mptcp: add the outgoing RM_ADDR support

This patch added a new signal named rm_addr_signal in PM. On outgoing path,
we called mptcp_pm_should_rm_signal to check if rm_addr_signal has been
set. If it has been, we sent out the RM_ADDR option.
Suggested-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/options.c

@@ -614,6 +614,31 @@ static bool mptcp_established_options_add_addr(struct sock *sk,
 	return true;
 }
 
+static bool mptcp_established_options_rm_addr(struct sock *sk,
+					      unsigned int *size,
+					      unsigned int remaining,
+					      struct mptcp_out_options *opts)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	u8 rm_id;
+
+	if (!mptcp_pm_should_rm_signal(msk) ||
+	    !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_id)))
+		return false;
+
+	if (remaining < TCPOLEN_MPTCP_RM_ADDR_BASE)
+		return false;
+
+	*size = TCPOLEN_MPTCP_RM_ADDR_BASE;
+	opts->suboptions |= OPTION_MPTCP_RM_ADDR;
+	opts->rm_id = rm_id;
+
+	pr_debug("rm_id=%d", opts->rm_id);
+
+	return true;
+}
+
 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 			       unsigned int *size, unsigned int remaining,
 			       struct mptcp_out_options *opts)
@@ -644,6 +669,10 @@ bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 		*size += opt_size;
 		remaining -= opt_size;
 		ret = true;
+	} else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
+		*size += opt_size;
+		remaining -= opt_size;
+		ret = true;
 	}
 
 	return ret;

net/mptcp/pm.c

@@ -174,6 +174,29 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
 	return ret;
 }
 
+bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
+			     u8 *rm_id)
+{
+	int ret = false;
+
+	spin_lock_bh(&msk->pm.lock);
+
+	/* double check after the lock is acquired */
+	if (!mptcp_pm_should_rm_signal(msk))
+		goto out_unlock;
+
+	if (remaining < TCPOLEN_MPTCP_RM_ADDR_BASE)
+		goto out_unlock;
+
+	*rm_id = msk->pm.rm_id;
+	WRITE_ONCE(msk->pm.rm_addr_signal, false);
+	ret = true;
+
+out_unlock:
+	spin_unlock_bh(&msk->pm.lock);
+	return ret;
+}
+
 int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc)
 {
 	return mptcp_pm_nl_get_local_id(msk, skc);
@@ -185,8 +208,10 @@ void mptcp_pm_data_init(struct mptcp_sock *msk)
 	msk->pm.add_addr_accepted = 0;
 	msk->pm.local_addr_used = 0;
 	msk->pm.subflows = 0;
+	msk->pm.rm_id = 0;
 	WRITE_ONCE(msk->pm.work_pending, false);
 	WRITE_ONCE(msk->pm.add_addr_signal, false);
+	WRITE_ONCE(msk->pm.rm_addr_signal, false);
 	WRITE_ONCE(msk->pm.accept_addr, false);
 	WRITE_ONCE(msk->pm.accept_subflow, false);
 	msk->pm.status = 0;

net/mptcp/protocol.h

@@ -163,6 +163,7 @@ struct mptcp_pm_data {
 	spinlock_t	lock;		/*protects the whole PM data */
 
 	bool		add_addr_signal;
+	bool		rm_addr_signal;
 	bool		server_side;
 	bool		work_pending;
 	bool		accept_addr;
@@ -176,6 +177,7 @@ struct mptcp_pm_data {
 	u8		local_addr_max;
 	u8		subflows_max;
 	u8		status;
+	u8		rm_id;
 };
 
 struct mptcp_data_frag {
@@ -443,6 +445,11 @@ static inline bool mptcp_pm_should_add_signal(struct mptcp_sock *msk)
 	return READ_ONCE(msk->pm.add_addr_signal);
 }
 
+static inline bool mptcp_pm_should_rm_signal(struct mptcp_sock *msk)
+{
+	return READ_ONCE(msk->pm.rm_addr_signal);
+}
+
 static inline unsigned int mptcp_add_addr_len(int family)
 {
 	if (family == AF_INET)
@@ -452,6 +459,8 @@ static inline unsigned int mptcp_add_addr_len(int family)
 
 bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
 			      struct mptcp_addr_info *saddr);
+bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
+			     u8 *rm_id);
 int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);
 
 void __init mptcp_pm_nl_init(void);