netdev - [PATCH net 1/3] mptcp: set msk local address earlier

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Date:   Fri, 21 Oct 2022 15:58:54 -0700
From:   Mat Martineau <mathew.j.martineau@...ux.intel.com>
To:     netdev@...r.kernel.org
Cc:     Paolo Abeni <pabeni@...hat.com>, davem@...emloft.net,
        kuba@...nel.org, edumazet@...gle.com, dmytro@...tyi.net,
        benjamin.hesmans@...sares.net, matthieu.baerts@...sares.net,
        mptcp@...ts.linux.dev,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>
Subject: [PATCH net 1/3] mptcp: set msk local address earlier

From: Paolo Abeni <pabeni@...hat.com>

The mptcp_pm_nl_get_local_id() code assumes that the msk local address
is available at that point. For passive sockets, we initialize such
address at accept() time.

Depending on the running configuration and the user-space timing, a
passive MPJ subflow can join the msk socket before accept() completes.

In such case, the PM assigns a wrong local id to the MPJ subflow
and later PM netlink operations will end-up touching the wrong/unexpected
subflow.

All the above causes sporadic self-tests failures, especially when
the host is heavy loaded.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/308
Fixes: 01cacb00b35c ("mptcp: add netlink-based PM")
Fixes: d045b9eb95a9 ("mptcp: introduce implicit endpoints")
Reviewed-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
---
 net/mptcp/protocol.c | 3 +--
 net/mptcp/protocol.h | 1 +
 net/mptcp/subflow.c  | 7 +++++++
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index f599ad44ed24..e33f9caf409d 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2952,7 +2952,7 @@ static void mptcp_close(struct sock *sk, long timeout)
 	sock_put(sk);
 }
 
-static void mptcp_copy_inaddrs(struct sock *msk, const struct sock *ssk)
+void mptcp_copy_inaddrs(struct sock *msk, const struct sock *ssk)
 {
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 	const struct ipv6_pinfo *ssk6 = inet6_sk(ssk);
@@ -3699,7 +3699,6 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
 		if (mptcp_is_fully_established(newsk))
 			mptcp_pm_fully_established(msk, msk->first, GFP_KERNEL);
 
-		mptcp_copy_inaddrs(newsk, msk->first);
 		mptcp_rcv_space_init(msk, msk->first);
 		mptcp_propagate_sndbuf(newsk, msk->first);
 
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index c0b5b4628f65..be19592441df 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -599,6 +599,7 @@ int mptcp_is_checksum_enabled(const struct net *net);
 int mptcp_allow_join_id0(const struct net *net);
 unsigned int mptcp_stale_loss_cnt(const struct net *net);
 int mptcp_get_pm_type(const struct net *net);
+void mptcp_copy_inaddrs(struct sock *msk, const struct sock *ssk);
 void mptcp_subflow_fully_established(struct mptcp_subflow_context *subflow,
 				     struct mptcp_options_received *mp_opt);
 bool __mptcp_retransmit_pending_data(struct sock *sk);
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 07dd23d0fe04..02a54d59697b 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -723,6 +723,8 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 				goto dispose_child;
 			}
 
+			if (new_msk)
+				mptcp_copy_inaddrs(new_msk, child);
 			subflow_drop_ctx(child);
 			goto out;
 		}
@@ -750,6 +752,11 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 			ctx->conn = new_msk;
 			new_msk = NULL;
 
+			/* set msk addresses early to ensure mptcp_pm_get_local_id()
+			 * uses the correct data
+			 */
+			mptcp_copy_inaddrs(ctx->conn, child);
+
 			/* with OoO packets we can reach here without ingress
 			 * mpc option
 			 */
-- 
2.38.1