MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK); +tcpfallback: + newsk->sk_kern_sock = kern; + lock_sock(newsk); + __inet_accept(sock, newsock, newsk); + /* we are being invoked after accepting a non-mp-capable + * flow: sk is a tcp_sk, not an mptcp one. + * + * Hand the socket over to tcp so all further socket ops + * bypass mptcp. + */ + WRITE_ONCE(newsock->sk->sk_socket->ops, + mptcp_fallback_tcp_ops(newsock->sk)); } release_sock(newsk);
