mptcp: create subflow or signal addr for newly added address

Currently, when a new MPTCP endpoint is added, the existing MPTCP
sockets are not affected.

This patch implements a new function mptcp_nl_add_subflow_or_signal_addr,
invoked when an address is added from PM netlink. This function traverses
the MPTCP sockets list and invokes mptcp_pm_create_subflow_or_signal_addr
to try to create a subflow or signal an address for the newly added
address, if local constraint allows that.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/19Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/pm_netlink.c

@@ -850,6 +850,31 @@ static struct pm_nl_pernet *genl_info_pm_nl(struct genl_info *info)
 	return net_generic(genl_info_net(info), pm_nl_pernet_id);
 }
 
+static int mptcp_nl_add_subflow_or_signal_addr(struct net *net)
+{
+	struct mptcp_sock *msk;
+	long s_slot = 0, s_num = 0;
+
+	while ((msk = mptcp_token_iter_next(net, &s_slot, &s_num)) != NULL) {
+		struct sock *sk = (struct sock *)msk;
+
+		if (!READ_ONCE(msk->fully_established))
+			goto next;
+
+		lock_sock(sk);
+		spin_lock_bh(&msk->pm.lock);
+		mptcp_pm_create_subflow_or_signal_addr(msk);
+		spin_unlock_bh(&msk->pm.lock);
+		release_sock(sk);
+
+next:
+		sock_put(sk);
+		cond_resched();
+	}
+
+	return 0;
+}
+
 static int mptcp_nl_cmd_add_addr(struct sk_buff *skb, struct genl_info *info)
 {
 	struct nlattr *attr = info->attrs[MPTCP_PM_ATTR_ADDR];
@@ -875,6 +900,8 @@ static int mptcp_nl_cmd_add_addr(struct sk_buff *skb, struct genl_info *info)
 		return ret;
 	}
 
+	mptcp_nl_add_subflow_or_signal_addr(sock_net(skb->sk));
+
 	return 0;
 }