[PATCH RFC 2/4] mptcp: introduce and use mptcp_pm_send_ack()

[Paolo Abeni <pabeni@redhat.com>]

The in-kernel PM has a bit of duplicate code related to ack
generation. Create a new helper factoring out the PM-specific
needs and use it in a couple of places.

Note that this additionally moves a few unsafe subflow socket
access under the relevant socket lock.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 net/mptcp/pm_netlink.c | 45 ++++++++++++++++++++++++------------------
 net/mptcp/protocol.c   | 11 ++++++++---
 net/mptcp/protocol.h   |  2 +-
 3 files changed, 35 insertions(+), 23 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 2b2bb3599781..91f6ed2a076a 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -463,6 +463,29 @@ static unsigned int fill_remote_addresses_vec(struct mptcp_sock *msk, bool fullm
 	return i;
 }
 
+static void mptcp_pm_send_ack(struct mptcp_sock *msk, struct mptcp_subflow_context *subflow,
+			      bool prio, bool backup)
+{
+	struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+	bool slow;
+
+	spin_unlock_bh(&msk->pm.lock);
+	pr_debug("send ack for %s",
+		 prio ? "mp_prio" : (mptcp_pm_should_add_signal(msk) ? "add_addr" : "rm_addr"));
+
+	slow = lock_sock_fast(ssk);
+	if (prio) {
+		subflow->send_mp_prio = 1;
+		subflow->backup = backup;
+		subflow->request_bkup = backup;
+	}
+
+	__mptcp_subflow_send_ack(ssk);
+	unlock_sock_fast(ssk, slow);
+
+	spin_lock_bh(&msk->pm.lock);
+}
+
 static struct mptcp_pm_addr_entry *
 __lookup_addr_by_id(struct pm_nl_pernet *pernet, unsigned int id)
 {
@@ -705,16 +728,8 @@ void mptcp_pm_nl_addr_send_ack(struct mptcp_sock *msk)
 		return;
 
 	subflow = list_first_entry_or_null(&msk->conn_list, typeof(*subflow), node);
-	if (subflow) {
-		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
-
-		spin_unlock_bh(&msk->pm.lock);
-		pr_debug("send ack for %s",
-			 mptcp_pm_should_add_signal(msk) ? "add_addr" : "rm_addr");
-
-		mptcp_subflow_send_ack(ssk);
-		spin_lock_bh(&msk->pm.lock);
-	}
+	if (subflow)
+		mptcp_pm_send_ack(msk, subflow, false, false);
 }
 
 static int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk,
@@ -736,16 +751,8 @@ static int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk,
 
 		if (subflow->backup != bkup)
 			msk->last_snd = NULL;
-		subflow->backup = bkup;
-		subflow->send_mp_prio = 1;
-		subflow->request_bkup = bkup;
 		__MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIOTX);
-
-		spin_unlock_bh(&msk->pm.lock);
-		pr_debug("send ack for mp_prio");
-		mptcp_subflow_send_ack(ssk);
-		spin_lock_bh(&msk->pm.lock);
-
+		mptcp_pm_send_ack(msk, subflow, true, bkup);
 		return 0;
 	}
 
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index b1fae2f747c9..874344f7e0fa 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -502,13 +502,18 @@ static inline bool tcp_can_send_ack(const struct sock *ssk)
 	       (TCPF_SYN_SENT | TCPF_SYN_RECV | TCPF_TIME_WAIT | TCPF_CLOSE | TCPF_LISTEN));
 }
 
-void mptcp_subflow_send_ack(struct sock *ssk)
+void __mptcp_subflow_send_ack(struct sock *ssk)
+{
+	if (tcp_can_send_ack(ssk))
+		tcp_send_ack(ssk);
+}
+
+static void mptcp_subflow_send_ack(struct sock *ssk)
 {
 	bool slow;
 
 	slow = lock_sock_fast(ssk);
-	if (tcp_can_send_ack(ssk))
-		tcp_send_ack(ssk);
+	__mptcp_subflow_send_ack(ssk);
 	unlock_sock_fast(ssk, slow);
 }
 
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 95c9ace1437b..a92b6276a03c 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -609,7 +609,7 @@ void __init mptcp_subflow_init(void);
 void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how);
 void mptcp_close_ssk(struct sock *sk, struct sock *ssk,
 		     struct mptcp_subflow_context *subflow);
-void mptcp_subflow_send_ack(struct sock *ssk);
+void __mptcp_subflow_send_ack(struct sock *ssk);
 void mptcp_subflow_reset(struct sock *ssk);
 void mptcp_subflow_queue_clean(struct sock *ssk);
 void mptcp_sock_graft(struct sock *sk, struct socket *parent);
-- 
2.35.3