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Date: Tue, 19 Dec 2023 22:31:04 +0100
From: Matthieu Baerts <matttbe@...nel.org>
To: mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org>,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Shuah Khan <shuah@...nel.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org, Matthieu Baerts <matttbe@...nel.org>,
Davide Caratti <dcaratti@...hat.com>
Subject: [PATCH net-next 1/4] mptcp: don't overwrite sock_ops in
mptcp_is_tcpsk()
From: Davide Caratti <dcaratti@...hat.com>
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@...gle.com>
Signed-off-by: Davide Caratti <dcaratti@...hat.com>
Acked-by: Paolo Abeni <pabeni@...hat.com>
Signed-off-by: Matthieu Baerts <matttbe@...nel.org>
---
net/mptcp/protocol.c | 108 +++++++++++++++++++++------------------------------
1 file changed, 44 insertions(+), 64 deletions(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index bc81ea53a049..5cbbd1221030 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -55,28 +55,14 @@ static u64 mptcp_wnd_end(const struct mptcp_sock *msk)
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)
@@ -3258,44 +3244,6 @@ void mptcp_rcv_space_init(struct mptcp_sock *msk, const struct sock *ssk)
WRITE_ONCE(msk->wnd_end, msk->snd_nxt + tcp_sk(ssk)->snd_wnd);
}
-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;
@@ -3739,7 +3687,6 @@ 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,
@@ -3849,18 +3796,36 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
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.
@@ -3882,6 +3847,21 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
if (unlikely(list_is_singular(&msk->conn_list)))
inet_sk_state_store(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);
--
2.40.1
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